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Sample records for zusammenhang zwischen dem

  1. Wechselwirkung zwischen auslegung und fertigung von brennstäben

    NASA Astrophysics Data System (ADS)

    Mayer, Hartmut; Steinmetz, Bernhard

    1982-04-01

    ZusammenfassungZiel dieser Darstellung ist es an Beispielen aus der Auslegung von Mischoxid (PuO 2-UO 2)-Brennstäben für KNK (Kompakte Natriumgekühlte Kernenergieanlage, Karlsruhe) zu zeigen, welche Möglichkeiten und Grenzen der Ausleger hat, einen Mittelweg zwischen günstigen Herstellbedingungen und den vom Betreiber erwarteten Betriebseigenschaften zu finden. In enger Kooperation mit dem Hersteller wurden die jeweils wichtigen Parameter identifiziert und der Einfluβ von Parameteränderungen untersucht. Es werden jedoch weiterhin Fragen zum erwarteten Brennstabverhalten auftreten, die nicht quantitativ, sondern nur durch qualitative Ermessensbeurteilung entschieden werden können.

  2. ASTER DEM performance

    USGS Publications Warehouse

    Fujisada, H.; Bailey, G.B.; Kelly, Glen G.; Hara, S.; Abrams, M.J.

    2005-01-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument onboard the National Aeronautics and Space Administration's Terra spacecraft has an along-track stereoscopic capability using its a near-infrared spectral band to acquire the stereo data. ASTER has two telescopes, one for nadir-viewing and another for backward-viewing, with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. Parameters such as the line-of-sight vectors and the pointing axis were adjusted during the initial operation period to generate Level-1 data products with a high-quality stereo system performance. The evaluation of the digital elevation model (DEM) data was carried out both by Japanese and U.S. science teams separately using different DEM generation software and reference databases. The vertical accuracy of the DEM data generated from the Level-1A data is 20 m with 95% confidence without ground control point (GCP) correction for individual scenes. Geolocation accuracy that is important for the DEM datasets is better than 50 m. This appears to be limited by the spacecraft position accuracy. In addition, a slight increase in accuracy is observed by using GCPs to generate the stereo data. ?? 2005 IEEE.

  3. Theorie der unelastischen Stösse zwischen Atomen

    NASA Astrophysics Data System (ADS)

    Das Problem des unelastisehen Stosses zwischen zwei Atomen reduziert sich, wenn es erlaubt ist nur zwei Elcktronenzustände jedes Atoms zu berücksichtigen, immer auf unendlich viele Systeme von je zwei gekoppelten linearen Differentialgleichungen zweiter Ordnung mit einer unabhängigen Variabeln r, welche den Abstand zwischen den beiden Systemschwerpunkten darstellt.

  4. The Oracle of DEM

    NASA Astrophysics Data System (ADS)

    Gayley, Kenneth

    2013-06-01

    The predictions of the famous Greek oracle of Delphi were just ambiguous enough to seem to convey information, yet the user was only seeing their own thoughts. Are there ways in which X-ray spectral analysis is like that oracle? It is shown using heuristic, generic response functions to mimic actual spectral inversion that the widely known ill conditioning, which makes formal inversion impossible in the presence of random noise, also makes a wide variety of different source distributions (DEMs) produce quite similar X-ray continua and resonance-line fluxes. Indeed, the sole robustly inferable attribute for a thermal, optically thin resonance-line spectrum with normal abundances in CIE is its average temperature. The shape of the DEM distribution, on the other hand, is not well constrained, and may actually depend more on the analysis method, no matter how sophisticated, than on the source plasma. The case is made that X-ray spectra can tell us average temperature, and metallicity, and absorbing column, but the main thing it cannot tell us is the main thing it is most often used to infer: the differential emission measure distribution.

  5. Hydrologic enforcement of lidar DEMs

    USGS Publications Warehouse

    Poppenga, Sandra K.; Worstell, Bruce B.; Danielson, Jeffrey J.; Brock, John C.; Evans, Gayla A.; Heidemann, H. Karl

    2014-01-01

    Hydrologic-enforcement (hydro-enforcement) of light detection and ranging (lidar)-derived digital elevation models (DEMs) modifies the elevations of artificial impediments (such as road fills or railroad grades) to simulate how man-made drainage structures such as culverts or bridges allow continuous downslope flow. Lidar-derived DEMs contain an extremely high level of topographic detail; thus, hydro-enforced lidar-derived DEMs are essential to the U.S. Geological Survey (USGS) for complex modeling of riverine flow. The USGS Coastal and Marine Geology Program (CMGP) is integrating hydro-enforced lidar-derived DEMs (land elevation) and lidar-derived bathymetry (water depth) to enhance storm surge modeling in vulnerable coastal zones.

  6. Radar and Lidar Radar DEM

    NASA Technical Reports Server (NTRS)

    Liskovich, Diana; Simard, Marc

    2011-01-01

    Using radar and lidar data, the aim is to improve 3D rendering of terrain, including digital elevation models (DEM) and estimates of vegetation height and biomass in a variety of forest types and terrains. The 3D mapping of vegetation structure and the analysis are useful to determine the role of forest in climate change (carbon cycle), in providing habitat and as a provider of socio-economic services. This in turn will lead to potential for development of more effective land-use management. The first part of the project was to characterize the Shuttle Radar Topography Mission DEM error with respect to ICESat/GLAS point estimates of elevation. We investigated potential trends with latitude, canopy height, signal to noise ratio (SNR), number of LiDAR waveform peaks, and maximum peak width. Scatter plots were produced for each variable and were fitted with 1st and 2nd degree polynomials. Higher order trends were visually inspected through filtering with a mean and median filter. We also assessed trends in the DEM error variance. Finally, a map showing how DEM error was geographically distributed globally was created.

  7. Evaluation of DEM generation based on Interferometric SAR using TanDEM-X data in Tokyo

    NASA Astrophysics Data System (ADS)

    Avtar, Ram; Yunus, Ali P.; Kraines, Steven; Yamamuro, Masumi

    This study is focused on the evaluation of a Digital Elevation Model (DEM) for Tokyo, Japan from data collected by the recently launched TerraSAR add-on for Digital Elevation Measurements (TanDEM-X), satellite of the German Aerospace Center (DLR). The aim of the TanDEM-X mission is to use Interferometric SAR techniques to generate a consistent high resolution global DEM dataset. In order to generate an accurate global DEM using TanDEM-X data, it is important to evaluate the accuracy at different sites around the world. Here, we report our efforts to generate a high-resolution DEM of the Tokyo metropolitan region using TanDEM-X data. We also compare the TanDEM-X DEM with other existing DEMs for the Tokyo region. Statistical techniques were used to calculate the elevation differences between the TanDEM-X DEM and the reference data. Two high-resolution LiDAR DEMs are used as independent reference data. The vertical accuracy of the TanDEM-X DEM evaluated using the Root Mean Square Error (RMSE) is considerably higher than the existing global digital elevation models. However, the local area DEM generated by Geospatial Information Authority of Japan (GSI DEM) showed the highest accuracy among all non-LiDAR DEM's. The vertical accuracy in terms of RMSE estimated using the 2 m LiDAR as reference is 3.20 m for TanDEM-X, 2.44 m for the GSI, 7.00 m for SRTM DEM and 10.24 m for ASTER-GDEM. We also compared the accuracy of TanDEM-X with the other DEMs for different types of land cover classes. The results show that the absolute elevation error of TanDEM-X is higher for urban and vegetated areas, likewise to those observed for other global DEM's. This is probably because the radar signals used by TanDEM-X tend to measure the first reflective surface that is encountered, which is often the top of the buildings or canopy. Hence, the TanDEM-X based DEM is more akin to a Digital Surface Model (DSM).

  8. Das Informatik-Forum Stuttgart - mehr Dialog zwischen Theorie und Anwendung notwendig

    NASA Astrophysics Data System (ADS)

    Hieber, Ludwig

    Mit der Gründung des Informatik- Forum Stuttgart wird seit 1996 eine Plattform angeboten, die den Dialog zwischen der universitären Forschung, der Informatikausbildung und der IT-Wirtschaft in der Region Stuttgart intensivieren soll. In der Informatik hat sich eine Lücke zwischen Theorie und Anwendung entwickelt. Es ist nicht erkennbar, dass diese Lücke kleiner wird, eher das Gegenteil zeichnet sich ab. Verglichen mit anderen Branchen besteht die Gefahr, dass Anwender wesentlich später von Erkenntnissen aus der Forschung profitieren. Der entstandene Interaktionsstau zwischen Theorie und Anwendung der Informatik sollte abgebaut werden. An einigen Beispielen wird aufgezeigt, wo das besonders wichtig erscheint.

  9. Urban DEM generation, analysis and enhancements using TanDEM-X

    NASA Astrophysics Data System (ADS)

    Rossi, Cristian; Gernhardt, Stefan

    2013-11-01

    This paper analyzes the potential of the TanDEM-X mission for the generation of urban Digital Elevation Models (DEMs). The high resolution of the sensors and the absence of temporal decorrelation are exploited. The interferometric chain and the problems encountered for correct mapping of urban areas are analyzed first. The operational Integrated TanDEM-X Processor (ITP) algorithms are taken as reference. The ITP main product is called the raw DEM. Whereas the ITP coregistration stage is demonstrated to be robust enough, large improvements in the raw DEM such as fewer percentages of phase unwrapping errors, can be obtained by using adaptive fringe filters instead of the conventional ones in the interferogram generation stage. The shape of the raw DEM in the layover area is also shown and determined to be regular for buildings with vertical walls. Generally, in the presence of layover, the raw DEM exhibits a height ramp, resulting in a height underestimation for the affected structure. Examples provided confirm the theoretical background. The focus is centered on high resolution DEMs produced using spotlight acquisitions. In particular, a raw DEM over Berlin (Germany) with a 2.5 m raster is generated and validated. For this purpose, ITP is modified in its interferogram generation stage by adopting the Intensity Driven Adaptive Neighbourhood (IDAN) algorithm. The height Root Mean Square Error (RMSE) between the raw DEM and a reference is about 8 m for the two classes defining the urban DEM: structures and non-structures. The result can be further improved for the structure class using a DEM generated with Persistent Scatterer Interferometry. A DEM fusion is thus proposed and a drop of about 20% in the RMSE is reported.

  10. Operational TanDEM-X DEM calibration and first validation results

    NASA Astrophysics Data System (ADS)

    Gruber, Astrid; Wessel, Birgit; Huber, Martin; Roth, Achim

    2012-09-01

    In June 2010, the German TanDEM-X satellite was launched. Together with its twin satellite TerraSAR-X it flies in a close formation enabling single-pass SAR interferometry. The primary goal of the TanDEM-X mission is the derivation of a global digital elevation model (DEM) with unprecedented global accuracies of 10 m in absolute and 2 m in relative height. A significant calibration effort is required to achieve this high quality world-wide. In spite of an intensive instrument calibration and a highly accurate orbit and baseline determination, some systematic height errors like offsets and tilts in the order of some meters remain in the interferometric DEMs and have to be determined and removed during the TanDEM-X DEM calibration. The objective of this article is the presentation of an approach for the estimation of correction parameters for remaining systematic height errors applicable to interferometric height models. The approach is based on a least-squares block adjustment using the elevation of ICESat GLA 14 data as ground control points and connecting points of adjacent, overlapping DEMs as tie-points. In the first part its implementation in DLR's ground segment is outlined. In the second part the approach is applied and validated for two of the first TanDEM-X DEM test sites. Therefore, independent reference data, in particular high resolution reference DEMs and GPS tracks, are used. The results show that the absolute height errors of the TanDEM-X DEM are small in these cases, mostly in the order of 1-2 m. An additional benefit of the proposed block adjustment method is that it improves the relative accuracy of adjacent DEMs.

  11. Elektromagnetische Strahlung. Informationen aus dem Weltall.

    NASA Astrophysics Data System (ADS)

    Schäfer, H.

    Contents: Informationen aus dem Weltall. Neue und zukünftige Geräte. Wichtiges und Interessantes aus der Positionsastronomie. Die Helligkeit der Sterne und anderer astronomischer Objekte. Spektroskopie und Spektralanalyse. Beobachtungen außerhalb des optischen Bereiches.

  12. Nonlocal similarity based DEM super resolution

    NASA Astrophysics Data System (ADS)

    Xu, Zekai; Wang, Xuewen; Chen, Zixuan; Xiong, Dongping; Ding, Mingyue; Hou, Wenguang

    2015-12-01

    This paper discusses a new topic, DEM super resolution, to improve the resolution of an original DEM based on its partial new measurements obtained with high resolution. A nonlocal algorithm is introduced to perform this task. The original DEM was first divided into overlapping patches, which were classified either as "test" or "learning" data depending on whether or not they are related to high resolution measurements. For each test patch, the similar patches in the learning dataset were identified via template matching. Finally, the high resolution DEM of the test patch was restored by the weighted sum of similar patches under the condition that the reconstruction weights were the same in different resolution cases. A key assumption of this strategy is that there are some repeated or similar modes in the original DEM, which is quite common. Experiments were done to demonstrate that we can restore a DEM by preserving the details without introducing artifacts. Statistic analysis was also conducted to show that this method can obtain higher accuracy than traditional interpolation methods.

  13. Topographic Avalanche Risk: DEM Sensitivity Analysis

    NASA Astrophysics Data System (ADS)

    Nazarkulova, Ainura; Strobl, Josef

    2015-04-01

    GIS-based models are frequently used to assess the risk and trigger probabilities of (snow) avalanche releases, based on parameters and geomorphometric derivatives like elevation, exposure, slope, proximity to ridges and local relief energy. Numerous models, and model-based specific applications and project results have been published based on a variety of approaches and parametrizations as well as calibrations. Digital Elevation Models (DEM) come with many different resolution (scale) and quality (accuracy) properties, some of these resulting from sensor characteristics and DEM generation algorithms, others from different DEM processing workflows and analysis strategies. This paper explores the impact of using different types and characteristics of DEMs for avalanche risk modeling approaches, and aims at establishing a framework for assessing the uncertainty of results. The research question is derived from simply demonstrating the differences in release risk areas and intensities by applying identical models to DEMs with different properties, and then extending this into a broader sensitivity analysis. For the quantification and calibration of uncertainty parameters different metrics are established, based on simple value ranges, probabilities, as well as fuzzy expressions and fractal metrics. As a specific approach the work on DEM resolution-dependent 'slope spectra' is being considered and linked with the specific application of geomorphometry-base risk assessment. For the purpose of this study focusing on DEM characteristics, factors like land cover, meteorological recordings and snowpack structure and transformation are kept constant, i.e. not considered explicitly. Key aims of the research presented here are the development of a multi-resolution and multi-scale framework supporting the consistent combination of large area basic risk assessment with local mitigation-oriented studies, and the transferability of the latter into areas without availability of higher resolution elevation modes. Worked examples are provided from different DEMs for Alpine as well as Central Asian study areas (including an avalanche cadaster of a mountain road in the Kyrgyz Republic), exploring the transfer of uncertainty parameters into regions where only lower resolution DEMs are available.

  14. Technical report: SRTM DEM updating using selected InSAR DEM elevations based on coherence value selection method

    NASA Astrophysics Data System (ADS)

    Yu, Jung Hum; Ge, Linlin; Rizos, Chris

    2010-11-01

    The Shuttle Radar Topography Mission (SRTM) was revolutionary because it generated global digital elevation model (DEM) using space-borne radar imaging technology. The SRTM mapped almost 80 percent of the Earth's surface to a 1-arc-second (~30 m) resolution, but generated a lower resolution 3-arc-second (~90 m) DEM. Currently, the low resolution SRTM DEM is updated and interpolated using other higher resolution DEMs obtained from different sources or techniques, such as InSAR, photogrammetry, and airborne laser scanning. Of the many DEM techniques, the InSAR DEM generation technique is recommended due to the large-coverage and the fact that it is a similar technique to that used for the SRTM DEM. This paper describes a method for updating the SRTM DEM, using InSAR DEM based on the coherence value selection method.

  15. Gefahr aus dem All. Die Erde im Visier.

    NASA Astrophysics Data System (ADS)

    von Rétyi, A.

    Contents: 1. Geheimnisse des Universums. 2. Aus dem Dunkel des Raumes. 3. Auf Kollisionskurs. 4. Tief in der Kreide - das Sterben der Dinosaurier. 5. Keime aus dem Kosmos. 6. Schattenseiten der Sonne.

  16. SHADED RELIEF, HILLSHADE, DIGITAL ELEVATION MODEL (DEM), NEVADA

    EPA Science Inventory

    Shaded relief of the state of Nevada developed from 1-degree US Geological Survey (USGS) Digital Elevation Models (DEMs). DEM is a terminology adopted by the USGS to describe terrain elevation data sets in a digital raster form.

  17. SHADED RELIEF, HILLSHADE, DIGITAL ELEVATION MODEL (DEM), ARIZONA

    EPA Science Inventory

    Shaded relief of the state of Arizona developed from 1-degree US Geological Survey (USGS) Digital Elevation Models (DEMs). DEM is a terminology adopted by the USGS to describe terrain elevation data sets in a digital raster form.

  18. Quality assessment of TanDEM-X DEMs using airborne LiDAR, photogrammetry and ICESat elevation data

    NASA Astrophysics Data System (ADS)

    Rao, Y. S.; Deo, R.; Nalini, J.; Pillai, A. M.; Muralikrishnan, S.; Dadhwal, V. K.

    2014-11-01

    TanDEM-X mission has been acquiring InSAR data to produce high resolution global DEM with greater vertical accuracy since 2010. In this study, TanDEM-X CoSSC data were processed to produce DEMs at 6 m spatial resolution for two test areas of India. The generated DEMs were compared with DEMs available from airborne LiDAR, photogrammetry, SRTM and ICESat elevation point data. The first test site is in Bihar state of India with almost flat terrain and sparse vegetation cover and the second test site is around Godavari river in Andhra Pradesh (A.P.) state of India with flat to moderate hilly terrain. The quality of the DEMs in these two test sites has been specified in terms of most widely used accuracy measures viz. mean, standard deviation, skew and RMSE. The TanDEM-X DEM over Bihar test area gives 5.0 m RMSE by taking airborne LiDAR data as reference. With ICESat elevation data available at 9000 point locations, RMSE of 5.9 m is obtained. Similarly, TanDEM-X DEM for Godavari area was compared with high resolution aerial photogrammetric DEM and SRTM DEM and found RMSE of 5.3 m and 7.5 m respectively. When compared with ICESat elevation data at several point location and also the same point locations of photogrammetric DEM and SRTM, the RMS errors are 4.1 m, 3.5 m and 4.3 m respectively. DEMs were also compared for open-pit coal mining area where elevation changes from -147 m to 189 m. X- and Y-profiles of all DEMs were also compared to see their trend and differences.

  19. Some DEM applications in SAR imagery

    NASA Astrophysics Data System (ADS)

    Perlant, Frederic P.

    1993-09-01

    With the increasing availability of SAR satellites (ERS1, ALMAZ, J-ERS, RADARSAT) along with optical remote sensing platforms (LANDSAT, SPOT), it is critical to be able to register, compare and analyze data from different sources. In this paper we will show how DEM can be used to help in these various processes in particular for SAR imagery. DEM as well as orbitographic data along with the sensor description are required to generate terrain geocoded registered products. In the case of SAR imagery these 'ancillary data' can also be used to generate by-products such as overlays, shadows, compressions and dilatations thematic maps. These maps will help in further analysis and resampling of the SAR data. Applications for improved SAR terrain geocoding as well as special radar products, SAR image interpretation and SAR interferometry will be described.

  20. Incorporating DEM Uncertainty in Coastal Inundation Mapping

    PubMed Central

    Leon, Javier X.; Heuvelink, Gerard B. M.; Phinn, Stuart R.

    2014-01-01

    Coastal managers require reliable spatial data on the extent and timing of potential coastal inundation, particularly in a changing climate. Most sea level rise (SLR) vulnerability assessments are undertaken using the easily implemented bathtub approach, where areas adjacent to the sea and below a given elevation are mapped using a deterministic line dividing potentially inundated from dry areas. This method only requires elevation data usually in the form of a digital elevation model (DEM). However, inherent errors in the DEM and spatial analysis of the bathtub model propagate into the inundation mapping. The aim of this study was to assess the impacts of spatially variable and spatially correlated elevation errors in high-spatial resolution DEMs for mapping coastal inundation. Elevation errors were best modelled using regression-kriging. This geostatistical model takes the spatial correlation in elevation errors into account, which has a significant impact on analyses that include spatial interactions, such as inundation modelling. The spatial variability of elevation errors was partially explained by land cover and terrain variables. Elevation errors were simulated using sequential Gaussian simulation, a Monte Carlo probabilistic approach. 1,000 error simulations were added to the original DEM and reclassified using a hydrologically correct bathtub method. The probability of inundation to a scenario combining a 1 in 100 year storm event over a 1 m SLR was calculated by counting the proportion of times from the 1,000 simulations that a location was inundated. This probabilistic approach can be used in a risk-aversive decision making process by planning for scenarios with different probabilities of occurrence. For example, results showed that when considering a 1% probability exceedance, the inundated area was approximately 11% larger than mapped using the deterministic bathtub approach. The probabilistic approach provides visually intuitive maps that convey uncertainties inherent to spatial data and analysis. PMID:25250763

  1. Incorporating DEM uncertainty in coastal inundation mapping.

    PubMed

    Leon, Javier X; Heuvelink, Gerard B M; Phinn, Stuart R

    2014-01-01

    Coastal managers require reliable spatial data on the extent and timing of potential coastal inundation, particularly in a changing climate. Most sea level rise (SLR) vulnerability assessments are undertaken using the easily implemented bathtub approach, where areas adjacent to the sea and below a given elevation are mapped using a deterministic line dividing potentially inundated from dry areas. This method only requires elevation data usually in the form of a digital elevation model (DEM). However, inherent errors in the DEM and spatial analysis of the bathtub model propagate into the inundation mapping. The aim of this study was to assess the impacts of spatially variable and spatially correlated elevation errors in high-spatial resolution DEMs for mapping coastal inundation. Elevation errors were best modelled using regression-kriging. This geostatistical model takes the spatial correlation in elevation errors into account, which has a significant impact on analyses that include spatial interactions, such as inundation modelling. The spatial variability of elevation errors was partially explained by land cover and terrain variables. Elevation errors were simulated using sequential Gaussian simulation, a Monte Carlo probabilistic approach. 1,000 error simulations were added to the original DEM and reclassified using a hydrologically correct bathtub method. The probability of inundation to a scenario combining a 1 in 100 year storm event over a 1 m SLR was calculated by counting the proportion of times from the 1,000 simulations that a location was inundated. This probabilistic approach can be used in a risk-aversive decision making process by planning for scenarios with different probabilities of occurrence. For example, results showed that when considering a 1% probability exceedance, the inundated area was approximately 11% larger than mapped using the deterministic bathtub approach. The probabilistic approach provides visually intuitive maps that convey uncertainties inherent to spatial data and analysis. PMID:25250763

  2. Towards AN Urban dem Generation with Satellite SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Rossi, C.; Fritz, T.; Eineder, M.; Erten, E.; Zhu, X. X.; Gernhardt, S.

    2012-07-01

    This paper analyzes the potentials offered by the TanDEM-X mission for the generation of urban DEMs. Operationally acquired urban Raw DEMs are validated using as reference a LiDAR DEM. The approach used for the validation is application-oriented as a subproduct is a derivation of a urban volume map. The mean buildings absolute height error is found to be below 5 meters. Neglecting the buildings geolocation errors, this value drops below 60 centimeters. Nevertheless, the operational municipal mapping is limited to the standard resolution of 12 meters. The limitation is attenuated with the use of high resolution spotlight data. High-resolution raw DEMs over Las Vegas and Berlin are first analyzed. Some modifications to the interferometric processing chain necessary to produce high quality DEMs are studied. The obtained results open a new perspective to the urban DEM generation with satellite SAR interferometry.

  3. DEM from Cartosat data and comparison to DEM from other sources

    NASA Astrophysics Data System (ADS)

    Tsombos, Panagiotis I.; Nikolakopoulos, Konstantinos G.; Lathourakis, Georgios

    2008-10-01

    Until a few years ago DEMs were used only by specialized scientists for terrain analysis, product development and decision making and by the army for military operations planning. Recently the DEM are used in a variety of both commercial and public business and management fields within telecommunications, navigation, constructions, energy, disaster management, transportation, weather forecast, remote sensing, geology, land cover classification, civil engineering and many more. All these applications could be summarised in four major categories: Commercial applications, Industrial applications, Military applications and Environmental-Ecological applications. Thus, there is a huge pressure for very accurate elevation data covering the entire planet surface. Image stereopairs form satellite sensors seem to provide a quite accurate and cost affordable source of elevation data. One of the newest satellite sensors with stereo collection capability is Cartosat. It can acquire stereopairs along the track with a 2,5m spatial resolution covering areas of 30X30km. In this study we compare a DEM created from a Cartosat stereopair to DEM created from other elevation data sources: 1/50.000 topographic maps, SRTM data, airphotos stereo-pair. The area of study is situated in Chalkidiki Peninsula, Greece. After a first control for random or systematic errors a statistical analysis was done. Points of known elevation have been used to estimate the accuracy of these three DEMs. The elevation difference between the different DEMs was calculated. Elevation profiles and derived maps (slope and aspect) were created and compared. 2D RMSE, correlation and the percentile value were also computed and the results are presented.

  4. DEM simulation of experimental dense granular packing

    SciTech Connect

    Hanifpour, Maryam; Allaei, Mehdi Vaez; Francois, Nicolas; Saadatfar, Mohammad

    2013-06-18

    In this study we present numerical analysis performed on the experimental results of sphere packings of mono-sized hard sphere whose packing fraction spans across a wide range of 0.59<{Phi}<0.72. Using X-ray Computed Tomography (XCT), we have full access to the 3D structure of the granular packings. Numerical analysis performed on thr data provides the first experimental proofs of how densification affects local order parameters. Furthermore by combining Discrete Element Method (DEM) and the experimental results from XCT, we investigate how the intergranular forces change with the onset of crystallization.

  5. Precise Global DEM Generation by ALOS PRISM

    NASA Astrophysics Data System (ADS)

    Tadono, T.; Ishida, H.; Oda, F.; Naito, S.; Minakawa, K.; Iwamoto, H.

    2014-04-01

    The Japan Aerospace Exploration Agency (JAXA) generated the global digital elevation/surface model (DEM/DSM) and orthorectified image (ORI) using the archived data of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi"), which was operated from 2006 to 2011. PRISM consisted of three panchromatic radiometers that acquired along-track stereo images. It had a spatial resolution of 2.5 m in the nadir-looking radiometer and achieved global coverage, making it a suitable potential candidate for precise global DSM and ORI generation. In the past 10 years or so, JAXA has conducted the calibration of the system corrected standard products of PRISM in order to improve absolute accuracies as well as to validate the high-level products such as DSM and ORI. In this paper, we introduce an overview of the global DEM/DSM dataset generation project, including a summary of ALOS and PRISM, in addition to the global data archive status. It is also necessary to consider data processing strategies, since the processing capabilities of the level 1 standard product and the high-level products must be developed in terms of both hardware and software to achieve the project aims. The automatic DSM/ORI processing software and its test processing results are also described.

  6. DEM time series of an agricultural watershed

    NASA Astrophysics Data System (ADS)

    Pineux, Nathalie; Lisein, Jonathan; Swerts, Gilles; Degré, Aurore

    2014-05-01

    In agricultural landscape soil surface evolves notably due to erosion and deposition phenomenon. Even if most of the field data come from plot scale studies, the watershed scale seems to be more appropriate to understand them. Currently, small unmanned aircraft systems and images treatments are improving. In this way, 3D models are built from multiple covering shots. When techniques for large areas would be to expensive for a watershed level study or techniques for small areas would be too time consumer, the unmanned aerial system seems to be a promising solution to quantify the erosion and deposition patterns. The increasing technical improvements in this growth field allow us to obtain a really good quality of data and a very high spatial resolution with a high Z accuracy. In the center of Belgium, we equipped an agricultural watershed of 124 ha. For three years (2011-2013), we have been monitoring weather (including rainfall erosivity using a spectropluviograph), discharge at three different locations, sediment in runoff water, and watershed microtopography through unmanned airborne imagery (Gatewing X100). We also collected all available historical data to try to capture the "long-term" changes in watershed morphology during the last decades: old topography maps, soil historical descriptions, etc. An erosion model (LANDSOIL) is also used to assess the evolution of the relief. Short-term evolution of the surface are now observed through flights done at 200m height. The pictures are taken with a side overlap equal to 80%. To precisely georeference the DEM produced, ground control points are placed on the study site and surveyed using a Leica GPS1200 (accuracy of 1cm for x and y coordinates and 1.5cm for the z coordinate). Flights are done each year in December to have an as bare as possible ground surface. Specific treatments are developed to counteract vegetation effect because it is know as key sources of error in the DEM produced by small unmanned aircraft systems. The poster will present the older and more recent changes of relief in this intensely exploited watershed and notably show how unmanned airborne imagery might be of help in DEM dynamic modelling to support soil conservation research.

  7. Zusatz- und Weiterqualifikation nach dem Studium

    NASA Astrophysics Data System (ADS)

    Domnick, Ivonne

    Ist der Bachelor geschafft, stellt sich die Frage nach einer Weiterqualifizierung. Neben einem Einstieg ins Berufsleben kann auch ein Masterstudium eventuell weitere entscheidende Bonuspunkte für den Lebenslauf bringen. Mit Zusatzqualifikationen aus fachfremden Bereichen wie Betriebswirtschaft oder Marketing ist es für Naturwissenschaftler leichter, den Einstieg ins Berufsleben zu schaffen. Viele Arbeitgeber sehen gerade bei Naturwissenschaftlern eine Promotion gerne. Hier sollte genau abgewogen werden, ob sie innerhalb einer bestimmten Zeitspanne zu schaffen ist. Auch nach einem Einstieg in den Job lässt sich der Doktortitel unter Umständen noch nachholen. Ebenso ist eine Weiterbildung neben dem Beruf in Teilzeit oder in einem Fernkurs möglich. Zusätzlich gibt es viele mehrwöchige oder mehrmonatige Kurse privater Anbieter, in denen man BWL-Grundkenntnisse erwerben kann.

  8. Development of digital elevation models (DEMs) for agricultural applications

    NASA Astrophysics Data System (ADS)

    Abd Aziz, Samsuzana

    Terrain modeling is one of the prime approaches that can be used to assess the spatial variability of agricultural fields and their surrounding ecosystems. The representation of terrain in the form of digital elevation models (DEMs) can be used to help the implementation of the applications of precision conservation management practices. GPS-equipped farm vehicles enable landowners to utilize elevation data during normal field operations for the development of agricultural field DEM. Generation of DEMs from measurements acquired with such systems provided users with additional benefits from the original capital investment in the equipment. This research provided extensive but useful guidance on appropriate procedures involved in the development of field DEMs for land users to take full advantage of the existing technology. Digital elevation models, like other maps, are models that deviate from reality. Depending on process, methods and procedures to generate the DEMs, the topographic parameters derived from a DEM contain uncertainties. In this study, the uncertainty of DEM estimates was assessed and found to be useful to enhance the sampling strategy in improving the accuracy of the DEMs. The effect of DEM uncertainty on topographic parameters was investigated and found that DEM uncertainty has a substantial impact on soil erosion prediction which may affect the consequence management decisions such as the decision on how much biomass need to be removed from the field for conservation practice. Many users particularly farmers, may not be knowledgeable about the theory, so they will appreciate the guidance about appropriate analysis that helps them make good choices for their data and applications.

  9. Effects of DEM Resolutions for Site Classification in Southeastern Korea

    NASA Astrophysics Data System (ADS)

    Kang, S.; Kim, K.; Suk, B.

    2010-12-01

    Site characteristic is an important input parameter in the hazard assessments of earthquakes, liquefactions, landslides and other natural disasters. We prepared a preliminary site classification map using the geologic and topographic maps of Korea in the previous study, in which slope and elevation data derived from digital elevation model (DEM) were used as important indicators to infer the shear wave velocity in the upper 30 m (Vs30). We may use DEMs in different resolution, which may influence the results of the site classification. In order to explore the effects of different DEM resolutions, three DEMs in 3, 9, and 30 arc-seconds are used to develop and to compare independent site classification maps of southeastern Korea. We observed the largest difference (approximately 5%) in site C classified by the slope criteria using 9 and 30 arc-sec DEMs. We also found variations as large as 3% in site B and E. In the area where large variation of slope occurs, for example mountainous region with occasional flat topography, high resolution DEM can detect variations over short distance. However, site classification map developed using a low resolution DEM is characterized by smoother variations in topography, thus results in averaged site classes. We also note only minor differences (less than 0.7%) in the elevation-based site classification maps using three different DEMs. Apparently, it is suitable to use a higher resolution DEM to represent the rugged topography in southeastern Korea. Finally, the site classification using higher resolution DEM will provide useful information in the study of regional hazard estimation and risk management.

  10. Validation of SRTM X Band DEM over Himalayan Mountain

    NASA Astrophysics Data System (ADS)

    Gupta, R. D.; Singh, M. K.; Snehmani, S.; Ganju, A.

    2014-04-01

    The present research study assesses the accuracy of the SRTM X band DEM with respect to high accuracy photogrammetric Digital Elevation Model (DEM) for parts of the Himalaya. The high resolution DEM was generated for Manali and nearby areas using digital aerial photogrammetric survey data of 40 cm Ground Sampling Distance (GSD) captured through airborne ADS80 pushbroom camera for the first time in Indian Himalayan context. This high resolution DEM was evaluated with Differential Global Positioning System (DGPS) points for accuracy assessment. The ADS80-DEM gave root mean square error (RMSE) of ~<1m and linear error of 1.60 m at 90 % confidence (LE 90) when compared with the DGPS points. The overall RMSE in vertical accuracy was 73.36 m while LE 90 was 75.20 m with regard to ADS80 DEM. It is observed that the accuracy achieved for part of Himalayan region is far less as compared to the values officially claimed. Thus, SRTM X band DEM should be used with due care in mountainous regions of Himalaya.

  11. The generation of DEM from ALOS in the Himalayas

    NASA Astrophysics Data System (ADS)

    Ye, Q.

    2009-12-01

    Glacier volume changes needs an integrated study and correction on generated DEMs from multi-sources remote sensing data and evaluation of the vertical errors and accuracy. Here, we produced DEMs over mountain glaciers from ASTER and ALOS/PRISM on the northern slope of Mt. Qomolangma (hereafter called the Mt. Qomolangma region), also known as the Mt. Everest, located in the middle Himalayan Mountains. A series of digital images, include Aster images on 23 Oct 2003, 3 scenes of ALOS/PRISM on 04 Dec 2006, 1:50,000 topographic maps with contour interval of 20 m produced from aerial photographs acquired in 1974 and the 1:50,000 DEM (cell size: 25 m) generated from the topographic maps were used.The DEM was generated based on the three scenes from ALOS/PRISM images and PCI Orthoengine module. The process of DEM generation from ASTER images is very similar to that of ALOS/PRISM. The difference is that: only two images ASTER from nadir and backward views were used here. Compared various kinds of products of the generated DEMs in the non-glacierized area with the 1:50,000 topographic maps using 215 random points, we found that the mean difference of PRISM DEM to the topographic maps is 1.7 m. However, the mean difference of ASTER GDEM (ASTER_GDEM) is 45m, which is the released Version 1 of the ASTER Global DEM on 29 June, 2009. Our result shows that the quality of ALOS/PRISM DEM is better than that of ASTER GDEM.

  12. EMDataBank unified data resource for 3DEM

    PubMed Central

    Lawson, Catherine L.; Patwardhan, Ardan; Baker, Matthew L.; Hryc, Corey; Garcia, Eduardo Sanz; Hudson, Brian P.; Lagerstedt, Ingvar; Ludtke, Steven J.; Pintilie, Grigore; Sala, Raul; Westbrook, John D.; Berman, Helen M.; Kleywegt, Gerard J.; Chiu, Wah

    2016-01-01

    Three-dimensional Electron Microscopy (3DEM) has become a key experimental method in structural biology for a broad spectrum of biological specimens from molecules to cells. The EMDataBank project provides a unified portal for deposition, retrieval and analysis of 3DEM density maps, atomic models and associated metadata (emdatabank.org). We provide here an overview of the rapidly growing 3DEM structural data archives, which include maps in EM Data Bank and map-derived models in the Protein Data Bank. In addition, we describe progress and approaches toward development of validation protocols and methods, working with the scientific community, in order to create a validation pipeline for 3DEM data. PMID:26578576

  13. High-resolution DEM Effects on Geophysical Flow Models

    NASA Astrophysics Data System (ADS)

    Williams, M. R.; Bursik, M. I.; Stefanescu, R. E. R.; Patra, A. K.

    2014-12-01

    Geophysical mass flow models are numerical models that approximate pyroclastic flow events and can be used to assess the volcanic hazards certain areas may face. One such model, TITAN2D, approximates granular-flow physics based on a depth-averaged analytical model using inputs of basal and internal friction, material volume at a coordinate point, and a GIS in the form of a digital elevation model (DEM). The volume of modeled material propagates over the DEM in a way that is governed by the slope and curvature of the DEM surface and the basal and internal friction angles. Results from TITAN2D are highly dependent upon the inputs to the model. Here we focus on a single input: the DEM, which can vary in resolution. High resolution DEMs are advantageous in that they contain more surface details than lower-resolution models, presumably allowing modeled flows to propagate in a way more true to the real surface. However, very high resolution DEMs can create undesirable artifacts in the slope and curvature that corrupt flow calculations. With high-resolution DEMs becoming more widely available and preferable for use, determining the point at which high resolution data is less advantageous compared to lower resolution data becomes important. We find that in cases of high resolution, integer-valued DEMs, very high-resolution is detrimental to good model outputs when moderate-to-low (<10-15°) slope angles are involved. At these slope angles, multiple adjacent DEM cell elevation values are equal due to the need for the DEM to approximate the low slope with a limited set of integer values for elevation. The first derivative of the elevation surface thus becomes zero. In these cases, flow propagation is inhibited by these spurious zero-slope conditions. Here we present evidence for this "terracing effect" from 1) a mathematically defined simulated elevation model, to demonstrate the terracing effects of integer valued data, and 2) a real-world DEM where terracing must be addressed. We discuss the effect on the flow model output and present possible solutions for rectification of the problem.

  14. Precise Baseline Determination for the TanDEM-X Mission

    NASA Astrophysics Data System (ADS)

    Moon, Y.; Koenig, R.; Wermuth, M.; Montenbruck, O.; Jaeggi, A.

    2011-12-01

    The principal goal of the TanDEM-X mission is the generation of a global Digital Elevation Model (DEM) with 2 meters relative vertical accuracy. To achieve this requirement, the relative trajectory between TerraSAR-X and TanDEM-X, called baseline, should be determined with an accuracy of 1 millimeter. For this purpose, the German Research Centre for Geosciences (GFZ) has provided the Tracking, Occultation and Ranging (TOR) payload for both TerraSAR-X and TanDEM-X. Using the geodetic grade GPS data from the TOR instruments installed on both satellites, GFZ has been providing operationally TanDEM-X baseline products since the launch of the TanDEM-X in June 2011. In this contribution, an overview of the TanDEM-X project, the role of the baseline and its operational provision from three different software solutions within the ground segment and future prospects are given. The quality of the different baseline products will be assessed using one-year of operationally generated baseline products from GFZ and DLR. Two baseline solutions from the EPOS and BERNESE software packages by GFZ and one solution from the GHOST/FRNS software package by DLR are compared in terms of standard deviation and mean of the differences. The long-term series provides a focus on the bias track between the baseline solutions. Then the topic of calibrating the bias of the baselines via SAR data taken over test areas is discussed. In a final step, the different baseline solutions are corrected for their bias and merged for noise reduction into an optimal baseline being input to the operational DEM production.

  15. Construction of lunar DEMs based on reflectance modelling

    NASA Astrophysics Data System (ADS)

    Grumpe, Arne; Belkhir, Fethi; Wöhler, Christian

    2014-06-01

    Existing lunar DEMs obtained based on laser altimetry or photogrammetric image analysis are characterised by high large-scale accuracies while their lateral resolution is strongly limited by noise or interpolation artifacts. In contrast, image-based photometric surface reconstruction approaches reveal small-scale surface detail but become inaccurate on large spatial scales. The framework proposed in this study therefore combines photometric image information of high lateral resolution and DEM data of comparably low lateral resolution in order to obtain DEMs of high lateral resolution which are also accurate on large spatial scales. Our first approach combines an extended photoclinometry scheme and a shape from shading based method. A novel variational surface reconstruction method further increases the lateral resolution of the DEM such that it reaches that of the underlying images. We employ the Hapke IMSA and AMSA reflectance models with two different formulations of the single-particle scattering function, such that the single-scattering albedo of the surface particles and optionally the asymmetry parameter of the single-particle scattering function can be estimated pixel-wise. As our DEM construction methods require co-registered images, an illumination-independent image registration scheme is developed. An evaluation of our framework based on synthetic image data yields an average elevation accuracy of the constructed DEMs of better than 20 m as long as the correct reflectance model is assumed. When comparing our DEMs to LOLA single track data, absolute elevation accuracies around 30 m are obtained for test regions that cover an elevation range of several thousands of metres. The proposed illumination-independent image registration method yields subpixel accuracy even in the presence of 3D perspective distortions. The pixel-wise reflectance parameters estimated simultaneously with the DEM reflect compositional contrasts between different surface units. Specifically, the detected variations of the parameter of the single-particle scattering function indicate small-scale variations of the regolith particle size, possibly as a result of differences in soil maturity.

  16. N-to-One-Provisionierung zwischen internen Satellitenverzeichnissen des IntegraTUM-Metadirectory

    NASA Astrophysics Data System (ADS)

    Boursas, Latifa

    Dieser Beitrag beschreibt und analysiert die Synchronisationslösungen zur Verwaltung von Benutzerdaten, die Konnektoren aus verschiedenen Quellsystemen und zwischen Verzeichnisdiensten übertragen müssen. Der Schwerpunkt dieser Analyse liegt dabei auf den Transformationen, die zwei Datenmodelle mit unterschiedlichen Strukturen des Directory Information Tree (DIT) innerhalb des IntegraTUM-Metadirectory miteinander abgleichen. Besonders herausfordernd ist, diesen Abgleich mittels des Novell DirXML-Treibers zu realisieren, weil das DirXML-Datenmodell für die Synchronisation der LDAP-Objekte auf eins zu eins Synchronisation ausgelegt ist. In diesem Beitrag wird unsere Lösung für die Synchronisation mehreren LDAP-Objekte auf ein einziges Objekt detailliert und ihre Integrierbarkeit in anderen Hochschulen vorgestellt.

  17. Shading-based DEM refinement under a comprehensive imaging model

    NASA Astrophysics Data System (ADS)

    Peng, Jianwei; Zhang, Yi; Shan, Jie

    2015-12-01

    This paper introduces an approach to refine coarse digital elevation models (DEMs) based on the shape-from-shading (SfS) technique using a single image. Different from previous studies, this approach is designed for heterogeneous terrain and derived from a comprehensive (extended) imaging model accounting for the combined effect of atmosphere, reflectance, and shading. To solve this intrinsic ill-posed problem, the least squares method and a subsequent optimization procedure are applied in this approach to estimate the shading component, from which the terrain gradient is recovered with a modified optimization method. Integrating the resultant gradients then yields a refined DEM at the same resolution as the input image. The proposed SfS method is evaluated using 30 m Landsat-8 OLI multispectral images and 30 m SRTM DEMs. As demonstrated in this paper, the proposed approach is able to reproduce terrain structures with a higher fidelity; and at medium to large up-scale ratios, can achieve elevation accuracy 20-30% better than the conventional interpolation methods. Further, this property is shown to be stable and independent of topographic complexity. With the ever-increasing public availability of satellite images and DEMs, the developed technique is meaningful for global or local DEM product refinement.

  18. Gauss-Newton method for DEM co-registration

    NASA Astrophysics Data System (ADS)

    Wang, Kunlun; Zhang, Tonggang

    2015-12-01

    Digital elevation model (DEM) co-registration is one of the hottest research problems, and it is the critical technology for multi-temporal DEM analysis, which has wide potential application in many fields, such as geological hazards. Currently, the least-squares principle is used in most DEM co-registration methods, in which the matching parameters are obtained by iteration; the surface co-registration is then accomplished. To improve the iterative convergence rate, a Gauss-Newton method for DEM co-registration (G-N) is proposed in this paper. A gradient formula based on a gridded discrete surface is derived in theory, and then the difficulty of applying the Gauss-Newton method to DEM matching is solved. With the G-N algorithm, the surfaces approach each other along the maximal gradient direction, and therefore the iterative convergence and the performance efficiency of the new method can be enhanced greatly. According to experimental results based on the simulated datasets, the average convergence rates of rotation and translation parameters of the G-N algorithm are increased by 40 and 15% compared to those of the ICP algorithm, respectively. The performance efficiency of the G-N algorithm is 74.9% better.

  19. The effects of wavelet compression on Digital Elevation Models (DEMs)

    USGS Publications Warehouse

    Oimoen, M.J.

    2004-01-01

    This paper investigates the effects of lossy compression on floating-point digital elevation models using the discrete wavelet transform. The compression of elevation data poses a different set of problems and concerns than does the compression of images. Most notably, the usefulness of DEMs depends largely in the quality of their derivatives, such as slope and aspect. Three areas extracted from the U.S. Geological Survey's National Elevation Dataset were transformed to the wavelet domain using the third order filters of the Daubechies family (DAUB6), and were made sparse by setting 95 percent of the smallest wavelet coefficients to zero. The resulting raster is compressible to a corresponding degree. The effects of the nulled coefficients on the reconstructed DEM are noted as residuals in elevation, derived slope and aspect, and delineation of drainage basins and streamlines. A simple masking technique also is presented, that maintains the integrity and flatness of water bodies in the reconstructed DEM.

  20. Evaluating the Accuracy of dem Generation Algorithms from Uav Imagery

    NASA Astrophysics Data System (ADS)

    Ruiz, J. J.; Diaz-Mas, L.; Perez, F.; Viguria, A.

    2013-08-01

    In this work we evaluated how the use of different positioning systems affects the accuracy of Digital Elevation Models (DEMs) generated from aerial imagery obtained with Unmanned Aerial Vehicles (UAVs). In this domain, state-of-the-art DEM generation algorithms suffer from typical errors obtained by GPS/INS devices in the position measurements associated with each picture obtained. The deviations from these measurements to real world positions are about meters. The experiments have been carried out using a small quadrotor in the indoor testbed at the Center for Advanced Aerospace Technologies (CATEC). This testbed houses a system that is able to track small markers mounted on the UAV and along the scenario with millimeter precision. This provides very precise position measurements, to which we can add random noise to simulate errors in different GPS receivers. The results showed that final DEM accuracy clearly depends on the positioning information.

  1. Extract relevant features from DEM for groundwater potential mapping

    NASA Astrophysics Data System (ADS)

    Liu, T.; Yan, H.; Zhai, L.

    2015-06-01

    Multi-criteria evaluation (MCE) method has been applied much in groundwater potential mapping researches. But when to data scarce areas, it will encounter lots of problems due to limited data. Digital Elevation Model (DEM) is the digital representations of the topography, and has many applications in various fields. Former researches had been approved that much information concerned to groundwater potential mapping (such as geological features, terrain features, hydrology features, etc.) can be extracted from DEM data. This made using DEM data for groundwater potential mapping is feasible. In this research, one of the most widely used and also easy to access data in GIS, DEM data was used to extract information for groundwater potential mapping in batter river basin in Alberta, Canada. First five determining factors for potential ground water mapping were put forward based on previous studies (lineaments and lineament density, drainage networks and its density, topographic wetness index (TWI), relief and convergence Index (CI)). Extraction methods of the five determining factors from DEM were put forward and thematic maps were produced accordingly. Cumulative effects matrix was used for weight assignment, a multi-criteria evaluation process was carried out by ArcGIS software to delineate the potential groundwater map. The final groundwater potential map was divided into five categories, viz., non-potential, poor, moderate, good, and excellent zones. Eventually, the success rate curve was drawn and the area under curve (AUC) was figured out for validation. Validation result showed that the success rate of the model was 79% and approved the method's feasibility. The method afforded a new way for researches on groundwater management in areas suffers from data scarcity, and also broaden the application area of DEM data.

  2. Discrete Element Modeling (DEM) of Triboelectrically Charged Particles: Revised Experiments

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Calle, Carlos I.; Curry, D. R.; Weitzman, P. S.

    2008-01-01

    In a previous work, the addition of basic screened Coulombic electrostatic forces to an existing commercial discrete element modeling (DEM) software was reported. Triboelectric experiments were performed to charge glass spheres rolling on inclined planes of various materials. Charge generation constants and the Q/m ratios for the test materials were calculated from the experimental data and compared to the simulation output of the DEM software. In this paper, we will discuss new values of the charge generation constants calculated from improved experimental procedures and data. Also, planned work to include dielectrophoretic, Van der Waals forces, and advanced mechanical forces into the software will be discussed.

  3. Precise baseline determination for the TanDEM-X mission

    NASA Astrophysics Data System (ADS)

    Koenig, Rolf; Moon, Yongjin; Neumayer, Hans; Wermuth, Martin; Montenbruck, Oliver; Jäggi, Adrian

    The TanDEM-X mission will strive for generating a global precise Digital Elevation Model (DEM) by way of bi-static SAR in a close formation of the TerraSAR-X satellite, already launched on June 15, 2007, and the TanDEM-X satellite to be launched in May 2010. Both satellites carry the Tracking, Occultation and Ranging (TOR) payload supplied by the GFZ German Research Centre for Geosciences. The TOR consists of a high-precision dual-frequency GPS receiver, called Integrated GPS Occultation Receiver (IGOR), and a Laser retro-reflector (LRR) for precise orbit determination (POD) and atmospheric sounding. The IGOR is of vital importance for the TanDEM-X mission objectives as the millimeter level determination of the baseline or distance between the two spacecrafts is needed to derive meter level accurate DEMs. Within the TanDEM-X ground segment GFZ is responsible for the operational provision of precise baselines. For this GFZ uses two software chains, first its Earth Parameter and Orbit System (EPOS) software and second the BERNESE software, for backup purposes and quality control. In a concerted effort also the German Aerospace Center (DLR) generates precise baselines independently with a dedicated Kalman filter approach realized in its FRNS software. By the example of GRACE the generation of baselines with millimeter accuracy from on-board GPS data can be validated directly by way of comparing them to the intersatellite K-band range measurements. The K-band ranges are accurate down to the micrometer-level and therefore may be considered as truth. Both TanDEM-X baseline providers are able to generate GRACE baselines with sub-millimeter accuracy. By merging the independent baselines by GFZ and DLR, the accuracy can even be increased. The K-band validation however covers solely the along-track component as the K-band data measure just the distance between the two GRACE satellites. In addition they inhibit an un-known bias which must be modelled in the comparison, so the differences between the computed baselines and the K-band ranges vary around a mean. In the end a systematic deviation or bias cannot be detected this way. A 3-D assessment of the baseline accuracies including biases can be gained by comparison of independently derived baselines as here from GFZ and DLR. Indeed it turns out that the different baselines show systematic differences of a few millimeters. From this it can be concluded that for the TanDEM-X mission an unknown bias in the baselines is possible which in turn would hurt the anticipated DEM accuracy limit. In order to control a possible baseline bias, a calibration chain via SAR calibration data takes has been invented in the TanDEM-X ground segment. This chain delivers corrections to the baseline bias so that unbiased baselines with sub-millimeter accuracies can be provided to secure the DEM accuracy requirement.

  4. DEM-based research on the landform features of China

    NASA Astrophysics Data System (ADS)

    Tang, Guoan; Liu, Aili; Li, Fayuan; Zhou, Jieyu

    2006-10-01

    Landforms can be described and identified by parameterization of digital elevation model (DEM). This paper discusses the large-scale geomorphological characteristics of China based on numerical analysis of terrain parameters and develop a methodology for characterizing landforms from DEMs. The methodology is implemented as a two-step process. First, terrain variables are derived from a 1-km DEM in a given statistical unit including local relief, the earth's surface incision, elevation variance coefficient, roughness, mean slope and mean elevation. Second, every parameter regarded as a single-band image is combined into a multi-band image. Then ISODATA unsupervised classification and the Bayesian technique of Maximum Likelihood supervised classification are applied for landform classification. The resulting landforms are evaluated by the means of Stratified Sampling with respect to an existing map and the overall classification accuracy reaches to rather high value. It's shown that the derived parameters carry sufficient physiographic information and can be used for landform classification. Since the classification method integrates manifold terrain indexes, conquers the limitation of the subjective cognition, as well as a low cost, apparently it could represent an applied foreground in the classification of macroscopic relief forms. Furthermore, it exhibits significance in consummating the theory and the methodology of DEMs on digital terrain analysis.

  5. Spatial Characterization of Landscapes through Multifractal Analysis of DEM

    PubMed Central

    Aguado, P. L.; Del Monte, J. P.; Moratiel, R.; Tarquis, A. M.

    2014-01-01

    Landscape evolution is driven by abiotic, biotic, and anthropic factors. The interactions among these factors and their influence at different scales create a complex dynamic. Landscapes have been shown to exhibit numerous scaling laws, from Horton's laws to more sophisticated scaling of heights in topography and river network topology. This scaling and multiscaling analysis has the potential to characterise the landscape in terms of the statistical signature of the measure selected. The study zone is a matrix obtained from a digital elevation model (DEM) (map 10 × 10 m, and height 1 m) that corresponds to homogeneous region with respect to soil characteristics and climatology known as “Monte El Pardo” although the water level of a reservoir and the topography play a main role on its organization and evolution. We have investigated whether the multifractal analysis of a DEM shows common features that can be used to reveal the underlying patterns and information associated with the landscape of the DEM mapping and studied the influence of the water level of the reservoir on the applied analysis. The results show that the use of the multifractal approach with mean absolute gradient data is a useful tool for analysing the topography represented by the DEM. PMID:25177728

  6. Entwicklungsperspektiven von Social Software und dem Web 2.0

    NASA Astrophysics Data System (ADS)

    Raabe, Alexander

    Der Artikel beschäftigt sich zunächst mit dem derzeitigen und zukünftigen Einsatz von Social Software in Unternehmen. Nach dem großen Erfolg von Social Software im Web beginnen viele Unternehmen eigene Social Software-Initiativen zu entwickeln. Der Artikel zeigt die derzeit wahrgenommenen Einsatzmöglichkeiten von Social Software im Unternehmen auf, erörtert Erfolgsfaktoren für die Einführung und präsentiert mögliche Wege für die Zukunft. Nach der Diskussion des Spezialfalles Social Software in Unternehmen werden anschließend die globalen Trends und Zukunftsperspektiven des Web 2.0 in ihren technischen, wirtschaftlichen und sozialen Dimensionen dargestellt. Wie aus den besprochenen Haupttrends hervorgeht, wird die Masse an digital im Web verfügbaren Informationen stetig weiterwachsen. So stellt sich die Frage, wie es in Zukunft möglich sein wird, die Qualität der Informationssuche und der Wissensgenerierung zu verbessern. Mit dem Einsatz von semantischen Technologien im Web wird hier eine revolutionäre Möglichkeit geboten, Informationen zu filtern und intelligente, gewissermaßen verstehende" Anwendungen zu entwerfen. Auf dem Weg zu einem intelligenten Web werden sich das Semantic Web und Social Software annähern: Anwendungen wie Semantic Wikis, Semantic Weblogs, lightweight Semantic Web-Sprachen wie Microformats oder auch kommerzielle Angebote wie Freebase von Metaweb werden die ersten Vorzeichen einer dritten Generation des Webs sein.

  7. Using LIDAR-based DEM to orthorectify Ikonos panchromatic images

    NASA Astrophysics Data System (ADS)

    Elaksher, Ahmed F.

    2009-06-01

    Recent development in remote sensing technologies has stimulated a great interest in its application in large-scale mapping. For example, the Ikonos satellite images, available since 2000, have an improved resolution of 1 m that afford mapping of a lot of ground objects from the satellite images. However, the use of these images in high-accuracy mapping applications has been limited since the sensor model parameters are not yet released. On the other hand, Light Detection and Ranging (LIDAR) is a fast method for sampling the earth's surface with a high density and high accuracy point cloud that is used to generate high density and high accuracy Digital Elevation Models (DEMs) and DSMs. Integrating both technologies makes it possible to provide reliable and automatic solutions for large-scale mapping applications, 3-D visualization, GIS and change detection. In this research a 1-m resolution LIDAR-based DEM is used to orthorectify a single Geo-panchromatic Ikonos image. The LIDAR-based DEM is first rectified using 12 Ground Control Points (GCPs) surveyed using the Differential GPS (DGPS) technique. The LIDAR-based DEM is then used as a source for other GCPs that are used to orthorectify the Ikonos image. Different 2-D transformation models are used with different sets and distributions of GCPs. The planimetric Root Mean Square Errors (RMSE) achieved, using these models, is about 5 m. The relationship between the planimetric errors and the elevations of the checkpoints suggested using 3-D to 2-D transformation models. Three different types of these models are examined and their results are reported. The results showed that less than 2 m mapping accuracy could be achieved using the 3-D to 2-D transformation models. These results suggest that using a single panchromatic Ikonos image together with a 1-m resolution LIDAR-based DEM could achieve the required planimetric accuracy for 1:5000 topographic maps.

  8. Tanzendes Tier oder exzentrische Positionalität - Philosophische Anthropologie zwischen Darwinismus und Kulturalismus

    NASA Astrophysics Data System (ADS)

    Fischer, Joachim

    Zunächst kurz vorweg zu den Formeln im Titel: "exzentrische Positionalität“ ist der Kategorienvorschlag der Philosophischen Anthropologie (genauer: von Helmuth Plessner) für den Menschen, für seine "Sonderstellung“ unter den Lebewesen - ich werde diesen Begriff erläutern. So viel kann man sagen: Der Terminus ist nicht schwieriger als "Transzendentalität“ oder das "Apriori“ oder "Autopoiesis“, also Begriffe, mit deren Orientierungswert in der intellektuellen Öffentlichkeit bereits gespielt wird, bietet aber möglicherweise mehr Erschließungskraft als die Kunstbegriffe z. B. von Kant, Maturana oder Luhmann. Und "tanzendes Tier“ ist ein glücklicher Anschauungsbegriff, eine Art Übersetzung für "exzentrische Positionalität“ - also ein "verrücktes“ Lebewesen, eine Verrückung im evolutionären Leben, die dieses Lebewesen von Natur aus zu einer bestimmten Art von Lebensführung, nämlich Kultur nötigt. Die Absicht des Beitrages ist es, die Philosophische Anthropologie als eine spezifische Theorietechnik zu präsentieren, um einen adäquaten Begriff des Menschen zu erreichen, und zwar eine Theoriestrategie angesichts des cartesianischen Dualismus - also des Dualismus zwischen Naturalismus und Kulturalismus.

  9. Application of TanDEM-X interferometry in volcano monitoring

    NASA Astrophysics Data System (ADS)

    Kubanek, Julia; Westerhaus, Malte; Heck, Bernhard

    2013-04-01

    Traditional repeat-pass SAR interferometry (InSAR) has proven to be useful to monitor deformations at active volcanoes. In this so called monostatic mode, images recorded during different satellite passes from slightly changing antenna positions are used to map topographic changes of the earth surface on centimeter scale. However, problems regarding changing atmospheric conditions between the different satellite passes influence the quality of the results. Moreover, the backscattering conditions between two passes need to be tolerably stable to be used for interferometry. As far as the changes in the volcanic environment are slow, repeat-pass InSAR is a great monitoring tool. However, fast changing backscattering conditions result in low coherency, making a classical interferometric deformation analysis impossible. Especially dome-building volcanoes can change on meter scale per second in active phases, preventing the observation with repeat-pass InSAR. To solve these problems, we are currently testing the ability of the German TanDEM-X mission to monitor large deformations at active volcanos. The bistatic TanDEM-X mission consists of two radar satellites (TerraSAR-X and TanDEM-X) flying in a close formation, taking images of the earth surface at the same time. In contrast to the repeat pass mode, this results in two nearly absolutely coherent images, which means that there are no atmospheric disturbances and backscattering errors in the interferometric pair. This allows generating digital elevation models (DEMs) at several times. A simple time series analysis of the models enables for the first time to quantify large topographic changes at active dome-building volcanoes. We chose Volcán de Colima, Mexico as test site. While being a dome building volcano, phases of quiescence are interrupted every few years by dome collapses, pyroclastic flows and deposition of volcanic material. At present, Volcán de Colima seems to be stable. Nevertheless, an explosion at the crater rim signaled the end of magma ascent in June 2011. The bistatic TanDEM-X data gives important information on this explosion as we can observe material changes in the summit area when comparing datasets taken before and after the explosion. Our results indicate that repeated DEMs with great detail and good accuracy are obtainable, enabling a quantitative estimation of finite volume changes in the summit area of the volcano. Additionally, we highlight the importance of employing remote sensing methods to collect data in volcano research.

  10. Reconstructing Stellar DEMs from X-ray Spectra

    NASA Astrophysics Data System (ADS)

    Kang, H.; van Dyk, D.; Kashyap, V.; Connors, A.

    2004-08-01

    The temperature distribution of Emission Measure is a powerful tool to characterize and understand the composition and physical structure of stellar coronae. Numerous methods have been proposed in the literature to compute the Differential Emission Measure (DEM) based on line fluxes measured from identifiable lines in high-resolution EUV and X-ray spectra. Here we describe a new and powerful method that we have developed to reconstruct DEMs that improves significantly on previous algorithms and further allows for incorporating atomic data errors into the calculations. Some notable features of our algorithm are: an ability to fit to either a selected subset of lines with measured fluxes or to perform a global fit to all lines over the full wavelength range of the instrument, to fully incorporate line blends, to obtain error bars to determine the significance of features seen in the reconstructed DEM, and to directly incorporate prior information such as atomic line sequences, known atomic data errors, systematic effects due to calibration uncertainties, etc. We use highly structured models to account for the mixing of the ion/temperature specific spectra, the mixing of continuum photons with those from the multitude of spectral lines, instrumental response, the effective area of the instrument, and background contamination. We introduce the statistical framework of data augmentation (e.g., EM algorithms and MCMC samplers), in which we treat photon count in each level of the hierarchical structure as missing data. We implement a multi-scale (wavelet-like) prior distribution to smooth the DEM, which gives us the flexibility to overcome lack of information especially with low count data. In this talk we provide several simulation studies with both high-count and low-count data to evaluate the proposed method. We also provide several DEM reconstruction results of the active star alpha Aur (Capella), and validate the method by comparing our results to previous estimates of the Capella DEMs. The authors gratefully acknowledge funding for this project partially provided by NSF grant DMS-01-04129 and by NASA Contract NAS8-39073 (Chandra X-ray Center).

  11. Improving the TanDEM-X DEM for flood modelling using flood extents from Synthetic Aperture Radar images.

    NASA Astrophysics Data System (ADS)

    Mason, David; Trigg, Mark; Garcia-Pintado, Javier; Cloke, Hannah; Neal, Jeffrey; Bates, Paul

    2015-04-01

    Many floodplains in the developed world have now been imaged with high resolution airborne LiDAR or InSAR, giving accurate DEMs that facilitate accurate flood inundation modelling. This is not always the case for remote rivers in developing countries. However, the accuracy of DEMs produced for modelling studies on such rivers should be enhanced in the near future by the high resolution TanDEM-X World DEM. In a parallel development, increasing use is now being made of flood extents derived from high resolution SAR images for calibrating, validating and assimilating observations into flood inundation models in order to improve these. The paper discusses an additional use of SAR flood extents to improve the accuracy of the TanDEM-X DEM in the floodplain covered by the flood extents, thereby permanently improving the DEM for future flood modelling studies in this area. The method is based on the fact that for larger rivers the water elevation changes only slowly along a reach, so that the boundary of the flood extent (the waterline) can be regarded locally as a quasi-contour. As a result, heights of adjacent pixels along a small section of waterline can be regarded as a sample of heights with a common population mean. The height of the central pixel in the section can be replaced with the average of these heights, leading to a more accurate height estimate. While this will result in a reduction in the height errors along a waterline, the waterline is a linear feature in a two-dimensional space. However, improvements to the DEM heights between adjacent pairs of waterlines can also be made, because DEM heights enclosed by the higher waterline of a pair must be at least no higher than the refined heights along the higher waterline, whereas DEM heights not enclosed by the lower waterline must be no lower than the refined heights along the lower waterline. In addition, DEM heights between the higher and lower waterlines can also be assigned smaller errors because of the reduced errors on the refined waterline heights. The method was tested on a section of the TanDEM-X Intermediate DEM (IDEM) covering an 11km reach of the Warwickshire Avon, England. Flood extents from four COSMO-SKyMed images were available at various stages of a flood in November 2012. Waterlines were detected automatically using the method described in [1]. The 12.5m resolution IDEM was re-sampled to the 2.5m resolution of the CSK images using nearest neighbour interpolation. Improvements to the IDEM were attempted only in regions of low slope and low vegetation, so that the DEM could be regarded as the DTM. The height of a pixel on a waterline was replaced by the average of the waterline pixel heights in an 11 x 11 IDEM pixel window centred on the current CSK pixel (but selecting only one waterline height per IDEM pixel to reduce correlations). Original and refined IDEM heights were compared to corresponding airborne LiDAR heights. Along the waterlines, it was found that the original IDEM heights had a standard deviation of 1.1m and a bias of 0.2m, while the refined heights had a standard deviation of only 0.6m and a similar bias. Between two adjacent waterlines, on average approximately 25% of IDEM heights were above the higher waterline, and 20% below the lower waterline. When compared to LiDAR, the original higher heights had a mean difference from the LiDAR height of 2.4m with standard deviation 3.0m, while after correction the mean difference was 0.5m with standard deviation 1.0m. The corrected heights below the lower waterline were similarly improved. The height errors of a further 40% of IDEM heights between the higher and lower waterlines were also reduced, because of the reduced errors on the refined waterline heights. 1. Mason DC, Davenport IJ, Neal JC, Schumann GJ-P and Bates PD (2012). Near real-time flood detection in urban and rural areas using high resolution Synthetic Aperture Radar images. IEEE. Trans. Geoscience Rem. Sens., 50(8), 3041-3052.

  12. A description of rotations for DEM models of particle systems

    NASA Astrophysics Data System (ADS)

    Campello, Eduardo M. B.

    2015-06-01

    In this work, we show how a vector parameterization of rotations can be adopted to describe the rotational motion of particles within the framework of the discrete element method (DEM). It is based on the use of a special rotation vector, called Rodrigues rotation vector, and accounts for finite rotations in a fully exact manner. The use of fictitious entities such as quaternions or complicated structures such as Euler angles is thereby circumvented. As an additional advantage, stick-slip friction models with inter-particle rolling motion are made possible in a consistent and elegant way. A few examples are provided to illustrate the applicability of the scheme. We believe that simple vector descriptions of rotations are very useful for DEM models of particle systems.

  13. The Shuttle Radar Topography Mission: A Global DEM

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Kobrick, Mike

    2000-01-01

    Digital topographic data are critical for a variety of civilian, commercial, and military applications. Scientists use Digital Elevation Models (DEM) to map drainage patterns and ecosystems, and to monitor land surface changes over time. The mountain-building effects of tectonics and the climatic effects of erosion can also be modeled with DEW The data's military applications include mission planning and rehearsal, modeling and simulation. Commercial applications include determining locations for cellular phone towers, enhanced ground proximity warning systems for aircraft, and improved maps for backpackers. The Shuttle Radar Topography Mission (SRTM) (Fig. 1), is a cooperative project between NASA and the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense. The mission is designed to use a single-pass radar interferometer to produce a digital elevation model of the Earth's land surface between about 60 degrees north and south latitude. The DEM will have 30 m pixel spacing and about 15 m vertical errors.

  14. Development of parallel DEM for the open source code MFIX

    SciTech Connect

    Gopalakrishnan, Pradeep; Tafti, Danesh

    2013-02-01

    The paper presents the development of a parallel Discrete Element Method (DEM) solver for the open source code, Multiphase Flow with Interphase eXchange (MFIX) based on the domain decomposition method. The performance of the code was evaluated by simulating a bubbling fluidized bed with 2.5 million particles. The DEM solver shows strong scalability up to 256 processors with an efficiency of 81%. Further, to analyze weak scaling, the static height of the fluidized bed was increased to hold 5 and 10 million particles. The results show that global communication cost increases with problem size while the computational cost remains constant. Further, the effects of static bed height on the bubble hydrodynamics and mixing characteristics are analyzed.

  15. DEM interpolation weight calculation modulus based on maximum entropy

    NASA Astrophysics Data System (ADS)

    Chen, Tian-wei; Yang, Xia

    2015-12-01

    There is negative-weight in traditional interpolation of gridding DEM, in the article, the principle of Maximum Entropy is utilized to analyze the model system which depends on modulus of space weight. Negative-weight problem of the DEM interpolation is researched via building Maximum Entropy model, and adding nonnegative, first and second order's Moment constraints, the negative-weight problem is solved. The correctness and accuracy of the method was validated with genetic algorithm in matlab program. The method is compared with the method of Yang Chizhong interpolation and quadratic program. Comparison shows that the volume and scaling of Maximum Entropy's weight is fit to relations of space and the accuracy is superior to the latter two.

  16. A comparative appraisal of hydrological behavior of SRTM DEM at catchment level

    NASA Astrophysics Data System (ADS)

    Sharma, Arabinda; Tiwari, K. N.

    2014-11-01

    The Shuttle Radar Topography Mission (SRTM) data has emerged as a global elevation data in the past one decade because of its free availability, homogeneity and consistent accuracy compared to other global elevation dataset. The present study explores the consistency in hydrological behavior of the SRTM digital elevation model (DEM) with reference to easily available regional 20 m contour interpolated DEM (TOPO DEM). Analysis ranging from simple vertical accuracy assessment to hydrological simulation of the studied Maithon catchment, using empirical USLE model and semidistributed, physical SWAT model, were carried out. Moreover, terrain analysis involving hydrological indices was performed for comparative assessment of the SRTM DEM with respect to TOPO DEM. Results reveal that the vertical accuracy of SRTM DEM (±27.58 m) in the region is less than the specified standard (±16 m). Statistical analysis of hydrological indices such as topographic wetness index (TWI), stream power index (SPI), slope length factor (SLF) and geometry number (GN) shows a significant differences in hydrological properties of the two studied DEMs. Estimation of soil erosion potentials of the catchment and conservation priorities of microwatersheds of the catchment using SRTM DEM and TOPO DEM produce considerably different results. Prediction of soil erosion potential using SRTM DEM is far higher than that obtained using TOPO DEM. Similarly, conservation priorities determined using the two DEMs are found to be agreed for only 34% of microwatersheds of the catchment. ArcSWAT simulation reveals that runoff predictions are less sensitive to selection of the two DEMs as compared to sediment yield prediction. The results obtained in the present study are vital to hydrological analysis as it helps understanding the hydrological behavior of the DEM without being influenced by the model structural as well as parameter uncertainty. It also reemphasized that SRTM DEM can be a valuable dataset for hydrological analysis provided any error/uncertainty therein is being properly evaluated and characterized.

  17. Designing Tunnel Support in Jointed Rock Masses Via the DEM

    NASA Astrophysics Data System (ADS)

    Boon, C. W.; Houlsby, G. T.; Utili, S.

    2015-03-01

    A systematic approach of using the distinct element method (DEM) to provide useful insights for tunnel support in moderately jointed rock masses is illustrated. This is preceded by a systematic study of common failure patterns for unsupported openings in a rock mass intersected by three independent sets of joints. The results of our simulations show that a qualitative description of the failure patterns using specific descriptors is unattainable. Then, it is shown that DEM analyses can be employed in the preliminary design phase of tunnel supports to determine the main parameters of a support consisting of rock bolts or one lining or a combination of both. A comprehensive parametric analysis investigating the effect of bolt bonded length, bolt spacing, bolt length, bolt pretension, bolt stiffness and lining thickness on the tunnel convergence is illustrated. The highlight of the proposed approach of preliminary support design is the use of a rock bolt and lining interaction diagram to evaluate the relative effectiveness of rock bolts and lining thickness in the design of the tunnel support. The concept of interaction diagram can be used to assist the engineer in making preliminary design decisions given a target maximum allowable convergence. In addition, DEM simulations were validated against available elastic solutions. To the authors' knowledge, this is the first verification of DEM calculations for supported openings against elastic solutions. The methodologies presented in this article are illustrated through 2-D plane strain analyses for the preliminary design stage. More rigorous analyses incorporating 3-D effects have not been attempted in this article because the longitudinal displacement profile is highly sensitive to the joint orientations with respect to the tunnel axis, and cannot be established accurately in 2-D. The methodologies and concepts discussed in this article, however, have the potential to be extended to 3-D analyses.

  18. BOREAS Regional DEM in Raster Format and AEAC Projection

    NASA Technical Reports Server (NTRS)

    Knapp, David; Verdin, Kristine; Hall, Forrest G. (Editor)

    2000-01-01

    This data set is based on the GTOPO30 Digital Elevation Model (DEM) produced by the United States Geological Survey EROS Data Center (USGS EDC). The BOReal Ecosystem-Atmosphere Study (BOREAS) region (1,000 km x 1000 km) was extracted from the GTOPO30 data and reprojected by BOREAS staff into the Albers Equal-Area Conic (AEAC) projection. The pixel size of these data is 1 km. The data are stored in binary, image format files.

  19. Development of a 'bare-earth' SRTM DEM product

    NASA Astrophysics Data System (ADS)

    O'Loughlin, Fiachra; Paiva, Rodrigo; Durand, Michael; Alsdorf, Douglas; Bates, Paul

    2015-04-01

    We present the methodology and results from the development of a near-global 'bare-earth' Digital Elevation Model (DEM) derived from the Shuttle Radar Topography Mission (SRTM) data. Digital Elevation Models are the most important input for hydraulic modelling, as the DEM quality governs the accuracy of the model outputs. While SRTM is currently the best near-globally [60N to 60S] available DEM, it requires adjustments to reduce the vegetation contamination and make it useful for hydrodynamic modelling over heavily vegetated areas (e.g. tropical wetlands). Unlike previous methods of accounting for vegetation contamination, which concentrated on correcting relatively small areas and usually applied a static adjustment, we account for vegetation contamination globally and apply a spatial varying correction, based on information about canopy height and density. In creating the final 'bare-earth' SRTM DEM dataset, we produced three different 'bare-earth' SRTM products. The first applies global parameters, while the second and third products apply parameters that are regionalised based on either climatic zones or vegetation types, respectively. We also tested two different canopy density proxies of different spatial resolution. Using ground elevations obtained from the ICESat GLA14 satellite altimeter, we calculate the residual errors for the raw SRTM and the three 'bare-earth' SRTM products and compare performances. The three 'bare-earth' products all show large improvements over the raw SRTM in vegetated areas with the overall mean bias reduced by between 75 and 92% from 4.94 m to 0.40 m. The overall standard deviation is reduced by between 29 and 33 % from 7.12 m to 4.80 m. As expected, improvements are higher in areas with denser vegetation. The final 'bare-earth' SRTM dataset is available at 3 arc-second with lower vertical height errors and less noise than the original SRTM product.

  20. A simplified DEM numerical simulation of vibroflotation without backfill

    NASA Astrophysics Data System (ADS)

    Jiang, M. J.; Liu, W. W.; He, J.; Sun, Y.

    2015-09-01

    Vibroflotation is one of the deep vibratory compaction techniques for ground reinforcement. This method densities the soil and improves its mechanical properties, thus helps to protect people's lives and property from geological disasters. The macro reinforcement mechanisms of vibroflotation method have been investigated by numerical simulations, laboratory and in-situ experiments. However, little attention has been paid on its micro - mechanism, which is essential to fully understand the principle of the ground reinforcement. Discrete element method (DEM), based on discrete mechanics, is more powerful to solve large deformation and failure problems. This paper investigated the macro-micro mechanism of vibroflotation without backfill under two conditions, i.e., whether or not the ground water was considered, by incorporating inter-particle rolling resistance model in the DEM simulations. Conclusions obtained are as follows: The DEM simulations incorporating rolling resistance well replicate the mechanical response of the soil assemblages and are in line with practical observations. The void ratio of the granular soil fluctuates up and down in the process of vibroflotation, and finally reduces to a lower value. It is more efficient to densify the ground without water compared to the ground with water.

  1. Interpolation and elevation errors: the impact of the DEM resolution

    NASA Astrophysics Data System (ADS)

    Achilleos, Georgios A.

    2015-06-01

    Digital Elevation Models (DEMs) are developing and evolving at a fast pace, given the progress of computer science and technology. This development though, is not accompanied by an advancement of knowledge on the quality of the models and their indigenous inaccuracy. The user on most occasions is not aware of this quality thus in not aware of the correlating product uncertainty. Extensive research has been conducted - and still is - towards this direction. In the research presented in this paper there is an analysis of elevation errors behavior which are recorded in a DEM. The behavior of these elevation errors, is caused by altering the DEM resolution upon the application of the algorithm interpolation. Contour lines are used as entry data from a topographical map. Elevation errors are calculated in the positions of the initial entry data and wherever the elevation is known. The elevation errors that are recorded, are analyzed, in order to reach conclusions about their distribution and the way in which they occur.

  2. Efficient parallel CFD-DEM simulations using OpenMP

    NASA Astrophysics Data System (ADS)

    Amritkar, Amit; Deb, Surya; Tafti, Danesh

    2014-01-01

    The paper describes parallelization strategies for the Discrete Element Method (DEM) used for simulating dense particulate systems coupled to Computational Fluid Dynamics (CFD). While the field equations of CFD are best parallelized by spatial domain decomposition techniques, the N-body particulate phase is best parallelized over the number of particles. When the two are coupled together, both modes are needed for efficient parallelization. It is shown that under these requirements, OpenMP thread based parallelization has advantages over MPI processes. Two representative examples, fairly typical of dense fluid-particulate systems are investigated, including the validation of the DEM-CFD and thermal-DEM implementation with experiments. Fluidized bed calculations are performed on beds with uniform particle loading, parallelized with MPI and OpenMP. It is shown that as the number of processing cores and the number of particles increase, the communication overhead of building ghost particle lists at processor boundaries dominates time to solution, and OpenMP which does not require this step is about twice as fast as MPI. In rotary kiln heat transfer calculations, which are characterized by spatially non-uniform particle distributions, the low overhead of switching the parallelization mode in OpenMP eliminates the load imbalances, but introduces increased overheads in fetching non-local data. In spite of this, it is shown that OpenMP is between 50-90% faster than MPI.

  3. Validation of DEM prediction for granular avalanches on irregular terrain

    NASA Astrophysics Data System (ADS)

    Mead, Stuart R.; Cleary, Paul W.

    2015-09-01

    Accurate numerical simulation can provide crucial information useful for a greater understanding of destructive granular mass movements such as rock avalanches, landslides, and pyroclastic flows. It enables more informed and relatively low cost investigation of significant risk factors, mitigation strategy effectiveness, and sensitivity to initial conditions, material, or soil properties. In this paper, a granular avalanche experiment from the literature is reanalyzed and used as a basis to assess the accuracy of discrete element method (DEM) predictions of avalanche flow. Discrete granular approaches such as DEM simulate the motion and collisions of individual particles and are useful for identifying and investigating the controlling processes within an avalanche. Using a superquadric shape representation, DEM simulations were found to accurately reproduce transient and static features of the avalanche. The effect of material properties on the shape of the avalanche deposit was investigated. The simulated avalanche deposits were found to be sensitive to particle shape and friction, with the particle shape causing the sensitivity to friction to vary. The importance of particle shape, coupled with effect on the sensitivity to friction, highlights the importance of quantifying and including particle shape effects in numerical modeling of granular avalanches.

  4. Effect of DEM mesh size on AnnAGNPS simulation and slope correction.

    PubMed

    Wang, Xiaoyan; Lin, Q

    2011-08-01

    The objective of this paper is to study the impact of the mesh size of the digital elevation model (DEM) on terrain attributes within an Annualized AGricultural NonPoint Source pollution (AnnAGNPS) Model simulation at watershed scale and provide a correction of slope gradient for low resolution DEMs. The effect of different grid sizes of DEMs on terrain attributes was examined by comparing eight DEMs (30, 40, 50, 60, 70, 80, 90, and 100 m). The accuracy of the AnnAGNPS stimulation on runoff, sediments, and nutrient loads is evaluated. The results are as follows: (1) Rnoff does not vary much with decrease of DEM resolution whereas soil erosion and total nitrogen (TN) load change prominently. There is little effect on runoff simulation of AnnAGNPS modeling by the amended slope using an adjusted 50 m DEM. (2) A decrease of sediment yield and TN load is observed with an increase of DEM mesh size from 30 to 60 m; a slight decrease of sediment and TN load with the DEM mesh size bigger than 60 m. There is similar trend for total phosphorus (TP) variation, but with less range of variation, the simulation of sediment, TN, and TP increase, in which sediment increase up to 1.75 times compared to the model using unadjusted 50 m DEM. In all, the amended simulation still has a large difference relative to the results using 30 m DEM. AnnAGNPS is less reliable for sediment loading prediction in a small hilly watershed. (3) Resolution of DEM has significant impact on slope gradient. The average, minimum, maximum of slope from the various DEMs reduced obviously with the decrease of DEM precision. For the grade of 0?15, the slopes at lower resolution DEM are generally bigger than those at higher resolution DEM. But for the grade bigger than 15, the slopes at lower resolution DEM are generally smaller than those at higher resolution DEM. So it is necessary to adjust the slope with a fitting equation. A cubic model is used for correction of slope gradient from lower resolution to that from higher resolution. Results for Dage watershed showed that fine meshes are desired to avoid large underestimates of sediment and total nitrogen loads and moderate underestimates of total phosphorus loads even with the slopes for the 50 m DEM adjusted to be more similar to the slopes from the 30 m DEM. Decreasing the mesh size beyond this threshold does not substantially affect the computed runoff flux but generated prediction errors for nitrogen and sediment yields. So the appropriate DEM will control error and make simulation at acceptable level. PMID:20953988

  5. The Global Tandem-X Dem: Production Status and First Validation Results

    NASA Astrophysics Data System (ADS)

    Huber, M.; Gruber, A.; Wendleder, A.; Wessel, B.; Roth, A.; Schmitt, A.

    2012-07-01

    The TanDEM-X mission will derive a global digital elevation model (DEM) with satellite SAR interferometry. Two radar satellites (TerraSAR-X and TanDEM-X) will map the Earth in a resolution and accuracy with an absolute height error of 10m and a relative height error of 2m for 90% of the data. In order to fulfill the height requirements in general two global coverages are acquired and processed. Besides the final TanDEM-X DEM, an intermediate DEM with reduced accuracy is produced after the first coverage is completed. The last step in the whole workflow for generating the TanDEM-X DEM is the calibration of remaining systematic height errors and the merge of single acquisitions to 1°x1° DEM tiles. In this paper the current status of generating the intermediate DEM and first validation results based on GPS tracks, laser scanning DEMs, SRTM data and ICESat points are shown for different test sites.

  6. In need of combined topography and bathymetry DEM

    NASA Astrophysics Data System (ADS)

    Kisimoto, K.; Hilde, T.

    2003-04-01

    In many geoscience applications, digital elevation models (DEMs) are now more commonly used at different scales and greater resolution due to the great advancement in computer technology. Increasing the accuracy/resolution of the model and the coverage of the terrain (global model) has been the goal of users as mapping technology has improved and computers get faster and cheaper. The ETOPO5 (5 arc minutes spatial resolution land and seafloor model), initially developed in 1988 by Margo Edwards, then at Washington University, St. Louis, MO, has been the only global terrain model for a long time, and it is now being replaced by three new topographic and bathymetric DEMs, i.e.; the ETOPO2 (2 arc minutes spatial resolution land and seafloor model), the GTOPO30 land model with a spatial resolution of 30 arc seconds (c.a. 1km at equator) and the 'GEBCO 1-MINUTE GLOBAL BATHYMETRIC GRID' ocean floor model with a spatial resolution of 1 arc minute (c.a. 2 km at equator). These DEMs are products of projects through which compilation and reprocessing of existing and/or new datasets were made to meet user's new requirements. These ongoing efforts are valuable and support should be continued to refine and update these DEMs. On the other hand, a different approach to create a global bathymetric (seafloor) database exists. A method to estimate the seafloor topography from satellite altimetry combined with existing ships' conventional sounding data was devised and a beautiful global seafloor database created and made public by W.H. Smith and D.T. Sandwell in 1997. The big advantage of this database is the uniformity of coverage, i.e. there is no large area where depths are missing. It has a spatial resolution of 2 arc minute. Another important effort is found in making regional, not global, seafloor databases with much finer resolutions in many countries. The Japan Hydrographic Department has compiled and released a 500m-grid topography database around Japan, J-EGG500, in 1999. Although the coverage of this database is only a small portion of the Earth, the database has been highly appreciated in the academic community, and accepted in surprise by the general public when the database was displayed in 3D imagery to show its quality. This database could be rather smoothly combined with the finer land DEM of 250m spatial resolution (Japan250m.grd, K. Kisimoto, 2000). One of the most important applications of this combined DEM of topography and bathymetry is tsunami modeling. Understanding of the coastal environment, management and development of the coastal region are other fields in need of these data. There is, however, an important issue to consider when we create a combined DEM of topography and bathymetry in finer resolutions. The problem arises from the discrepancy of the standard datum planes or reference levels used for topographic leveling and bathymetric sounding. Land topography (altitude) is defined by leveling from the single reference point determined by average mean sea level, in other words, land height is measured from the geoid. On the other hand, depth charts are made based on depth measured from locally determined reference sea surface level, and this value of sea surface level is taken from the long term average of the lowest tidal height. So, to create a combined DEM of topography and bathymetry in very fine scale, we need to avoid this inconsistency between height and depth across the coastal region. Height and depth should be physically continuous relative to a single reference datum across the coast within such new high resolution DEMs. (N.B. Coast line is not equal to 'altitude-zero line' nor 'depth-zero line'. It is defined locally as the long term average of the highest tide level.) All of this said, we still need a lot of work on the ocean side. Global coverage with detailed bathymetric mapping is still poor. Seafloor imaging and other geophysical measurements/experiments should be organized and conducted internationally and interdisciplinary ways more than ever. We always need greater technological advancement and application of this technology in marine sciences, and more enthusiastic minds of seagoing researchers as well. Recent seafloor mapping technology/quality both in bathymetry and imagery is very promising and even favorably compared with the terrain mapping. We discuss and present on recent achievement and needs on the seafloor mapping using several most up-to-date global- and regional- DEMs available for science community at the poster session.

  7. A coupled DEM-CFD method for impulse wave modelling

    NASA Astrophysics Data System (ADS)

    Zhao, Tao; Utili, Stefano; Crosta, GiovanBattista

    2015-04-01

    Rockslides can be characterized by a rapid evolution, up to a possible transition into a rock avalanche, which can be associated with an almost instantaneous collapse and spreading. Different examples are available in the literature, but the Vajont rockslide is quite unique for its morphological and geological characteristics, as well as for the type of evolution and the availability of long term monitoring data. This study advocates the use of a DEM-CFD framework for the modelling of the generation of hydrodynamic waves due to the impact of a rapid moving rockslide or rock-debris avalanche. 3D DEM analyses in plane strain by a coupled DEM-CFD code were performed to simulate the rockslide from its onset to the impact with still water and the subsequent wave generation (Zhao et al., 2014). The physical response predicted is in broad agreement with the available observations. The numerical results are compared to those published in the literature and especially to Crosta et al. (2014). According to our results, the maximum computed run up amounts to ca. 120 m and 170 m for the eastern and western lobe cross sections, respectively. These values are reasonably similar to those recorded during the event (i.e. ca. 130 m and 190 m respectively). In these simulations, the slope mass is considered permeable, such that the toe region of the slope can move submerged in the reservoir and the impulse water wave can also flow back into the slope mass. However, the upscaling of the grains size in the DEM model leads to an unrealistically high hydraulic conductivity of the model, such that only a small amount of water is splashed onto the northern bank of the Vajont valley. The use of high fluid viscosity and coarse grain model has shown the possibility to model more realistically both the slope and wave motions. However, more detailed slope and fluid properties, and the need for computational efficiency should be considered in future research work. This aspect has also been investigated by Crosta et al. (2014) via 2D and 3D FEM ALE modelling without considering the water seepage in the slope mass has been used. Their results can be a good way to estimate the slope and wave motion for fast sliding conditions. The 3D modelling can also clarify the lateral motion of water and estimate the potential risk of water overtopping the dam crest. The DEM and FEM ALE modelling can be used together to analyse fast moving rockslides (i.e. flowslides, rockslides, rock and debris avalanches) both in dry conditions and for their interaction with water basins. References Zhao, T., Utili, S., Crosta, G.B. Rockslide and impulse wave modelling in the Vajont reservoir by DEM-CFD analyses. Rock Mechanics and rock Engineering, under review. Crosta, G.B., Imposimato, S. & Roddeman, D. 2014. Landslide spreading, impulse waves and modelling of the Vajont rockslide. Rock Mechanics and Rock Engineering, under review.

  8. Assessment of Reference Height Models on Quality of Tandem-X dem

    NASA Astrophysics Data System (ADS)

    Mirzaee, S.; Motagh, M.; Arefi, H.

    2015-12-01

    The aim of this study is to investigate the effect of various Global Digital Elevation Models (GDEMs) in producing high-resolution topography model using TanDEM-X (TDX) Coregistered Single Look Slant Range Complex (CoSSC) images. We selected an image acquired on Jun 12th, 2012 over Doroud region in Lorestan, west of Iran and used 4 external digital elevation models in our processing including DLR/ASI X-SAR DEM (SRTM-X, 30m resolution), ASTER GDEM Version 2 (ASTER-GDEMV2, 30m resolution), NASA SRTM Version 4 (SRTM-V4, 90m resolution), and a local photogrammetry-based DEM prepared by National Cartographic Center (NCC DEM, 10m resolution) of Iran. InSAR procedure for DEM generation was repeated four times with each of the four external height references. The quality of each external DEM was initially assessed using ICESat filtered points. Then, the quality of, each TDX-based DEM was assessed using the more precise external DEM selected in the previous step. Results showed that both local (NCC) DEM and SRTM X-band performed the best (RMSE< 9m) for TDX-DEM generation. In contrast, ASTER GDEM v2 and SRTM C-band v4 showed poorer quality.

  9. Evaluation of vertical accuracy of open source Digital Elevation Model (DEM)

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sandip; Joshi, P. K.; Mukherjee, Samadrita; Ghosh, Aniruddha; Garg, R. D.; Mukhopadhyay, Anirban

    2013-04-01

    Digital Elevation Model (DEM) is a quantitative representation of terrain and is important for Earth science and hydrological applications. DEM can be generated using photogrammetry, interferometry, ground and laser surveying and other techniques. Some of the DEMs such as ASTER, SRTM, and GTOPO 30 are freely available open source products. Each DEM contains intrinsic errors due to primary data acquisition technology and processing methodology in relation with a particular terrain and land cover type. The accuracy of these datasets is often unknown and is non-uniform within each dataset. In this study we evaluate open source DEMs (ASTER and SRTM) and their derived attributes using high postings Cartosat DEM and Survey of India (SOI) height information. It was found that representation of terrain characteristics is affected in the coarse postings DEM. The overall vertical accuracy shows RMS error of 12.62 m and 17.76 m for ASTER and SRTM DEM respectively, when compared with Cartosat DEM. The slope and drainage network delineation are also violated. The terrain morphology strongly influences the DEM accuracy. These results can be highly useful for researchers using such products in various modeling exercises.

  10. DEM Data for Lahar Modeling: Lahars From Popocatépetl Volcano (Mexico)

    NASA Astrophysics Data System (ADS)

    Huggel, C.; Schneider, D.; Julio-Miranda, P.; Delgado-Granados, H.; Kääb, A.

    2007-05-01

    Modeling of lahars has become important for related hazards assessment, particularly in regions with scarce geologic record. Digital terrain data is a crucial element for mass-flow modeling but limited by availability of DEM's. Remote sensing technology offers perspectives for DEM generation. DEMs derived from ASTER stereo satellite images and SRTM from Popocatépetl Volcano, taken on 2001, were evaluated using two simple, non-dynamic lahar models LAHARZ and MSF. Laharic volumes were based on the 1995-2001 events. Results of model runs for the Huiloac gorge based on the ASTER-DEM show that only lahars with a volume of 5x106 m3 or larger reach towns 11km away. Lahars modeled with SRTM-DEM travel 1.8 km further downstream. The ASTER-based model tends to a stronger lateral distribution of the flow volume, thus limiting the longitudinal distribution. In comparison to the observed lahar of corresponding volume in 1997, the modeled lahars fit in travel distance by ca. 2 and 4 km for SRTM and ASTER, respectively. The flow paths for the ASTER and SRTM DEMs are consistent except for the middle section where an erroneous flow-routing of the ASTER model can be observed, caused by an error of the respective DEM. ASTER and SRTM DEMs, are suitable for use with LAHARZ and MSF. Flow path prediction is more reliable with SRTM data but with coarser spatial resolution. Errors of the ASTER DEM affecting the prediction of flow paths are mainly identified in deeply incised gorges with north-facing slopes due to the sensor geometry. LAHARZ is more sensitive to errors of the ASTER DEM than the MSF model. Lahar modeling with the ASTER-DEM results in a finer spaced predicted inundation area but does not add any significant information in comparison with the SRTM DEM. The verification and sensitivity of the DEM used is fundamental when deriving hazards maps to forecast inundation areas.

  11. Integration of SAR and DEM data: Geometrical considerations

    NASA Technical Reports Server (NTRS)

    Kropatsch, Walter G.

    1991-01-01

    General principles for integrating data from different sources are derived from the experience of registration of SAR images with digital elevation models (DEM) data. The integration consists of establishing geometrical relations between the data sets that allow us to accumulate information from both data sets for any given object point (e.g., elevation, slope, backscatter of ground cover, etc.). Since the geometries of the two data are completely different they cannot be compared on a pixel by pixel basis. The presented approach detects instances of higher level features in both data sets independently and performs the matching at the high level. Besides the efficiency of this general strategy it further allows the integration of additional knowledge sources: world knowledge and sensor characteristics are also useful sources of information. The SAR features layover and shadow can be detected easily in SAR images. An analytical method to find such regions also in a DEM needs in addition the parameters of the flight path of the SAR sensor and the range projection model. The generation of the SAR layover and shadow maps is summarized and new extensions to this method are proposed.

  12. DEM, tide and velocity over sulzberger ice shelf, West Antarctica

    USGS Publications Warehouse

    Baek, S.; Shum, C.K.; Lee, H.; Yi, Y.; Kwoun, Oh-Ig; Lu, Zhiming; Braun, Andreas

    2005-01-01

    Arctic and Antarctic ice sheets preserve more than 77% of the global fresh water and could raise global sea level by several meters if completely melted. Ocean tides near and under ice shelves shifts the grounding line position significantly and are one of current limitations to study glacier dynamics and mass balance. The Sulzberger ice shelf is an area of ice mass flux change in West Antarctica and has not yet been well studied. In this study, we use repeat-pass synthetic aperture radar (SAR) interferometry data from the ERS-1 and ERS-2 tandem missions for generation of a high-resolution (60-m) Digital Elevation Model (DEM) including tidal deformation detection and ice stream velocity of the Sulzberger Ice Shelf. Other satellite data such as laser altimeter measurements with fine foot-prints (70-m) from NASA's ICESat are used for validation and analyses. The resulting DEM has an accuracy of-0.57??5.88 m and is demonstrated to be useful for grounding line detection and ice mass balance studies. The deformation observed by InSAR is found to be primarily due to ocean tides and atmospheric pressure. The 2-D ice stream velocities computed agree qualitatively with previous methods on part of the Ice Shelf from passive microwave remote-sensing data (i.e., LANDSAT). ?? 2005 IEEE.

  13. A photogrammetric DEM of Greenland based on 1978-1987 aerial photos: validation and integration with laser altimetry and satellite-derived DEMs

    NASA Astrophysics Data System (ADS)

    Korsgaard, N. J.; Kjaer, K. H.; Nuth, C.; Khan, S. A.

    2014-12-01

    Here we present a DEM of Greenland covering all ice-free terrain and the margins of the GrIS and local glaciers and ice caps. The DEM is based on the 3534 photos used in the aero-triangulation which were recorded by the Danish Geodata Agency (then the Geodetic Institute) in survey campaigns spanning the period 1978-1987. The GrIS is covered tens of kilometers into the interior due to the large footprints of the photos (30 x 30 km) and control provided by the aero-triangulation. Thus, the data are ideal for providing information for analysis of ice marginal elevation change and also control for satellite-derived DEMs.The results of the validation, error assessments and predicted uncertainties are presented. We test the DEM using Airborne Topographic Mapper (IceBridge ATM) as reference data; evaluate the a posteriori covariance matrix from the aero-triangulation; and co-register DEM blocks of 50 x 50 km to ICESat laser altimetry in order to evaluate the coherency.We complement the aero-photogrammetric DEM with modern laser altimetry and DEMs derived from stereoscopic satellite imagery (AST14DMO) to examine the mass variability of the Northeast Greenland Ice Stream (NEGIS). Our analysis suggests that dynamically-induced mass loss started around 2003 and continued throughout 2014.

  14. High-resolution TanDEM-X DEM: An accurate method to estimate lava flow volumes at Nyamulagira Volcano (D. R. Congo)

    NASA Astrophysics Data System (ADS)

    Albino, F.; Smets, B.; d'Oreye, N.; Kervyn, F.

    2015-06-01

    Nyamulagira and Nyiragongo are two of the most active volcanoes in Africa, but their eruptive histories are poorly known. Assessing lava flow volumes in the region remains difficult, as field surveys are often impossible and available Digital Elevation Models (DEMs) do not have adequate spatial or temporal resolutions. We therefore use TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) interferometry to produce a series of 0.15 arc sec (˜5 m) DEMs from between 2011 and 2012 over these volcanoes. TanDEM-X DEMs have an absolute vertical accuracy of 1.6 m, resulting from the comparison of elevation with GPS measurements acquired around Nyiragongo. The difference between TanDEM-X-derived DEMs from before and after the 2011-2012 eruption of Nyamulagira provides an accurate thickness map of the lava flow emplaced during that activity. Values range from 3 m along the margins to 35 m in the middle, with a mean of 12.7 m. The erupted volume is 305.2 ± 36.0 × 106 m3. Height errors on thickness depend on the land covered by the flow and range from 0.4 m in old lavas to 5.5 m in dense vegetation. We also reevaluate the volume of historical eruptions at Nyamulagira since 2001 from the difference between TanDEM-X and SRTM 1 arc sec DEMs and compare them to previous work. Planimetric methods used in literature are consistent with our results for short-duration eruptions but largely underestimate the volume of the long-lived 2011-2012 eruption. Our new estimates of erupted volumes suggest that the mean eruption rate and the magma supply rate were relatively constant at Nyamulagira during 2001-2012, respectively, 23.1 m3 s-1 and 0.9 m3 s-1.

  15. A seamless, high-resolution digital elevation model (DEM) of the north-central California coast

    USGS Publications Warehouse

    Foxgrover, Amy C.; Barnard, Patrick L.

    2012-01-01

    A seamless, 2-meter resolution digital elevation model (DEM) of the north-central California coast has been created from the most recent high-resolution bathymetric and topographic datasets available. The DEM extends approximately 150 kilometers along the California coastline, from Half Moon Bay north to Bodega Head. Coverage extends inland to an elevation of +20 meters and offshore to at least the 3 nautical mile limit of state waters. This report describes the procedures of DEM construction, details the input data sources, and provides the DEM for download in both ESRI Arc ASCII and GeoTIFF file formats with accompanying metadata.

  16. Influence of DEM resolution on drainage network extraction: A multifractal analysis

    NASA Astrophysics Data System (ADS)

    Ariza-Villaverde, A. B.; Jiménez-Hornero, F. J.; Gutiérrez de Ravé, E.

    2015-07-01

    Different hydrological algorithms have been developed to automatically extract drainage networks from digital elevation models (DEMs). D8 is the most widely used algorithm to delineate drainage networks and catchments from a DEM. This algorithm has certain advantages such as simplicity, the provision of a reasonable representation for convergent flow conditions and consistency among flow patterns, calculated contributing areas and the spatial representation of subcatchments. However, it has limitations in selecting suitable flow accumulation threshold values to determine the pixels that belong to drainage networks. Although the effects of DEM resolution on some terrain attributes, stream characterisation and watershed delineation have been studied, analyses of the influence of DEM resolution on flow accumulation threshold values have been limited. Recently, multifractal analyses have been successfully used to find appropriate flow accumulation threshold values. The application of this type of analysis to evaluate the relationship between DEM resolution and flow accumulation threshold value needs to be explored. Therefore, this study tested three DEM resolutions for four drainage basins with different levels of drainage network distribution by comparing the Rényi spectra of the drainage networks that were obtained with the D8 algorithm against those determined by photogrammetric restitution. According to the results, DEM resolution influences the selected flow accumulation threshold value and the simulated network morphology. The suitable flow accumulation threshold value increases as the DEM resolution increases and shows greater variability for basins with lower drainage densities. The links between DEM resolution and terrain attributes were also examined.

  17. Extraction of Hydrological Proximity Measures from DEMs using Parallel Processing

    SciTech Connect

    Tesfa, Teklu K.; Tarboton, David G.; Watson, Daniel W.; Schreuders, Kimberly A.; Baker, Matthew M.; Wallace, Robert M.

    2011-12-01

    Land surface topography is one of the most important terrain properties which impact hydrological, geomorphological, and ecological processes active on a landscape. In our previous efforts to develop a soil depth model based upon topographic and land cover variables, we extracted a set of hydrological proximity measures (HPMs) from a Digital Elevation Model (DEM) as potential explanatory variables for soil depth. These HPMs may also have other, more general modeling applicability in hydrology, geomorphology and ecology, and so are described here from a general perspective. The HPMs we derived are variations of the distance up to ridge points (cells with no incoming flow) and variations of the distance down to stream points (cells with a contributing area greater than a threshold), following the flow path. These HPMs were computed using the D-infinity flow model that apportions flow between adjacent neighbors based on the direction of steepest downward slope on the eight triangular facets constructed in a 3 x 3 grid cell window using the center cell and each pair of adjacent neighboring grid cells in turn. The D-infinity model typically results in multiple flow paths between 2 points on the topography, with the result that distances may be computed as the minimum, maximum or average of the individual flow paths. In addition, each of the HPMs, are calculated vertically, horizontally, and along the land surface. Previously, these HPMs were calculated using recursive serial algorithms which suffered from stack overflow problems when used to process large datasets, limiting the size of DEMs that could be analyzed using that method to approximately 7000 x 7000 cells. To overcome this limitation, we developed a message passing interface (MPI) parallel approach for calculating these HPMs. The parallel algorithms of the HPMs spatially partition the input grid into stripes which are each assigned to separate processes for computation. Each of those processes then uses a queue data structure to order the processing of cells so that each cell is visited only once and the cross-process communications that are a standard part of MPI are handled in an efficient manner. This parallel approach allows analysis of much larger DEMs as compared to the serial recursive algorithms. In this paper, we present the definitions of the HPMs, the serial and parallel algorithms used in their extraction and their potential applications in hydrology, geomorphology and ecology.

  18. Release of a 10-m-resolution DEM for the Italian territory: Comparison with global-coverage DEMs and anaglyph-mode exploration via the web

    NASA Astrophysics Data System (ADS)

    Tarquini, Simone; Vinci, Stefano; Favalli, Massimiliano; Doumaz, Fawzi; Fornaciai, Alessandro; Nannipieri, Luca

    2012-01-01

    The 10-m-resolution TINITALY/01 DEM ( Tarquini et al., 2007) is compared with the two, coarser-resolution, global-coverage, spaceborne-based SRTM and ASTER DEMs and with a high-resolution, LIDAR-derived DEM. Afterwards, we presented a webGIS which allows to explore a 10-m-resolution anaglyph layer showing the landforms of the whole Italian territory in 3D. The webGIS ( http://tinitaly.pi.ingv.it/) is open to the public, and can be used to carry out a preliminary analysis of landforms. The TINITALY/01 DEM is available for scientific purposes on the basis of a research agreement (see the above website or write to tinitaly@pi.ingv.it).

  19. Melker Meilensteine auf dem Weg in ein naturwissenschaftliches Zeitalter - Glanzlichter der Ausstellung zum Internationalen Astronomiejahr 2009 in der Melker Stiftsbibliothek.

    NASA Astrophysics Data System (ADS)

    Beck, Paul G.; Zotti, Georg

    2009-06-01

    Das Mittelalter wird weithin als die dunkle Epoche in der Geschichte der Europäischen Wissenschaften betrachtet, und insbesondere das Leben in den Klöstern galt lange Zeit als frei von jeglichem Interesse für Naturwissenschaften abseits der Medizin. Im Mittelalter galt die Astronomie bloß als Mittel zum Zweck, um religiöse und zivile Kalender erstellen zu können. Durch den Bestand der Handschriftenkammer der Melker Stiftsbibliothek eröffnet sich uns eine neue Sichtweise auf das gegen Ende des Mittelalters wachsende Interesse an den Naturwissenschaften. Dies wurde durch die starke Aufwertung der Klosterbibliothek im Rahmen der 'Melker Reform' im 15. Jahrhundert noch weiter verstärkt. Diese Epoche fällt mit der Frühphase der Universität Wien und der 'ersten Wiener Schule der Astronomie' zusammen. Dieser Artikel beleuchtet ausgewählte astronomischen Werke in der Melker Stiftsbibliothek zwischen dem frühen 9 und dem 18. Jahrhundert. Einen Schwerpunkt stellt das Wirken der Wiener Schule der Astronomie dar, wobei wir u.a. die Melker Abschrift von Peuerbachs Gutachten über den Kometen von 1456 sowie die im Stift Melk durchgeführte Beobachtung der Mondfinsternis von 1457 durch Regiomontanus und Peuerbach beleuchten. Dieser Beitrag ist der einführende Übersichtsartikel zum Ausstellungsprojekt in der Melker Stiftsbibliothek im Rahmen des Internationalen Jahres der Astronomie 2009. The medieval period is commonly seen as a dark epoch for science in Europe. Especially monasteries were seen as institutions without interest in natural sciences except for medicine. Astronomy was allegedly only a tool to construct religious and civil calendars. The inventory of the medieval manuscript collection of the library of the Abbey of Melk allows a new view on the growing interest in the exact sciences towards the end of the medieval ages. This interest was intensified through the increased importance of the monastery library due to the monastery reform concept, created in Melk Abbey in the 15th century. This epoch coincides with the early phase of the University of Vienna and the first Viennese School of Astronomy. This paper discusses selected pieces of astronomical works between the early 9th and the 18th century. The focus is set on the interaction with the members of the Viennese School of Astronomy, e.g., the transcript of Peuerbach's expertise on the comet of 1456 which was presumably produced by a monk of Melk, and the observations of the lunar eclipse 1457 by Peuerbach and Regiomontanus in Melk Abbey. This paper is the introductory overview article on the exhibition in the monastery library of Melk Abbey for the International Year of Astronomy, IYA2009.

  20. TanDEM-X Mission: Overview and Evaluation of intermediate Results

    NASA Astrophysics Data System (ADS)

    Soergel, U.; Jacobsen, K.; Schack, L.

    2013-10-01

    The German Aerospace Center (DLR, Deutsches Zentrum für Luft- und Raumfahrt) currently conducts the bistatic interferometric synthetic aperture radar (SAR) Mission TanDEM-X, which shall result in a DEM of global coverage in an unprecedented resolution and accuracy according to DTED level 3 standard. The mission is based on the two SAR satellites TerraSAR-X and TanDEM-X that have been launched in June 2007 and 2010, respectively. After the commissioning phase of TanDEM satellite and the orbital adjustment the bistatic image acquisition in close formation began end of 2010. The data collection for the mission is scheduled to last about three years, i.e., the bigger part of the required data have been already gathered. Based on this data DLR will conduct several processing steps in order to come up finally with a global and seamless DEM of the Earth's landmass which shall meet the envisaged specifications. Since the entire mission is an endeavor in the framework of a private-public-partnership, the private partner, Astrium, will eventually commercialize the DEM product. In this paper, we will provide an overview of the data collection and the deliverables that will come along with TanDEM-X mission. Furthermore, we will analyze a DEM derived from early stage immediate products of the mission.

  1. Evaluating the influence of spatial resolutions of DEM on watershed runoff and sediment yield using SWAT

    NASA Astrophysics Data System (ADS)

    Reddy, A. Sivasena; Reddy, M. Janga

    2015-10-01

    Digital elevation model (DEM) of a watershed forms key basis for hydrologic modelling and its resolution plays a key role in accurate prediction of various hydrological processes. This study appraises the effect of different DEMs with varied spatial resolutions (namely TOPO 20 m, CARTO 30 m, ASTER 30 m, SRTM 90 m, GEO-AUS 500 m and USGS 1000 m) on hydrological response of watershed using Soil and Water Assessment Tool (SWAT) and applied for a case study of Kaddam watershed in India for estimating runoff and sediment yield. From the results of case study, it was observed that reach lengths, reach slopes, minimum and maximum elevations, sub-watershed areas, land use mapping areas within the sub-watershed and number of HRUs varied substantially due to DEM resolutions, and consequently resulted in a considerable variability in estimated daily runoff and sediment yields. It was also observed that, daily runoff values have increased (decreased) on low (high) rainy days respectively with coarser resolution of DEM. The daily sediment yield values from each sub-watershed decreased with coarser resolution of the DEM. The study found that the performance of SWAT model prediction was not influenced much for finer resolution DEMs up to 90 m for estimation of runoff, but it certainly influenced the estimation of sediment yields. The DEMs of TOPO 20 m and CARTO 30 m provided better estimates of sub-watershed areas, runoff and sediment yield values over other DEMs.

  2. Digital elevation model (DEM) of Cascadia, latitude 39N-53N, longitude 116W-133W

    USGS Publications Warehouse

    Haugerud, Ralph A.

    1999-01-01

    This report contains a 250-meter digital elevation model (DEM) for Cascadia (latitude 39N - 53N, longitude 116W - 133W), a region that encompasses the Cascade volcanic arc, the Cascadia subduction zone, and the Juan de Fuca Ridge system. The DEM is distributed as file cascdem.tar.gz (39 MB; 78MB uncompressed).

  3. A Comparative Study of Radar Stereo and Interferometry for DEM Generation

    NASA Astrophysics Data System (ADS)

    Gelautz, M.; Paillou, P.; Chen, C. W.; Zebker, H. A.

    2004-06-01

    In this experiment, we derive and compare radar stereo and interferometric elevation models (DEMs) of a study site in Djibouti, East Africa. As test data, we use a Radarsat stereo pair and ERS-2 and Radarsat interferometric data. Comparison of the reconstructed DEMs with a SPOT reference DEM shows that in regions of high coherence the DEMs produced by interferometry are of much better quality than the stereo result. However, the interferometric error histograms also show some pronounced outliers due to decorrelation and phase unwrapping problems on forested mountain slopes. The more robust stereo result is able to capture the general terrain shape, but finer surface details are lost. A fusion experiment demonstrates that merging the stereoscopic and interferometric DEMs by utilizing coherence- derived weights can significantly improve the accuracy of the computed elevation maps.

  4. A practical method for SRTM DEM correction over vegetated mountain areas

    NASA Astrophysics Data System (ADS)

    Su, Yanjun; Guo, Qinghua

    2014-01-01

    Digital elevation models (DEMs) are essential to various applications in topography, geomorphology, hydrology, and ecology. The Shuttle Radar Topographic Mission (SRTM) DEM data set is one of the most complete and most widely used DEM data sets; it provides accurate information on elevations over bare land areas. However, the accuracy of SRTM data over vegetated mountain areas is relatively low as a result of the high relief and the penetration limitation of the C-band used for obtaining global DEM products. The objective of this study is to assess the performance of SRTM DEMs and correct them over vegetated mountain areas with small-footprint airborne Light Detection and Ranging (Lidar) data, which can develop elevation products and vegetation products [e.g., vegetation height, Leaf Area Index (LAI)] of high accuracy. The assessing results show that SRTM elevations are systematically higher than those of the actual land surfaces over vegetated mountain areas. The mean difference between SRTM DEM and Lidar DEM increases with vegetation height, whereas the standard deviation of the difference increases with slope. To improve the accuracy of SRTM DEM over vegetated mountain areas, a regression model between the SRTM elevation bias and vegetation height, LAI, and slope was developed based on one control site. Without changing any coefficients, this model was proved to be applicable in all the nine study sites, which have various topography and vegetation conditions. The mean bias of the corrected SRTM DEM at the nine study sites using this model (absolute value) is 89% smaller than that of the original SRTM DEM, and the standard deviation of the corrected SRTM elevation bias is 11% smaller.

  5. Stress analysis during slope failure from DEM simulations

    NASA Astrophysics Data System (ADS)

    Katz, O.; Morgan, J. K.

    2012-04-01

    We used Discrete Element Method (DEM) simulations to study the initiation and evolution of landsliding, with a focus on the development and propagation of the sliding plane, and on the effects of material strength on the behavior of the slope material during landsliding. Our simulated slopes were constructed of homogeneous materials, settled under gravity, bonded, and excavated to produce 70 deg slopes of 1050 m in height. Nine simulations were carried out, each using a different value of cohesions, ranging from 0.7 to 4.2 MPa (quantified through DEM direct shear simulations on representative materials). In each of our simulations, failure initiated at the foot of the slope, accompanied by disintegration of the slope material. Failure then propagated upward to the slope crest with further material disintegration. A discrete detachment surface formed below the disintegrated material. Downslope movement of the failed material (i.e. landsliding) occurred only after the failure plane intersected the upper slope face. By the end of landsliding, the disintegrated slope material formed a talus like deposit at the foot of the slope. The value of initial material cohesion influenced the nature of the landslide deposit and its dimension. Higher material strengths produced smaller landslides, as well as the occurrence of discrete landslide blocks, which originated from the shallow slopes, and became entrained within the finer talus. Stress analysis of the slope failure process clarifies how failure initiates and landsliding evolves, and further constrains the limiting failure criteria that define each simulated material. The local proximity to failure throughout the slope can be tracked during the simulation, revealing that high failure potential (high shear stress relative to mean stress) exists at the toe of the slope immediately following excavation. As material disintegrates near the toe of the slope, high tensile stresses develop in the overlying mass, causing the break-up of the shallower slope materials. The detachment surface defines the boundary between the mobile material undergoing disintegration and the coherent material below. With increased cohesion within the slope, less material reaches this failure condition, and the detachment surface shallows, causing a decrease in the in-slope extent of the landslide, the volume of the final deposit and type of failure (slump vs. rock-slide). These numerical simulations provide important insights into the stress evolution within a failing slope, and an understanding of how these control the final type, geometry and size of landlides.

  6. Effect of DEM Source and Resolution on Extracting River Network and Watershed within Multi-Lake Area in Tibet

    NASA Astrophysics Data System (ADS)

    Li, Yang; Li, Gang; Lin, Hui

    2014-11-01

    DEM defines drainage structures and basin through conducting overland flow simulation. Two matured DEM Sources are SRTM DEM (Shuttle Radar Topographic Mission) and ASTER GDEM (Advanced Space borne Thermal Emission and Reflection Radiometer Global Digital Elevation Model); The accuracy of hydrological characters that derived from DEM decreased from high resolution to coarse resolution and appeared to be different in different data source (Vaze,Teng, & Spencer, 2010).

  7. Evaluation of DEM generation accuracy from UAS imagery

    NASA Astrophysics Data System (ADS)

    Santise, M.; Fornari, M.; Forlani, G.; Roncella, R.

    2014-06-01

    The growing use of UAS platform for aerial photogrammetry comes with a new family of Computer Vision highly automated processing software expressly built to manage the peculiar characteristics of these blocks of images. It is of interest to photogrammetrist and professionals, therefore, to find out whether the image orientation and DSM generation methods implemented in such software are reliable and the DSMs and orthophotos are accurate. On a more general basis, it is interesting to figure out whether it is still worth applying the standard rules of aerial photogrammetry to the case of drones, achieving the same inner strength and the same accuracies as well. With such goals in mind, a test area has been set up at the University Campus in Parma. A large number of ground points has been measured on natural as well as signalized points, to provide a comprehensive test field, to check the accuracy performance of different UAS systems. In the test area, points both at ground-level and features on the buildings roofs were measured, in order to obtain a distributed support also altimetrically. Control points were set on different types of surfaces (buildings, asphalt, target, fields of grass and bumps); break lines, were also employed. The paper presents the results of a comparison between two different surveys for DEM (Digital Elevation Model) generation, performed at 70 m and 140 m flying height, using a Falcon 8 UAS.

  8. DEM Simulation of Particle Clogging in Fiber Filtration

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Yang, Mengmeng; Li, Shuiqing

    2015-11-01

    The formation of porous particle deposits plays a crucial role in determining the efficiency of filtration process. In this work, an adhesive discrete element method (DEM), in combination with CFD, is developed to dynamically describe these porous deposit structures and the changed flow field between two parallel fibers under the periodic boundary conditions. For the first time, it is clarified that the structures of clogged particles are dependent on both the adhesion parameter (defined as the ratio of interparticle adhesion to particle inertia) and the Stokes number (as an index of impaction efficiency). The relationship between the pressure-drop gradient and the coordination number along the filtration time is explored, which can be used to quantitatively classify the different filtration regimes, i.e., clean filter stage, clogging stage and cake filtration stage. Finally, we investigate the influence of the fiber separation distance on the particle clogging behavior, which affects the collecting efficiency of the fibers significantly. The results suggest that changing the arrangement of fibers can improve the filter performance. This work has been funded by the National Key Basic Research and Development Program (2013CB228506).

  9. Investigation of the Critical State in Soil Mechanics Using DEM

    SciTech Connect

    Pena, Andres A.; Garcia-Rojo, Ramon; Alonso-Marroquin, Fernando; Herrmann, Hans J.

    2009-06-18

    The existence and uniqueness of the so-called critical state in soil mechanics is validated in our DEM simulations of irregular polygonal particles. For different particle shape characteristics, the critical state is independent of the initial stress and density conditions. We retain low stress levels, since we do not take into account the crushing of particles. In biaxial test simulations isotropic particles evolve toward a limiting state in which the system reaches a critical void ratio and deforms with constant volume, deviatoric stress, fabric anisotropy, and mechanical coordination number. The last one has been found to be the first variable to attain a critical value making possible for the rest of micro-and-macro-mechanical variables the convergence to the critical state. In periodic shear cell tests, for large shear deformations samples with anisotropic particles reach at the macro-mechanical level the same critical value for both shear force and void ratio. At the micro-mechanical level the components of the stress tensor, the fabric tensor and the inertia tensor of the particles also reach the same stationary state. By varying the aspect ratio of the particles we stated the strong influence of particle shape anisotropy on the parameters that the granular packing attained at the critical state.

  10. How does modifying a DEM to reflect known hydrology affect subsequent terrain analysis?

    NASA Astrophysics Data System (ADS)

    Callow, John Nikolaus; Van Niel, Kimberly P.; Boggs, Guy S.

    2007-01-01

    SummaryMany digital elevation models (DEMs) have difficulty replicating hydrological patterns in flat landscapes. Efforts to improve DEM performance in replicating known hydrology have included a variety of soft (i.e. algorithm-based approaches) and hard techniques, such as " Stream burning" or "surface reconditioning" (e.g. Agree or ANUDEM). Using a representation of the known stream network, these methods trench or mathematically warp the original DEM to improve how accurately stream position, stream length and catchment boundaries replicate known hydrological conditions. However, these techniques permanently alter the DEM and may affect further analyses (e.g. slope). This paper explores the impact that commonly used hydrological correction methods ( Stream burning, Agree.aml and ANUDEM v4.6.3 and ANUDEM v5.1) have on the overall nature of a DEM, finding that different methods produce non-convergent outcomes for catchment parameters (such as catchment boundaries, stream position and length), and differentially compromise secondary terrain analysis. All hydrological correction methods successfully improved calculation of catchment area, stream position and length as compared to using the DEM without any modification, but they all increased catchment slope. No single method performing best across all categories. Different hydrological correction methods changed elevation and slope in different spatial patterns and magnitudes, compromising the ability to derive catchment parameters and conduct secondary terrain analysis from a single DEM. Modification of a DEM to better reflect known hydrology can be useful, however knowledge of the magnitude and spatial pattern of the changes are required before using a DEM for subsequent analyses.

  11. Incorporating the effect of DEM resolution and accuracy for improved flood inundation mapping

    NASA Astrophysics Data System (ADS)

    Saksena, Siddharth; Merwade, Venkatesh

    2015-11-01

    Topography plays a major role in determining the accuracy of flood inundation areas. However, many areas in the United States and around the world do not have access to high quality topographic data in the form of Digital Elevation Models (DEM). For such areas, an improved understanding of the effects of DEM properties such as horizontal resolution and vertical accuracy on flood inundation maps may eventually lead to improved flood inundation modeling and mapping. This study attempts to relate the errors arising from DEM properties such as spatial resolution and vertical accuracy to flood inundation maps, and then use this relationship to create improved flood inundation maps from coarser resolution DEMs with low accuracy. The results from the five stream reaches used in this study show that water surface elevations (WSE) along the stream and the flood inundation area have a linear relationship with both DEM resolution and accuracy. This linear relationship is then used to extrapolate the water surface elevations from coarser resolution DEMs to get water surface elevations corresponding to a finer resolution DEM. Application of this approach show that improved results can be obtained from flood modeling by using coarser and less accurate DEMs, including public domain datasets such as the National Elevation Dataset and Shuttle Radar Topography Mission (SRTM) DEMs. The improvement in the WSE and its application to obtain better flood inundation maps is dependent on the study reach characteristics such as land use, valley shape, reach length and width. Application of the approach presented in this study on more reaches may lead to development of guidelines for flood inundation mapping using coarser resolution and less accurate topographic datasets.

  12. Scenario-Based Validation of Moderate Resolution DEMs Freely Available for Complex Himalayan Terrain

    NASA Astrophysics Data System (ADS)

    Singh, Mritunjay Kumar; Gupta, R. D.; Snehmani; Bhardwaj, Anshuman; Ganju, Ashwagosha

    2016-02-01

    Accuracy of the Digital Elevation Model (DEM) affects the accuracy of various geoscience and environmental modelling results. This study evaluates accuracies of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM Version-2 (GDEM V2), the Shuttle Radar Topography Mission (SRTM) X-band DEM and the NRSC Cartosat-1 DEM V1 (CartoDEM). A high resolution (1 m) photogrammetric DEM (ADS80 DEM), having a high absolute accuracy [1.60 m linear error at 90 % confidence (LE90)], resampled at 30 m cell size was used as reference. The overall root mean square error (RMSE) in vertical accuracy was 23, 73, and 166 m and the LE90 was 36, 75, and 256 m for ASTER GDEM V2, SRTM X-band DEM and CartoDEM, respectively. A detailed error analysis was performed for individual as well as combinations of different classes of aspect, slope, land-cover and elevation zones for the study area. For the ASTER GDEM V2, forest areas with North facing slopes (0°-5°) in the 4th elevation zone (3773-4369 m) showed minimum LE90 of 0.99 m, and barren with East facing slopes (>60°) falling under the 2nd elevation zone (2581-3177 m) showed maximum LE90 of 166 m. For the SRTM DEM, pixels with South-East facing slopes of 0°-5° in the 4th elevation zone covered with forest showed least LE90 of 0.33 m and maximum LE90 of 521 m was observed in the barren area with North-East facing slope (>60°) in the 4th elevation zone. In case of the CartoDEM, the snow pixels in the 2nd elevation zone with South-East facing slopes of 5°-15° showed least LE90 of 0.71 m and maximum LE90 of 1266 m was observed for the snow pixels in the 3rd elevation zone (3177-3773 m) within the South facing slope of 45°-60°. These results can be highly useful for the researchers using DEM products in various modelling exercises.

  13. The influence of slope profile extraction techniques and DEM resolution on 2D rockfall simulation

    NASA Astrophysics Data System (ADS)

    Wang, X.; Frattini, P.; Agliardi, F.; Crosta, G. B.

    2012-04-01

    The development of advanced 3D rockfall modelling algorithms and tools during the last decade has allowed to gain insights in the topographic controls on the quality and reliability of rockfall simulation results. These controls include DEM resolution and roughness, and depend on the adopted rockfall simulation approach and DEM generation techniques. Despite the development of 3D simulations, the 2D modelling approach still remains suitable and convenient in some cases. Therefore, the accuracy of high-quality 3D descriptions of topography must be preserved when extracting slope profiles for 2D simulations. In this perspective, this study compares and evaluates three different techniques commonly used to extract slope profiles from DEM, in order to assess their suitability and effects on rockfall simulation results. These methods include: (A) an "interpolated shape" method (ESRI 3D Analyst), (B) a raw raster sampling method (EZ Profiler), and (C) a vector TIN sampling method (ESRI 3D Analyst). The raster DEMs used in the study were all derived from the same TIN DEM used for method C. For raster DEM, the "interpolated shape" method (A) extracts the profile by bi-linear interpolating the elevation among the four neighbouring cells at each sampling location along the profile trace. The EZ Profiler extension (B) extracts the profile by sampling elevation values directly from the DEM raster grid at each sampling location. These methods have been compared to the extraction of profiles from TIN DEM (C), where slope profile elevations are directly obtained by sampling the TIN triangular facets. 2D rockfall simulations performed using a widely used commercial software (RocfallTM) with the different profiles show that: (1) method A and C provide similar results; (2) runout simulated using profiles obtained by method A is usually shorter than method C; (3) method B presents abrupt horizontal steps in the profiles, resulting in unrealistic runout. To study the influence of DEM resolution on rockfall simulation, profiles have been extracted from 1m, 5m, 10m and 15m gridded DEMs. The 2D rockfall simulations with the different resolution show that: (1) the effect of different resolution depends on topographic characteristics of the slope (e.g., steep or flat); (2) for steep slopes the rockfall motion is dominated by bouncing, and the coarser DEMs result in lower bouncing and lower kinematic energies and velocities; (3) for flat slopes, the motion is dominated by rolling and sliding, and the effect is the opposite: the coarser the DEM, the longer the runout.

  14. Morphological changes at Mt. Etna detected by TanDEM-X

    NASA Astrophysics Data System (ADS)

    Wegmuller, Urs; Bonforte, Alessandro; De Beni, Emanuela; Guglielmino, Francesco; Strozzi, Tazio

    2014-05-01

    We produced a DEM of the Mt. Etna volcano using TanDEM-X data collected on October 9, 2012. The TanDEM-X data were acquired in bistatic mode with TSX as master sensor and TDX as receive only sensor. The pre-existing SRTM DEM was used for geometrical reference (geocoding, initial height model, large scale reference). The interferogram was computed with 4 looks in range and 4 looks in azimuth. After compensation of the SRTM heights, the differential TanDEM-X interferogram looked overall quite flat but showed local deviations related to noise (e.g. over the sea), topographic effects related to the low resolution of the SRTM DEM, and deviations related to actual changes of the topography, as observed in the Mount Etna peak region. After phase unwrapping, addressed with a minimum-cost flow algorithm and slight spatial filtering, the unwrapped phases were converted to relative heights. In order to move to absolute heights the SRTM height reference was used under the assumption that the deviation from the SRTM DEM is zero at large scale and without any linear trend. Finally, the height model was resampled into geographical coordinates. In the framework of the MED-SUV project, and thanks to the availability of a dense GPS network of more than 100 benchmarks periodically measured by INGV_OE, the TanDEM-X model has been validated. By computing the difference of the elevations provided by TanDEM-X with those measured by GPS we obtained a mean difference of 0.7 m and a standard deviation of 5.2 m. These values are biased by a few GPS benchmarks located in steep areas unfavorable illuminated by the radar. Without considerations of the two more unfavorable GPS stations, the height mean difference and a standard deviation are 0.6 m and 4.3 m respectively. We also performed correlation analyses of the height differences with respect to topography, latitude and longitude and we could exclude any elevation-related errors or geometrical ramp distortions. In the following, we compared the 2012 TanDEM-X model with the 2000 SRTM DEM in order to evaluate the morphological changes occurred on the volcano during the 12 years time lap. The pixel size of SRTM-DEM is about 90 m and we resampled the TanDEM-X model to fit this value. The results show that most of the variations occurred in the Valle del Bove and on the summit crater areas. In order to compare DEMs with the same pixel size, we performed a further comparison with a 5m ground resolution optical DEM, produced in 2004 and covering only the summit area. The variations in topography have been compared with ground mapping surveys, confirming a good correlation with the spatial extension of the lava flows and of the pyroclastic deposits occurred on Mt. Etna in the last seven years. The comparison between the two DEM's (2004-2012) allows calculating the amount of volcanics emitted and to clearly monitoring the growth and development of the New South East Crater (NSEC). TanDEM-X is a useful tools to monitor volcanic area characterized by a quit frequent activity (a paroxysm every 5-10 days), such us Mt. Etna, especially if concentrated in areas not easily accessible.

  15. HELI-DEM portal for geo-processing services

    NASA Astrophysics Data System (ADS)

    Cannata, Massimiliano; Antonovic, Milan; Molinari, Monia

    2014-05-01

    HELI-DEM (Helvetia-Italy Digital Elevation Model) is a project developed in the framework of Italy/Switzerland Operational Programme for Trans-frontier Cooperation 2007-2013 whose major aim is to create a unified digital terrain model that includes the alpine and sub-alpine areas between Italy and Switzerland. The partners of the project are: Lombardy Region, Piedmont Region, Polytechnic of Milan, Polytechnic of Turin and Fondazione Politecnico from Italy; Institute of Earth Sciences (SUPSI) from Switzerland. The digital terrain model has been produced by integrating and validating the different elevation data available for the areas of interest, characterized by different reference frame, resolutions and accuracies: DHM at 25 m resolution from Swisstopo, DTM at 20 m resolution from Lombardy Region, DTM at 5 m resolution from Piedmont Region and DTM LiDAR PST-A at about 1 m resolution, that covers the main river bed areas and is produced by the Italian Ministry of the Environment. Further results of the project are: the generation of a unique Italian Swiss geoid with an accuracy of few centimeters (Gilardoni et al. 2012); the establishment of a GNSS permanent network, prototype of a transnational positioning service; the development of a geo-portal, entirely based on open source technologies and open standards, which provides the cross-border DTM and offers some capabilities of analysis and processing through the Internet. With this talk, the authors want to present the main steps of the project with a focus on the HELI-DEM geo-portal development carried out by the Institute of Earth Sciences, which is the access point to the DTM outputted from the project. The portal, accessible at http://geoservice.ist.supsi.ch/helidem, is a demonstration of open source technologies combined for providing access to geospatial functionalities to wide non GIS expert public. In fact, the system is entirely developed using only Open Standards and Free and Open Source Software (FOSS) both on the server side (services) and on the client side (interface). In addition to self developed code the system relies mainly on teh software GRASS 7 [1], ZOO-project [2], Geoserver [3] and OpenLayers [4] and the standards WMS [5], WCS [6] and WPS [7]. At the time of writing, the portal offers features like profiling, contour extraction, watershed delineation and analysis, derivatives calculation, data extraction, coordinate conversion but it is evolving and it is planned to extend to a series of environmental modeling that the IST developed in the past like dam break simulation, landslide run-out estimation and floods due to landslide impact in artificial basins. [1] Neteler M., Mitasova H., Open Source GIS: A GRASS GIS Approach. 3rd Ed. 406 pp, Springer, New York, 2008. [2] Fenoy G., Bozon N., Raghavan V., ZOO Project: The Open Wps Platform. Proceeding of 1st International Workshop on Pervasive Web Mapping, Geoprocessing and Services (WebMGS). Como, http://www.isprs.org/proceedings/XXXVIII/4-W13/ID_32.pdf, 26-27 agosto 2010. [3] Giannecchini S., Aime A., GeoServer, il server open source per la gestione interoperabile dei dati geospaziali. Atti 15a Conferenza Nazionale ASITA. Reggia di Colorno, 15-18 novembre 2011. [4] Perez A.S., OpenLayers Cookbook. Packt Publishing, 2012. ISBN 1849517843. [5] OGC, OpenGIS Web Map Server Implementation Specification, http://www.opengeospatial.org/standards/wms, 2006. [6] OGC, OGC WCS 2.0 Interface Standard - Core, http://portal.opengeospatial.org/files/?artifact_id=41437, 2010b. [7] OGC, OpenGIS Web Processing Service, http://portal.opengeospatial.org/files/?artifact_id=24151, 2007.

  16. ASTER Global DEM contribution to GEOSS demonstrates open data sharing

    NASA Astrophysics Data System (ADS)

    Sohre, T.; Duda, K. A.; Meyer, D. J.; Behnke, J.; Nasa Esdis Lp Daac

    2010-12-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing instrument on the Terra spacecraft has been acquiring images of Earth since launch in 1999. Throughout this time data products have been openly available to the general public through sites in the U.S. and Japan. As the ASTER mission matured, a spatially broad and temporally deep data archive was gradually established. With this extensive accumulation of Earth observations, it became possible to create a new global digital elevation product, the ASTER Global Digital Elevation Model (GDEM), using multi-temporal data, resulting in over 22,000 static 10 X 10 tiles. The ASTER GDEM was contributed by Japan’s Ministry of Economy Trade and Industry (METI) and the U.S. National Aeronautics and Space Administration (NASA) to the Global Earth Observation System of Systems (GEOSS) for distribution at no cost to users. As such, both METI and NASA desired to understand the uses of the ASTER GDEM, expressed as one of the GEOSS applications themes: disasters, health, energy, climate, water, weather, ecosystems, agriculture or biodiversity. This required both the registration of users, and restrictions on redistribution, to capture the intended use in terms of the GEOSS themes. The ASTER GDEM was made available to users worldwide via electronic download from the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan and from NASA’s Land Processes Distributed Active Archive Center (LP DAAC). During the first three months after product release, over 4 million GDEM tiles were distributed from the LP DAAC and ERSDAC. The ASTER GDEM release generated nearly 20,000 new user registrations in the NASA EOS ClearingHOuse (ECHO)/WIST and the ERSDAC systems. By the end of 2009, over 6.5 Million GDEM tiles were distributed by the LP DAAC and ERSDAC. Users have requested tiles over specific areas of interest as well as the entire dataset for global research. Intense global interest in the GDEM across all the GEOSS Societal Benefit areas was shown. The release of the global tiled research-grade DEM resulted in a significant increase in demand for ASTER elevation models, and increased awareness of related products. No cost access to these data has also promoted new applications of remotely sensed data, increasing their use across the full range of the GEOSS societal benefit areas. In addition, the simplified data access and greatly expanded pool of users resulted in a number of suggestions from researchers in many disciplines for possible enhancements to future versions of the ASTER GDEM. The broad distribution of the product can be directly attributed to the adoption of fundamental GEOSS data sharing principles, which are directed toward expanded access by minimizing time delay and cost, thus facilitating data use for education, research, and a range of other applications. The ASTER GDEM demonstrated the need and user demand for an improved global DEM product as well as the added benefit of not only “full and open” distribution, but “free and open” distribution.

  17. Modelling of Singapore's topographic transformation based on DEMs

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Belle, Iris; Hassler, Uta

    2015-02-01

    Singapore's topography has been heavily transformed by industrialization and urbanization processes. To investigate topographic changes and evaluate soil mass flows, historical topographic maps of 1924 and 2012 were employed, and basic topographic features were vectorized. Digital elevation models (DEMs) for the two years were reconstructed based on vector features. Corresponding slope maps, a surface difference map and a scatter plot of elevation changes were generated and used to quantify and categorize the nature of the topographic transformation. The surface difference map is aggregated into five main categories of changes: (1) areas without significant height changes, (2) lowered-down areas where hill ranges were cut down, (3) raised-up areas where valleys and swamps were filled in, (4) reclaimed areas from the sea, and (5) new water-covered areas. Considering spatial proximity and configurations of different types of changes, topographic transformation can be differentiated as either creating inland flat areas or reclaiming new land from the sea. Typical topographic changes are discussed in the context of Singapore's urbanization processes. The two slope maps and elevation histograms show that generally, the topographic surface of Singapore has become flatter and lower since 1924. More than 89% of height changes have happened within a range of 20 m and 95% have been below 40 m. Because of differences in land surveying and map drawing methods, uncertainties and inaccuracies inherent in the 1924 topographic maps are discussed in detail. In this work, a modified version of a traditional scatter plot is used to present height transformation patterns intuitively. This method of deriving categorical maps of topographical changes from a surface difference map can be used in similar studies to qualitatively interpret transformation. Slope maps and histograms were also used jointly to reveal additional patterns of topographic change.

  18. Automated sinkhole detection using a DEM subsetting technique and fill tools at Mammoth Cave National Park

    NASA Astrophysics Data System (ADS)

    Wall, J.; Bohnenstiehl, D. R.; Levine, N. S.

    2013-12-01

    An automated workflow for sinkhole detection is developed using Light Detection and Ranging (Lidar) data from Mammoth Cave National Park (MACA). While the park is known to sit within a karst formation, the generally dense canopy cover and the size of the park (~53,000 acres) creates issues for sinkhole inventorying. Lidar provides a useful remote sensing technology for peering beneath the canopy in hard to reach areas of the park. In order to detect sinkholes, a subsetting technique is used to interpolate a Digital Elevation Model (DEM) thereby reducing edge effects. For each subset, standard GIS fill tools are used to fill depressions within the DEM. The initial DEM is then subtracted from the filled DEM resulting in detected depressions or sinkholes. Resulting depressions are then described in terms of size and geospatial trend.

  19. IPY: An excellent opportunity to improve Arctic DEMs and document today's Arctic for future generations

    NASA Astrophysics Data System (ADS)

    Nolan, M.

    2003-12-01

    Digital Elevation Models (DEMs) are an essential resource for any field or modeling study in the terrestrial Arctic, yet the DEMs available there are currently the worst on the planet. Efforts in the past decade have led to the acquisition of new DEMs for the entire Antarctic continent (Radarsat Antarctic Mapping Project, RAMP) and for nearly all of the planet within +/- 60 degrees latitude (Space Shuttle Radar Topography Mission, SRTM). Thus, the U.S. Arctic is left with 1:63,360 maps made during the IGY times, which does not meet the USGS' own standards for accuracy. Other countries are left in similar circumstances, with DEMs created from paper maps with usually no better than 1:50,000 scale, and there is as yet no central circum-polar clearinghouse for such DEMs. And because nearly all of these DEMs were created by digitizing paper base maps, most contain artifacts of the digitizing process that further reduce their quality. It could be argued that DEMs of the polar regions of the planet Mars are more accurate, consistent, and easily available than those from the Earth's Arctic. Only an organized international effort could possibly manage such a data collection task, and the project seems well suited to the goals of the International Polar Year. Perhaps being last in line for new DEMs is actually beneficial in this case, as technological improvements have led to new acquisition systems that are more accurate than those used in SRTM and RAMP. For example, airborne synthetic aperture radar (SAR) interferometry has demonstrated the capability to acquire DEMs with 5 meter postings, 1 cm vertical resolution, and 2 m vertical accuracies, in addition to an orthorectified radar backscatter image at 2.5 meter postings; compare this with the 60m x 90m posting available currently and no associated orthoimagery. That is, for the price of an Arctic DEM, we would also get a picture of the Arctic at 2.5 meter resolution, and this picture can be merged with color Landsat to create stunning orthorectified images. These SAR systems, flying on a LearJet, can rapidly acquire day or night in a wide range of weather, eliminating most of the logistical delays common to other systems. Airborne Lidar, a laser based system, is also advanced to the stage where near-shore coastal bathymetry can be measured, such that we could seamlessly integrate DEMs and bathymetry. While the price of such acquisitions is high, it is comparable to DEM acquisitions on the rest of the planet and Mars, and the benefits would be enormous to a wide variety of polar researchers - perfect for the IPY. Presented in this poster will be several examples of how new DEMs have improved our Arctic research at UAF. McCall Glacier was originally an IGY field site and now has the longest record of mass balance observations of any glacier in the US Arctic, but our measurement program is hampered by the lack of decent topographic maps there. Our research using a new DEM in the Kuparuk River watershed in Alaska has shown that these DEMs substantially improve our hydrological modeling in such low gradient watersheds. With DEMs of such high accuracy and resolution, we can also begin a program of repeat-topographic mapping, to document changes not only to glaciers, but subtler permafrost phenomena with decimeter-scale changes such as pingos, thermokarsts, polygons, and oriented lakes. The time to acquire such data is now, however, before widespread changes occur. Thus the upcoming IPY can perhaps leave no better legacy than to replace the IGY-era, mediocre topographic maps with an accurate, high-resolution digital elevation model representing today's Arctic, which will remain valuable to generations of polar scientists.

  20. DEM automatic extraction on Rio de Janeiro from WV2 stereo pair images

    NASA Astrophysics Data System (ADS)

    Malinverni, E. S.

    2014-02-01

    The use of three-dimensional data has become, for a lot of mapping applications, very important. DEM are applied for modelling purposes, i.e. the 3D city model generation, but principally for imagery orthorectification. In aerial photogrammetry is well known the suitable use of stereo imagery to produce an accurate DEM, but the limits of the process (cost, schedule of data collection, highly technical staff) and the new advanced digital image processing algorithms have open the work scenario to the remote sensing data. This research has wanted to investigate the possibility to obtain accurate DEMs by means of automatic terrain extraction algorithms implemented in Leica Photogrammetry Suite (LPS) from stereoscopic remote sensing images collected by DigitalGlobe's WorldView-2 (WV2) satellite. The DEM of Rio de Janeiro (Brazil) and the correspondent digital orthoimages have been the results.

  1. TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 1: Drainage network preprocessing and stream profile analysis

    NASA Astrophysics Data System (ADS)

    Shahzad, Faisal; Gloaguen, Richard

    2011-02-01

    We present TecDEM, a software shell implemented in MATLAB that applies tectonic geomorphologic tasks to digital elevation models (DEMs). The first part of this paper series describes drainage partitioning schemes and stream profile analysis. The graphical user interface of TecDEM provides several options: determining flow directions, stream vectorization, watershed delineation, Strahler order labeling, stream profile generation, knickpoints selection, Concavity, Steepness and Hack indices calculations. The knickpoints along selected streams as well as stream profile analysis, and Hack index per stream profile are computed using a semi-automatic method. TecDEM was used to extract and investigate the stream profiles in the Kaghan Valley (Northern Pakistan). Our interpretations of the TecDEM results correlate well with previous tectonic evolution models for this region. TecDEM is designed to assist geoscientists in applying complex tectonic geomorphology tasks to global DEM data.

  2. What is the effect of LiDAR-derived DEM resolution on large-scale watershed model results?

    SciTech Connect

    Ping Yang; Daniel B. Ames; Andre Fonseca; Danny Anderson; Rupesh Shrestha; Nancy F. Glenn; Yang Cao

    2014-08-01

    This paper examines the effect of raster cell size on hydrographic feature extraction and hydrological modeling using LiDAR derived DEMs. LiDAR datasets for three experimental watersheds were converted to DEMs at various cell sizes. Watershed boundaries and stream networks were delineated from each DEM and were compared to reference data. Hydrological simulations were conducted and the outputs were compared. Smaller cell size DEMs consistently resulted in less difference between DEM-delineated features and reference data. However, minor differences been found between streamflow simulations resulted for a lumped watershed model run at daily simulations aggregated at an annual average. These findings indicate that while higher resolution DEM grids may result in more accurate representation of terrain characteristics, such variations do not necessarily improve watershed scale simulation modeling. Hence the additional expense of generating high resolution DEM's for the purpose of watershed modeling at daily or longer time steps may not be warranted.

  3. Hydrologic validation of a structure-from-motion DEM derived from low-altitude UAV imagery

    NASA Astrophysics Data System (ADS)

    Steiner, Florian; Marzolff, Irene; d'Oleire-Oltmanns, Sebastian

    2015-04-01

    The increasing ease of use of current Unmanned Aerial Vehicles (UAVs) and 3D image processing software has spurred the number of applications relying on high-resolution topographic datasets. Of particular significance in this field is "structure from motion" (SfM), a photogrammetric technique used to generate low-cost digital elevation models (DEMs) for erosion budgeting, measuring of glaciers/lava-flows, archaeological applications and others. It was originally designed to generate 3D-models of buildings, based on unordered collections of images and has become increasingly common in geoscience applications during the last few years. Several studies on the accuracy of this technique already exist, in which the SfM data is mostly compared with Lidar-generated terrain data. The results are mainly positive, indicating that the technique is suitable for such applications. This work aims at validating very high resolution SfM DEMs with a different approach: Not the original elevation data is validated, but data on terrain-related hydrological and geomorphometric parameters derived from the DEM. The study site chosen for this analysis is an abandoned agricultural field near the city of Taroudant, in the semi-arid southern part of Morocco. The site is characterized by aggressive rill and gully erosion and is - apart from sparsely scattered shrub cover - mainly featureless. An area of 5.7 ha, equipped with 30 high-precision ground control points (GCPs), was covered with an unmanned aerial vehicle (UAV) in two different heights (85 and 170 m). A selection of 160 images was used to generate several high-resolution DEMs (2 and 5 cm resolution) of the area using the fully automated SfM software AGISOFT Photoscan. For comparison purposes, a conventional photogrammetry-based workflow using the Leica Photogrammetry Suite was used to generate a DEM with a resolution of 5 cm (LPS DEM). The evaluation is done by comparison of the SfM DEM with the derived orthoimages and the LPS DEM. Parameters evaluated include the flow accumulation, the extracted thalweg networks, slope and exposition. Thus, the question asked is not "Is the height at this specific point accurate compared to a true reference height?", but rather "Does the surface runoff modelled from this DEM behave in the same way as it does in reality?". This means that the DEM will be validated on a functional basis, examining the accuracy of hydrological connectivity and networks. The results of this work may help in the establishment of the SfM technique in geoscience applications, and give an idea of the hydrologic accuracy and reliability of such DEMs.

  4. Sterblichkeit: der paradoxe Kunstgriff des Lebens - Eine Betrachtung vor dem Hintergrund der modernen Biologie

    NASA Astrophysics Data System (ADS)

    Verbeek, Bernhard

    Leben gibt es auf der Erde seit fast 4 Mio. Jahren, trotz allen Katastrophen. Die Idee des Lebens scheint unsterblich. Der Tod aber offenbar auch. Jedes Lebewesen ist davon bedroht, ja für Menschen und andere "höhere“ Lebewesen ist er im Lebensprogramm eingebaut - todsicher. Diese Tatsache ist alles andere als selbstverständlich. Ist sie überhaupt kompatibel mit dem Prinzip der Evolution, nach dem der am besten Angepasste überlebt?

  5. Radiometric Calibration of High Resolution UAVSAR Data Using Low Resolution SRTM DEMs

    NASA Astrophysics Data System (ADS)

    Riel, B. V.; Simard, M.

    2010-12-01

    Airborne and spaceborne Synthetic Aperture Radar (SAR) backscatter data have the potential to retrieve information on forest structure, above-ground biomass, and moisture content. However, SAR backscatter data contain both geometric and radiometric distortions due to underlying topography and the radar viewing geometry. These distortions can significantly affect the estimation of various scientific quantities. For example, a backscatter error of 1 dB can result in a biomass estimation error on the order of 10-15 Mg/ha. Thus, science applications based on SAR backscatter require accurate absolute radiometric calibration. The calibration process for topography involves estimation of the local radar scattering area through knowledge of the imaged terrain, which is often obtained through digital elevation models (DEMs). For this study, we radiometrically calibrate high resolution UAVSAR L-band radar data over a temperate forest site in New Hampshire using a low resolution (30m) SRTM DEM. Different calibration methods were tested and compared. We found that homomorphic methods based on the local incidence or projection angle do not estimate the scattering area as well as heteromorphic methods utilizing DEM integration techniques. Errors in the area estimation resulted in calibration differences less than 0.5 dB. The impact of low DEM resolution on calibration performance was assessed using a Fourier analysis of a large range of topographic classes. Power spectra were computed for high-resolution, bare-earth airborne lidar DEMs acquired over steep, moderate, and flat terrain. Similar power spectra were computed for oversampled SRTM DEMs over the same terrain. Errors for an SRTM DEM associated with a particular topographic class could be quantified through a comparison of its power spectrum with that from the lidar. We present a Fourier based method to systematically propagate errors in slope and aspect estimations to radiometric calibration accuracy. The methodology was validated by comparing slope and aspect derived from SRTM and lidar DEMs.

  6. An improved method to represent DEM uncertainty in glacial lake outburst flood propagation using stochastic simulations

    NASA Astrophysics Data System (ADS)

    Watson, Cameron S.; Carrivick, Jonathan; Quincey, Duncan

    2015-10-01

    Modelling glacial lake outburst floods (GLOFs) or 'jökulhlaups', necessarily involves the propagation of large and often stochastic uncertainties throughout the source to impact process chain. Since flood routing is primarily a function of underlying topography, communication of digital elevation model (DEM) uncertainty should accompany such modelling efforts. Here, a new stochastic first-pass assessment technique was evaluated against an existing GIS-based model and an existing 1D hydrodynamic model, using three DEMs with different spatial resolution. The analysis revealed the effect of DEM uncertainty and model choice on several flood parameters and on the prediction of socio-economic impacts. Our new model, which we call MC-LCP (Monte Carlo Least Cost Path) and which is distributed in the supplementary information, demonstrated enhanced 'stability' when compared to the two existing methods, and this 'stability' was independent of DEM choice. The MC-LCP model outputs an uncertainty continuum within its extent, from which relative socio-economic risk can be evaluated. In a comparison of all DEM and model combinations, the Shuttle Radar Topography Mission (SRTM) DEM exhibited fewer artefacts compared to those with the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM), and were comparable to those with a finer resolution Advanced Land Observing Satellite Panchromatic Remote-sensing Instrument for Stereo Mapping (ALOS PRISM) derived DEM. Overall, we contend that the variability we find between flood routing model results suggests that consideration of DEM uncertainty and pre-processing methods is important when assessing flow routing and when evaluating potential socio-economic implications of a GLOF event. Incorporation of a stochastic variable provides an illustration of uncertainty that is important when modelling and communicating assessments of an inherently complex process.

  7. Uncertainty of SWAT model at different DEM resolutions in a large mountainous watershed.

    PubMed

    Zhang, Peipei; Liu, Ruimin; Bao, Yimeng; Wang, Jiawei; Yu, Wenwen; Shen, Zhenyao

    2014-04-15

    The objective of this study was to enhance understanding of the sensitivity of the SWAT model to the resolutions of Digital Elevation Models (DEMs) based on the analysis of multiple evaluation indicators. The Xiangxi River, a large tributary of Three Gorges Reservoir in China, was selected as the study area. A range of 17 DEM spatial resolutions, from 30 to 1000 m, was examined, and the annual and monthly model outputs based on each resolution were compared. The following results were obtained: (i) sediment yield was greatly affected by DEM resolution; (ii) the prediction of dissolved oxygen load was significantly affected by DEM resolutions coarser than 500 m; (iii) Total Nitrogen (TN) load was not greatly affected by the DEM resolution; (iv) Nitrate Nitrogen (NO₃-N) and Total Phosphorus (TP) loads were slightly affected by the DEM resolution; and (v) flow and Ammonia Nitrogen (NH₄-N) load were essentially unaffected by the DEM resolution. The flow and dissolved oxygen load decreased more significantly in the dry season than in the wet and normal seasons. Excluding flow and dissolved oxygen, the uncertainties of the other Hydrology/Non-point Source (H/NPS) pollution indicators were greater in the wet season than in the dry and normal seasons. Considering the temporal distribution uncertainties, the optimal DEM resolutions for flow was 30-200 m, for sediment and TP was 30-100 m, for dissolved oxygen and NO₃-N was 30-300 m, for NH₄-N was 30 to 70 m and for TN was 30-150 m. PMID:24509347

  8. Monitoring lava dome changes by means of differential DEMs from TanDEM-X interferometry: Examples from Merapi, Indonesia and Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Kubanek, J.; Westerhaus, M.; Heck, B.

    2013-12-01

    Estimating the amount of erupted material during a volcanic crisis is one of the major challenges in volcano research. One way to do this and to discriminate between juvenile and non-juvenile fraction is to assess topographic changes before and after an eruption while using area-wide 3D data. LiDAR or other airborne systems may be a good source, but the recording fails when clouds due to volcanic activity obstruct the sight. In addition, costs as well as logistics are high for local observatories. When dealing with dome-building volcanoes, acquiring the data gets further complicated. As the volcano dome can change rapidly in active phases, it is nearly impossible to collect data at the right time. However, when dealing with gross volume change estimates, at least two data sets - taken directly before and after the eruption - are essential. The innovative German Earth observation mission TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is of great importance to overcome some of these problems. The two almost identical radar satellites TerraSAR-X and TanDEM-X fly in a close formation, thus recording images of the same place on the Earth surface at the same time (bistatic mode). As the radar signal penetrates clouds, digital elevation models (DEMs) of the area of investigation can be generated without problems even with cloud cover. A time series analysis of the differential DEMs therefore opens the possibility to assess volume changes at active lava domes. We choose Merapi in Indonesia and Volcán de Colima in Mexico as test sites. Both volcanoes reside in a state of long term effusive eruption, interrupted every few years by phases of dome destruction, generation of pyroclastic flows and deposition of volcanic material. The availability of extensive ground truth data for both test sites further enables to validate the spaceborne data and results. Here, we analyze lava dome changes due to the hazardous Merapi 2010 eruption. We show a series of DEMs derived by TanDEM-X interferometry taken before and after the eruption. Our results reveal that the eruption had led to a topographic change of up to 200 m in the summit area of Merapi. We further show the ability of the TanDEM-X data to observe much smaller topographic changes using Volcán de Colima as second test site. An explosion at the crater rim signaled the end of magma ascent in June 2011. The bistatic TanDEM-X data give important information on this explosion as we can observe topographic changes of up to 20 m and less in the summit area when comparing datasets taken before and after the event. We further analyzed datasets from the beginning of the year 2013 when Colima got active again after a dormant period. Our results indicate that repeated DEMs with great detail and good accuracy are obtainable, enabling a quantitative estimation of volume changes in the summit area of the volcano. As the TanDEM-X mission is an innovative mission, the present study serves as a test to employ data of a new satellite mission in volcano research. An error analysis of the DEMs to evaluate the volume quantifications was therefore also conducted.

  9. ArcGeomorphometry: A toolbox for geomorphometric characterisation of DEMs in the ArcGIS environment

    NASA Astrophysics Data System (ADS)

    Rigol-Sanchez, Juan P.; Stuart, Neil; Pulido-Bosch, Antonio

    2015-12-01

    A software tool is described for the extraction of geomorphometric land surface variables and features from Digital Elevation Models (DEMs). The ArcGeomorphometry Toolbox consists of a series of Python/Numpy processing functions, presented through an easy-to-use graphical menu for the widely used ArcGIS package. Although many GIS provide some operations for analysing DEMs, the methods are often only partially implemented and can be difficult to find and used effectively. Since the results of automated characterisation of landscapes from DEMs are influenced by the extent being considered, the resolution of the source DEM and the size of the kernel (analysis window) used for processing, we have developed a tool to allow GIS users to flexibly apply several multi-scale analysis methods to parameterise and classify a DEM into discrete land surface units. Users can control the threshold values for land surface classifications. The size of the processing kernel can be used to identify land surface features across a range of landscape scales. The pattern of land surface units from each attempt at classification is displayed immediately and can then be processed in the GIS alongside additional data that can assist with a visual assessment and comparison of a series of results. The functionality of the ArcGeomorphometry toolbox is described using an example DEM.

  10. Recent Release of the ASTER Global DEM Product

    NASA Astrophysics Data System (ADS)

    Behnke, J.; Hall, A.; Meyer, D.; Sohre, T.; Doescher, C.

    2009-12-01

    On June 29th, the ASTER Global Digital Elevation Model (DEM) release was announced to the public and to a very eager audience. ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) is an imaging instrument flying on Terra, a satellite launched in December 1999 as part of NASA's Earth Observing System (EOS). ASTER is a cooperative effort between NASA, Japan's Ministry of Economy, Trade and Industry (METI) and Japan's Earth Remote Sensing Data Analysis Center (ERSDAC). On June 21, NASA Headquarters along with colleagues in Japan (METI) signed a plan for distribution of this product. The global digital elevation model of Earth is available online to users everywhere at no cost from NASA's Land Processes Distributed Active Archive Center (DAAC) located at Sioux Falls, SD. The DAAC is a joint project of NASA and the USGS and is a key component of NASA's EOSDIS. The new ASTER GDEM was created from nearly 1.3 million individual stereo-pair images acquired by the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) instrument aboard NASA’s Terra satellite. The ASTER elevation model was jointly developed by NASA and METI under contract to Sensor Information Laboratory Corp., Tsukuba, Japan. On June 29, the NASA press release was picked up quickly by numerous news organizations and online sites. Response to the product was incredible! The news of the release of the product was carried on websites across the globe, this fueled a tremendous response from users. Here are a few interesting metrics about the release: - over 41,000 unique visitors to website in first week following release - top countries in order were: US (approx. 20%), Germany, U.K., Brazil, Austria, Canada, Spain, Switzerland, Japan - approximately 29,000 visitors came to the news page in the first week and about 11,000 of these users downloaded the actual press release - by the end of August, over 2 Million ASTER GDEM files had been downloaded from the Land Processes DAAC This presentation covers the issues associated with the release of this very popular product, including issues raised by many of our users.

  11. Crucial Points of Interferometric Processing for dem Generation Using High Resolution SAR Data

    NASA Astrophysics Data System (ADS)

    Sefercik, U. G.; Dana, I.

    2011-09-01

    Data collection for digital elevation model (DEM) generation can be carried out by two main methods in space-borne remote sensing such as stereoscopy using optical or radar satellite imagery (stereophotogrammetry, respectively radargrammetry) and interferometry based on interferometric synthetic aperture radar (InSAR) data. These techniques have advantages and disadvantages in comparison against each other. Especially filling the gaps which arise from the problem of cloud coverage in DEM generation by optical imagery, InSAR became operational in recent years and DEMs became the most demanded interferometric products. Essentially, in comparison, DEM generation from synthetic aperture radar (SAR) images is not a simple manner like generation from optical satellite imagery. Interferometric processing has several complicated steps for the production of a DEM. The quality of the data set and used software package come into prominence for the stability of the generated DEM. In the paper, the interferometric processing steps for DEM generation from InSAR data and the crucial threshold values are tried to be explained. For DEM generation, a part of Istanbul (historical peninsula and near surroundings) was selected as the test field because of data availability. The data sets of two different imaging modes (StripMap ~ 3 m resolution and High Resolution Spotlight ~ 1 m resolution) of TerraSAR-X have been used. At the implementation, besides the determination of crucial points at interferometric processing steps, to define the effect of computer software, DEM production have been performed using two different software packages in parallel and the products have been compared In the result section of the paper, besides the colorful visualizations of final products along with the height scales, accuracy evaluations have been performed for both DEMs with the help of a more accurate reference digital terrain model (DTM). This reference model has been achieved by large scale aerial photos. Normally, it has a 5 m original grid spacing, however it has been resampled at a spacing of 1 m towards the needs of the research.

  12. The generation of DEM from ALOS/PRISM and ice volume change in Mt. Qomolangma region

    NASA Astrophysics Data System (ADS)

    Ye, Qinghua

    2010-05-01

    Calculation on glacier volume variations are still greatly limited by the vertical accurate of various data sources till now (Stevens et al., 2004). Therefore, one of the major methodological gaps in the observation of glaciers from space is the measurement of glacier volume changes (Kääb, 2008). Glacier volume changes needs an integrated study and correction on generated DEMs from multi-sources remote sensing data and evaluation of the vertical errors and accuracy. Here, we produced DEMs over mountain glaciers from ASTER and ALOS/PRISM on the northern slope of Mt. Qomolangma (hereafter called the Mt. Qomolangma region), also known as the Mt. Everest, located in the middle Himalayan Mountains, 27° 59-28° 11´N and 86° 44´- 86° 59´E. A series of digital images, include Aster images on 23 Oct 2003, ALOS/AVNIR-2 on 19 Jan 2007, ALOS/AVNIR-2 on 24 Oct 2008, 3 scenes of ALOS/PRISM on 04 Dec 2006, 1:50,000 topographic maps with contour interval of 20 m produced from aerial photographs acquired in 1974 and the 1:50,000 DEM (cell size: 25 m) generated from the topographic maps were used. The DEM was generated based on the three scenes from ALOS/PRISM images and PCI Orthoengine module. The process of DEM generation from ASTER images is very similar to that of ALOS/PRISM. The difference is that: only two images ASTER from nadir and backward views were used here. Table 1 The differences between generated DEMs and the 1:50,000 topographic maps in the non-glacierized area dem5wdemasterprism12_50mprism13_50mprism14_25mprism15_100mSRTM DEMASTER_GDEM Maximum 80.0 920.0 218.0 174.0 258.0 168.0 240.0 437.0 Minimum -123.0 -331.0 -297.0 -367.0 -459.0 -393.0 -315.0 -182.0 aveDEV 23.8 84.0 33.9 36.0 31.3 45.9 67.6 57.9 AVERAGE6.9 75.3 11.3 5.9 1.7 17.2 32.3 45.0 StDEV 30.5 128.0 55.7 59.4 60.6 64.4 85.8 77.2 RMSe 31.2 148.3 56.7 59.6 60.5 66.5 91.5 89.2 Compared various kinds of products of the generated DEMs in the non-glacierized area with the 1:50,000 topographic maps using 215 random points, we found that the mean difference of PRISM DEM to the topographic maps is 1.7 m. However, the mean difference of ASTER GDEM (ASTER_GDEM) is 45m, which is released Version 1 of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) on 29 June, 2009. Our result shows that the quality of ALOS/PRISM DEM is better than that of ASTER GDEM, and the calibrated ALOS/PRISM DEM based on the relationship between aspect and DEM difference was more accurate than the original generated one. Fig.1 The generated ASTER DEM on 23 Oct 2003 Fig.2 the generated PRISM DEM on 04 Dec 2006

  13. Perspective - synthetic DEMs: A vital underpinning for the quantitative future of landform analysis?

    NASA Astrophysics Data System (ADS)

    Hillier, J. K.; Sofia, G.; Conway, S. J.

    2015-12-01

    Physical processes, including anthropogenic feedbacks, sculpt planetary surfaces (e.g. Earth's). A fundamental tenet of geomorphology is that the shapes created, when combined with other measurements, can be used to understand those processes. Artificial or synthetic digital elevation models (DEMs) might be vital in progressing further with this endeavour in two ways. First, synthetic DEMs can be built (e.g. by directly using governing equations) to encapsulate the processes, making predictions from theory. A second, arguably underutilised, role is to perform checks on accuracy and robustness that we dub "synthetic tests". Specifically, synthetic DEMs can contain a priori known, idealised morphologies that numerical landscape evolution models, DEM-analysis algorithms, and even manual mapping can be assessed against. Some such tests, for instance examining inaccuracies caused by noise, are moderately commonly employed, whilst others are much less so. Derived morphological properties, including metrics and mapping (manual and automated), are required to establish whether or not conceptual models represent reality well, but at present their quality is typically weakly constrained (e.g. by mapper inter-comparison). Relatively rare examples illustrate how synthetic tests can make strong "absolute" statements about landform detection and quantification; for example, 84 % of valley heads in the real landscape are identified correctly. From our perspective, it is vital to verify such statistics quantifying the properties of landscapes as ultimately this is the link between physics-driven models of processes and morphological observations that allows quantitative hypotheses to be tested. As such the additional rigour possible with this second usage of synthetic DEMs feeds directly into a problem central to the validity of much of geomorphology. Thus, this note introduces synthetic tests and DEMs and then outlines a typology of synthetic DEMs along with their benefits, challenges, and future potential to provide constraints and insights. The aim is to discuss how we best proceed with uncertainty-aware landscape analysis to examine physical processes.

  14. Error modeling of DEMs from topographic surveys of rivers using fuzzy inference systems

    NASA Astrophysics Data System (ADS)

    Bangen, Sara; Hensleigh, James; McHugh, Peter; Wheaton, Joseph

    2016-02-01

    Digital elevation models (DEMs) have become common place in the earth sciences as a tool to characterize surface topography and set modeling boundary conditions. All DEMs have a degree of inherent error that is propagated to subsequent models and analyses. While previous research has shown that DEM error is spatially variable it is often represented as spatially uniform for analytical simplicity. Fuzzy inference systems (FIS) offer a tractable approach for modeling spatially variable DEM error, including flexibility in the number of inputs and calibration of outputs based on survey technique and modeling environment. We compare three FIS error models for DEMs derived from TS surveys of wadeable streams and test them at 34 sites in the Columbia River basin. The models differ in complexity regarding the number/type of inputs and degree of site-specific parameterization. A 2-input FIS uses inputs derived from the topographic point cloud (slope, point density). A 4-input FIS adds interpolation error and 3-D point quality. The 5-input FIS adds bed-surface roughness estimates. Both the 4 and 5-input FIS model output were parameterized to site-specific values. In the wetted channel we found (i) the 5-input FIS resulted in lower mean δz due to including roughness, and (ii) the 4 and 5-input FIS resulted in a higher standard deviation and maximum δz due to the inclusion of site-specific bank heights. All three FIS gave plausible estimates of DEM error, with the two more complicated models offering an improvement in the ability to detect spatially localized areas of DEM uncertainty.

  15. Acute environmental toxicity and persistence of DEM, a chemical agent simulant: Diethyl malonate. [Diethyl malonate

    SciTech Connect

    Cataldo, D.A.; Ligotke, M.W.; Harvey, S.D.; Fellows, R.J.; Li, Shu-mei W.; Van Voris, P.; Wentsel, R.S.

    1990-05-01

    The purpose of the following chemical simulant studies is to assess the potential acute environmental effects and persistence of diethyl malonate (DEM). Deposition velocities for DEM to soil surfaces ranged from 0.04 to 0.2 cm/sec. For foliar surfaces, deposition velocities ranged from 0.0002 cm/sec at low air concentrations to 0.05 cm/sec for high dose levels. The residence times or half-lives of DEM deposited to soils was 2 h for the fast component and 5 to 16 h for the residual material. DEM deposited to foliar surfaces also exhibited biphasic depuration. The half-life of the short residence time component ranged from 1 to 3 h, while the longer time component had half-times of 16 to 242 h. Volatilization and other depuration mechanisms reduce surface contaminant levels in both soils and foliage to less than 1% of initial dose within 96 h. DEM is not phytotoxic at foliar mass loading levels of less than 10 {mu}m/cm{sup 2}. However, severe damage is evident at mass loading levels in excess of 17 {mu}g/cm{sup 2}. Tall fescue and sagebrush were more affected than was short-needle pine, however, mass loading levels were markedly different. Regrowth of tall fescue indicated that the effects of DEM are residual, and growth rates are affected only at higher mass loadings through the second harvest. Results from in vitro testing of DEM indicated concentrations below 500 {mu}g/g dry soil generally did not negatively impact soil microbial activity. Short-term effects of DEM were more profound on soil dehydrogenase activity than on soil phosphatase activity. No enzyme inhibition or enhancement was observed after 28 days in incubation. Results of the earthworm bioassay indicate survival to be 86 and 66% at soil doses of 107 and 204 {mu}g DEM/cm{sup 2}, respectively. At higher dose level, activity or mobility was judged to be affected in over 50% of the individuals. 21 refs., 10 figs., 15 tabs.

  16. DEM generation from SPOT-5 3-fold along track stereoscopic imagery using autocalibration

    NASA Astrophysics Data System (ADS)

    Kornus, W.; Alamús, R.; Ruiz, A.; Talaya, J.

    This paper describes the derivation and accuracy assessment of Digital Elevation Models (DEM) from 3-fold along-track stereoscopic SPOT-5 imagery. The work was conducted in the scope of the HRS (Haute Résolution Stéréoscopique)-Scientific Assessment Program, organized by the Centre National d'Études Spatiales (CNES) and the International Society of Photogrammetry and Remote Sensing (ISPRS). The orientation of the SPOT-5 image scene is reconstructed by bundle adjustment using ground control points. The functional model is based on correction polynomials and permits autocalibration. At 17 independent check points a RMS-error of 2 m was achieved. DEM are produced in two different ways: The more rigorous way employs an automatic region growing image matching process generating a dense point cloud in image space, transforms it into the object space using the estimated model parameters and converts it into a regular grid DEM. In a second approach the commercial software ISAE and rational functions are applied. The comparison with a digital terrain model (DTM) of superior accuracy yields standard deviations better than 5 m in flat and moderate terrain and better than 10 m in mountainous regions. With ISAE a DEM for the entire image area (approx. 60 × 80 km) is produced with a standard deviation of approximately 8 m. All grid points were generated fully automatically, i.e. the presented standard deviations still include the effect of large differences between the produced DEM and the DTM.

  17. An advanced distributed automated extraction of drainage network model on high-resolution DEM

    NASA Astrophysics Data System (ADS)

    Mao, Y.; Ye, A.; Xu, J.; Ma, F.; Deng, X.; Miao, C.; Gong, W.; Di, Z.

    2014-07-01

    A high-resolution and high-accuracy drainage network map is a prerequisite for simulating the water cycle in land surface hydrological models. The objective of this study was to develop a new automated extraction of drainage network model, which can get high-precision continuous drainage network on high-resolution DEM (Digital Elevation Model). The high-resolution DEM need too much computer resources to extract drainage network. The conventional GIS method often can not complete to calculate on high-resolution DEM of big basins, because the number of grids is too large. In order to decrease the computation time, an advanced distributed automated extraction of drainage network model (Adam) was proposed in the study. The Adam model has two features: (1) searching upward from outlet of basin instead of sink filling, (2) dividing sub-basins on low-resolution DEM, and then extracting drainage network on sub-basins of high-resolution DEM. The case study used elevation data of the Shuttle Radar Topography Mission (SRTM) at 3 arc-second resolution in Zhujiang River basin, China. The results show Adam model can dramatically reduce the computation time. The extracting drainage network was continuous and more accurate than HydroSHEDS (Hydrological data and maps based on Shuttle Elevation Derivatives at multiple Scales).

  18. Perspective - synthetic DEMs: a vital underpinning for the quantitative future of landform analysis?

    NASA Astrophysics Data System (ADS)

    Hillier, J. K.; Sofia, G.; Conway, S. J.

    2015-07-01

    Physical processes, including anthropogenic feedbacks, sculpt planetary surfaces (e.g., Earth's). A fundamental tenet of Geomorphology is that the shapes created, when combined with other measurements, can be used to understand those processes. Artificial or synthetic Digital Elevation Models (DEMs) might be vital in progressing further with this endeavour. Morphological data, including metrics and mapping (manual and automated) are a key resource, but at present their quality is typically weakly constrained (e.g., by mapper inter-comparison). In addition to examining inaccuracies caused by noise, relatively rare examples illustrate how synthetic DEMs containing a priori known, idealised morphologies can be used perform "synthetic tests" to make strong "absolute" statements about landform detection and quantification; e.g., 84 % of valley heads in the real landscape are identified correctly. From our perspective, it is vital to verify such statistics as ultimately they link physics-driven models of processes to morphological observations, allowing quantitative hypotheses to be formulated and tested. Synthetic DEMs built by directly using governing equations that encapsulate processes are another key part of forming this link. Thus, this note introduces synthetic tests and DEMs, then it outlines a typology of synthetic DEMs along with their benefits, challenges and future potential to provide constraints and insights. The aim is to discuss how we best proceed with uncertainty-aware landscape analysis to examine physical processes.

  19. TecDEM: A MATLAB Based Toolbox for understanding Tectonics from Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Shahzad, F.; Mahmood, S. A.; Gloaguen, R.

    2009-04-01

    TecDEM is a MATLAB based tool box for understanding the tectonics from digital elevation models (DEMs) of any area. These DEMs can be derived from data of any spatial resolution (Low, medium and High). In the first step we extract drainage network from the DEMs using flow grid approach. Drainage network is a group of streams having elevation and catchment area information as a function of spatial locations. We implement an array of stream structure to study this drainage network. Knickpoints can be identified on each stream of the drainage network by a graphical user interface and are helpful for understanding stream morphology. Stream profile analysis in steady state condition is applied on all streams to calculate geomorphic parameters and regional uplift rates. Hack index is calculated for all the profiles at a certain interval and over the change of knickpoints. Reports menu of this tool box generates detailed statistics report, complete tabulated report, graphical output of each analyzed stream profile and Hack index profile. All the calculated values are part of stream structure and is saved as .mat file for later use with this tool box. The spatial distribution of geomorphic parameters, uplift rates and knickpoints are exported as a shape files for visualization in professional GIS software. We test this tool box on DEMs from different tectonic settings worldwide and received verifiable results with other studies.

  20. Identifying LiDAR sample uncertainty on terrain features from DEM simulation

    NASA Astrophysics Data System (ADS)

    Chu, Hone-Jay; Chen, Ruey-An; Tseng, Yi-Hsing; Wang, Cheng-Kai

    2014-01-01

    Light detection and ranging (LiDAR) is an effective technology to detect highly dense-point elevation data from terrain surfaces. The density of LiDAR data points significantly affects the level of detail of a high-resolution digital elevation model (DEM). In this study, the conditioned Latin hypercube sampling (cLHS) and simple random sampling (SRS) methods select sufficient LiDAR samples, and sequential Gaussian simulation (SGS) generates multiple DEM realizations that are a set of simulated DEM maps subject to a specified mean, variance, and spatial structure of measured data. Based on DEM realizations, the uncertainty of a spatial feature with a specified elevation is determined. The results suggest that LiDAR sampling patterns, including the size and configuration, affect the spatial distribution of the feature uncertainty, especially when the sample size is small. The accuracy of a DEM is dependent on the choice of sampling techniques for low sampling density data. Unlike random sampling, the cLHS method replicates the distribution of spatial elevation patterns in small sample sizes. Hence, the integrated method can assess the uncertainty of spatial features efficiently in geomorphic monitoring and management.

  1. DEM Extraction from High-Resolution Stereoscopic Worldview 1 & 2 Imagery of Polar Outlet Glaciers

    NASA Astrophysics Data System (ADS)

    Porter, C. C.; Morin, P. J.; Howat, I. M.; Niebuhr, S.; Smith, B. E.

    2011-12-01

    There are few reliable digital elevation models (DEMs) in polar regions and most are of low resolution (on the order of 100's of meters to km) or of poor quality. Polar environments are changing rapidly and accurate DEMs are critical for correcting imagery, measuring glacier thickness changes and modeling ice flow and surface melt water drainage. Using in-track stereoscopic images from Worldview-1 and Worldview-2, we derived high-resolution DEMs for outlet glaciers and other areas of interest in Antarctica and the Arctic. We used ERDAS Imagine's LPS eATE (enhanced automated terrain extraction) algorithm to derive a dense point cloud of matches. The resulting point cloud is comparable in density to that obtained by LiDAR flown at 10,000 feet. Preliminary comparisons of our results to ground control points collected by field teams and airborne and satellite laser altimeters show 0.5 - 10 meter vertical error over glaciers and 2 - 10 meter error over ice-free terrain. The error is primarily due to approximations in the sensor model and is consistent across the DEM. Our results indicate that refinements in the sensor model and point matching algorithm will improve accuracy. Given the increasing interest in glacier change detection around the globe, DEMs extracted from frequent satellite stereo pairs can be used to monitor and quantify changes in both movement and volume.

  2. Austauschskräfte zwischen Elementarteilchen und Fermische Theorie des β-Zerfalls als Konsquenzen einer möglichen Feldtheorie der Materie [26

    NASA Astrophysics Data System (ADS)

    Inhalt: Elektron, Neutrino, Proton und Neutron werden als vier verschiedene Quantenzustände einer einzigen Elementpartikel angesehen. Quantensprünge zwischen diesen Zuständen erklären den β-Zerfall (gemäss der Theorie von Fermi) und geben zur HEISENBEBe-MAJOKANA'schen Neutron-Proton-Austauschkraft Anlass. Die Pestsetzung, dass negatives Elektron und positives Proton "Partikel"-Zustände (im Gegensatz zu "Antipartikel") sind, verbietet Zerstrahlungsprozesse der schweren Teilchen. Die umgekehrte Festsetzung (positives Elektron und positives Proton sind Partikel) führt zu Zerstrahlungsprozessen (siehe Zusammenfassung).

  3. Integration of 2-D hydraulic model and high-resolution LiDAR-derived DEM for floodplain flow modeling

    NASA Astrophysics Data System (ADS)

    Shen, D.; Wang, J.; Cheng, X.; Rui, Y.; Ye, S.

    2015-02-01

    The rapid progress of Light Detection And Ranging (LiDAR) technology has made acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially with regards to the study of floodplain flow modeling. High-resolution DEM data include many redundant interpolation points, needs a high amount of calculation, and does not match the size of computational mesh. These disadvantages are a common problem for floodplain flow modeling studies. Two-dimensional (2-D) hydraulic modeling, a popular method of analyzing floodplain flow, offers high precision of elevation parameterization for computational mesh while ignoring much micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, enabling the calculation of flood water levels in DEM grid cells through local inverse distance weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of the connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha polder, a flood storage area of Dongting Lake, using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than DEM only simulations.

  4. DEM analyses of shear behaviour of rock joints by a novel bond contact model

    NASA Astrophysics Data System (ADS)

    Jiang, M. J.; Liu, J.; Sun, C.; Chen, H.

    2015-09-01

    The failure of rock joints is one of the potential causes for the local and general rock instability, which may trigger devastating geohazards such as landslide. In this paper, the Distinct Element Method (DEM) featured by a novel bond contact model was utilized to simulate shear behaviour of centre/non-coplanar rock joints. The DEM results show that the complete shear behaviour of jointed rock includes four stages: elastic shearing phase, crack propagation, the failure of rock bridges and the through-going discontinuity. The peak shear strength of centre joint increases as the joint connectivity rate decreases. For intermittent noncoplanar rock joints, as the inclination of the rock joints increases, its shear capacity decreases when the inclination angle is negative while increase when positive. Comparison with the experimental results proves the capability of this DEM model in capturing the mechanical properties of the jointed rocks.

  5. Flow Dynamics of green sand in the DISAMATIC moulding process using Discrete element method (DEM)

    NASA Astrophysics Data System (ADS)

    Hovad, E.; Larsen, P.; Walther, J. H.; Thorborg, J.; Hattel, J. H.

    2015-06-01

    The DISAMATIC casting process production of sand moulds is simulated with DEM (discrete element method). The main purpose is to simulate the dynamics of the flow of green sand, during the production of the sand mould with DEM. The sand shot is simulated, which is the first stage of the DISAMATIC casting process. Depending on the actual casting geometry the mould can be geometrically quite complex involving e.g. shadowing effects and this is directly reflected in the sand flow during the moulding process. In the present work a mould chamber with “ribs” at the walls is chosen as a baseline geometry to emulate some of these important conditions found in the real moulding process. The sand flow is simulated with the DEM and compared with corresponding video footages from the interior of the chamber during the moulding process. The effect of the rolling resistance and the static friction coefficient is analysed and discussed in relation to the experimental findings.

  6. TanDEM-X: A radar interferometer with two formation-flying satellites

    NASA Astrophysics Data System (ADS)

    Krieger, Gerhard; Zink, Manfred; Bachmann, Markus; Bräutigam, Benjamin; Schulze, Daniel; Martone, Michele; Rizzoli, Paola; Steinbrecher, Ulrich; Walter Antony, John; De Zan, Francesco; Hajnsek, Irena; Papathanassiou, Kostas; Kugler, Florian; Rodriguez Cassola, Marc; Younis, Marwan; Baumgartner, Stefan; López-Dekker, Paco; Prats, Pau; Moreira, Alberto

    2013-08-01

    TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is an innovative formation-flying radar mission that opens a new era in spaceborne radar remote sensing. The primary objective is the acquisition of a global digital elevation model (DEM) with unprecedented accuracy (12 m horizontal resolution and 2 m relative height accuracy). This goal is achieved by extending the TerraSAR-X synthetic aperture radar (SAR) mission by a second, TerraSAR-X like satellite (TDX) flying in close formation with TerraSAR-X (TSX). Both satellites form together a large single-pass SAR interferometer with the opportunity for flexible baseline selection. This enables the acquisition of highly accurate cross-track interferograms without the inherent accuracy limitations imposed by repeat-pass interferometry due to temporal decorrelation and atmospheric disturbances. Besides the primary goal of the mission, several secondary mission objectives based on along-track interferometry as well as new bistatic and multistatic SAR techniques have been defined, representing an important and innovative asset of the TanDEM-X mission. TanDEM-X is implemented in the framework of a public-private partnership between the German Aerospace Center (DLR) and EADS Astrium GmbH. The TanDEM-X satellite was successfully launched in June 2010 and the mission started its operational data acquisition in December 2010. This paper provides an overview of the TanDEM-X mission and summarizes its actual status and performance. Furthermore, results from several scientific radar experiments are presented that show the great potential of future formation-flying interferometric SAR missions to serve novel remote sensing applications.

  7. Quality assessment of Digital Elevation Model (DEM) in view of the Altiplano hydrological modeling

    NASA Astrophysics Data System (ADS)

    Satgé, F.; Arsen, A.; Bonnet, M.; Timouk, F.; Calmant, S.; Pilco, R.; Molina, J.; Lavado, W.; Crétaux, J.; HASM

    2013-05-01

    Topography is crucial data input for hydrological modeling but in many regions of the world, the only way to characterize topography is the use of satellite-based Digital Elevation Models (DEM). In some regions, the quality of these DEMs remains poor and induces modeling errors that may or not be compensated by model parameters tuning. In such regions, the evaluation of these data uncertainties is an important step in the modeling procedure. In this study, which focuses on the Altiplano region, we present the evaluation of the two freely available DEM. The shuttle radar topographic mission (SRTM), a product of the National Aeronautics and Space Administration (NASA) and the Advanced Space Born Thermal Emission and Reflection Global Digital Elevation Map (ASTER GDEM), data provided by the Ministry of Economy, Trade and Industry of Japan (MESI) in collaboration with the NASA, are widely used. While the first represents a resolution of 3 arc seconds (90m) the latter is 1 arc second (30m). In order to select the most reliable DEM, we compared the DEM elevation with high qualities control points elevation. Because of its large spatial coverture (track spaced of 30 km with a measure of each 172 m) and its high vertical accuracy which is less than 15 cm in good weather conditions, the Geoscience Laser Altimeter System (GLAS) on board on the Ice, Cloud and Land elevation Satellite of NASA (ICESat) represent the better solution to establish a high quality elevation database. After a quality check, more than 150 000 ICESat/GLAS measurements are suitable in terms of accuracy for the Altiplano watershed. This data base has been used to evaluate the vertical accuracy for each DEM. Regarding to the full spatial coverture; the comparison has been done for both, all kind of land coverture, range altitude and mean slope.

  8. Discrete Element Method (DEM) Application to The Cone Penetration Test Using COUPi Model

    NASA Astrophysics Data System (ADS)

    Kulchitsky, A. V.; Johnson, J.; Wilkinson, A.; DeGennaro, A. J.; Duvoy, P.

    2011-12-01

    The cone penetration test (CPT) is a soil strength measurement method to determine the tip resistance and sleeve friction versus depth while pushing a cone into regolith with controlled slow quasi-static speed. This test can also be used as an excellent tool to validate the discrete element method (DEM) model by comparing tip resistance and sleeve friction from experiments to model results. DEM by nature requires significant computational resources even for a limited number of particles. Thus, it is important to find particle and ensemble parameters that produce valuable results within reasonable computation times. The Controllable Objects Unbounded Particles Interaction (COUPi) model is a general physical DEM code being developed to model machine/regolith interactions as part of a NASA Lunar Science Institute sponsored project on excavation and mobility modeling. In this work, we consider how different particle shape and size distributions defined in the DEM influence the cone tip and friction sleeve resistance in a CPT DEM simulation. The results are compared to experiments with cone penetration in JSC-1A lunar regolith simulant. The particle shapes include spherical particles, particles composed from the union of three spheres, and some simple polyhedra. This focus is driven by the soil mechanics rule of thumb that particle size and shape distributions are the two most significant factors affecting soil strength. In addition to the particle properties, the packing configuration of an ensemble strongly affects soil strength. Bulk density of the regolith is an important characteristic that significantly influences the tip resistance and sleeve friction (Figure 1). We discuss different approaches used to control granular density in the DEM, including how to obtain higher bulk densities, using numerical "shaking" techniques and varying the friction coefficient during computations.

  9. How large is the Upper Indus Basin? The pitfalls of auto-delineation using DEMs

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Richards, Keith S.; Parker, Geoffrey T.; McRobie, Allan; Mukhopadhyay, Biswajit

    2014-02-01

    Extraction of watershed areas from Digital Elevation Models (DEMs) is increasingly required in a variety of environmental analyses. It is facilitated by the availability of DEMs based on remotely sensed data, and by Geographical Information System (GIS) software. However, accurate delineation depends on the quality of the DEM and the methodology adopted. This paper considers automated and supervised delineation in a case study of the Upper Indus Basin (UIB), Pakistan, for which published estimates of the basin area show significant disagreement, ranging from 166,000 to 266,000 km2. Automated delineation used ArcGIS Archydro and hydrology tools applied to three good quality DEMs (two from SRTM data with 90m resolution, and one from 30m resolution ASTER data). Automatic delineation defined a basin area of c.440,000 km2 for the UIB, but included a large area of internal drainage in the western Tibetan Plateau. It is shown that discrepancies between different estimates reflect differences in the initial extent of the DEM used for watershed delineation, and the unchecked effect of iterative pit-filling of the DEM (going beyond the filling of erroneous pixels to filling entire closed basins). For the UIB we have identified critical points where spurious addition of catchment area has arisen, and use Google Earth to examine the geomorphology adjacent to these points, and also examine the basin boundary data provided by the HydroSHEDS database. We show that the Pangong Tso watershed and some other areas in the western Tibetan plateau are not part of the UIB, but are areas of internal drainage. Our best estimate of the area of the Upper Indus Basin (at Besham Qila) is 164,867 km2 based on the SRTM DEM, and 164,853 km2 using the ASTER DEM). This matches the catchment area measured by WAPDA SWHP. An important lesson from this investigation is that one should not rely on automated delineation, as iterative pit-filling can produce spurious drainage networks and basins, when there are areas of internal drainage nearby.

  10. Developmental Eye Movement (DEM) Test Norms for Mandarin Chinese-Speaking Chinese Children

    PubMed Central

    Tong, Meiling; Zhang, Min; Li, Tingting; Xu, Yaqin; Guo, Xirong; Hong, Qin; Chi, Xia

    2016-01-01

    The Developmental Eye Movement (DEM) test is commonly used as a clinical visual-verbal ocular motor assessment tool to screen and diagnose reading problems at the onset. No established norm exists for using the DEM test with Mandarin Chinese-speaking Chinese children. This study aims to establish the normative values of the DEM test for the Mandarin Chinese-speaking population in China; it also aims to compare the values with three other published norms for English-, Spanish-, and Cantonese-speaking Chinese children. A random stratified sampling method was used to recruit children from eight kindergartens and eight primary schools in the main urban and suburban areas of Nanjing. A total of 1,425 Mandarin Chinese-speaking children aged 5 to 12 years took the DEM test in Mandarin Chinese. A digital recorder was used to record the process. All of the subjects completed a symptomatology survey, and their DEM scores were determined by a trained tester. The scores were computed using the formula in the DEM manual, except that the “vertical scores” were adjusted by taking the vertical errors into consideration. The results were compared with the three other published norms. In our subjects, a general decrease with age was observed for the four eye movement indexes: vertical score, adjusted horizontal score, ratio, and total error. For both the vertical and adjusted horizontal scores, the Mandarin Chinese-speaking children completed the tests much more quickly than the norms for English- and Spanish-speaking children. However, the same group completed the test slightly more slowly than the norms for Cantonese-speaking children. The differences in the means were significant (P<0.001) in all age groups. For several ages, the scores obtained in this study were significantly different from the reported scores of Cantonese-speaking Chinese children (P<0.005). Compared with English-speaking children, only the vertical score of the 6-year-old group, the vertical-horizontal time ratio of the 8-year-old group and the errors of 9-year-old group had no significant difference (P>0.05); compared with Spanish-speaking children, the scores were statistically significant (P<0.001) for the total error scores of the age groups, except the 6-, 9-, 10-, and 11-year-old age groups (P>0.05). DEM norms may be affected by differences in language, cultural, and educational systems among various ethnicities. The norms of the DEM test are proposed for use with Mandarin Chinese-speaking children in Nanjing and will be proposed for children throughout China. PMID:26881754

  11. Developmental Eye Movement (DEM) Test Norms for Mandarin Chinese-Speaking Chinese Children.

    PubMed

    Xie, Yachun; Shi, Chunmei; Tong, Meiling; Zhang, Min; Li, Tingting; Xu, Yaqin; Guo, Xirong; Hong, Qin; Chi, Xia

    2016-01-01

    The Developmental Eye Movement (DEM) test is commonly used as a clinical visual-verbal ocular motor assessment tool to screen and diagnose reading problems at the onset. No established norm exists for using the DEM test with Mandarin Chinese-speaking Chinese children. This study aims to establish the normative values of the DEM test for the Mandarin Chinese-speaking population in China; it also aims to compare the values with three other published norms for English-, Spanish-, and Cantonese-speaking Chinese children. A random stratified sampling method was used to recruit children from eight kindergartens and eight primary schools in the main urban and suburban areas of Nanjing. A total of 1,425 Mandarin Chinese-speaking children aged 5 to 12 years took the DEM test in Mandarin Chinese. A digital recorder was used to record the process. All of the subjects completed a symptomatology survey, and their DEM scores were determined by a trained tester. The scores were computed using the formula in the DEM manual, except that the "vertical scores" were adjusted by taking the vertical errors into consideration. The results were compared with the three other published norms. In our subjects, a general decrease with age was observed for the four eye movement indexes: vertical score, adjusted horizontal score, ratio, and total error. For both the vertical and adjusted horizontal scores, the Mandarin Chinese-speaking children completed the tests much more quickly than the norms for English- and Spanish-speaking children. However, the same group completed the test slightly more slowly than the norms for Cantonese-speaking children. The differences in the means were significant (P<0.001) in all age groups. For several ages, the scores obtained in this study were significantly different from the reported scores of Cantonese-speaking Chinese children (P<0.005). Compared with English-speaking children, only the vertical score of the 6-year-old group, the vertical-horizontal time ratio of the 8-year-old group and the errors of 9-year-old group had no significant difference (P>0.05); compared with Spanish-speaking children, the scores were statistically significant (P<0.001) for the total error scores of the age groups, except the 6-, 9-, 10-, and 11-year-old age groups (P>0.05). DEM norms may be affected by differences in language, cultural, and educational systems among various ethnicities. The norms of the DEM test are proposed for use with Mandarin Chinese-speaking children in Nanjing and will be proposed for children throughout China. PMID:26881754

  12. Stochastic Discrete Equation Method (sDEM) for two-phase flows

    SciTech Connect

    Abgrall, R.; Congedo, P.M.; Geraci, G.; Rodio, M.G.

    2015-10-15

    A new scheme for the numerical approximation of a five-equation model taking into account Uncertainty Quantification (UQ) is presented. In particular, the Discrete Equation Method (DEM) for the discretization of the five-equation model is modified for including a formulation based on the adaptive Semi-Intrusive (aSI) scheme, thus yielding a new intrusive scheme (sDEM) for simulating stochastic two-phase flows. Some reference test-cases are performed in order to demonstrate the convergence properties and the efficiency of the overall scheme. The propagation of initial conditions uncertainties is evaluated in terms of mean and variance of several thermodynamic properties of the two phases.

  13. LULC Classification and Topographic Correction of Landsat-7 ETM+ Imagery in the Yangjia River Watershed: the Influence of DEM Resolution.

    PubMed

    Gao, Yongnian; Zhang, Wanchang

    2009-01-01

    DEM-based topographic corrections on Landsat-7 ETM+ imagery from rugged terrain, as an effective processing techniques to improve the accuracy of Land Use/Land Cover (LULC) classification as well as land surface parameter retrievals with remotely sensed data, has been frequently reported in the literature. However, few studies have investigated the exact effects of DEM with different resolutions on the correction of imagery. Taking the topographic corrections on the Landsat-7 ETM+ images acquired from the rugged terrain of the Yangjiahe river basin (P.R. China) as an example, the present work systematically investigates such issues by means of two commonly used topographic correction algorithms with the support of different spatial resolution DEMs. After the pre-processing procedures, i.e. atmospheric correction and geo-registration, were applied to the ETM+ images, two topographic correction algorithms, namely SCS correction and Minnaert correction, were applied to assess the effects of different spatial resolution DEMs obtained from two sources in the removal of topographic effects and LULC classifications. The results suggested that the topographic effects were tremendously reduced with these two algorithms under the support of different spatial resolution DEMs, and the performance of the topographic correction with the 1:50,000-topographic-map DEM was similar to that achieved using SRTM DEM. Moreover, when the same topographic correction algorithm was applied the accuracy of LULC classification after topographic correction based on 1:50,000-topographic-map DEM was similar as that based on SRTM DEM, which implies that the 90 m SRTM DEM can be used as an alternative for the topographic correction of ETM+ imagery when high resolution DEM is unavailable. PMID:22573996

  14. Influence of Lossy Compressed DEM on Radiometric Correction for Land Cover Classification of Remote Sensing Images

    NASA Astrophysics Data System (ADS)

    Moré, G.; Pesquer, L.; Blanes, I.; Serra-Sagristà, J.; Pons, X.

    2012-12-01

    World coverage Digital Elevation Models (DEM) have progressively increased their spatial resolution (e.g., ETOPO, SRTM, or Aster GDEM) and, consequently, their storage requirements. On the other hand, lossy data compression facilitates accessing, sharing and transmitting large spatial datasets in environments with limited storage. However, since lossy compression modifies the original information, rigorous studies are needed to understand its effects and consequences. The present work analyzes the influence of DEM quality -modified by lossy compression-, on the radiometric correction of remote sensing imagery, and the eventual propagation of the uncertainty in the resulting land cover classification. Radiometric correction is usually composed of two parts: atmospheric correction and topographical correction. For topographical correction, DEM provides the altimetry information that allows modeling the incidence radiation on terrain surface (cast shadows, self shadows, etc). To quantify the effects of the DEM lossy compression on the radiometric correction, we use radiometrically corrected images for classification purposes, and compare the accuracy of two standard coding techniques for a wide range of compression ratios. The DEM has been obtained by resampling the DEM v.2 of Catalonia (ICC), originally having 15 m resolution, to the Landsat TM resolution. The Aster DEM has been used to fill the gaps beyond the administrative limits of Catalonia. The DEM has been lossy compressed with two coding standards at compression ratios 5:1, 10:1, 20:1, 100:1 and 200:1. The employed coding standards have been JPEG2000 and CCSDS-IDC; the former is an international ISO/ITU-T standard for almost any type of images, while the latter is a recommendation of the CCSDS consortium for mono-component remote sensing images. Both techniques are wavelet-based followed by an entropy-coding stage. Also, for large compression ratios, both techniques need a post processing for correctly delimiting coastline, avoiding the confusion between elevation and no-data values. Six (from March 2005 to May 2007) geometrically corrected Landsat-5 images on the path-row 197-031 have been used. The six optical bands and the NDVI for each date have been introduced in a powerful hybrid classification process. The training areas and the ground truth have been obtained from the Mapa de Cobertes del Sòl de Catalunya (v. 3), a land cover map created by photointerpretation of 0.5 m orthophotomaps acquired between 2005 and 2007 and covering all the extension of Catalonia. The legend has been reduced from 233 categories to 21. Preliminary results have shown that the effect on land cover classification of applying lossy compression to the DEM used in the radiometric correction is small (lower than 1%) even for compression ratios up to 200:1. Comparing classification performance after a compression of 5:1 and and a compression of 200:1 with both coding standards showed that: a) the percentage of correctly classified image was 73%; b) 20% was wrongly classified; c) 3.5% was wrongly classified at compression ratio 5:1; and d) also 3.5% was wrongly classified at compression ratio 200:1. These results are the first in the literature to analyze the effect of DEM lossy compressing when DEM are employed for radiometric correction.

  15. Synergy of Image and Digital Elevation Models (DEMS) Information for Virtual Reality

    NASA Astrophysics Data System (ADS)

    Maire, C.; Datcu, M.

    2004-09-01

    In the framework of 3D visualization and real-time rendering of large remote sensing image databases, several signal processing techniques are presented and evaluated to filter/enhance SAR Digital Elevation Models (DEMs). Through the SRTM DEM, the interest of InSAR data for such applications is illustrated. A non stationary bayesian filter is presented to remove noise and small artefacts which pervade the SAR DEM while preserving structures and information content. Results obtained are very good, nevertheless large artefacts cannot be filtered and some artefacts remain. Therefore, image information have to be inserted to produce more realistic views. This second step is done by using a segmentation algorithm on the image data. By a topology analysis, the extracted objects are classified/stored in a tree structure to describe the topologic relations between the objects and reflect their interdependencies. An interactive learning procedure is done through a Graphical User Interface to link the signal classes to the semantic ones, i.e. to include human knowledge in the system. The selected information in form of objets are merged/fused in the DEM by assigning regularisation constraints.

  16. A simplified DEM-CFD approach for pebble bed reactor simulations

    SciTech Connect

    Li, Y.; Ji, W.

    2012-07-01

    In pebble bed reactors (PBR's), the pebble flow and the coolant flow are coupled with each other through coolant-pebble interactions. Approaches with different fidelities have been proposed to simulate similar phenomena. Coupled Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) approaches are widely studied and applied in these problems due to its good balance between efficiency and accuracy. In this work, based on the symmetry of the PBR geometry, a simplified 3D-DEM/2D-CFD approach is proposed to speed up the DEM-CFD simulation without significant loss of accuracy. Pebble flow is simulated by a full 3-D DEM, while the coolant flow field is calculated with a 2-D CFD simulation by averaging variables along the annular direction in the cylindrical geometry. Results show that this simplification can greatly enhance the efficiency for cylindrical core, which enables further inclusion of other physics such as thermal and neutronic effect in the multi-physics simulations for PBR's. (authors)

  17. Perspective - Synthetic DEMs: A vital underpinning for the quantitative future of landform analysis?

    NASA Astrophysics Data System (ADS)

    Hillier, John K.; Sofia, Giulia; Conway, Susan

    2015-04-01

    Physical processes, including anthropogenic feedbacks, sculpt planetary surfaces (e.g., Earth's). A fundamental tenet of Geomorphology is that the shapes created, when combined with other measurements, can be used to understand those processes. Morphological data, including metrics and mapping (manual and automated), are a key resource in this endeavour. However, how good are these data that analyses rely on? Artificial or synthetic DEMs are widely used to examine the distortions of 'noise' (e.g., on topographic parameters), but only rarely to make strong 'absolute' statements about landform detection and quantification; e.g., 84% of the river channels in the real landscape are found, or 47% of all actual drumlins H > 3 m are mapped. In theory synthetic DEMs a priori containing known, idealised components can give such absolute conclusions regarding effectiveness if they can be constructed so as to represent well the actual landscapes. So, do we need good realistic synthetic DEMs, how can we best construct them, and what for? From our perspective, they are vital to verify the statistics that will link physics-driven models of processes to morphological observations, allowing quantitative hypotheses to be formulated and tested. We will outline current approaches, and some speculations about the future, but we are seeking a discussion on how best to construct realistic synthetic DEMs and proceed with uncertainty-aware landscape analysis to examine physical processes.

  18. Discrete element modelling (DEM) input parameters: understanding their impact on model predictions using statistical analysis

    NASA Astrophysics Data System (ADS)

    Yan, Z.; Wilkinson, S. K.; Stitt, E. H.; Marigo, M.

    2015-09-01

    Selection or calibration of particle property input parameters is one of the key problematic aspects for the implementation of the discrete element method (DEM). In the current study, a parametric multi-level sensitivity method is employed to understand the impact of the DEM input particle properties on the bulk responses for a given simple system: discharge of particles from a flat bottom cylindrical container onto a plate. In this case study, particle properties, such as Young's modulus, friction parameters and coefficient of restitution were systematically changed in order to assess their effect on material repose angles and particle flow rate (FR). It was shown that inter-particle static friction plays a primary role in determining both final angle of repose and FR, followed by the role of inter-particle rolling friction coefficient. The particle restitution coefficient and Young's modulus were found to have insignificant impacts and were strongly cross correlated. The proposed approach provides a systematic method that can be used to show the importance of specific DEM input parameters for a given system and then potentially facilitates their selection or calibration. It is concluded that shortening the process for input parameters selection and calibration can help in the implementation of DEM.

  19. The effect of DEM resolution on slope estimation and sediment predictions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Moderate resolution (30 m) digital elevation models (DEMs) are normally used to estimate slope for the parameterization of non-point source process-based water quality models. These models, such as the Soil and Water Assessment Tool (SWAT), utilize the Modified Universal Soil Loss Equation (MUSLE) ...

  20. How Can the TanDEM-X Digital Elevation Model Support Terrestrial Impact Crater Studies?

    NASA Astrophysics Data System (ADS)

    Gottwald, M.; Fritz, T.; Breit, H.; Schaettler, B.; Harris, A.

    2015-09-01

    The German Aerospace Center operated the X-band radar satellites TerraSAR-X and TanDEM-X as a single-pass SAR interferometer. Data acquisition occurred over the entire land surface for the generation of a very high quality digital elevation model.

  1. Extracting DEM from airborne X-band data based on PolInSAR

    NASA Astrophysics Data System (ADS)

    Hou, X. X.; Huang, G. M.; Zhao, Z.

    2015-06-01

    Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) is a new trend of SAR remote sensing technology which combined polarized multichannel information and Interferometric information. It is of great significance for extracting DEM in some regions with low precision of DEM such as vegetation coverage area and building concentrated area. In this paper we describe our experiments with high-resolution X-band full Polarimetric SAR data acquired by a dual-baseline interferometric airborne SAR system over an area of Danling in southern China. Pauli algorithm is used to generate the double polarimetric interferometry data, Singular Value Decomposition (SVD), Numerical Radius (NR) and Phase diversity (PD) methods are used to generate the full polarimetric interferometry data. Then we can make use of the polarimetric interferometric information to extract DEM with processing of pre filtering , image registration, image resampling, coherence optimization, multilook processing, flat-earth removal, interferogram filtering, phase unwrapping, parameter calibration, height derivation and geo-coding. The processing system named SARPlore has been exploited based on VC++ led by Chinese Academy of Surveying and Mapping. Finally compared optimization results with the single polarimetric interferometry, it has been observed that optimization ways can reduce the interferometric noise and the phase unwrapping residuals, and improve the precision of DEM. The result of full polarimetric interferometry is better than double polarimetric interferometry. Meanwhile, in different terrain, the result of full polarimetric interferometry will have a different degree of increase.

  2. Inter-agency comparison of TanDEM-X baseline solutions

    NASA Astrophysics Data System (ADS)

    Jggi, A.; Montenbruck, O.; Moon, Y.; Wermuth, M.; Knig, R.; Michalak, G.; Bock, H.; Bodenmann, D.

    2012-07-01

    TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is the first Synthetic Aperture Radar (SAR) mission using close formation flying for bistatic SAR interferometry. The primary goal of the mission is to generate a global digital elevation model (DEM) with 2 m height precision and 10 m ground resolution from the configurable SAR interferometer with space baselines of a few hundred meters. As a key mission requirement for the interferometric SAR processing, the relative position, or baseline vector, of the two satellites must be determined with an accuracy of 1 mm (1D RMS) from GPS measurements collected by the onboard receivers. The operational baseline products for the TanDEM-X mission are routinely generated by the German Research Center for Geosciences (GFZ) and the German Space Operations Center (DLR/GSOC) using different software packages (EPOS/BSW, GHOST) and analysis strategies. For a further independent performance assessment, TanDEM-X baseline solutions are generated at the Astronomical Institute of the University of Bern (AIUB) on a best effort basis using the Bernese Software (BSW). Dual-frequency baseline solutions are compared for a 1-month test period in January 2011. Differences of reduced-dynamic baseline solutions exhibit a representative standard deviation (STD) of 1 mm outside maneuver periods, while biases are below 1 mm in all directions. The achieved baseline determination performance is close to the mission specification, but independent SAR calibration data takes acquired over areas with a well known DEM from previous missions will be required to fully meet the 1 mm 1D RMS target. Besides the operational solutions, single-frequency baseline solutions are tested. They benefit from a more robust ambiguity fixing and show a slightly better agreement of below 1 mm STD, but are potentially affected by errors caused by an incomplete compensation of differential ionospheric path delays.

  3. Validation of DEMs Derived from High Resolution SAR Data: a Case Study on Barcelona

    NASA Astrophysics Data System (ADS)

    Sefercik, U. G.; Schunert, A.; Soergel, U.; Watanabe, K.

    2012-07-01

    In recent years, Synthetic Aperture Radar (SAR) data have been widely used for scientific applications and several SAR missions were realized. The active sensor principle and the signal wavelength in the order of centimeters provide all-day and all-weather capabilities, respectively. The modern German TerraSAR-X (TSX) satellite provides high spatial resolution down to one meter. Based on such data SAR Interferometry may yield high quality digital surface models (DSMs), which includes points located on 3d objects such as vegetation, forest, and elevated man-made structures. By removing these points, digital elevation model (DEM) representing the bare ground of Earth is obtained. The primary objective of this paper is the validation of DEMs obtained from TSX SAR data covering Barcelona area, Spain, in the framework of a scientific project conducted by ISPRS Working Group VII/2 "SAR Interferometry" that aims the evaluation of DEM derived from data of modern SAR satellite sensors. Towards this purpose, a DSM was generated with 10 m grid spacing using TSX StripMap mode SAR data and converted to a DEM by filtering. The accuracy results have been presented referring the comparison with a more accurate (10 cm-1 m) digital terrain model (DTM) derived from large scale photogrammetry. The results showed that the TSX DEM is quite coherent with the topography and the accuracy is in between ±8-10 m. As another application, the persistent scatterer interferometry (PSI) was conducted using TSX data and the outcomes were compared with a 3d city model available in Google Earth, which is known to be very precise because it is based on LIDAR data. The results showed that PSI outcomes are quite coherent with reference data and the RMSZ of differences is around 2.5 m.

  4. Three-dimensional simulation of a solid-liquid flow by the DEM-SPH method

    NASA Astrophysics Data System (ADS)

    Sun, Xiaosong; Sakai, Mikio; Yamada, Yoshinori

    2013-09-01

    In this paper, we describe a new Lagrangian-Lagrangian algorithm, which is referred to be the DEM-SPH method, for solid-liquid flows involving free surfaces. The DEM solid phase and the SPH liquid phase are coupled using the local averaging technique described by Lagrangian approaches, where both the continuity equation and the interaction force, i.e. drag force, are connected with the local mean voidage. Conservative forms of momentum transformation are derived for the DEM-SPH interaction via a variational approach. By introducing a correction to the SPH approximation with explicit inclusion of boundary information, arbitrary boundaries can be modeled without any extra wall particles, where the boundary is used commonly for both DEM and SPH phases. We deploy level-set distance functions to efficiently construct and evaluate this boundary model. To examine the validity of the present method, we perform three-dimensional simulations of a dynamic flow in a solid-liquid dam break and a quasi-steady flow in a rotating cylindrical tank; and we conduct validation experiments to justify the simulation results. In the dam-break problem, positions of wave fronts during the collapse are computed and compared with experimental measurements; for the circulating tank, some macroscopic aspects of the steady flow, e.g. the shape, dimension and velocity profile of the solid bed, are obtained for validation data. In both cases, the simulation results are in good agreement with those of the experiment. Consequently, the DEM-SPH method is proved to be adequate in modeling solid-liquid flows through this study.

  5. Quantifying geological structures of the Nigde province in central Anatolia, Turkey using SRTM DEM data

    NASA Astrophysics Data System (ADS)

    Demirkesen, A. C.

    2009-01-01

    A digital terrain model and a 3D fly-through model of the Nigde province in central Anatolia, Turkey were generated and quantitatively analyzed employing the shuttle radar topographic mission (SRTM) digital elevation model (DEM). Besides, stream drainage patterns, lineaments and structural-geological features were extracted and analyzed. In the process of analyzing and interpreting the DEM for landforms, criteria such as color and color tones (attributes of heights), topography (shaded DEM and 3D fly-through model) and stream drainage patterns were employed to acquire geo-information about the land, such as hydrologic, geomorphologic, topographic and tectonic structures. In this study, the SRTM DEM data of the study region were experimentally used for both DEM classification and quantitative analysis of the digital terrain model. The results of the DEM classification are: (1) low plain including the plains of Bor and Altunhisar (20.7%); (2) high plain including the Misli (Konakli) plain (28.8%); (3) plateau plain including the Melendiz (Ciftlik) plateau plain (1.0%); (4) mountain including the Nigde massif (33.3%); and (5) high mountain (16.2%). High mountain areas include a caldera complex of Mt Melendiz, Mt Hasan and Mt Pozanti apart from the Ala mountains called Aladaglar and the Bolkar mountains called Bolkarlar in the study region (7,312 km2). Analysis of both the stream drainage patterns and the lineaments revealed that the Nigde province has a valley zone called Karasu valley zone (KVZ) or Nigde valley zone (NVZ), where settlements and agricultural plains, particularly the Bor plain in addition to settlements of the Bor town and the central city of Nigde have the most flooding risk when a heavy raining occurs. The study revealed that the NVZ diagonally divides the study region roughly into two equal parts, heading from northeast to southwest. According to the map created in this study, the right side of the NVZ has more mountainous area, where the Aladaglar is a wildlife national park consisting of many species of fauna and flora whereas the left side of the NVZ has more agricultural plain, with exception of a caldera complex of Mt Melendiz and volcanic Mt Hasan. The south of the study region includes the Bolkarlar. In addition, the Ecemis fault zone (EFZ) lying along the Ecemis rivulet, running from north to south at the west side of the Aladaglar, forms the most important and sensitive location in the region in terms of the tectonics.

  6. Visualising DEM-related flood-map uncertainties using a disparity-distance equation algorithm

    NASA Astrophysics Data System (ADS)

    Brandt, S. Anders; Lim, Nancy J.

    2016-05-01

    The apparent absoluteness of information presented by crisp-delineated flood boundaries can lead to misconceptions among planners about the inherent uncertainties associated in generated flood maps. Even maps based on hydraulic modelling using the highest-resolution digital elevation models (DEMs), and calibrated with the most optimal Manning's roughness (n) coefficients, are susceptible to errors when compared to actual flood boundaries, specifically in flat areas. Therefore, the inaccuracies in inundation extents, brought about by the characteristics of the slope perpendicular to the flow direction of the river, have to be accounted for. Instead of using the typical Monte Carlo simulation and probabilistic methods for uncertainty quantification, an empirical-based disparity-distance equation that considers the effects of both the DEM resolution and slope was used to create prediction-uncertainty zones around the resulting inundation extents of a one-dimensional (1-D) hydraulic model. The equation was originally derived for the Eskilstuna River where flood maps, based on DEM data of different resolutions, were evaluated for the slope-disparity relationship. To assess whether the equation is applicable to another river with different characteristics, modelled inundation extents from the Testebo River were utilised and tested with the equation. By using the cross-sectional locations, water surface elevations, and DEM, uncertainty zones around the original inundation boundary line can be produced for different confidences. The results show that (1) the proposed method is useful both for estimating and directly visualising model inaccuracies caused by the combined effects of slope and DEM resolution, and (2) the DEM-related uncertainties alone do not account for the total inaccuracy of the derived flood map. Decision-makers can apply it to already existing flood maps, thereby recapitulating and re-analysing the inundation boundaries and the areas that are uncertain. Hence, more comprehensive flood information can be provided when determining locations where extra precautions are needed. Yet, when applied, users must also be aware that there are other factors that can influence the extent of the delineated flood boundary.

  7. Effects of DEM scale on the spatial distribution of the TOPMODEL topographic wetness index and its correlations to watershed characteristics

    NASA Astrophysics Data System (ADS)

    Drover, D. R.; Jackson, C. R.; Bitew, M.; Du, E.

    2015-11-01

    Topographic wetness indices (TWIs) calculated from digital elevation models (DEMs) are meant to predict relative landscape wetness and should have predictive power for soil and vegetation attributes. While previous researchers have shown cumulative TWI distributions shift to larger values as DEM resolution decreases, there has been little work assessing how DEM scales affect TWI spatial distributions and correlations with soil and vegetation properties. We explored how various DEM resolutions (2, 5, 10, 20, 30, and 50 m) subsampled from high definition LiDAR altered the spatial distribution of TWI values and the correlations of these values with soil characteristics determined from point samples, Natural Resources Conservation Service (NRCS) soil units, depths to groundwater, and managed vegetation distributions within a first order basin in the Upper Southeastern Coastal Plain with moderate slopes, flat valleys, and several wetlands. Point-scale soil characteristics were determined by laboratory analysis of point samples collected from riparian transects and hillslope grids. DEM scale affected the spatial distribution of TWI values in ways that affect our interpretation of landscape processes. At the finest DEM resolutions, valleys disappeared as TWI values were driven by local microtopography and not basin position. Spatial distribution of TWI values most closely matched the spatial distribution of soils, depth to groundwater, and vegetation stands for the 10, 20, and 30 m resolutions. DEM resolution affected the shape and direction of relationships between soil nitrogen and carbon contents and TWI values, but TWI values provided poor prediction of soil chemistry at all resolutions.

  8. On the suitability of the SRTM DEM and ASTER GDEM for the compilation of topographic parameters in glacier inventories

    NASA Astrophysics Data System (ADS)

    Frey, Holger; Paul, Frank

    2012-08-01

    Topographic parameters in glacier inventories are of vital importance for several subsequent applications. In combination with digital elevation models (DEMs) with near global coverage, such parameters can in principle be derived for all digital glacier outlines. In this study we investigate the suitability of the SRTM DEM and the ASTER GDEM for the compilation of seven glacier-specific topographic parameters for a sample of 1786 Swiss glaciers. Both DEMs were applied in two different resolutions, and the obtained parameter values were compared to values derived from the Swiss national DEM (DHM25), which served as the reference. The analysis revealed that large differences of the values can occur on individual glaciers, but they average out for larger glacier samples. Parameters that depend on a single DEM value (e.g. minimum or maximum elevation) show a larger variability than parameters that are averaged over the entire glacier area (e.g. mean elevation or mean slope). Besides artifacts, also changes due to different acquisition dates and techniques (radar, optical) have an influence on the inventory parameters. Although the SRTM DEM yielded slightly better results than the ASTER GDEM, both DEMs are suitable for the compilation of topographic parameters in glacier inventories.

  9. Integration of 2-D hydraulic model and high-resolution lidar-derived DEM for floodplain flow modeling

    NASA Astrophysics Data System (ADS)

    Shen, D.; Wang, J.; Cheng, X.; Rui, Y.; Ye, S.

    2015-08-01

    The rapid progress of lidar technology has made the acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially in regards to the study of floodplain flow. However, high-resolution DEM data pose several disadvantages for floodplain modeling studies; e.g., the data sets contain many redundant interpolation points, large numbers of calculations are required to work with data, and the data do not match the size of the computational mesh. Two-dimensional (2-D) hydraulic modeling, which is a popular method for analyzing floodplain flow, offers highly precise elevation parameterization for computational mesh while ignoring much of the micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, thus enabling the calculation of flood water levels in DEM grid cells through local inverse distance-weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha detention basin, which is a flood storage area of Dongting Lake in China, by using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than simulations only with DEM.

  10. DEM simulation of particles of complex shapes using the multisphere method: Application for additive manufacturing

    NASA Astrophysics Data System (ADS)

    Parteli, Eric J. R.

    2013-06-01

    Additive manufacturing constitutes a promising production technology with potential application in a broad range of industrial areas. In this type of manufacturing process, objects are created from powder particles by adding layers of material upon one another through selectively melting particles from the powder bed. However, understanding the mechanical behavior of the powder during manufacturing as a function of material properties and particle shape is an essential pre-requisite for optimizing the production process. Here we develop a numerical tool for modeling the dynamics of powder particles during additive manufacturing based on force-based simulations by means of the Discrete Element Method (DEM). An existing DEM software (LIGGGHTS) is extended in order to study the transport of powder particles of complex geometric shapes through accounting for the boundary conditions inherent to the manufacturing process.

  11. The slowly varying corona from DEMs with the EVE data set

    NASA Astrophysics Data System (ADS)

    Schonfeld, Samuel J.; White, Stephen M.; Hock, Rachel A.; McAteer, James

    2016-05-01

    We present a differential emission measure (DEM) analysis of the slowly varying corona during the first half of solar cycle 24. Using the Extreme ultraviolet Variability Experiment (EVE) and the CHIANTI atomic line database we identify strong isolated iron emission lines present in the non-flaring spectrum with peak emissions covering the coronal temperature range of 5.7 < log(T) < 6.5. These lines are used to generate daily DEMs from EVE spectra to observe the long term variability of global coronal thermal properties. We discuss the choice of emission lines and the implications of this data set for the relationship between EUV and the F10.7 radio flux.

  12. Implementing a global DEM database on the sphere based on spherical wavelets

    NASA Astrophysics Data System (ADS)

    Zhao, Di; Zhao, Xuesheng; Shan, Shigang; Yao, Liangjun

    2010-11-01

    Wavelets have been proven to be an exceedingly powerful and highly efficient tool for fast computational algorithms in the fields of image data analysis and compression. Traditionally, the classical constructed wavelets are often employed to Euclidean infinite domains (such as the real line R and plane R2). In this paper, a spherical wavelet constructed for discrete DEM data based on the sphere is approached. Firstly, the discrete biorthogonal spherical wavelet with custom properties is constructed with the lifting scheme based on wavelet toolbox in Matlab. Then, the decomposition and reconstruction algorithms are proposed for efficient computation and the related wavelet coefficients are obtained. Finally, different precise images are displayed and analyzed at the different percentage of wavelet coefficients. The efficiency of this spherical wavelet algorithm is tested by using the GTOPO30 DEM data and the results show that at the same precision, the spherical wavelet algorithm consumes smaller storage volume. The results are good and acceptable.

  13. DEM modelling of the penetration process of the HP3 Mole

    NASA Astrophysics Data System (ADS)

    Poganski, J.; Kargl, G.; Schweiger, H.; Kömle, N.

    2015-10-01

    The NASA InSight Mission will be launched in March 2016 and will reach the surface of Mars roughly nine months later in the Elysium Region. One of the instruments on board is the HP³ Mole to measure the planetary heat flow. For this purpose it needs to penetrate five meters deep into the surface of Mars and thus offers also the possibility to analyse the soil properties. For the reconstruction of the soil behaviour and also to predict the mole performance and maximum reachable depth in advance, numerical simulations are used. The simulation of the soil during the hammering process of the HP³ Mole requires a substantial numerical effort due to the local high dynamics and large soil deformations that occur. After comparing the capability of various simulation methods (FEM, MPM and DEM) a discrete element method (DEM) was chosen.

  14. Study of interactions between sediment particles in sheet flow using CFD-DEM

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Xiao, Heng

    2015-11-01

    CFD-DEM simulation is a promising approach in the study of sediment transport. However, the study of sediment transport in sheet flow is still lacking. In this work, a parallelized CFD-DEM solver sediFoam, which has been extensively validated, is applied to the study of sediment transport. Numerical simulations of sediment bed of different characteristics under various waves are studied and compared with the results obtained in the literature, including sediment transport flux, solid volume fraction, and movable bed height. The micro-structures (e.g., contact network) and macroscopic solid phase stresses of the sediment bed are analyzed to gain insight into the inter-particle interactions during the transport process. Additionally, the microstructural properties and solid phase stresses in wave-induced sheet flow are compared to those obtained in unidirectional currents, and significant difference is observed.

  15. DEM generation and tidal deformation detection for sulzberger ice shelf, West Antarctica using SAR interferometry

    USGS Publications Warehouse

    Baek, S.; Kwoun, Oh-Ig; Bassler, M.; Lu, Zhiming; Shum, C.K.; Dietrich, R.

    2004-01-01

    In this study we generated a relative Digital Elevation Model (DEM) over the Sulzberger Ice Shelf, West Antarctica using ERS1/2 synthetic aperture radar (SAR) interferometry data. Four repeat pass differential interferograms are used to find the grounding zone and to classify the study area. An interferometrically derived DEM is compared with laser altimetry profile from ICESat. Standard deviation of the relative height difference is 5.12 m and 1.34 m in total length of the profile and at the center of the profile respectively. The magnitude and the direction of tidal changes estimated from interferogram are compared with those predicted tidal differences from four ocean tide models. Tidal deformation measured in InSAR is -16.7 cm and it agrees well within 3 cm with predicted ones from tide models.

  16. Coupled DEM-CFD Investigation of Granular Transport in a Fluid Channel

    NASA Astrophysics Data System (ADS)

    Zhao, T.; Dai, F.; Xu, N. W.

    2015-09-01

    This paper presents three dimensional numerical investigations of granular transport in fluids, analysed by the Discrete Element Method (DEM) coupled with Computational Fluid Mechanics (CFD). By employing this model, the relevance of flow velocity and granular depositional morphology has been clarified. The larger the flow velocity is, the further distance the grains can be transported to. In this process, the segregation of solid grains has been clearly identified. This research reveals that coarse grains normally accumulate near the grain source region, while the fine grains can be transported to the flow front. Regardless of the different flow velocities used in these simulations, the intensity of grains segregation remains almost unchanged. The results obtained from the DEM-CFD coupled simulations can reasonably explain the grain transport process occurred in natural environments, such as river scouring, evolution of river/ocean floor, deserts and submarine landslides.

  17. A hybrid FEM-DEM approach to the simulation of fluid flow laden with many particles

    NASA Astrophysics Data System (ADS)

    Casagrande, Marcus V. S.; Alves, José L. D.; Silva, Carlos E.; Alves, Fábio T.; Elias, Renato N.; Coutinho, Alvaro L. G. A.

    2016-01-01

    In this work we address a contribution to the study of particle laden fluid flows in scales smaller than TFM (two-fluid models). The hybrid model is based on a Lagrangian-Eulerian approach. A Lagrangian description is used for the particle system employing the discrete element method (DEM), while a fixed Eulerian mesh is used for the fluid phase modeled by the finite element method (FEM). The resulting coupled DEM-FEM model is integrated in time with a subcycling scheme. The aforementioned scheme is applied in the simulation of a seabed current to analyze which mechanisms lead to the emergence of bedload transport and sediment suspension, and also quantify the effective viscosity of the seabed in comparison with the ideal no-slip wall condition. A simulation of a salt plume falling in a fluid column is performed, comparing the main characteristics of the system with an experiment.

  18. High resolution DEM from Tandem-X interferometry: an accurate tool to characterize volcanic activity

    NASA Astrophysics Data System (ADS)

    Albino, Fabien; Kervyn, Francois

    2013-04-01

    Tandem-X mission was launched by the German agency (DLR) in June 2010. It is a new generation high resolution SAR sensor mainly dedicated to topographic applications. For the purpose of our researches focused on the study of the volcano-tectonic activity in the Kivu Rift area, a set of Tandem-X bistatic radar images were used to produce a high resolution InSAR DEM of the Virunga Volcanic Province (VVP). The VVP is part of the Western branch of the African rift, situated at the boundary between D.R. Congo, Rwanda and Uganda. It has two highly active volcanoes, Nyiragongo and Nyamulagira. A first task concerns the quantitative assessment of the vertical accuracy that can be achieved with these new data. The new DEMs are compared to other space borne datasets (SRTM, ASTER) but also to field measurements given by differential GPS. Multi-temporal radar acquisitions allow us to produce several DEM of the same area. This appeared to be very useful in the context of an active volcanic context where new geomorphological features (faults, fissures, volcanic cones and lava flows) appear continuously through time. For example, since the year 2000, time of the SRTM acquisition, we had one eruption at Nyiragongo (2002) and six eruptions at Nyamulagira (2001, 2002, 2004, 2006, 2010 and 2011) which all induce large changes in the landscape with the emplacement of new lava fields and scoria cones. From our repetitive Tandem-X DEM production, we have a tool to identify and also quantify in term of size and volume all the topographic changes relative to this past volcanic activity. These parameters are high value information to improve the understanding of the Virunga volcanoes; the accurate estimation of erupted volume and knowledge of structural features associated to past eruptions are key parameters to understand the volcanic system, to ameliorate the hazard assessment, and finally contribute to risk mitigation in a densely populated area.

  19. Prophylaxe beim hereditären Angioödem (HAE) mit C1-Inhibitormangel.

    PubMed

    Greve, Jens; Strassen, Ulrich; Gorczyza, Marina; Dominas, Nina; Frahm, Uta-Marie; Mühlberg, Heike; Wiednig, Michaela; Zampeli, Vasiliki; Magerl, Markus

    2016-03-01

    Das hereditäre Angioödem (engl.: hereditary angioedema, HAE) ist eine seltene angeborene Erkrankung, die durch wiederkehrende Episoden subkutaner oder submuköser Ödeme charakterisiert ist. Kehlkopf-Manifestationen können lebensbedrohlich sein. In den meisten Fällen kann die Erkrankung mit einem On-Demand-Ansatz angemessen behandelt werden - in einigen Fällen ist jedoch eine Kurz- oder Langzeitprophylaxe angebracht. Attenuierte Androgene waren einmal das Standardmedikament; sie werden jedoch mit erheblichen Nebenwirkungen in Verbindung gebracht und sind in den deutschsprachigen Ländern der EU nicht mehr kommerziell erhältlich. Zurzeit werden sie von wirksameren und besser verträglichen Therapien wie C1-Esterase-Inhibitoren, dem Kallikrein-Inhibitor Ecallantid und dem B2-Rezeptorantagonisten Icatibant verdrängt, welche kürzlich auf dem Markt zugelassen wurden. Diese neuen Medikamente hatten einen erheblichen Einfluss, insbesondere auf die Indikationsstellung und das Vorgehen bei einer Langzeitprophylaxe. Nach den neuesten internationalen Konsenspapieren und unserer eigenen Erfahrung sind selbstverabreichte C1-Inhibitoren nun die erste Option bei der Langzeitprophylaxe. Die Entscheidung für eine Prophylaxe sollte nicht länger auf der Grundlage einzelner Parameter wie der Häufigkeit der Anfälle getroffen werden, sondern auf einer adäquaten allgemeinen Krankheitskontrolle, einschließlich der Lebensqualität. Zurzeit werden weitere Medikamente entwickelt, welche zu weiteren Veränderungen bei den Behandlungsalgorithmen des HAE führen könnten. PMID:26972190

  20. a Hadoop-Based Algorithm of Generating dem Grid from Point Cloud Data

    NASA Astrophysics Data System (ADS)

    Jian, X.; Xiao, X.; Chengfang, H.; Zhizhong, Z.; Zhaohui, W.; Dengzhong, Z.

    2015-04-01

    Airborne LiDAR technology has proven to be the most powerful tools to obtain high-density, high-accuracy and significantly detailed surface information of terrain and surface objects within a short time, and from which the Digital Elevation Model of high quality can be extracted. Point cloud data generated from the pre-processed data should be classified by segmentation algorithms, so as to differ the terrain points from disorganized points, then followed by a procedure of interpolating the selected points to turn points into DEM data. The whole procedure takes a long time and huge computing resource due to high-density, that is concentrated on by a number of researches. Hadoop is a distributed system infrastructure developed by the Apache Foundation, which contains a highly fault-tolerant distributed file system (HDFS) with high transmission rate and a parallel programming model (Map/Reduce). Such a framework is appropriate for DEM generation algorithms to improve efficiency. Point cloud data of Dongting Lake acquired by Riegl LMS-Q680i laser scanner was utilized as the original data to generate DEM by a Hadoop-based algorithms implemented in Linux, then followed by another traditional procedure programmed by C++ as the comparative experiment. Then the algorithm's efficiency, coding complexity, and performance-cost ratio were discussed for the comparison. The results demonstrate that the algorithm's speed depends on size of point set and density of DEM grid, and the non-Hadoop implementation can achieve a high performance when memory is big enough, but the multiple Hadoop implementation can achieve a higher performance-cost ratio, while point set is of vast quantities on the other hand.

  1. DEM simulation for landslide process and barrier dam formation on the mountainous highway

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Kai; Lee, Ching-Fang; Wei, Lun-Wei; Chou, Hsien-Ter; Chu, Sheng-Shin

    2013-04-01

    A barrier dam induced by landslide in Hanyuan, Sichuan, China occurred on August 6th, 2009. An approximately 9x106 m3 sliding mass dumped rapidly into the Dadu River and buried the new highway S306. After the major landslide, the large-scale debris mass caused the secondary shallow avalanche at the opposite bank and even formed a barrier dam with a length of 100 m and a height of 40 m crossing the Dadu River. The corresponding backwater effect submerged the upstream village over 10 km. This study adopts DEM simulation to examine the dynamic landslide process and understand the triggering mechanism of barrier dam. Based on the numerical investigation, the results showed that the sliding behavior can be classified into three stages: first initial stage with high potential energy, primary sliding with fast velocity, and final stage of impacting river channel. In addition, the energy balance principle for dynamic landslide is also verified with the DEM simulation. With respect to the consideration of hazard managements, one hopes the result can assist engineers to evaluate dangerous potential region and plan protecting construction on the steep mountainous area. Keywords:Landslide, barrier dam, DEM, dynamic process, backwater.

  2. A Review of Discrete Element Method (DEM) Particle Shapes and Size Distributions for Lunar Soil

    NASA Technical Reports Server (NTRS)

    Lane, John E.; Metzger, Philip T.; Wilkinson, R. Allen

    2010-01-01

    As part of ongoing efforts to develop models of lunar soil mechanics, this report reviews two topics that are important to discrete element method (DEM) modeling the behavior of soils (such as lunar soils): (1) methods of modeling particle shapes and (2) analytical representations of particle size distribution. The choice of particle shape complexity is driven primarily by opposing tradeoffs with total number of particles, computer memory, and total simulation computer processing time. The choice is also dependent on available DEM software capabilities. For example, PFC2D/PFC3D and EDEM support clustering of spheres; MIMES incorporates superquadric particle shapes; and BLOKS3D provides polyhedra shapes. Most commercial and custom DEM software supports some type of complex particle shape beyond the standard sphere. Convex polyhedra, clusters of spheres and single parametric particle shapes such as the ellipsoid, polyellipsoid, and superquadric, are all motivated by the desire to introduce asymmetry into the particle shape, as well as edges and corners, in order to better simulate actual granular particle shapes and behavior. An empirical particle size distribution (PSD) formula is shown to fit desert sand data from Bagnold. Particle size data of JSC-1a obtained from a fine particle analyzer at the NASA Kennedy Space Center is also fitted to a similar empirical PSD function.

  3. Dissipation consistent fabric tensor definition from DEM to continuum for granular media

    NASA Astrophysics Data System (ADS)

    Li, X. S.; Dafalias, Y. F.

    2015-05-01

    In elastoplastic soil models aimed at capturing the impact of fabric anisotropy, a necessary ingredient is a measure of anisotropic fabric in the form of an evolving tensor. While it is possible to formulate such a fabric tensor based on indirect phenomenological observations at the continuum level, it is more effective and insightful to have the tensor defined first based on direct particle level microstructural observations and subsequently deduce a corresponding continuum definition. A practical means able to provide such observations, at least in the context of fabric evolution mechanisms, is the discrete element method (DEM). Some DEM defined fabric tensors such as the one based on the statistics of interparticle contact normals have already gained widespread acceptance as a quantitative measure of fabric anisotropy among researchers of granular material behavior. On the other hand, a fabric tensor in continuum elastoplastic modeling has been treated as a tensor-valued internal variable whose evolution must be properly linked to physical dissipation. Accordingly, the adaptation of a DEM fabric tensor definition to a continuum constitutive modeling theory must be thermodynamically consistent in regards to dissipation mechanisms. The present paper addresses this issue in detail, brings up possible pitfalls if such consistency is violated and proposes remedies and guidelines for such adaptation within a recently developed Anisotropic Critical State Theory (ACST) for granular materials.

  4. Radiosensitization by misonidazole during recovery of cellular thiols following depletion by BSO or DEM

    SciTech Connect

    McNally, N.J.; Soranson, J.A.

    1989-05-01

    V79 cells have been depleted of their endogenous thiols by treatment with 100 microM BSO for 16-18 hr, or 0.5 mM DEM for 1 hr. The recovery of cellular thiols after removal of the drugs was determined by h.p.l.c. or flow cytometry and the sensitizer enhancement ratio for 100 microM misonidazole was measured as a function of time after removal of the drugs. The SER of 1.2 for control (hypoxic) cells increased to 1.8 for BSO treated (hypoxic) cells and 2.2 for DEM treated ones, when thiol levels were below 10% of controls. The SER and thiol levels returned to control values within 5 hr of removing DEM. After BSO there was little change during the first 5 hr and then a gradual return to normal values by 24 hrs. The major fall in the SER after removal of the drugs occurred as the cellular thiols increased to 60% of control values.

  5. Pre-2014 mudslides at Oso revealed by InSAR and multi-source DEM analysis

    NASA Astrophysics Data System (ADS)

    Kim, J. W.; Lu, Z.; QU, F.

    2014-12-01

    The landslide is a process that results in the downward and outward movement of slope-reshaping materials including rocks and soils and annually causes the loss of approximately $3.5 billion and tens of casualties in the United States. The 2014 Oso mudslide was an extreme event costing nearly 40 deaths and damaging civilian properties. Landslides are often unpredictable, but in many cases, catastrophic events are repetitive. Historic record in the Oso mudslide site indicates that there have been serial events in decades, though the extent of sliding events varied from time to time. In our study, the combination of multi-source DEMs, InSAR, and time-series InSAR analysis has enabled to characterize the Oso mudslide. InSAR results from ALOS PALSAR show that there was no significant deformation between mid-2006 and 2011. The combination of time-series InSAR analysis and old-dated DEM indicated revealed topographic changes associated the 2006 sliding event, which is confirmed by the difference of multiple LiDAR DEMs. Precipitation and discharge measurements before the 2006 and 2014 landslide events did not exhibit extremely anomalous records, suggesting the precipitation is not the controlling factor in determining the sliding events at Oso. The lack of surface deformation during 2006-2011 and weak correlation between the precipitation and the sliding event, suggest other factors (such as porosity) might play a critical role on the run-away events at this Oso and other similar landslides.

  6. A Seamless, High-Resolution, Coastal Digital Elevation Model (DEM) for Southern California

    USGS Publications Warehouse

    Barnard, Patrick L.; Hoover, Daniel

    2010-01-01

    A seamless, 3-meter digital elevation model (DEM) was constructed for the entire Southern California coastal zone, extending 473 km from Point Conception to the Mexican border. The goal was to integrate the most recent, high-resolution datasets available (for example, Light Detection and Ranging (Lidar) topography, multibeam and single beam sonar bathymetry, and Interferometric Synthetic Aperture Radar (IfSAR) topography) into a continuous surface from at least the 20-m isobath to the 20-m elevation contour. This dataset was produced to provide critical boundary conditions (bathymetry and topography) for a modeling effort designed to predict the impacts of severe winter storms on the Southern California coast (Barnard and others, 2009). The hazards model, run in real-time or with prescribed scenarios, incorporates atmospheric information (wind and pressure fields) with a suite of state-of-the-art physical process models (tide, surge, and wave) to enable detailed prediction of water levels, run-up, wave heights, and currents. Research-grade predictions of coastal flooding, inundation, erosion, and cliff failure are also included. The DEM was constructed to define the general shape of nearshore, beach and cliff surfaces as accurately as possible, with less emphasis on the detailed variations in elevation inland of the coast and on bathymetry inside harbors. As a result this DEM should not be used for navigation purposes.

  7. Shoreline Mapping with Integrated HSI-DEM using Active Contour Method

    NASA Astrophysics Data System (ADS)

    Sukcharoenpong, Anuchit

    Shoreline mapping has been a critical task for federal/state agencies and coastal communities. It supports important applications such as nautical charting, coastal zone management, and legal boundary determination. Current attempts to incorporate data from hyperspectral imagery to increase the efficiency and efficacy of shoreline mapping have been limited due to the complexity in processing its data as well as its inferior spatial resolution when compared to multispectral imagery or to sensors such as LiDAR. As advancements in remote-sensing technologies increase sensor capabilities, the ability to exploit the spectral formation carried in hyperspectral images becomes more imperative. This work employs a new approach to extracting shorelines from AVIRIS hyperspectral images by combination with a LiDAR-based DEM using a multiphase active contour segmentation technique. Several techniques, such as study of object spectra and knowledge-based segmentation for initial contour generation, have been employed in order to achieve a sub-pixel level of accuracy and maintain low computational expenses. Introducing a DEM into hyperspectral image segmentation proves to be a useful tool to eliminate misclassifications and improve shoreline positional accuracy. Experimental results show that mapping shorelines from hyperspectral imagery and a DEM can be a promising approach as many further applications can be developed to exploit the rich information found in hyperspectral imagery.

  8. Applying DEM-SRTM for reconstructing a late Quaternary paleodrainage in Amazonia

    NASA Astrophysics Data System (ADS)

    Hayakawa, Ericson H.; Rossetti, Dilce F.; Valeriano, Márcio M.

    2010-08-01

    Remote sensing is a particularly invaluable tool that has helped the detection of paleomorphologies produced by river dislocation in a variety of landscapes, which has contributed in reconstructing the geological evolution of many fluvial systems. This technique might provide useful information to discuss the evolution of large fluvial systems, in special those located in areas of difficult access where the acquisition of field data is difficult. Application of remote sensing for paleodrainage characterization in densely vegetated tropical areas is scarce in the literature. This work records processing of the Digital Elevation Model (DEM) derived from the Shuttle Radar Topography Mission (SRTM), which succeeded in revealing an ancient drainage complex of the Madeira River, one of the main Amazonas tributaries, where other remote sensing products failed the detection. Analysis of this paleodrainage and of its modern counterpart within the geological framework available for this region leads to propose that activity along pre-existent faults during the latest Quaternary would have promoted the southeastward dislocation of a nearly 200 km long segment of the Madeira River. During this process, an impressive paleodrainage network was left behind, which was only able to be detected using the DEM-SRTM. Application of this technique might be of great help to the detection of paleodrainage morphologies in densely vegetated areas similar to the Amazonas lowland. The dynamics of channel migration in this and many other large scale tropical river systems might benefit from the investigation based on data derived from DEM-SRTM.

  9. New Local DEM Derived from Combination of High-Resolution Viking Images and the High-Precision MOLA Data Set

    NASA Astrophysics Data System (ADS)

    Baratoux, D. B.; Delacourt, C. D.; Allemand, P. A.

    2001-03-01

    Topographic mapping is essential for understanding geologic processes. DEM of Mars can be computed from interpolated MOLA or stereophotogrammetric analysis of Viking images. We present a method to registrate and combine these two data sets.

  10. Validation Of DEM Data Dvied From World View 3 Stero Imagery For Low Elevation Majuro Atoll, Marchall Islands

    EPA Science Inventory

    The availability of surface elevation data for the Marshall Islands has been identified as a "massive" data gap for conducting vulnerability assessments and the subsequent development of climate change adaption strategies. Specifically, digital elevation model (DEM) data are nee...

  11. Validation of DEM Data Derived from World View 3 Stereo Imagery for Low Elevation Majuro Atoll, Marshall Islands

    EPA Science Inventory

    The availability of surface elevation data for the Marshall Islands has been identified as a massive data gap for conducting vulnerability assessments and the subsequent development of climate change adaption strategies. Specifically, digital elevation model (DEM) data are need...

  12. DEM modelling, vegetation characterization and mapping of aspen parkland rangeland using LIDAR data

    NASA Astrophysics Data System (ADS)

    Su, Guangquan

    Detailed geographic information system (GIS) studies on plant ecology, animal behavior and soil hydrologic characteristics across spatially complex landscapes require an accurate digital elevation model (DEM). Following interpolation of last return LIDAR data and creation of a LIDAR-derived DEM, a series of 260 points, stratified by vegetation type, slope gradient and off-nadir distance, were ground-truthed using a total laser station, GPS, and 27 interconnected benchmarks. Despite an overall mean accuracy of +2 cm across 8 vegetation types, it created a RMSE (square root of the mean square error) of 1.21 m. DEM elevations were over-estimated within forested areas by an average of 20 cm with a RMSE of 1.05 m, under-estimated (-12 cm, RMSE = 1.36 m) within grasslands. Vegetation type had the greatest influence on DEM accuracy, while off-nadir distance (P = 0.48) and slope gradient (P = 0.49) did not influence DEM accuracy; however, the latter factors did interact (P < 0.10) to effect accuracy. Vegetation spatial structure (i.e., physiognomy) including plant height, cover, and vertical or horizontal heterogeneity, are important factors influencing biodiversity. Vegetation over and understory were sampled for height, canopy cover, and tree or shrub density within 120 field plots, evenly stratified by vegetation formation (grassland, shrubland, and aspen forest). Results indicated that LIDAR data could be used for estimating the maximum height, cover, and density, of both closed and semi-open stands of aspen (P < 0.001). However, LIDAR data could not be used to assess understory (<1.5 m) height within aspen stands, nor grass height and cover. Recognition and mapping of vegetation types are important for rangelands as they provide a basis for the development and evaluation of management policies and actions. In this study, LIDAR data were found to be superior to digital classification schedules for their mapping accuracy in aspen forest and grassland, but not shrubland. No single classification schedule created a high classification accuracy map for all types; however, the integration of LIDAR data and digital images achieved maps with corresponding overall accuracies of 91% and 83.9% with 3 and 8 classes of vegetation.

  13. Combined DEM Extration Method from StereoSAR and InSAR

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Zhang, J. X.; Duan, M. Y.; Huang, G. M.; Yang, S. C.

    2015-06-01

    A pair of SAR images acquired from different positions can be used to generate digital elevation model (DEM). Two techniques exploiting this characteristic have been introduced: stereo SAR and interferometric SAR. They permit to recover the third dimension (topography) and, at the same time, to identify the absolute position (geolocation) of pixels included in the imaged area, thus allowing the generation of DEMs. In this paper, StereoSAR and InSAR combined adjustment model are constructed, and unify DEM extraction from InSAR and StereoSAR into the same coordinate system, and then improve three dimensional positioning accuracy of the target. We assume that there are four images 1, 2, 3 and 4. One pair of SAR images 1,2 meet the required conditions for InSAR technology, while the other pair of SAR images 3,4 can form stereo image pairs. The phase model is based on InSAR rigorous imaging geometric model. The master image 1 and the slave image 2 will be used in InSAR processing, but the slave image 2 is only used in the course of establishment, and the pixels of the slave image 2 are relevant to the corresponding pixels of the master image 1 through image coregistration coefficient, and it calculates the corresponding phase. It doesn't require the slave image in the construction of the phase model. In Range-Doppler (RD) model, the range equation and Doppler equation are a function of target geolocation, while in the phase equation, the phase is also a function of target geolocation. We exploit combined adjustment model to deviation of target geolocation, thus the problem of target solution is changed to solve three unkonwns through seven equations. The model was tested for DEM extraction under spaceborne InSAR and StereoSAR data and compared with InSAR and StereoSAR methods respectively. The results showed that the model delivered a better performance on experimental imagery and can be used for DEM extraction applications.

  14. Use of thermal infrared pictures for retrieving intertidal DEM by the waterline method: advantages and limitations

    NASA Astrophysics Data System (ADS)

    Gaudin, D.; Delacourt, C.; Allemand, P.

    2010-12-01

    Digital Elevation Models (DEM) of the intertidal zones have a growing interest for ecological and land development purposes. They are also a fundamental tool for monitoring current sedimentary movements in those low energy environments. Such DEMs have to be constructed with a centimetric resolution as the topographic changes are not predictable and as sediment displacements are weak. Direct construction of DEM by GPS in these muddy environment is difficult: photogrammetric techniques are not efficient on uniform coloured surfaces and terrestrial laser scans are difficult to stabilize on the mud, due to humidity. In this study, we propose to improve and to apply the waterline method to retrieve DEMs in intertidal zones. This technique is based on monitoring accurately the boundary between sand and water during a whole tide rise with thermal infrared images. The DEM is made by stacking all these lines calibrated by an immersed pressure sensor. Using thermal infrared pictures, instead of optical ones, improves the detection of the waterline, since mud and water have very different responses to sun heating and a large emissivity contrast. However, temperature retrieving from thermal infrared data is not trivial, since the luminance of an object is the sum of a radiative part and a reflexive part, whose relative proportions are given by the emissivity. In the following equation, B accounts for the equivalent blackbody luminance, and Linc is the incident luminance : Ltot}=L{rad}+L_{refl=ɛ B+(1-ɛ )Linc The infrared waterline technique has been used for the monitoring of a beach located on the Aber Benoit, 8.5km away from the open sea. The site is mainly constituted of mud, and waves are very small (less than one centimeter high), which are the ideal conditions for using the waterline method. A few measurements have been made to make differential heigh maps of sediments. We reached a mean resolution of 2cm and a vertical accuracy better than one centimeter. The results have been validated by terrestrial laser scanning. We discuss here the main sources of error due to the very high resolution and suggest methods to minimize its effects : diffuse limit between water and mud due to the heating delay, the difficulty to precisely calibrate thermal camera optics, effects of light reflexion from clouds or cliffs. This technique may be used in the future with satellites, planes or unmanned platforms images, to cover extended areas.

  15. Coastal Digital Elevation Models (DEMs) for tsunami hazard assessment on the French coasts

    NASA Astrophysics Data System (ADS)

    Maspataud, Aurélie; Biscara, Laurie; Hébert, Hélène; Schmitt, Thierry; Créach, Ronan

    2015-04-01

    Building precise and up-to-date coastal DEMs is a prerequisite for accurate modeling and forecasting of hydrodynamic processes at local scale. Marine flooding, originating from tsunamis, storm surges or waves, is one of them. Some high resolution DEMs are being generated for multiple coast configurations (gulf, embayment, strait, estuary, harbor approaches, low-lying areas…) along French Atlantic and Channel coasts. This work is undertaken within the framework of the TANDEM project (Tsunamis in the Atlantic and the English ChaNnel: Definition of the Effects through numerical Modeling) (2014-2017). DEMs boundaries were defined considering the vicinity of French civil nuclear facilities, site effects considerations and potential tsunamigenic sources. Those were identified from available historical observations. Seamless integrated topographic and bathymetric coastal DEMs will be used by institutions taking part in the study to simulate expected wave height at regional and local scale on the French coasts, for a set of defined scenarii. The main tasks were (1) the development of a new capacity of production of DEM, (2) aiming at the release of high resolution and precision digital field models referred to vertical reference frameworks, that require (3) horizontal and vertical datum conversions (all source elevation data need to be transformed to a common datum), on the basis of (4) the building of (national and/or local) conversion grids of datum relationships based on known measurements. Challenges in coastal DEMs development deal with good practices throughout model development that can help minimizing uncertainties. This is particularly true as scattered elevation data with variable density, from multiple sources (national hydrographic services, state and local government agencies, research organizations and private engineering companies) and from many different types (paper fieldsheets to be digitized, single beam echo sounder, multibeam sonar, airborne laser bathymetric and topographic data, …) were gathered. Consequently, datasets were first assessed internally for both quality and accuracy and then externally with other to ensure consistency and gradual topographic/bathymetric transitioning along limits of the datasets. The heterogeneous ages of the input data also stress the importance of taking into account the temporal variability of bathymetric features, especially in the active areas (sandbanks, estuaries, channels). Locally, gaps between marine (hydrographic surveys) and terrestrial (topographic LIDAR) data have required the introduction of new methods and tools to solve interpolation. Through these activities the goal is to improve the production line and to enhance tools and procedures used for the improvement of processing, validation and qualification algorithms of bathymetric data, data collection work, automation of processing and integration process for conception of improved both bathymetric and topographic DEMs, merging data collected. This work is supported by a French ANR program in the frame of "Investissements d'Avenir", under the grant ANR-11-RSNR-00023-01.

  16. On the COSMO-SkyMed Exploitation for Interferometric DEM Generation

    NASA Astrophysics Data System (ADS)

    Teresa, C. M.; Raffaele, N.; Oscar, N. D.; Fabio, B.

    2011-12-01

    DEM products for Earth observation space-borne applications are being to play a role of increasing importance due to the new generation of high resolution sensors (both optical and SAR). These new sensors demand elevation data for processing and, on the other hand, they provide new possibilities for DEM generation. Till now, for what concerns interferometric DEM, the Shuttle Radar Topography Mission (SRTM) has been the reference product for scientific applications all over the world. SRTM mission [1] had the challenging goal to meet the requirements for a homogeneous and reliable DEM fulfilling the DTED-2 specifications. However, new generation of high resolution sensors (including SAR) pose new requirements for elevation data in terms of vertical precision and spatial resolution. DEM are usually used as ancillary input in different processing steps as for instance geocoding and Differential SAR Interferometry. In this context, the recent SAR missions of DLR (TerraSAR-X and TanDEM-X) and ASI (COSMO-SkyMed) can play a promising role thanks to their high resolution both in space and time. In particular, the present work investigates the potentialities of the COSMO/SkyMed (CSK) constellation for ground elevation measurement with particular attention devoted to the impact of the improved spatial resolution wrt the previous SAR sensors. The recent scientific works, [2] and [3], have shown the advantages of using CSK in the monitoring of terrain deformations caused by landslides, earthquakes, etc. On the other hand, thanks to the high spatial resolution, CSK appears to be very promising in monitoring man-made structures, such as buildings, bridges, railways and highways, thus enabling new potential applications (urban applications, precise DEM, etc.). We present results obtained by processing both SPOTLIGHT and STRIPMAP acquisitions through standard SAR Interferometry as well as multi-pass interferometry [4] with the aim of measuring ground elevation. Acknowledgments Work supported by ASI (Agenzia Spaziale Italiana) in the framework of the project "AO-COSMO Project ID-1462 - Feasibility of possible use of COSMO/SkyMed in bistatic SAR Earth observation - ASI Contract I/063/09/0". References [1] B. Rabus, M. Eineder, A. Roth, and R. Bamler, "The Shuttle Radar Topography Mission-A new class of digital elevation models acquired by spaceborne radar," ISPRS J. Photogramm. Remote Sens., vol. 57, no. 4, pp. 241-262, Feb. 2003. [2] F. BOVENGA, D. O. NITTI, R. NUTRICATO, M. T. CHIARADIA, "C- and X-band multi-pass InSAR analysis over Alpine and Apennine regions". In Proceedings of the European Space Agency Living Planet Symposium, June 28 - July 2, 2010, Bergen, Norway. [3] D. REALE, D. O. NITTI, D. PEDUTO, R. NUTRICATO, F. BOVENGA, G. FORNARO, "Postseismic Deformation Monitoring With The COSMO/SKYMED Constellation". IEEE Geoscience Remote Sensing Letters, 2011. DOI: 10.1109/LGRS.2010.2100364 [4] Nitti, D.O., Nutricato, R., Bovenga, F., Conte, D., Guerriero, L. & Milillo, G., "Quantitative Analysis of Stripmap And Spotlight SAR Interferometry with CosmoSkyMed constellation.", Proceedings if IEEE IGARSS 2009, July 13-17, 2009. Cape Town, South Africa.

  17. Creating High Quality DEMs of Large Scale Fluvial Environments Using Structure-from-Motion

    NASA Astrophysics Data System (ADS)

    Javernick, L. A.; Brasington, J.; Caruso, B. S.; Hicks, M.; Davies, T. R.

    2012-12-01

    During the past decade, advances in survey and sensor technology have generated new opportunities to investigate the structure and dynamics of fluvial systems. Key geomatic technologies include the Global Positioning System (GPS), digital photogrammetry, LiDAR, and terrestrial laser scanning (TLS). The application of such has resulted in a profound increase in the dimensionality of topographic surveys - from cross-sections to distributed 3d point clouds and digital elevation models (DEMs). Each of these technologies have been used successfully to derive high quality DEMs of fluvial environments; however, they often require specialized and expensive equipment, such as a TLS or large format camera, bespoke platforms such as survey aircraft, and consequently make data acquisition prohibitively expensive or highly labour intensive, thus restricting the extent and frequency of surveys. Recently, advances in computer vision and image analysis have led to development of a novel photogrammetric approach that is fully automated and suitable for use with simple compact (non-metric) cameras. In this paper, we evaluate a new photogrammetric method, Structure-from-Motion (SfM), and demonstrate how this can be used to generate DEMs of comparable quality to airborne LiDAR, using consumer grade cameras at low costs. Using the SfM software PhotoScan (version 0.8.5), high quality DEMs were produced for a 1.6 km reach and a 3.3 km reach of the braided Ahuriri River, New Zealand. Photographs used for DEM creation were acquired from a helicopter flying at 600 m and 800 m above ground level using a consumer grade 10.1mega-pixel, non-metric digital camera, resulting in object space resolution imagery of 0.12 m and 0.16 m respectively. Point clouds for the two study reaches were generated using 147 and 224 photographs respectively, and were extracted automatically in an arbitrary coordinate system; RTK-GPS located ground control points (GCPs) were used to define a 3d non-linear transformation to convert the point clouds to the absolute NZTM coordinate system, with average errors of 0.06 m in the horizontal and 0.11 m in the vertical dimensions. The final point clouds extracted had typical point spacings of 0.25 m, well above the metric resolution of airborne LiDAR. To improve data handling, the final point cloud was decimated to point spacings of 0.5 m using a recently developed gridding procedure (Rychkov, Brasington, & Vericat, 2012), and finally converted into a DEM using a Delaunay constrained TIN in ArcGIS. Results reveal SfM's ability to produce high quality terrain products of large scale fluvial environments that can outperform LiDAR, and can potentially compare with TLS. PhotoScan offers a straightforward method to generate, transform, and export DEMs that requires little user knowledge of photogrammetric processes. Further, the affordability and reduced field work offer low budget researchers the ability to produce repeat surveys for in-depth temporal studies. Funding supported by the New Zealand Department of Conservation.

  18. Coupling photogrammetric data with DFN-DEM model for rock slope hazard assessment

    NASA Astrophysics Data System (ADS)

    Donze, Frederic; Scholtes, Luc; Bonilla-Sierra, Viviana; Elmouttie, Marc

    2013-04-01

    Structural and mechanical analyses of rock mass are key components for rock slope stability assessment. The complementary use of photogrammetric techniques [Poropat, 2001] and coupled DFN-DEM models [Harthong et al., 2012] provides a methodology that can be applied to complex 3D configurations. DFN-DEM formulation [Scholtès & Donzé, 2012a,b] has been chosen for modeling since it can explicitly take into account the fracture sets. Analyses conducted in 3D can produce very complex and unintuitive failure mechanisms. Therefore, a modeling strategy must be established in order to identify the key features which control the stability. For this purpose, a realistic case is presented to show the overall methodology from the photogrammetry acquisition to the mechanical modeling. By combining Sirovision and YADE Open DEM [Kozicki & Donzé, 2008, 2009], it can be shown that even for large camera to rock slope ranges (tested about one kilometer), the accuracy of the data are sufficient to assess the role of the structures on the stability of a jointed rock slope. In this case, on site stereo pairs of 2D images were taken to create 3D surface models. Then, digital identification of structural features on the unstable block zone was processed with Sirojoint software [Sirovision, 2010]. After acquiring the numerical topography, the 3D digitalized and meshed surface was imported into the YADE Open DEM platform to define the studied rock mass as a closed (manifold) volume to define the bounding volume for numerical modeling. The discontinuities were then imported as meshed planar elliptic surfaces into the model. The model was then submitted to gravity loading. During this step, high values of cohesion were assigned to the discontinuities in order to avoid failure or block displacements triggered by inertial effects. To assess the respective role of the pre-existing discontinuities in the block stability, different configurations have been tested as well as different degree of fracture persistency in order to enhance the possible contribution of rock bridges on the failure surface development. It is believed that the proposed methodology can bring valuable complementary information for rock slope stability analysis in presence of complex fractured system for which classical "Factor of Safety" is difficult to express. References • Harthong B., Scholtès L. & F.V. Donzé, Strength characterization of rock masses, using a coupled DEM-DFN model, Geophysical Journal International, doi: 10.1111/j.1365-246X.2012.05642.x, 2012. • Kozicki J & Donzé FV. YADE-OPEN DEM: an open--source software using a discrete element method to simulate granular material, Engineering Computations, 26(7):786-805, 2009 • Kozicki J, Donzé FV. A new open-source software developed for numerical simulations using discrete modeling methods, Comp. Meth. In Appl. Mech. And Eng. 197:4429-4443, 2008. • Poropat, G.V., New methods for mapping the structure of rock masses. In Proceedings, Explo 2001, Hunter Valley, New South Wales, 28-31 October 2001, pp. 253-260, 2001. • Scholtès, L. & Donzé FV. Modelling progressive failure in fractured rock masses using a 3D discrete element method, International Journal of Rock Mechanics and Mining Sciences, 52:18-30, 2012a. • Scholtès, L. & Donzé, F.-V., DEM model for soft and hard rocks: role of grain interlocking on strength, J. Mech. Phys. Solids, doi: 10.1016/j.jmps.2012.10.005, 2012b. • Sirovision, Commonwealth Scientific and Industrial Research Organisation CSIRO, Siro3D Sirovision 3D Imaging Mapping System Manual Version 4.1, 2010

  19. A new 100-m Digital Elevation Model of the Antarctic Peninsula derived from ASTER Global DEM: methods and accuracy assessment

    NASA Astrophysics Data System (ADS)

    Cook, A. J.; Murray, T.; Luckman, A.; Vaughan, D. G.; Barrand, N. E.

    2012-10-01

    A high resolution surface topography Digital Elevation Model (DEM) is required to underpin studies of the complex glacier system on the Antarctic Peninsula. A complete DEM with better than 200 m pixel size and high positional and vertical accuracy would enable mapping of all significant glacial basins and provide a dataset for glacier morphology analyses. No currently available DEM meets these specifications. We present a new 100-m DEM of the Antarctic Peninsula (63-70° S), based on ASTER Global Digital Elevation Model (GDEM) data. The raw GDEM products are of high-quality on the rugged terrain and coastal-regions of the Antarctic Peninsula and have good geospatial accuracy, but they also contain large errors on ice-covered terrain and we seek to minimise these artefacts. Conventional data correction techniques do not work so we have developed a method that significantly improves the dataset, smoothing the erroneous regions and hence creating a DEM with a pixel size of 100 m that will be suitable for many glaciological applications. We evaluate the new DEM using ICESat-derived elevations, and perform horizontal and vertical accuracy assessments based on GPS positions, SPOT-5 DEMs and the Landsat Image Mosaic of Antarctica (LIMA) imagery. The new DEM has a mean elevation difference of -4 m (± 25 m RMSE) from ICESat (compared to -13 m mean and ±97 m RMSE for the original ASTER GDEM), and a horizontal error of less than 2 pixels, although elevation accuracies are lower on mountain peaks and steep-sided slopes. The correction method significantly reduces errors on low relief slopes and therefore the DEM can be regarded as suitable for topographical studies such as measuring the geometry and ice flow properties of glaciers on the Antarctic Peninsula. The DEM is available for download from the NSIDC website: http://nsidc.org/data/nsidc-0516.html (doi:10.5060/D47P8W9D).

  20. Stream Morphologic Measurements from Airborne Laser Swath Mapping: Comparisons with Field Surveys, Traditional DEMs, and Aerial Photographs

    NASA Astrophysics Data System (ADS)

    Snyder, N. P.; Schultz, L. L.

    2005-12-01

    Precise measurement of stream morphology over entire watersheds is one of the great research opportunities provided by airborne laser swath mapping (ALSM). ALSM surveys allow for rapid quantification of factors, such as channel width and gradient, that control stream hydraulic and ecologic properties. We compare measurements from digital elevation models (DEMs) derived from ALSM data collected by the National Center for Airborne Laser Mapping (NCALM) to field surveys, traditional DEMs (rasterized from topographic maps), and aerial photographs. The field site is in the northern Black Mountains in arid Death Valley National Park (California). The area is unvegetated, and therefore is excellent for testing DEM analysis methods because the ALSM data required minimal filtering, and the resulting DEM contains relatively few unphysical sinks. Algorithms contained in geographic information systems (GIS) software used to extract stream networks from DEMs yield best results where streams are steep enough for resolvable pixel-to-pixel elevation change, and channel width is on the order of pixel resolution. This presents a new challenge with ALSM-derived DEMs because the pixel size (1 m) is often an order of magnitude or more smaller than channel width. We find the longitudinal profile of Gower Gulch in the northern Black Mountains (~4 km total length) extracted using the ALSM DEM and a flow accumulation algorithm is 14% longer than a traditional 10-m DEM, and 13% longer than a field survey. These differences in length (and therefore gradient) are due to the computed channel path following small-scale topographic variations within the channel bottom that are not relevant during high flows. However, visual analysis of shaded-relief images created from high-resolution ALSM data is an excellent method for digitizing channel banks and thalweg paths. We used these lines to measure distance, elevation, and width. In Gower Gulch, the algorithm-derived profile is 10% longer than that measured by tracing the thalweg on the ALSM imagery. By obtaining longitudinal profiles and widths from the same dataset, ALSM represents a major step forward from previous remote-sensing morphologic analyses, in which profiles are measured using traditional DEMs or topographic maps, and widths from aerial photographs. These combined analyses would be particularly powerful in regions of low relief and/or wide channels were traditional DEMs have limited utility.

  1. Computer vision: automating DEM generation of active lava flows and domes from photos

    NASA Astrophysics Data System (ADS)

    James, M. R.; Varley, N. R.; Tuffen, H.

    2012-12-01

    Accurate digital elevation models (DEMs) form fundamental data for assessing many volcanic processes. We present a photo-based approach developed within the computer vision community to produce DEMs from a consumer-grade digital camera and freely available software. Two case studies, based on the Volcán de Colima lava dome and the Puyehue Cordón-Caulle obsidian flow, highlight the advantages of the technique in terms of the minimal expertise required, the speed of data acquisition and the automated processing involved. The reconstruction procedure combines structure-from-motion and multi-view stereo algorithms (SfM-MVS) and can generate dense 3D point clouds (millions of points) from multiple photographs of a scene taken from different positions. Processing is carried out by automated software (e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/). SfM-MVS reconstructions are initally un-scaled and un-oriented so additional geo-referencing software has been developed. Although this step requires the presence of some control points, the SfM-MVS approach has significantly easier image acquisition and control requirements than traditional photogrammetry, facilitating its use in a broad range of difficult environments. At Colima, the lava dome surface was reconstructed from recent and archive images taken from light aircraft over flights (2007-2011). Scaling and geo-referencing was carried out using features identified in web-sourced ortho-imagery obtained as a basemap layer in ArcMap - no ground-based measurements were required. Average surface measurement densities are typically 10-40 points per m2. Over mean viewing distances of ~500-2500 m (for different surveys), RMS error on the control features is ~1.5 m. The derived DEMs (with 1-m grid resolution) are sufficient to quantify volumetric change, as well as to highlight the structural evolution of the upper surface of the dome following an explosion in June 2011. At Puyehue Cordón-Caulle, images of the active lava flow were taken on foot from a ridge overlooking the flow. To assess the evolution of the flow front, two DEMs were derived from collections of ~400 images taken on different days. To scale and geo-reference the data, one image sequence was accompanied by simultaneous collection of a GPS track using a consumer handheld GPS unit; no control points were used. The second survey was then scaled and georeferenced to the first, using features identifiable in both image sets, giving an RMS error of ~0.22 m. DEM comparison then allows advance rates and mechanisms to be identified, and comparisons drawn with emplacement processes of basaltic flows. In both case studies, the SfM-MVS approach allowed DEM generation when access or lack of dedicated surveying equipment and expertise prevented standard techniques from being deployed.olima dome 2011: 3D point cloud data

  2. High mobility of large mass movements: a study by means of FEM/DEM simulations

    NASA Astrophysics Data System (ADS)

    Manzella, I.; Lisjak, A.; Grasselli, G.

    2013-12-01

    Large mass movements, such as rock avalanches and large volcanic debris avalanches are characterized by extremely long propagation, which cannot be modelled using normal sliding friction law. For this reason several studies and theories derived from field observation, physical theories and laboratory experiments, exist to try to explain their high mobility. In order to investigate more into deep some of the processes recalled by these theories, simulations have been run with a new numerical tool called Y-GUI based on the Finite Element-Discrete Element Method FEM/DEM. The FEM/DEM method is a numerical technique developed by Munjiza et al. (1995) where Discrete Element Method (DEM) algorithms are used to model the interaction between different solids, while Finite Element Method (FEM) principles are used to analyze their deformability being also able to explicitly simulate material sudden loss of cohesion (i.e. brittle failure). In particular numerical tests have been run, inspired by the small-scale experiments done by Manzella and Labiouse (2013). They consist of rectangular blocks released on a slope; each block is a rectangular discrete element made of a mesh of finite elements enabled to fragment. These simulations have highlighted the influence on the propagation of block packing, i.e. whether the elements are piled into geometrical ordinate structure before failure or they are chaotically disposed as a loose material, and of the topography, i.e. whether the slope break is smooth and regular or not. In addition the effect of fracturing, i.e. fragmentation, on the total runout have been studied and highlighted.

  3. THE H{alpha} DIAGNOSTIC OF ELECTRON HEATING: THE CASE OF DEM L71

    SciTech Connect

    Rakowski, Cara E.; Ghavamian, Parviz; Laming, J. Martin

    2009-05-10

    Recently, the mechanisms and extent of immediate postshock heating of electrons at collisionless shocks have been under intense investigation. Several recent studies have suggested that the ratio of electron to proton temperature at the shock front scales approximately as the inverse square of the shock velocity. A specific interpretation of this dependence was first introduced by Ghavamian et al., who suggested electron heating by lower-hybrid waves in a cosmic ray (CR) precursor as a possible mechanism behind such a relationship. The best line diagnostics for the electron to proton temperature ratio behind collisionless shocks in partially neutral gas are the combination of broad and narrow H{alpha} lines emitted in the immediate vicinity of the shock front. In this work, we present extensive long-slit spectroscopy of the H{alpha} emission in the blast wave shock of supernova remnant DEM L71. We chose this remnant for two main reasons. First, the shock velocities in DEM L71 span the range of speeds where the electron to proton temperature ratio varies most rapidly with shock speed. Second, previous Fabry-Perot scans of the H{alpha} line complex indicated broad-to-narrow flux ratios lower than existing models predicted, but the spectral coverage of those observations was not broad enough to reliably measure the background emission around the broad component H{alpha} line. Our new high-resolution (R {approx}> 1600) spectra of DEM L71 provide extensive coverage of the background near the H{alpha} line and confirm our earlier Fabry-Perot results of consistently low ({approx}<1) broad-to-narrow flux ratios. Here, we present results of these observations and also outline the first results from spectra of radiative portions of DEM L71. We compare our results to the latest models of H{alpha} profiles from collisionless shocks. We conclude that the most likely explanation for the low broad-to-narrow flux ratio is the ionization and excitation of neutrals by electrons heated in the extended CR precursor.

  4. A 3D DEM-LBM approach for the assessment of the quick condition for sands

    NASA Astrophysics Data System (ADS)

    Mansouri, M.; Delenne, J.-Y.; El Youssoufi, M. S.; Seridi, A.

    2009-09-01

    We present a 3D numerical model to assess the quick condition (the onset of the boiling phenomenon) in a saturated polydisperse granular material. We use the Discrete Element Method (DEM) to study the evolution of the vertical intergranular stress in a granular sample subjected to an increasing hydraulic gradient. The hydrodynamic forces on the grains of the sample are computed using the Lattice Boltzmann Method (LBM). The principal assumption used is that grains remain at rest until the boiling onset. We show that the obtained critical hydraulic gradient is close to that defined in classical soil mechanics. To cite this article: M. Mansouri et al., C. R. Mecanique 337 (2009).

  5. DEM L241, A SUPERNOVA REMNANT CONTAINING A HIGH-MASS X-RAY BINARY

    SciTech Connect

    Seward, F. D.; Charles, P. A.; Foster, D. L.; Dickel, J. R.; Romero, P. S.; Edwards, Z. I.; Perry, M.; Williams, R. M.

    2012-11-10

    A Chandra observation of the Large Magellanic Cloud supernova remnant DEM L241 reveals an interior unresolved source which is probably an accretion-powered binary. The optical counterpart is an O5III(f) star making this a high-mass X-ray binary with an orbital period likely to be of the order of tens of days. Emission from the remnant interior is thermal and spectral information is used to derive density and mass of the hot material. Elongation of the remnant is unusual and possible causes of this are discussed. The precursor star probably had mass >25 M {sub Sun}.

  6. Sensitivity of watershed attributes to spatial resolution and interpolation method of LiDAR DEMs in three distinct landscapes

    NASA Astrophysics Data System (ADS)

    Goulden, T.; Hopkinson, C.; Jamieson, R.; Sterling, S.

    2014-03-01

    This study investigates scaling relationships of watershed area and stream networks delineated from LiDAR DEMs. The delineations are tested against spatial resolution, including 1, 5, 10, 25, and 50 m, and interpolation method, including Inverse Distance Weighting (IDW), Moving Average (MA), Universal Kriging (UK), Natural Neighbor (NN), and Triangular Irregular Networks (TIN). Study sites include Mosquito Creek, Scotty Creek, and Thomas Brook, representing landscapes with high, low, and moderate change in elevation, respectively. Results show scale-dependent irregularities in watershed area due to spatial resolution at Thomas Brook and Mosquito Creek. The highest sensitivity of watershed area to spatial resolution occurred at Scotty Creek, due to high incidence of LiDAR sensor measurement error and subtle changes in elevation. Length of drainage networks did not show a scaling relationship with spatial resolution, due to algorithmic complications of the stream initiation threshold. Stream lengths of main channels at Thomas Brook and Mosquito Creek displayed systematic increases in length with increasing spatial resolution, described through an average fractal dimension of 1.059. The scaling relationship between stream length and DEM resolution allows estimation of stream lengths from low-resolution DEMs in the absence of high-resolution DEMs. Single stream validation at Thomas Brook showed the 1 m DEM produced the lowest length error and highest spatial accuracy, at 3.7% and 71.3%, respectively. Single stream validation at Mosquito Creek showed the 25 m DEM produced the lowest length error, and the 1 m DEM the highest spatial accuracy, at 0.6% and 61.0%, respectively.

  7. Reanalysis of the DEMS nested case-control study of lung cancer and diesel exhaust: suitability for quantitative risk assessment.

    PubMed

    Crump, Kenny S; Van Landingham, Cynthia; Moolgavkar, Suresh H; McClellan, Roger

    2015-04-01

    The International Agency for Research on Cancer (IARC) in 2012 upgraded its hazard characterization of diesel engine exhaust (DEE) to "carcinogenic to humans." The Diesel Exhaust in Miners Study (DEMS) cohort and nested case-control studies of lung cancer mortality in eight U.S. nonmetal mines were influential in IARC's determination. We conducted a reanalysis of the DEMS case-control data to evaluate its suitability for quantitative risk assessment (QRA). Our reanalysis used conditional logistic regression and adjusted for cigarette smoking in a manner similar to the original DEMS analysis. However, we included additional estimates of DEE exposure and adjustment for radon exposure. In addition to applying three DEE exposure estimates developed by DEMS, we applied six alternative estimates. Without adjusting for radon, our results were similar to those in the original DEMS analysis: all but one of the nine DEE exposure estimates showed evidence of an association between DEE exposure and lung cancer mortality, with trend slopes differing only by about a factor of two. When exposure to radon was adjusted, the evidence for a DEE effect was greatly diminished, but was still present in some analyses that utilized the three original DEMS DEE exposure estimates. A DEE effect was not observed when the six alternative DEE exposure estimates were utilized and radon was adjusted. No consistent evidence of a DEE effect was found among miners who worked only underground. This article highlights some issues that should be addressed in any use of the DEMS data in developing a QRA for DEE. PMID:25857246

  8. Reanalysis of the DEMS Nested Case-Control Study of Lung Cancer and Diesel Exhaust: Suitability for Quantitative Risk Assessment

    PubMed Central

    Crump, Kenny S; Van Landingham, Cynthia; Moolgavkar, Suresh H; McClellan, Roger

    2015-01-01

    The International Agency for Research on Cancer (IARC) in 2012 upgraded its hazard characterization of diesel engine exhaust (DEE) to “carcinogenic to humans.” The Diesel Exhaust in Miners Study (DEMS) cohort and nested case-control studies of lung cancer mortality in eight U.S. nonmetal mines were influential in IARC’s determination. We conducted a reanalysis of the DEMS case-control data to evaluate its suitability for quantitative risk assessment (QRA). Our reanalysis used conditional logistic regression and adjusted for cigarette smoking in a manner similar to the original DEMS analysis. However, we included additional estimates of DEE exposure and adjustment for radon exposure. In addition to applying three DEE exposure estimates developed by DEMS, we applied six alternative estimates. Without adjusting for radon, our results were similar to those in the original DEMS analysis: all but one of the nine DEE exposure estimates showed evidence of an association between DEE exposure and lung cancer mortality, with trend slopes differing only by about a factor of two. When exposure to radon was adjusted, the evidence for a DEE effect was greatly diminished, but was still present in some analyses that utilized the three original DEMS DEE exposure estimates. A DEE effect was not observed when the six alternative DEE exposure estimates were utilized and radon was adjusted. No consistent evidence of a DEE effect was found among miners who worked only underground. This article highlights some issues that should be addressed in any use of the DEMS data in developing a QRA for DEE. PMID:25857246

  9. Evaluation of TanDEM-X elevation data for geomorphological mapping and interpretation in high mountain environments - A case study from SE Tibet, China

    NASA Astrophysics Data System (ADS)

    Pipaud, Isabel; Loibl, David; Lehmkuhl, Frank

    2015-10-01

    Digital elevation models (DEMs) are a prerequisite for many different applications in the field of geomorphology. In this context, the two near-global medium resolution DEMs originating from the SRTM and ASTER missions are widely used. For detailed geomorphological studies, particularly in high mountain environments, these datasets are, however, known to have substantial disadvantages beyond their posting, i.e., data gaps and miscellaneous artifacts. The upcoming TanDEM-X DEM is a promising candidate to improve this situation by application of state-of-the-art radar technology, exhibiting a posting of 12 m and less proneness to errors. In this study, we present a DEM processed from a single TanDEM-X CoSSC scene, covering a study area in the extreme relief of the eastern Nyainqêntanglha Range, southeastern Tibet. The potential of the resulting experimental TanDEM-X DEM for geomorphological applications was evaluated by geomorphometric analyses and an assessment of landform cognoscibility and artifacts in comparison to the ASTER GDEM and the recently released SRTM 1″ DEM. Detailed geomorphological mapping was conducted for four selected core study areas in a manual approach, based exclusively on the TanDEM-X DEM and its basic derivates. The results show that the self-processed TanDEM-X DEM yields a detailed and widely consistent landscape representation. It thus fosters geomorphological analysis by visual and quantitative means, allowing delineation of landforms down to footprints of ~ 30 m. Even in this premature state, the TanDEM-X elevation data are widely superior to the ASTER and SRTM datasets, primarily owing to its significantly higher resolution and its lower susceptibility to artifacts that hamper landform interpretation. Conversely, challenges toward interferometric DEM generation were identified, including (i) triangulation facets and missing topographic information resulting from radar layover on steep slopes facing toward the radar sensor, (ii) low coherence values on leeward slopes, (iii) decorrelation effects over water bodies, and (iv) challenges for phase unwrapping in settings of strong topographic contrasts. There is, however, a high probability that these drawbacks can be overcome by applying multiple interferograms exhibiting different perpendicular baselines as planned for the generation of the final TanDEM-X DEM product.

  10. Visualizing impact structures using high-resolution LiDAR-derived DEMs: A case study of two structures in Missouri

    USGS Publications Warehouse

    Finn, Michael P.; Krizanich, Gary W.; Evans, Kevin R.; Cox, Melissa R.; Yamamoto, Kristina H.

    2015-01-01

    Evidence suggests that a crypto-explosive hypothesis and a meteorite impact hypothesis may be partly correct in explaining several anomalous geological features in the middle of the United States. We used a primary geographic information science (GIScience) technique of creating a digital elevation model (DEM) of two of these features that occur in Missouri. The DEMs were derived from airborne light detection and ranging, or LiDAR. Using these DEMs, we characterized the Crooked Creek structure in southern Crawford County and the Weaubleau structure in southeastern St. Clair County, Missouri. The mensuration and study of exposed and buried impact craters implies that the craters may have intrinsic dimensions which could only be produced by collision. The results show elevations varying between 276 and 348 m for Crooked Creek and between 220 and 290 m for Weaubleau structure. These new high- resolution DEMs are accurate enough to allow for precise measurements and better interpretations of geological structures, particularly jointing in the carbonate rocks, and they show greater definition of the central uplift area in the Weaubleau structure than publicly available DEMs.

  11. Finding the service you need: human centered design of a Digital Interactive Social Chart in DEMentia care (DEM-DISC).

    PubMed

    van der Roest, H G; Meiland, F J M; Haaker, T; Reitsma, E; Wils, H; Jonker, C; Dröes, R M

    2008-01-01

    Community dwelling people with dementia and their informal carers experience a lot of problems. In the course of the disease process people with dementia become more dependent on others and professional help is often necessary. Many informal carers and people with dementia experience unmet needs with regard to information on the disease and on the available care and welfare offer, therefore they tend not to utilize the broad spectrum of available care and welfare services. This can have very negative consequences like unsafe situations, social isolation of the person with dementia and overburden of informal carers with consequent increased risk of illness for them. The development of a DEMentia specific Digital Interactive Social Chart (DEM-DISC) may counteract these problems. DEM-DISC is a demand oriented website for people with dementia and their carers, which is easy, accessible and provides users with customized information on healthcare and welfare services. DEM-DISC is developed according to the human centered design principles, this means that people with dementia, informal carers and healthcare professionals were involved throughout the development process. This paper describes the development of DEM-DISC from four perspectives, a domain specific content perspective, an ICT perspective, a user perspective and an organizational perspective. The aims and most important results from each perspective will be discussed. It is concluded that the human centered design was a valuable method for the development of the DEM-DISC. PMID:18560083

  12. Investigating sediment budgets and pathways using LiDAR DEMs of difference and a geomorphological map

    NASA Astrophysics Data System (ADS)

    Hilger, Ludwig; Becht, Michael; Heckmann, Tobias

    2014-05-01

    In alpine catchments sediment is moved from one landform to another as long as they are coupled by the activity of geomorphic processes. The spatial and functional interaction of these processes forms sediment cascades reaching from sediment sources or stores to sediment sinks, and ultimately to the catchment outlet. In study presented here, multitemporal high-resolution LiDAR datasets are used to establish morphological sediment budgets. These can be calculated on the raster cell scale, i.e. by differencing digital elevation models (DEM), and on the landform scale, by establishing the net balance of eroded and accumulated material; in the latter case, the spatial unit is a polygon identifying a particular landform on a detailed geomorphological map. The flow of mobilised sediment can be estimated on a DEM using a variety of flow routing algorithms, and the net balance (sediment eroded - sediment deposited) is accumulated along specific pathways. The results of landform-based sediment budgets can be used to validate the flow routing algorithms and to assess functional connectivity between landforms that are arranged along a toposequence. Graph theory is used to store and investigate resulting sediment pathways on different aggregation levels. The incorporation of the geomorphological map highlights potential advantages of object-based over pixel-based approaches to generating graph nodes and analysing sediment cascades.

  13. Tectonic development of the Northwest Bonaparte Basin, Australia by using Digital Elevation Model (DEM)

    NASA Astrophysics Data System (ADS)

    Wahid, Ali; Salim, Ahmed Mohamed Ahmed; Ragab Gaafar, Gamal; Yusoff, AP Wan Ismail Wan

    2016-02-01

    The Bonaparte Basin consist of majorly offshore part is situated at Australia's NW continental margin, covers an area of approx. 270,000km2. Bonaparte Basin having a number of sub-basins and platform areas of Paleozoic and Mesozoic is structurally complex. This research established the geologic and geomorphologic studies using Digital Elevation Model (DEM) as a substitute approach in morphostructural analysis to unravel the geological complexities. Although DEMs have been in practice since 1990s, they still have not become common tool for mapping studies. The research work comprised of regional structural analysis with the help of integrated elevation data, satellite imageries, available open topograhic images and internal geological maps with interpreted seismic. The structural maps of the study area have been geo-referenced which further overlaid onto SRTM data and satellite images for combined interpretation which facilitate to attain Digital Elevation Model of the study area. The methodology adopts is to evaluate and redefine development of geodynamic processes involved in formation of Bonaparte Basin. The main objectives is to establish the geological histories by using digital elevation model. The research work will be useful to incorporate different tectonic events occurred at different Geological times in a digital elevation model. The integrated tectonic analysis of different digital data sets benefitted substantially from combining them into a common digital database. Whereas, the visualization software facilitates the overlay and combined interpretation of different data sets which is helpful to reveal hidden information not obvious or accessible otherwise for regional analysis.

  14. Region-growing segmentation to automatically delimit synthetic drumlins in 'real' DEMs

    NASA Astrophysics Data System (ADS)

    Eisank, Clemens; Smith, Mike; Hillier, John

    2013-04-01

    Mapping or 'delimiting' landforms is one of geomorphology's primary tools. Computer-based techniques, such as terrain segmentation, may potentially provide terrain units that are close to the size and shape of landforms. Whether terrain units represent landforms heavily depends on the segmentation algorithm, its settings and the type of underlying land-surface parameters (LSPs). We assess a widely used region-growing technique, i.e. the multiresolution segmentation (MRS) algorithm as implemented in object-based image analysis software, for delimiting drumlins. Supervised testing was based on five synthetic DEMs that included the same set of perfectly known drumlins at different locations. This, for the first time, removes subjectivity from the reference data. Five LSPs were tested, and four variants were computed for each using two pre- and post-processing options. The automated method (1) employs MRS to partition the input LSP into 200 ever coarser terrain unit patterns, (2) identifies the spatially best matching terrain unit for each reference drumlin, and (3) computes four accuracy metrics for quantifying the aerial match between delimited and reference drumlins. MRS performed best on LSPs that are regional, derived from a decluttered DEM and then normalized. Median scale parameters (SPs) for segments best delineating drumlins were relatively stable for the same LSP, but varied significantly between LSPs. Larger drumlins were generally delimited at higher SPs. MRS indicated high robustness against variations in the location and distribution of drumlins.

  15. Automatic Detection and Boundary Extraction of Lunar Craters Based on LOLA DEM Data

    NASA Astrophysics Data System (ADS)

    Li, Bo; Ling, ZongCheng; Zhang, Jiang; Wu, ZhongChen

    2015-07-01

    Impact-induced circular structures, known as craters, are the most obvious geographic and geomorphic features on the Moon. The studies of lunar carters' patterns and spatial distributions play an important role in understanding geologic processes of the Moon. In this paper, we proposed a method based on digital elevation model (DEM) data from lunar orbiter laser altimeter to detect the lunar craters automatically. Firstly, the DEM data of study areas are converted to a series of spatial fields having different scales, in which all overlapping depressions are detected in order (larger depressions first, then the smaller ones). Then, every depression's true boundary is calculated by Fourier expansion and shape parameters are computed. Finally, we recognize the craters from training sets manually and build a binary decision tree to automatically classify the identified depressions into craters and non-craters. In addition, our crater-detection method can provides a fast and reliable evaluation of ages of lunar geologic units, which is of great significance in lunar stratigraphy studies as well as global geologic mapping.

  16. Open-Source MFIX-DEM Software for Gas-Solids Flows: Part II - Validation Studies

    SciTech Connect

    Li, Tingwen

    2012-04-01

    With rapid advancements in computer hardware and numerical algorithms, computational fluid dynamics (CFD) has been increasingly employed as a useful tool for investigating the complex hydrodynamics inherent in multiphase flows. An important step during the development of a CFD model and prior to its application is conducting careful and comprehensive verification and validation studies. Accordingly, efforts to verify and validate the open-source MFIX-DEM software, which can be used for simulating the gas–solids flow using an Eulerian reference frame for the continuum fluid and a Lagrangian discrete framework (Discrete Element Method) for the particles, have been made at the National Energy Technology Laboratory (NETL). In part I of this paper, extensive verification studies were presented and in this part, detailed validation studies of MFIX-DEM are presented. A series of test cases covering a range of gas–solids flow applications were conducted. In particular the numerical results for the random packing of a binary particle mixture, the repose angle of a sandpile formed during a side charge process, velocity, granular temperature, and voidage profiles from a bounded granular shear flow, lateral voidage and velocity profiles from a monodisperse bubbling fluidized bed, lateral velocity profiles from a spouted bed, and the dynamics of segregation of a binary mixture in a bubbling bed were compared with available experimental data, and in some instances with empirical correlations. In addition, sensitivity studies were conducted for various parameters to quantify the error in the numerical simulation.

  17. Open-source MFIX-DEM software for gas-solids flows: Part II Validation studies

    SciTech Connect

    Li, Tingwen; Garg, Rahul; Galvin, Janine; Pannala, Sreekanth

    2012-01-01

    With rapid advancements in computer hardware and numerical algorithms, computational fluid dynamics (CFD) has been increasingly employed as a useful tool for investigating the complex hydrodynamics inherent in multiphase flows. An important step during the development of a CFD model and prior to its application is conducting careful and comprehensive verification and validation studies. Accordingly, efforts to verify and validate the open-source MFIX-DEM software, which can be used for simulating the gas solids flow using an Eulerian reference frame for the continuum fluid and a Lagrangian discrete framework (Discrete Element Method) for the particles, have been made at the National Energy Technology Laboratory (NETL). In part I of this paper, extensive verification studies were presented and in this part, detailed validation studies of MFIX-DEM are presented. A series of test cases covering a range of gas solids flow applications were conducted. In particular the numerical results for the random packing of a binary particle mixture, the repose angle of a sandpile formed during a side charge process, velocity, granular temperature, and voidage profiles from a bounded granular shear flow, lateral voidage and velocity profiles from a monodisperse bubbling fluidized bed, lateral velocity profiles from a spouted bed, and the dynamics of segregation of a binary mixture in a bubbling bed were compared with available experimental data, and in some instances with empirical correlations. In addition, sensitivity studies were conducted for various parameters to quantify the error in the numerical simulation.

  18. DEM modeling of failure mechanisms induced by excavations on the Moon

    NASA Astrophysics Data System (ADS)

    jiang, mingjing; shen, zhifu; Utili, Stefano

    2013-04-01

    2D Discrete Element Method (DEM) analyses were performed for excavations supported by retaining walls in lunar environment. The lunar terrain is made of a layer of sand (regolith) which differs from terrestrial sands for two main features: the presence of adhesive attractive forces due to van der Waals interactions and grains being very irregular in shape leading to high interlocking. A simplified contact model based on linear elasticity and perfect plasticity was employed. The contact model includes a moment - relative rotation law to account for high interlocking among grains and a normal adhesion law to account for the van der Waals interactions. Analyses of the excavations were run under both lunar and terrestrial environments. Under lunar environment, gravity is approximately one sixth than the value on Earth and adhesion forces between grains of lunar regolith due to van der Waals interactions are not negligible. From the DEM simulations it emerged that van der Waals interactions may significantly increase the bending moment and deflection of the retaining wall, and the ground displacements. Hence this study indicates that an unsafe estimate of the wall response to an excavation on the Moon would be obtained from physical experiments performed in a terrestrial environment, i.e., considering the effect of gravity but neglecting the van der Waals interactions.

  19. Assessing volume change of tropical Peruvian glaciers from multi-temporal digital elevation models (DEMs)

    NASA Astrophysics Data System (ADS)

    Huh, K.; Mark, B. G.

    2012-12-01

    Although far smaller than large polar ice caps, mountain glaciers are significant contributors to sea level rise and tropical glaciers in particular are sources of critical water resources to regional societies. The glaciers in Cordillera Blanca, the Andes of Peru, hold important environmental and economic concerns of regional water supplies to communities in the arid western part of the country under continued global climate change. Yet steep relief and remote locations present challenges for measuring mass changes in tropical glaciers. Remotely sensed images provide feasible opportunities to measure glacier surface area changes. We use a combination of satellite and airborne remote sensing, digital photogrammetry and geospatial techniques to assess the surface area, volume and topographic changes of key glaciers in the Cordillera Blanca, Peru between 1962 and 2008. The intercomparison of digital elevation models (DEMs) from airborne Light Detection and Range (LiDAR) data of 2008, multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of 2001-2008 and stereo-paired airborne photographs of 1962 for deriving elevation differences over time reveal the data quality to measure the volume loss in the area. The DEMs over non-glacier areas in the study sites were selected and differentially corrected Global Positioning System (dGPS) data points were used for comparison as well. The motivation of this study is to refine a surface area to volume scaling for tropical glaciers to enable extrapolation of more detailed inventory of glacier volume and water resources.

  20. Improvement of dem Generation from Aster Images Using Satellite Jitter Estimation and Open Source Implementation

    NASA Astrophysics Data System (ADS)

    Girod, L.; Nuth, C.; Kääb, A.

    2015-12-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a source of stereoscopic images covering the whole globe at a 15m resolution at a consistent quality for over 15 years. The potential of this data in terms of geomorphological analysis and change detection in three dimensions is unrivaled and needs to be exploited. However, the quality of the DEMs and ortho-images currently delivered by NASA (ASTER DMO products) is often of insufficient quality for a number of applications such as mountain glacier mass balance. For this study, the use of Ground Control Points (GCPs) or of other ground truth was rejected due to the global "big data" type of processing that we hope to perform on the ASTER archive. We have therefore developed a tool to compute Rational Polynomial Coefficient (RPC) models from the ASTER metadata and a method improving the quality of the matching by identifying and correcting jitter induced cross-track parallax errors. Our method outputs more accurate DEMs with less unmatched areas and reduced overall noise. The algorithms were implemented in the open source photogrammetric library and software suite MicMac.

  1. DEM generation from digital photographs using computer vision: Accuracy and application

    NASA Astrophysics Data System (ADS)

    James, M. R.; Robson, S.

    2012-12-01

    Data for detailed digital elevation models (DEMs) are usually collected by expensive laser-based techniques, or by photogrammetric methods that require expertise and specialist software. However, recent advances in computer vision research now permit 3D models to be automatically derived from unordered collections of photographs, and offer the potential for significantly cheaper and quicker DEM production. Here, we review the advantages and limitations of this approach and, using imagery of the summit craters of Piton de la Fournaise, compare the precisions obtained with those from formal close range photogrammetry. The surface reconstruction process is based on a combination of structure-from-motion and multi-view stereo algorithms (SfM-MVS). Using multiple photographs of a scene taken from different positions with a consumer-grade camera, dense point clouds (millions of points) can be derived. Processing is carried out by automated 'reconstruction pipeline' software downloadable from the internet. Unlike traditional photogrammetric approaches, the initial reconstruction process does not require the identification of any control points or initial camera calibration and is carried out with little or no operator intervention. However, such reconstructions are initially un-scaled and un-oriented so additional software has been developed to permit georeferencing. Although this step requires the presence of some control points or features within the scene, it does not have the relatively strict image acquisition and control requirements of traditional photogrammetry. For accuracy, and to allow error analysis, georeferencing observations are made within the image set, rather than requiring feature matching within the point cloud. Application of SfM-MVS is demonstrated using images taken from a microlight aircraft over the summit of Piton de la Fournaise volcano (courtesy of B. van Wyk de Vries). 133 images, collected with a Canon EOS D60 and 20 mm fixed focus lens, were used to create a ~1.6 km wide DEM covering the summit craters. When compared with a DEM constructed using close-range photogrammetry the SfM-MVS results showed an RMS error of 1.0 m. The overall precision of the project can be considered by ratioing this against the average viewing distance (1000 m). This relative precision of 1:1000 is in line with the results of other projects carried out over a range of spatial scales (down to ~0.1 m), so appears to be a characteristic expected achievable precision for the SfM-MVS approach. Consequently, over shorter viewing distances, absolute precisions increase - e.g. centimeter-level precisions for outcrop-scale studies where viewing distances may be expected to be of order 10 m. Although SfM-MVS cannot deliver the accuracy and precision of formal close-range photogrammetry, it can approach the results that are achievable from single stereo image pairs. However, the main advantages of the technique lie in the enhanced flexibility in image collection and automated processing, both of which significantly decrease the level of expertise required. When compared with terrestrial laser scanning at outcrop scales, the data collection time in the field can be reduced by ~80%. SfM-MVS data quality is sufficient for the technique to provide valuable DEMs of active flows and domes where access to (or for) modern surveying equipment is restricted.

  2. Validation of DEM modeling of sintering using an in situ X-ray microtomography analysis of the sintering of NaCl powder

    NASA Astrophysics Data System (ADS)

    Martin, Sylvain; Navarro, Sebastián; Palancher, Hervé; Bonnin, Anne; Léchelle, Jacques; Guessasma, Mohamed; Fortin, Jérôme; Saleh, Khashayar

    2015-08-01

    This paper aims to validate the discrete element method (DEM) model of sintering. In situ X-ray microtomography experiments have been carried out at the ESRF to follow the sintering of NaCl powder, the properties of which are close to the DEM model assumptions. DEM simulations are then run using an improved implicit method. The comparison between experiment and simulation shows the capability of DEM to predict the behavior of the sample on both particle and packing scale. The main advantages and limits of this approach are finally discussed based on these results and those of previous studies.

  3. BOREAS HYD-8 DEM Data Over the NSA-MSA and SSA-MSA in the UTM Projection

    NASA Technical Reports Server (NTRS)

    Wang, Xue-Wen; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Band, L. E.; Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS HYD-8 team focused on describing the scaling behavior of water and carbon flux processes at local and regional scales. These DEMs were produced from digitized contours at a cell resolution of 100 meters. Vector contours of the area were used as input to a software package that interpolates between contours to create a DEM representing the terrain surface. The vector contours had a contour interval of 25 feet. The data cover the BOREAS MSAs of the SSA and NSA and are given in a UTM map projection. Most of the elevation data from which the DEM was produced were collected in the 1970s or 1980s. The data are stored in binary, image format files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  4. The EVE plus RHESSI DEM for Solar Flares, and Implications for Residual Non-Thermal X-Ray Emission

    NASA Astrophysics Data System (ADS)

    McTiernan, James; Caspi, Amir; Warren, Harry

    2016-05-01

    Solar flare spectra are typically dominated by thermal emission in the soft X-ray energy range. The low energy extent of non-thermal emission can only be loosely quantified using currently available X-ray data. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) to calculate the Differential Emission Measure (DEM) for solar flares. This improvement over the isothermal approximation helps to resolve the ambiguity in the range where the thermal and non-thermal components may have similar photon fluxes. This "crossover" range can extend up to 30 keV.Previous work (Caspi et.al. 2014ApJ...788L..31C) concentrated on obtaining DEM models that fit both instruments' observations well. For this current project we are interested in breaks and cutoffs in the "residual" non-thermal spectrum; i.e., the RHESSI spectrum that is left over after the DEM has accounted for the bulk of the soft X-ray emission. As in our earlier work, thermal emission is modeled using a DEM that is parametrized as multiple gaussians in temperature. Non-thermal emission is modeled as a photon spectrum obtained using a thin-target emission model ('thin2' from the SolarSoft Xray IDL package). Spectra for both instruments are fit simultaneously in a self-consistent manner.For this study, we have examined the DEM and non-thermal resuidual emission for a sample of relatively large (GOES M class and above) solar flares observed from 2011 to 2014. The results for the DEM and non-thermal parameters found using the combined EVE-RHESSI data are compared with those found using only RHESSI data.

  5. Automatic Delineation of Sea-Cliff Limits Using Lidar-Derived High-Resolution DEMs in Southern California

    NASA Astrophysics Data System (ADS)

    Palaseanu, M.; Danielson, J.; Foxgrover, A. C.; Barnard, P.; Thatcher, C.; Brock, J. C.

    2014-12-01

    Seacliff erosion is a serious hazard with implications for coastal management, and is often estimated using successive hand digitized cliff tops or bases (toe) to assess cliff retreat. Traditionally the recession of the cliff top or cliff base is obtained from aerial photographs, topographic maps, or in situ surveys. Irrespective of how or what is measured to categorize cliff erosion, the position of the cliff top and cliff base is important. Habitually, the cliff top and base are hand digitized even when using high resolution lidar derived DEMs. Even if efforts were made to standardize and eliminate as much as possible any digitizing subjectivity, the delineation of cliffs is time consuming, and depends on the analyst's interpretation. We propose an automatic procedure to delineate the cliff top and base from high resolution bare-earth DEMs. The method is based on bare-earth high-resolution DEMs, generalized coastal shorelines and approximate measurements of distance between the shoreline and the cliff top. The method generates orthogonal transects and profiles with a minimum spacing equal to the DEM resolution and extracts for each profile xyz coordinates for cliff's top and toe, as well as second major positive and negative inflections (second top and toe) along the profile. The difference between the automated and digitized top and toe, respectively, is smaller than the DEM error margin for over 82% of the top points and 86% of the toe points along a stretch of coast in Del Mar, CA. The larger errors were due either to the failure to remove all vegetation from the bare-earth DEM or errors of interpretation during hand digitizing. The automatic method was further applied between Point Conception and Los Angeles Harbor, CA. This automatic method is repeatable, takes advantage of the bare-earth high-resolution, and is more efficient.

  6. Calibration and validation of DEM rolling and sliding friction coefficients in angle of repose and shear measurements

    NASA Astrophysics Data System (ADS)

    Frankowski, Piotr; Morgeneyer, Martin

    2013-06-01

    Pile formation and rotating drum experiments followed by DEM simulations using glass beads (1.5 and 3.0 mm diameter) and polyamide spheres (3.0 mm diameter) were conducted. A wide range of rotation velocities was tested (from 1 to 90 rpm), the drum fill degree was set to 50%. The material inclination angles obtained in pile formation experiments were comparable with low speed rotating drum tests. The experimentally obtained results were used to determine DEM friction coefficients. Both, good qualitative and good quantitative agreements between experiments and simulations were found for rotation speeds up to 5 rpm, whereas for higher rotation speeds small discrepancies were observed.

  7. The Use of DEM to Capture the Dynamics of the Flow of Solid Pellets in a Single Screw Extruder

    NASA Astrophysics Data System (ADS)

    Hong, He; Covas, J. A.; Gaspar-Cunha, A.

    2007-05-01

    Despite of the numerical developments on the numerical modeling of polymer plasticating single screw extrusion, the initial stages of solids conveying are still treated unsatisfactorily, a simple plug flow condition being assumed. It is well known that this produces poor predictions of relevant process parameters, e.g., output. This work reports on attempt to model the process using the Discrete Element Method (DEM) with the aim of unveiling the dynamics of the process. Using DEM each pellet is taken as a separate unit, thus predictions of flow patterns, velocity fields and degree of filling are possible. We present the algorithm and a few preliminary results.

  8. Hydrologically Correct, Global Paleo-Digital Elevation Models (DEMs): a Maastrichtian (Late Cretaceous) Example

    NASA Astrophysics Data System (ADS)

    Markwick, P. J.

    2001-12-01

    The past surface relief of the Earth is an essential boundary condition for computer-based atmosphere and ocean modeling. It also provides the geographic context for understanding surface processes and biotic distributions and interactions. However, with increased model resolution and the addition of vegetation, soil (weathering) and chemical modules, there is now a need for more robust, detailed paleo-topographies and bathymetries that are fully integrated with the processes being modeled, especially the hydrological system (hydrologically correct). Here I present a new GIS-based, hydrologically correct, paleo-DEM for the Maastrichtian (Late Cretaceous). This project was initiated in 1995 while the author was a graduate at the University of Chicago using the plate reconstructions of Rowley (1995, unpublished). The Maastrichtian paleogeography used in this study is one of a series of 27 global maps, representing the Cretaceous and Cenozoic, being compiled simultaneously to ensure continuity between each time interval. Each map is generated at a scale of 1:30 million in ArcView GIS and ArcInfo, using data from the author's own databases of lithologic, tectonic and fossil information, the lithologic databases of the Paleogeographic Atlas Project (The University of Chicago), a survey of published literature, and DSDP / ODP data. Interpretations of elevation are derived following the methods outlined in Ziegler et al (1985), an understanding of the tectonic regime and evolution of each geographic feature, and the age-depth relationship for the ocean. The Maastrichtian has been completed first to provide the boundary conditions for a coupled atmosphere-ocean experiment. The hydrologically correct global DEM was derived using the elevation contours from the paleogeography and the suite of hydrological tools now available in ArcInfo GRID. The DEM has been constrained by defining areas of paleo-internal drainage, paleo-river mouths and known paleo-river courses. When integrated with the results of the coupled ocean-atmosphere model the result is a powerful tool for understanding surface processes and an important step towards the development of a fully evolving Earth Systems model. Ziegler, A.M., D.B. Rowley, A.L. Lottes, D.L. Sahagian, M.L. Hulver, and T.C. Gierlowski, 1985. Paleogeographic interpretation: with an example from the Mid-Cretaceous. In: G.W. Wetherill et al. (eds.). Annual Review of Earth and Planetary Sciences 13: 385-425. Palo Alto, CA: Annual Reviews, Inc.

  9. Turbidity Current Transport using DEM and FEM: a Hybrid Lagrangian-Eulerian Approach

    NASA Astrophysics Data System (ADS)

    Alves, J. L.; Guevara, N. O., Jr.; Silva, C. E.; Alves, F. T.; Gazoni, L. C.; Coutinho, A.; Camata, J.; Elias, R. N.; Paraizo, P.

    2013-05-01

    In this work we describe a contribution to the study of turbidity transport in scales smaller than TFM (two-fluid models), The intent of the work, part of a large scale simulation project, is to assess local, small scale parameters and their upscaling. The hybrid model is based on a Lagrangian-Eulerian approach under a class of the so called Unresolved Discrete Particle Method (UDPM). In this approach, a Lagrangian description is used for the particle system employing the Discrete Element Method (DEM) while a fixed Eulerian mesh is used for the fluid phase modeled by finite element method (FEM), Fluid motion is governed by Navier-Stokes equations which are solved by an appropriate FEM implementation. Closure equation are used to compute drag and lift forces over the particles in the DEM framework. Volume averaged momentum sink terms are included in the fluid equations. The resulting coupled DEM-FEM model is integrated in time with a subcycling scheme. The aforementioned scheme was applied in the simulation of a sedimentation basin as depicted in figures 1 and 2 to investigate flow and deposition features of the suspension in a finer scale. For this purpose a submodel of the basin was generated. Mapping variables back and forth the Eulerian (finite element) model and the Lagrangian (discrete element) model were performed during the subcycled integration of the hybrid model. References: [1] Hoomans, B.P.B., Kuipers, J.A.M., Swaaij, van W.P.M," Granular dynamics Simulation of segregation phenomena in bubbling gas-fluidised beds", Powder Technology, V 109, Issues 1-3, 3 April 2000, pp 41-48; [2] Cho, S.H., Choi,H.G, Yoo, J.Y.,"Direct numerical simulation of fluid flow laden with many particles", International Journal of Multiphase Flow, V 31, Issue 4, April 2005, pp 435-451;; Sedimentation basin: sectioning the turbidity plume in the Eulerian FE model for setting up the discrete particle model. ; Sedimentation Basin: section of the turbidity plume displaying the generated discrete particle model underneath.

  10. Structural and Volumetric re-evaluation of the Vaiont landslide using DEM techniques

    NASA Astrophysics Data System (ADS)

    Superchi, Laura; Pedrazzini, Andrea; Floris, Mario; Genevois, Rinaldo; Ghirotti, Monica; Jaboyedoff, Michel

    2010-05-01

    On the 9th October 1963 a catastrophic landslide occurred on the southern slope of the Vaiont dam reservoir. A mass of approximately 270 million m3 collapsed into the reservoir generating a wave which overtopped the dam and hit the town of Longarone and other villages: almost 2000 people lost their lives. The large volume and high velocity of the landslide combined with the great destruction and loss of life that occurred make the Vaiont landslide as a natural laboratory to investigate landslide failure mechanisms and propagation. Geological, structural, geomorphological, hydrogeological and geomechanical elements should be, then, re-analyzed using methods and techniques not available in the '60s. In order to better quantify the volume involved in the movement and to assess the mechanism of the failure, a structural study is a preliminary and necessary step. The structural features have been investigated based on a digital elevation model (DEM) of the pre- and post-landslide topography at a pixel size of 5m and associated software (COLTOP-3D) to create a colored shaded relief map revealing the orientation of morphological features. Besides,the results allowed to identify on both pre- and post-slide surface six main discontinuity sets, some of which influence directly the Vaiont landslide morphology. Recent and old field surveys allowed to validate the COLTOP-3D analysis results. To estimate the location and shape of the sliding surface and to evaluate the volume of the landslide, the SLBL (Sloping Local Base Level) method has been used, a simple and efficient tool that allows a geometric interpretation of the failure surface based on a DEM. The SLBL application required a geological interpretation to define the contours of the landslide and to estimate the possible curvature of the sliding surface, that is defined by interpolating between points considered as limits of the landslide. The SLBL surface of the Vaiont landslide, was obtained from the DEM reconstruction of limits of the landslide defined by using geomorphological features and by literature data observed. Once the sliding plane was defined the potential sliding volume has been calculated in a GIS, considering also six different cross-sections realized along the landslide area before and after the event.

  11. Semi-automated extraction of landslides in Taiwan based on SPOT imagery and DEMs

    NASA Astrophysics Data System (ADS)

    Eisank, Clemens; Hölbling, Daniel; Friedl, Barbara; Chen, Yi-Chin; Chang, Kang-Tsung

    2014-05-01

    The vast availability and improved quality of optical satellite data and digital elevation models (DEMs), as well as the need for complete and up-to-date landslide inventories at various spatial scales have fostered the development of semi-automated landslide recognition systems. Among the tested approaches for designing such systems, object-based image analysis (OBIA) stepped out to be a highly promising methodology. OBIA offers a flexible, spatially enabled framework for effective landslide mapping. Most object-based landslide mapping systems, however, have been tailored to specific, mainly small-scale study areas or even to single landslides only. Even though reported mapping accuracies tend to be higher than for pixel-based approaches, accuracy values are still relatively low and depend on the particular study. There is still room to improve the applicability and objectivity of object-based landslide mapping systems. The presented study aims at developing a knowledge-based landslide mapping system implemented in an OBIA environment, i.e. Trimble eCognition. In comparison to previous knowledge-based approaches, the classification of segmentation-derived multi-scale image objects relies on digital landslide signatures. These signatures hold the common operational knowledge on digital landslide mapping, as reported by 25 Taiwanese landslide experts during personal semi-structured interviews. Specifically, the signatures include information on commonly used data layers, spectral and spatial features, and feature thresholds. The signatures guide the selection and implementation of mapping rules that were finally encoded in Cognition Network Language (CNL). Multi-scale image segmentation is optimized by using the improved Estimation of Scale Parameter (ESP) tool. The approach described above is developed and tested for mapping landslides in a sub-region of the Baichi catchment in Northern Taiwan based on SPOT imagery and a high-resolution DEM. An object-based accuracy assessment is conducted by quantitatively comparing extracted landslide objects with landslide polygons that were visually interpreted by local experts. The applicability and transferability of the mapping system are evaluated by comparing initial accuracies with those achieved for the following two tests: first, usage of a SPOT image from the same year, but for a different area within the Baichi catchment; second, usage of SPOT images from multiple years for the same region. The integration of the common knowledge via digital landslide signatures is new in object-based landslide studies. In combination with strategies to optimize image segmentation this may lead to a more objective, transferable and stable knowledge-based system for the mapping of landslides from optical satellite data and DEMs.

  12. Issues with using high-resolution DEMs for fluvial geomorphology modelling

    NASA Astrophysics Data System (ADS)

    Castro, Andres

    2015-04-01

    It is widely recognized that undertaking detailed fluvial morphology studies can be a difficult and expensive task due to the high amount of resources, such as time and highly trained personnel, that such studies requires in order to obtain accurate results. Yet, for a wide range of projects that in one way or another require the understanding fluvial systems, engineers are frequently challenged with the daunting task of managing expenses within tight budgets and expecting high quality results. It is with this perspective that it is often desired to simplify processes while maintaining a high reliability of results. In an attempt to tackle this issue the current PhD research presents an alternative methodology to undertake river geomorphology studies, by applying an automated procedure to model stream power from DEMs generated from high resolution LiDAR data. The main aim of the research is to estimate the stream power distribution along selected UK catchments and link the estimated stream power values to floodplain development processes. The raw LiDAR data, in the form of ASCII text files, used for the study correspond to 1m, 2m and 10m resolutions. During the process of creating the DEM of one of the selected rivers, the River Teme, the presence of a number of "blank spots" within the mosaic was noted. These areas corresponded to NoData zones generated presumably from the deflection of the laser beam on a water surface. Given that the GIS software didn't consider the missing data areas as part of the DEM, even though most of the "blank spots" were located on the river channel, it was necessary to develop a procedure in order to eliminate the NoData zones and correct the DEM, prior to undertaking the hydrological analysis of the catchment, without compromising the quality of the rest of the data. In search of an improved quality of results it has been commonly assumed that the higher resolution of the data the better and more accurate results are to be obtained. In the past much attention was focused on how to obtain and process the high resolution data. Nowadays with the availability of very high resolution spatial data and very powerful hardware it is becoming apparent that the quality and accuracy of results depends greatly of the software performance, as it has been found of the current research. While performing the hydrological analysis on GIS of the aforementioned selected UK rivers it was found that very high (1m or 2m) resolution LiDAR data does not provide of the most accurate representation of the rivers' flow paths. When compared with 10m resolution data it becomes apparent that the "lower" resolution data produces better results than the 1m or 2m data, more adjusted to the river actual path. It is possible to argue that the reason for this resides in limitations of the software itself. It is also necessary to point out that, while the for the current research purposes the 10m resolution data provides of better results, for other applications, such as topographic analyses of the area, very high resolution data (1m or 2m) is probably more adequate.

  13. Mechanistic Based DEM Simulation of Particle Attrition in a Jet Cup

    SciTech Connect

    Xu, Wei; DeCroix, David; Sun, Xin

    2014-02-01

    The attrition of particles is a major industrial concern in many fluidization systems as it can have undesired effects on the product quality and on the reliable operation of process equipment. Therefore, to accomodate the screening and selection of catalysts for a specific process in fluidized beds, risers, or cyclone applications, their attrition propensity is usually estimated through jet cup attrition testing, where the test material is subjected to high gas velocities in a jet cup. However, this method is far from perfect despite its popularity, largely due to its inconsistency in different testing set-ups. In order to better understand the jet cup testing results as well as their sensitivity to different operating conditions, a coupled computational fluid dynamic (CFD) - discrete element method (DEM) model has been developed in the current study to investigate the particle attrition in a jet cup and its dependence on various factors, e.g. jet velocity, initial particle size, particle density, and apparatus geometry.

  14. A coupled DEM-DFN approach to rock mass strength characterization

    NASA Astrophysics Data System (ADS)

    Harthong, Barthelemy; Scholtes, Luc; Donze, Frederic

    2013-04-01

    An enhanced version of the discrete element method (DEM) has been specifically developed for the analysis of fractured rock masses [Scholtes L, Donze F, 2012]. In addition to the discrete representation of the intact medium which enables the description of the localized stress-induced damage caused by heterogeneities inherent to rocks, structural defects can be explicitly taken into account in the modeling to represent pre-existing fractures or discontinuities of size typically larger than the discrete element size. From laboratory scale simulations to slope stability case studies, the capability of this approach to simulate the progressive failure mechanisms occurring in jointed rock are presented is assessed on the basis of referenced experiments and in situ observations. For instance, the challenging wing crack extension, typical of brittle material fracturing, can be successfully reproduced under both compressive and shear loading path, as a result of the progressive coalescence of micro-cracks induced by stress concentration at the tips of pre-existing fractures. In this study, the dedicated DEM is coupled to a discrete fracture network (DFN) model to assess the influence of DFN properties on the mechanical behavior of fractured rock masses where progressive failure can occur. The DFN model assumes the distribution of fractures barycentres to be fractal and the distribution of fracture sizes to follow a power-law distribution [Davy P, Le Goc P, Darcel C, Bour O, de Dreuzy JR, Munier R, 2010]. The proposed DEM/DFN model is used to characterize the influence of clustering and size distribution of pre-existing fractures on the strength of fractured rock masses. The results show that the mechanical behaviour of fractured rock masses is mainly dependent on the fracture intensity. However, for a given fracture intensity, the strength can exhibit a 50 per cent variability depending on the size distribution of the pre-existing fractures. This difference can be attributed to the different mechanisms that involve sliding and crushing of blocks in the case of large interconnected fractures or progressive failure of the rock matrix through coalescence of cracks in the case of small unconnected fractures. Clustering of fractures was found to influence the spatial variability of the mechanical properties and therefore to have a scale effect on strength. The results outline the relevance of three parameters, the power-law exponent of the fracture size distribution, the clustering fractal dimension which fixes the fracture-to-fracture correlation number and the fracture intensity, to characterize the mechanical behaviour of rock masses. References: - Davy P, Le Goc P, Darcel C, Bour O, de Dreuzy JR, Munier R, 2010. A likely universal model of fracture scaling and its consequences for crustal hydromechanics. Journal of Geophysical Research; 115(B10), doi:10.1029/2009JB007043. - Harthong B, Scholtes L, Donze FV, 2012. Strength characterization of rock masses, using a coupled DEM-DFN model. Geophysical Journal International; 191:467-480. - Scholtes L, Donze F, 2012. Modelling progressive failure in fractured rock masses using a 3D discrete element method. Int J Rock Mech Min Sci; 52:18-30.

  15. Study of forest surface-fire spread simulation based on DEM

    NASA Astrophysics Data System (ADS)

    Xu, Ai-jun; Li, Qing-quan

    2006-10-01

    This paper uses the McArthur forest fire spread model, takes Visual C++ and OpenGL(Open Graphics Library) development kit, and experiments on the region of the Zhejiang Province Linan by using this city 1: 50000 DEM(Digital Elevation Model) data, investigations data of forest resources, unifies the real-time meteorological data, and researches the method of forest-fire spread simulation based on the 3D(three-dimension), which studies Forest fire production and the spread simulator method with its related algorithm in emphasis. The paper takes the forest fire production and spread method as the foundation to propose and design six algorithms to successively simulate the forest fire spread. Respectively: The fire that spreads in different directions algorithm, distributed fire points algorithm, scene of a fire region computation algorithm, mapping fire particle algorithm, flame production algorithm, and billboard technology application algorithm.

  16. Robust 3D Quantification of Glacial Landforms: A Use of Idealised Drumlins in a Real DEM

    NASA Astrophysics Data System (ADS)

    Hillier, J. K.; Smith, M. S.

    2012-04-01

    Drumlins' attributes, such as height (h) and volume (V ), may preserve important information about the dynamics of former ice sheets. However, measurement errors are large (e.g., 39.2% of V within ±25% of their real values for the 'cookie cutter') and, in general, poorly understood. To accurately quantify the morphology of glacial landforms, the relief belonging to that landform must be reliably isolated from other components of the landscape (e.g. buildings, hills). A number of techniques have been proposed for this regional-residual separation (RRS). Which is best? Justifications for those applied remain qualitative assertions. A recently developed, novel method using idealised drumlins of known size (hin, V in) in a real digital elevation model (DEM) is used to quantitatively determine the best RRS technique, allowing general guidelines for quantifying glacial landforms to be proposed. 184 drumlins with digitised outlines in western Central Scotland are used as a case study. The NEXTMap surface model (DSM) is the primary dataset employed. A variety of techniques are then investigated for their ability to recover sizes (hr, V r). A metric, ɛ, is used that maximises the number of Hr/Hin values near 1.0 whilst giving equal weight to different drumlin sizes: a metric dominated by the large number of small drumlins is not desirable. For simplicity, the semi-automated 'cookie cutter' technique is used as a baseline for comparison. This removes heights within a drumlin from a DEM, cuts a hole, then estimates its basal surface by interpolating across the space with a fully tensioned bi-cubic spline (-T1). Metrics for h and V are ɛh = 0.885 and ɛV = 0.247. Other tensions do not improve this significantly, with ɛV of 0.245 at best, but using Delauney triangulation reduces ɛV to 0.206. Windowed 'sliding median' filters, which do not require heights within drumlins to be removed, attain a minimum ɛV of 0.470 at a best width of 340 m (-Fm340). Finally, even crudely (-Fm60) removing clutter (e.g. trees and buildings) to estimate a terrain model (DTM) before processing improves ɛh dramatically to 0.412. Mean height (hin) of 6.8 m is then much better recovered at 7.1±0.3 (2σ), as opposed to 12.5 ± 0.6 (2σ) before decluttering. So, guidelines proposed to best quantify mapped glacial landforms are to i) declutter before ii) removing heights within the drumlin, then iii) interpolating to estimate a basal surface using Delauney triangulation. Mapping landforms' outlines from DTMs is not recommended since outlines are shifted by the distortions they contain, inducing errors. The 'synthetic' DEMs used have been demonstrated to be statistically valid, reliably representing reality. So, the optimal isolation method will now be used to assess the drumlins and their populations in the study area. Synthetic DEMs could be readily created to assess a variety of other landforms and other areas.

  17. Mechanical behavior modeling of sand-rubber chips mixtures using discrete element method (DEM)

    NASA Astrophysics Data System (ADS)

    Eidgahee, Danial Rezazadeh; Hosseininia, Ehsan Seyedi

    2013-06-01

    Rubber shreds in mixture with sandy soils are widely used in geotechnical purposes due to their specific controlled compressibility characteristics and light weight. Various studies have been carried out for sand or rubber chips content in order to restrain the compressibility of the mass in different structures such as backfills, road embankments, etc. Considering different rubber contents, sand-rubber mixtures can be made which lead mechanical properties of the blend to go through changes. The aim of this paper is to study the effect of adding different rubber portions on the global engineering properties of the mixtures. This study is performed by using Discrete Element Method (DEM). The simulations showed that adding rubber up to a particular fraction can improve maximum bearing stress characteristics comparing to sand alone masses. Taking the difference between sand and rubber stiffness into account, the result interpretation can be developed to other soft and rigid particle mixtures such as powders or polymers.

  18. Revealing topographic lineaments through IHS enhancement of DEM data. [Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Murdock, Gary

    1990-01-01

    Intensity-hue-saturation (IHS) processing of slope (dip), aspect (dip direction), and elevation to reveal subtle topographic lineaments which may not be obvious in the unprocessed data are used to enhance digital elevation model (DEM) data from northwestern Nevada. This IHS method of lineament identification was applied to a mosiac of 12 square degrees using a Cray Y-MP8/864. Square arrays from 3 x 3 to 31 x 31 points were tested as well as several different slope enhancements. When relatively few points are used to fit the plane, lineaments of various lengths are observed and a mechanism for lineament classification is described. An area encompassing the gold deposits of the Carlin trend and including the Rain in the southeast to Midas in the northwest is investigated in greater detail. The orientation and density of lineaments may be determined on the gently sloping pediment surface as well as in the more steeply sloping ranges.

  19. 3DEM Loupe: analysis of macromolecular dynamics using structures from electron microscopy

    PubMed Central

    Nogales-Cadenas, R.; Jonic, S.; Tama, F.; Arteni, A. A.; Tabas-Madrid, D.; Vázquez, M.; Pascual-Montano, A.; Sorzano, C. O. S.

    2013-01-01

    Electron microscopy (EM) provides access to structural information of macromolecular complexes in the 3–20 Å resolution range. Normal mode analysis has been extensively used with atomic resolution structures and successfully applied to EM structures. The major application of normal modes is the identification of possible conformational changes in proteins. The analysis can throw light on the mechanism following ligand binding, protein–protein interactions, channel opening and other functional macromolecular movements. In this article, we present a new web server, 3DEM Loupe, which allows normal mode analysis of any uploaded EM volume using a user-friendly interface and an intuitive workflow. Results can be fully explored in 3D through animations and movies generated by the server. The application is freely available at http://3demloupe.cnb.csic.es. PMID:23671335

  20. Analysis of initial drainage network evolution from aerial photography and a DEM time series

    NASA Astrophysics Data System (ADS)

    Schneider, Anna; Gerke, Horst H.; Maurer, Thomas; Nenov, Rossen; Raab, Thomas

    2013-04-01

    The evolution of erosion rill or gully networks is a formative process in initial landscape development. Digital representations of drainage networks are often derived from Digital Elevation Models (DEMs) based on morphometric parameters, or mapped in field surveys or from aerial photographs. This study attempted to reconstruct and analyze the first five years of erosion rill network evolution in the 6 ha artificial catchment 'Hühnerwasser', which serves as a real world-laboratory to study patterns and processes of initial ecosystem development. The drainage network was characterized in a twofold approach, based on the analysis of remotely-sensed data. We used high-resolution drone-based aerial photographs to map the actively eroding rill network for four states of development, and a time series of ten Digital Elevation Models to characterize the morphology of the surface. Rill network maps and morphometric parameters were combined to allow for region-specific analyses of morphometry for different parts of the rill network. After a rapid growth of the erosion rill network during the first two years of development, a reduction of the area of actively eroding rills was observed. Region-specific analysis of morphometry indicates an increase in flow accumulation in the central parts of the rill network, which suggests that locally evolving feedback cycles between flow accumulation and erosion affected rill network development, in addition to the effects of precipitation characteristics and the growth of vegetation cover. The combination of drainage network characterization from aerial photography and DEMs could improve analyses of initial drainage network development in experimental studies, as it allows for critical comparisons of flow accumulation patterns and the actual patterns of erosion rills or gullies.

  1. Quality of DEMs derived from Kite Aerial Photogrammety System: a case study of Dutch coastal environments.

    NASA Astrophysics Data System (ADS)

    Paron, Paolo; Smith, Mike J.; Anders, Niels; Meesuk, Vorawit

    2014-05-01

    Coastal protection is one of the main challenges for the Netherlands, where a large proportion of anthropogenic activity is located below sea level (both residential and economic). The Dutch government is implementing an innovative method of coastal replenishment using natural waves and winds to relocate sand from one side to the other of the country. This requires close monitoring of the spatio-temporal evolution of beaches in order to correctly model the future direction and amount of sand movement. To do so -on the onshore beach- we tested a Kite-Aerial Photography System for monitoring the beach dynamics at Zandmotor (http://www.dezandmotor.nl/en-GB/). The equipment used for data collection were a commercial DSLR camera (Nikon D7000 with a 20mm lens), gyro-levelled rig, Sutton Flowform 16 kite and Leica GNSS Viva GS10, with GSM connection to the Dutch geodetic network. We flew using a 115 m line with an average inclination of 40 to 45°; this gave a camera vertical distance of ~80 m and pixel size of ~20 mm. The methodology follows that of Smith et al. (2009), and of Paron & Smith (2013), applied to a highly dynamic environment with low texture and small relief conditions. Here we present a comparison of the quality of the digital elevation model (DEM) generated from the same dataset using two different systems: Structure from Motion (SfM) using Agisoft Photoscan Pro and traditional photogrammetry using Leica Photograpmmetry Suite. In addition the outputs from the two data processing methods are presented, including both an image mosaic and DEM, and highlighting pros and cons of both methods. References Smith, M. J. et al. 2009. High spatial resolution data acquisition for the geosciences: kite aerial photography. ESPL, 34(1), 155-161. Paron, P., Smith, M.J. 2013. Kite aerial photogrammetry system for monitoring coastal change in the Netherlands. 8th IAG International Conference on Geomorphology, Paris, August.

  2. A Progressive Black Top Hat Transformation Algorithm for Estimating Valley Volumes from DEM Data

    NASA Astrophysics Data System (ADS)

    Luo, W.; Pingel, T.; Heo, J.; Howard, A. D.

    2013-12-01

    The amount of valley incision and valley volume are important parameters in geomorphology and hydrology research, because they are related to the amount erosion (and thus the volume of sediments) and the amount of water needed to create the valley. This is not only the case for terrestrial research but also for planetary research as such figuring out how much water was on Mars. With readily available digital elevation model (DEM) data, the Black Top Hat (BTH) transformation, an image processing technique for extracting dark features on a variable background, has been applied to DEM data to extract valley depth and estimate valley volume. However, previous studies typically use one single structuring element size for extracting the valley feature and one single threshold value for removing noise, resulting in some finer features such as tributaries not being extracted and underestimation of valley volume. Inspired by similar algorithms used in LiDAR data analysis to separate above ground features and bare earth topography, here we propose a progressive BTH (PBTH) transformation algorithm, where the structuring elements size is progressively increased to extract valleys of different orders. In addition, a slope based threshold was introduced to automatically adjust the threshold values for structuring elements with different sizes. Connectivity and shape parameters of the masked regions were used to keep the long linear valleys while removing other smaller non-connected regions. Preliminary application of the PBTH to Grand Canyon and two sites on Mars has produced promising results. More testing and fine-tuning is in progress. The ultimate goal of the project is to apply the algorithm to estimate the volume of valley networks on Mars and the volume of water needed to form the valleys we observe today and thus infer the nature of the hydrologic cycle on early Mars. The project is funded by NASA's Mars Data Analysis program.

  3. "blue Line" Conditioning of A New Physically-based Method For Dem Interpolation

    NASA Astrophysics Data System (ADS)

    Grimaldi, S.; Teles, V.; Bras, R. L.

    A basic issue for Earth Science studies is the accurate representation of the topogra- phy. The increase of distributed modeling has stimulated the use of Digital Elevation Models (DEMs). Usually DEMs are created with mathematical and statistical interpo- lators that seek the best fit to the observed data. They generally create surfaces with unrealistic normal or log-normal distribution of slopes and curvatures. Landscape to- pography is known to have particular properties such as roughness and self-similar properties. The commonly used interpolators do not reproduce those characteristics. In order to build a topography with characteristic properties, a new physically-based approach was recently developed. This method consists in coupling a standard interpo- lation method and an erosion model, which constrains the interpolation with geomor- phologic laws. This new approach gives more realistic surfaces than the commonly- used interpolators. However, for some basins or when data are scarce, this method as well as common interpolators are not able to recognize the main channels and ridges. In these cases, the interpolated surface has a wrong drainage network and completely different landscape. In order to overcome this difficulty and to improve the physically- based model performance, a new procedure is able to use the "blue line" information to constrain the interpolated surface with the actual network. This information can be easily and accurately obtained from maps or aerial photographs, because only the planar coordinates of the network are needed as input. The steps of the "blue line" procedure are described. Some case studies show the improvement due to the "blue line" information.

  4. An Adaptive Integration Model of Vector Polyline to DEM Data Based on Spherical Degeneration Quadtree Grids

    NASA Astrophysics Data System (ADS)

    Zhao, X. S.; Wang, J. J.; Yuan, Z. Y.; Gao, Y.

    2013-10-01

    Traditional geometry-based approach can maintain the characteristics of vector data. However, complex interpolation calculations limit its applications in high resolution and multi-source spatial data integration at spherical scale in digital earth systems. To overcome this deficiency, an adaptive integration model of vector polyline and spherical DEM is presented. Firstly, Degenerate Quadtree Grid (DQG) which is one of the partition models for global discrete grids, is selected as a basic framework for the adaptive integration model. Secondly, a novel shift algorithm is put forward based on DQG proximity search. The main idea of shift algorithm is that the vector node in a DQG cell moves to the cell corner-point when the displayed area of the cell is smaller or equal to a pixel of screen in order to find a new vector polyline approximate to the original one, which avoids lots of interpolation calculations and achieves seamless integration. Detailed operation steps are elaborated and the complexity of algorithm is analyzed. Thirdly, a prototype system has been developed by using VC++ language and OpenGL 3D API. ASTER GDEM data and DCW roads data sets of Jiangxi province in China are selected to evaluate the performance. The result shows that time consumption of shift algorithm decreased about 76% than that of geometry-based approach. Analysis on the mean shift error from different dimensions has been implemented. In the end, the conclusions and future works in the integration of vector data and DEM based on discrete global grids are also given.

  5. Supernova Remnants in the Magellanic Clouds. VI. The DEM L316 Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Williams, R. M.; Chu, Y.-H.

    2005-12-01

    The DEM L316 system contains two shells, both with the characteristic signatures of supernova remnants (SNRs). We analyze Chandra and XMM-Newton data for DEM L316, investigating its spatial and spectral X-ray features. Our Chandra observations resolve the structure of the northeastern SNR (shell A) as a bright inner ring and a set of ``arcs'' surrounded by fainter diffuse emission. The spectrum is well fit by a thermal plasma model with a temperature of ~1.4 keV; we do not find significant spectral differences for different regions of this SNR. The southwestern SNR (shell B) exhibits an irregular X-ray outline, with a brighter interior ring of emission including a bright knot of emission. Overall, the emission of the SNR is well described by a thermal plasma of temperature ~0.6 keV. The bright knot, however, is spectrally distinct from the rest of the SNR, requiring the addition of a high-energy spectral component consistent with a power-law spectrum of photon index 1.6-1.8. We confirm the findings of Nishiuchi and coworkers that the spectra of these shells are notably different, with shell A requiring a high iron abundance for a good spectral fit, implying a Type Ia origin. We further explicitly compare abundance ratios to model predictions for Type Ia and Type II supernovae. The low ratios for shell A (O/Fe of 1.5 and Ne/Fe of 0.2) and the high ratios for shell B (O/Fe of 30-130 and Ne/Fe of 8-16) are consistent with Type Ia and Type II origins, respectively. The difference between the SNR progenitor types casts some doubt on the suggestion that these SNRs are interacting with one another.

  6. Vegetation and slope effects on accuracy of a LiDAR-derived DEM in the sagebrush steppe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study analyzed the errors associated with vegetation cover type and slope on a LiDAR derived DEM in a semiarid environment in southwestern Idaho, USA. Reference data were collected over a range of vegetation cover types and slopes. Reference data were compared to ground raster values and Root...

  7. BOREAS HYP-8 DEM Data Over The NSA-MSA and SSA-MSA in The AEAC Projection

    NASA Technical Reports Server (NTRS)

    Knapp, David E.; Hall, Forrest G. (Editor); Wang, Xue-Wen; Band, L. E.; Smith, David E. (Technical Monitor)

    2000-01-01

    These data were derived from the original Digital Elevation Models (DEMs) produced by the Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-8 team. The original DEMs were in the Universal Transverse Mercator (UTM) projection, while this product is projected in the Albers Equal-Area Conic (AEAC) projection. The pixel size of the data is 100 meters, which is appropriate for the 1:50,000-scale contours from which the DEMs were made. The original data were compiled from information available in the 1970s and 1980s. This data set covers the two Modeling Sub-Areas (MSAs) that are contained within the Southern Study Area (SSA) and the Northern Study Area (NSA). The data are stored in binary, image format files. The DEM data over the NSA-MSA and SSA-MSA in the AEAC projection are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  8. Multiresolution fusion of radar sounder and altimeter data for the generation of high resolution DEMs of ice sheets

    NASA Astrophysics Data System (ADS)

    Ilisei, Ana-Maria; Bruzzone, Lorenzo

    2015-10-01

    Understanding the dynamics and processes of the ice sheets is crucial for predicting the behavior of climate change. A potential approach to achieve this is by using high resolution (HR) digital elevation models (DEMs) of the ice surface derived from remote sensing radar or laser altimeters. Unfortunately, at present HR DEMs of large portions of the ice sheets are not available. To address this issue, in this paper we propose a multisensor data fusion technique for the generation of a HR DEM of the ice sheets, which fuses two types of data, i.e., radargrams acquired by radar sounder (RS) instruments and ice surface elevation data measured by altimeter (ALT) instruments. The aim of the technique is to generate a DEM of the ice surface at the best possible horizontal resolution by exploiting the complementary characteristics of the RS and ALT data. This is done by defining a novel processing scheme that involves image processing techniques based on data rescaling, geostatistical interpolation and multiresolution analysis (MRA). The method has been applied to a subset of RS and ALT data acquired over a portion of the Byrd Glacier in Antarctica. Experimental results confirm the effectiveness of the proposed method.

  9. Validation of DEM Data Derived from World View 3 Stereo Imagery for Low Elevation Majuro Atoll, Marshall Islands

    EPA Science Inventory

    The availability of surface elevation data for the Marshall Islands has been identified as a “massive” data gap for conducting vulnerability assessments and the subsequent development of climate change adaption strategies. Specifically, digital elevation model (DEM) data are need...

  10. Capturing Micro-topography of an Arctic Tundra Landscape through Digital Elevation Models (DEMs) Acquired from Various Remote Sensing Platforms

    NASA Astrophysics Data System (ADS)

    Vargas, S. A., Jr.; Tweedie, C. E.; Oberbauer, S. F.

    2013-12-01

    The need to improve the spatial and temporal scaling and extrapolation of plot level measurements of ecosystem structure and function to the landscape level has been identified as a persistent research challenge in the arctic terrestrial sciences. Although there has been a range of advances in remote sensing capabilities on satellite, fixed wing, helicopter and unmanned aerial vehicle platforms over the past decade, these present costly, logistically challenging (especially in the Arctic), technically demanding solutions for applications in an arctic environment. Here, we present a relatively low cost alternative to these platforms that uses kite aerial photography (KAP). Specifically, we demonstrate how digital elevation models (DEMs) were derived from this system for a coastal arctic landscape near Barrow, Alaska. DEMs of this area acquired from other remote sensing platforms such as Terrestrial Laser Scanning (TLS), Airborne Laser Scanning, and satellite imagery were also used in this study to determine accuracy and validity of results. DEMs interpolated using the KAP system were comparable to DEMs derived from the other platforms. For remotely sensing acre to kilometer square areas of interest, KAP has proven to be a low cost solution from which derived products that interface ground and satellite platforms can be developed by users with access to low-tech solutions and a limited knowledge of remote sensing.

  11. Ice dynamics of Himalayan glaciers (Himachal Pradesh, India) using TerraSAR-X/TanDEM-X data.

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2015-04-01

    Mountain glaciers are the natural indicators of climate change. Himalaya is a part of widely spread mountain range consisting of second largest ice mass after polar region. The glaciers in Himalaya are located in Himachal Pradesh and other territories of India. The precipitation in the region is influenced by both Indian summer monsoon and mid-latitude winter westerlies. The glacier discharge influences the river basins and provides fresh water for various infrastructural necessities of urbanization in the state. The study aims to estimate the ice thickness and volume change during the decade (2011-2000) and annually during 2011-2014. For this, TanDEM-X DEMs are subtracted from the SRTM C/X band DEM of 2000. In addition, ice flow dynamics are quantified by the constellation of TerraSAR-X/TanDEM-X data using SAR offset tracking method. The primary investigations reveal that the terminus velocity of Bada Shigri (G077683E32169N), the biggest glacier of the state, Chhota Shigri( G077513E32227N), a bench-mark glacier, and other glacier (G077547E32162N) in 2011 found out to be < 2cm/day. The upper stream velocities of the glaciers are increased linearly and influenced by glacier tributaries.

  12. Mapping hydrological environments in central Amazonia: ground validation and surface model based on SRTM DEM data corrected for deforestation

    NASA Astrophysics Data System (ADS)

    Moulatlet, G. M.; Rennó, C. D.; Costa, F. R. C.; Emilio, T.; Schietti, J.

    2014-07-01

    One of the most important freely available digital elevation models (DEMs) for Amazonia is the one obtained by the Shuttle Radar Topography Mission (SRTM). However, since SRTM tends to represent the vegetation surface instead of the ground surface, the broad use of SRTM DEM as a framework for terrain description in Amazonia is hampered by the presence of deforested areas. We present here two datasets: (1) a deforestation-corrected SRTM DEM for the interfluve between the Purus and Madeira rivers, in central Amazonia, which passed through a careful identification of different environments and has deforestation features corrected by a new method of increasing pixel values of the DEM; and (2) a set of eighteen hydrological-topographic descriptors based on the corrected SRTM DEM. The hydrological-topographic description was generated by the Height Above the Nearest Drainage (HAND) algorithm, which normalizes the terrain elevation (a.s.l.) by the elevation of the nearest hydrologically connected drainage. The validation of the HAND dataset was done by in situ hydrological description of 110 km of walking trails also available in this dataset. The new SRTM DEM expands the applicability of SRTM data for landscape modelling; and the datasets of hydrological features based on topographic modelling is undoubtedly appropriate for ecological modelling and an important contribution for environmental mapping of Amazonia. The deforestation-corrected SRTM DEM is available at http://ppbio.inpa.gov.br/knb/metacat/naman.318.3/ppbio; the polygons selected for deforestation correction are available at http://ppbio.inpa.gov.br/knb/metacat/naman.317.3/ppbio; the set of hydrological-topographic descriptors is available at http://ppbio.inpa.gov.br/knb/metacat/naman.544.2/ppbio; and the environmental description of access trails is available at http://ppbio.inpa.gov.br/knb/metacat/naman.541.2/ppbio.

  13. The effect of DEM resolution on the computation of the factor of safety using an infinite slope model

    NASA Astrophysics Data System (ADS)

    Fuchs, Michael; Torizin, Jewgenij; Kühn, Friedrich

    2014-11-01

    The quality of digital elevation models (DEMs) is essential for reliable landslide susceptibility assessments. In this paper, two DEMs derived from ASTER (ASTER GDEM v.2 with 30 m horizontal resolution) and TerraSAR-X (GeoElevation10 with 10 m horizontal resolution) data are compared to study the effects of resolution on the derived slope and wetness index parameters in the application of the infinite slope model for the computation of the factor of safety. Several slope stability scenarios representing different wetness conditions with 5, 10 and 100 mm d- 1 of steady-state recharge were calculated for the eastern flank of Mount Rinjani Volcano on Lombok Island, Indonesia. Each scenario was conducted by computing the static factor of safety with mean values of the bulk density, angle of internal friction, cohesion, and failure depth parameters, as well as for their normally distributed values by Monte Carlo simulation. All scenarios were applied to both DEMs. The scenarios were evaluated by calculating the success/prediction rate using the respective area under the curve (AUC) and an existing landslide inventory. Additionally, uncertainties in the estimated positions of landslides were taken into account. Depending on the particular scenario, the success rate of the GeoElevation10 model shows differences up to 3% compared to the ASTER GDEM model. This apparent improvement is mainly caused by the higher ground resolution in GeoElevation10. However, the success rate increases for the 10 mm d- 1 and decreases for the 100 mm d- 1 steady-state recharge conditions. Consequently, the more detailed flow direction in the GeoElevation10 DEM has the highest impact under conditions with lower water saturation. The slight improvement in the total model quality shows that the higher resolution of the DEM has a small impact on poorly parameterized models, in which the material properties are described by roughly estimated parameters. Therefore, the application of a high-resolution DEM to areas with a lack of data on the soil's physical properties is inefficient due to its low cost-benefit ratio. For quick analysis, the ASTER GDEM is of a suitable quality. To fully benefit from the high resolution of the DEMs, other parameters should be available in appropriate detail.

  14. Characterization of active fault scarps from medium to high resolution DEM: case studies from Central and Southern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Brunori, C.; Cinti, F. R.; Ventura, G.

    2013-12-01

    We identify geo-morphometric features of active fault scarps in Italy through a semiautomatic processing using GIS. Medium to high resolution DEM was used to characterize the geometry, structural, and erosive elements of two seismogenic normal faults in Central and Southern Apennines. The Pettino fault in L'Aquila area was detected using a 1 m pixel DEM derived from airborne LiDAR survey (Friuli Venezia Giulia Civil Protection). For the Castrovillari fault in northern Calabria region was used a 4 m pixel DEM (Regional Cartography Office of Regione Calabria). Scarp segments are region of planar discontinuities identified by selected values of DEM-derived Terrain Ruggedness Index (TRI) and Vector Ruggedness Measure (VRM). These planar discontinuities corresponds to landscape features such as, river terraces, roads scarps, and other natural or human features. The discrimination between these features have been accomplished overlaying extracted features on aerial photograph, geological and geomorphologic maps and in situ survey. After that, we perform the quantitative and statistical analysis of these areas identified as "fault scarps". The identification of elements relative to the scarps (e.g. base, crest, slope) is then obtained to derive the estimate of parameters describing the fault: altitude, height of the scarp, length, slope and aspect, Terrain Ruggedness Index (TRI) and Vector Ruggedness Measure (VRM). The spatial distribution of the extracted values was obtained through their statistical analysis. We analyze scarp parameters variations along the whole scarp extent, such as strike value from aspect variations, slope and profile curvature differences as indicators of tectonic and/or erosion activity. The combined analysis of the DEM-derived parameters allows us to (a) define aspects of three-dimensional scarp geometry, (b) decipher its geomorphological significance, and (c) estimate the long-term slip rate.

  15. EarthEnv-DEM90: A nearly-global, void-free, multi-scale smoothed, 90m digital elevation model from fused ASTER and SRTM data

    NASA Astrophysics Data System (ADS)

    Robinson, Natalie; Regetz, James; Guralnick, Robert P.

    2014-01-01

    A variety of DEM products are available to the public at no cost, though all are characterized by trade-offs in spatial coverage, data resolution, and quality. The absence of a high-resolution, high-quality, well-described and vetted, free, global consensus product was the impetus for the creation of a new DEM product described here, 'EarthEnv-DEM90'. This new DEM is a compilation dataset constructed via rigorous techniques by which ASTER GDEM2 and CGIAR-CSI v4.1 products were fused into a quality-enhanced, consistent grid of elevation estimates that spans ∼91% of the globe. EarthEnv-DEM90 was assembled using methods for seamlessly merging input datasets, thoroughly filling voids, and smoothing data irregularities (e.g. those caused by DEM noise) from the approximated surface. The result is a DEM product in which elevational artifacts are strongly mitigated from the input data fusion zone, substantial voids are filled in the northern-most regions of the globe, and the entire DEM exhibits reduced terrain noise. As important as the final product is a well defined methodology, along with new processing techniques and careful attention to final outputs, that extends the value and usability of the work beyond just this single product. Finally, we outline EarthEnv-DEM90 acquisition instructions and metadata availability, so that researchers can obtain this high-resolution, high-quality, nearly-global new DEM product for the study of wide-ranging global phenomena.

  16. Lava flow mapping and volume calculations for the 2012-2013 Tolbachik, Kamchatka, fissure eruption using bistatic TanDEM-X InSAR

    NASA Astrophysics Data System (ADS)

    Kubanek, Julia; Richardson, Jacob A.; Charbonnier, Sylvain J.; Connor, Laura J.

    2015-12-01

    The bistatic acquisition mode of the German TanDEM-X radar satellite mission provides a reliable source for measuring morphological changes associated with volcanic activity. We present the use of this system to measure key lava flow parameters including thickness, volume, runout, and flow extent by using two TanDEM-X data pairs to generate digital elevation models (DEMs) prior to and immediately following the 2012-2013 eruption of Tolbachik Volcano, Kamchatka. Morphometric parameters and areal distribution of the new lava flow field are determined using a cell-by-cell elevation difference between the two DEMs. A total flow volume of 0.53 ± 0.07 km3, a mean flow thickness of 14.5 m, and a modal thickness of 7.8 m are calculated. We use these calculated flow parameters as input to a volume-limited lava flow emplacement model. Model simulations are able to reproduce the SW portion of the 2012-2013 Tolbachik lava flow using a 75-m Shuttle Radar Topography Mission (SRTM) DEM and the 15-m TanDEM-X derived DEM, with goodness-of-fit measures of 56.3 and 59.6 %, respectively, based on the Jaccard similarity coefficient. The flow simulation done using SRTM data underestimates the observed 14.4 km flow runout by over 3 km, while the simulation with TanDEM-X data overestimates flow runout by about 1.5 km. Performance of the lava flow modeling algorithm is highly dependent on the modal lava thickness, highlighting the importance of using TanDEM-X DEMs to provide precise lava flow measurements in order to constrain input parameters for numerical modeling of lava flows.

  17. The accuracy of photo-based structure-from-motion DEMs

    NASA Astrophysics Data System (ADS)

    James, M. R.; Robson, S.

    2012-04-01

    Data for detailed digital elevation models (DEMs) are usually collected by expensive laser-based techniques, or by photogrammetric methods that require expertise and specialist software. However, recent advances in computer vision research now permit 3D models to be automatically derived from unordered collections of photographs, offering the potential for significantly cheaper and quicker DEM production. Here, we assess the accuracy of this approach for geomorphological applications using examples from a coastal cliff and a volcanic edifice. The reconstruction process is based on a combination of structure-from-motion and multi-view stereo algorithms (SfM-MVS). Using multiple photographs of a scene taken from different positions with a consumer-grade camera, dense point clouds (millions of points) can be derived. Processing is carried out by automated 'reconstruction pipeline' software downloadable from the internet, e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/. Unlike traditional photogrammetric approaches, the initial reconstruction process does not require the identification of any control points or initial camera calibration and is carried out with little or no operator intervention. However, such reconstructions are initally un-scaled and un-oriented so additional software (http://www.lancs.ac.uk/staff/jamesm/software/sfm_georef.htm) has been developed to permit georeferencing. Although this step requires the presence of some control points or features within the scene, it does not have the relatively strict image acquisition and control requirements of traditional photogrammetry. For accuracy, and to allow error analysis, georeferencing observations are made within the image set, rather than requiring feature matching within the point cloud. In our coastal example, 133 photos taken with a Canon EOS 450D and 28 mm prime lens, from viewing distances of ~20 m, were used to reconstruct a ~60 m long section of eroding cliff. The resulting surface model was compared with data collected by a Riegl LMS-Z210ii terrestrial laser scanner. Differences between the surfaces were dominated by the varying effects of occlusions on the techniques, and systematic distortion of the SfM-MVS model along the length of the cliff could not be resolved over the ±15 mm precision of the TLS data. For a larger-scale example, a ~1.6 km wide region over the summit of Piton de la Fournaise volcano was reconstructed using 133 photos taken with a Canon EOS D60 and 20 mm prime lens, from a microlight aircraft (with a representative viewing distance of 1.0 km). In this case, the resulting DEM showed an RMS error of 1.0 m when compared with the results from traditional photogrammetry and some areas of systematic error were evident. Such errors were minimised by reprocessing the SfM-MVS results with a more sophisticated camera model than is integrated into the reconstruction pipeline. In combination, the results indicate that, with a good, convergent image set, SfM-MVS can be anticipated to deliver relative precisions of 1:1000 or better, for geomorphological applications. However, under certain conditions, the restricted camera model used can result in detectable error. We highlight the requirement for new network design tools that will help optimise image collection, facilitate error visualisation and allow a user to determine whether their image network is fit for purpose.

  18. Creation of a Multiresolution and Multiaccuracy Dtm: Problems and Solutions for Heli-Dem Case Study

    NASA Astrophysics Data System (ADS)

    Biagi, L.; Carcano, L.; Lucchese, A.; Negretti, M.

    2013-01-01

    The work is part of "HELI-DEM" (HELvetia-Italy Digital Elevation Model) project, funded by the European Regional Development Fund within the Italy-Switzerland cooperation program. The aim of the project is the creation of a unique DTM for the alpine and subalpine area between Italy (Piedmont, Lombardy) and Switzerland (Ticino and Grisons Cantons); at present, different DTMs, that are in different reference frames and have been obtained with different technologies, accuracies, and resolutions, have been acquired. The final DTM should be correctly georeferenced and produced validating and integrating the data that are available for the project. DTMs are fundamental in hydrogeological studies, especially in alpine areas where hydrogeological risks may exist. Moreover, when an event, like for example a landslide, happens at the border between countries, a unique and integrated DTM which covers the interest area is useful to analyze the scenario. In this sense, HELI-DEM project is helpful. To perform analyses along the borders between countries, transnational geographic information is needed: a transnational DTM can be obtained by merging regional low resolution DTMs. Moreover high resolution local DTMs should be used where they are available. To be merged, low and high resolution DTMs should be in the same three dimensional reference frame, should not present biases and should be consistent in the overlapping areas. Cross-validation between the different DTMs is therefore needed. Two different problems should be solved: the merging of regional, partly overlapping low and medium resolution DTMs into a unique low/medium resolution DTM and the merging with other local high resolution/high accuracy height data. This paper discusses the preliminary processing of the data for the fusion of low and high resolution DTMs in a study-case area within the Lombardy region: Valtellina valley. In this region the Lombardy regional low resolution DTM is available, with a horizontal resolution of 20 meters; in addition a LiDAR DTM with a horizontal resolution of 1 meter, which covers only the main hydrographic basins, is also available. The two DTMs have been transformed into the same reference frame. The cross-validation of the two datasets has been performed comparing the low resolution DTM with the local high resolution DTM. Then, where significant differences are present, GPS survey have been used as external validation. The results are presented. Moreover, a possible strategy for the future fusion of the data, is shortly summarized at the end of the paper.

  19. Studying Glacial Melt Processes Using Sub-Centimeter dem Extraction and Digital Close-Range Photogrammetry

    NASA Astrophysics Data System (ADS)

    Sanz-Ablanedo, E.; Chandler, J. H.; Irvine-Fynn, T. D. L.

    2012-07-01

    Glaciers are sensitive to climatic variation and a particular developing area of investigation is in the field of "cryoconite", referring to dustlike residues which form on the glacier surface. Cryoconite absorbs the Sun's shortwave energy, accelerates ice melt and because of the localised distribution of dust creates localised melting which is highly spatially variable. There is therefore a need to quantify the detailed topographic surface of ice and measure its variability through time. This paper describes the use of close range photogrammetry to reconstruct the glacier surface at the sub-centimetre or micro scale, an approach which may allow the relationship between cryoconite and ice surface properties to be explored over either space or time. The field campaign was conducted at Midtre Lovénbreen, Svalbard (78.88° North 12.08° East), during the summer of 2010 and executed using simple equipment and procedures. A simple and ageing Nikon 5400 5 MP camera was used to acquire all imagery, proving sufficiently robust for the challenging field environment. The camera was handheld approximately 1.6 m above the ice surface, providing an oblique perspective. Images were acquired at three different camera/object distances, each generating coverage occupying three different areas. All imagery was processed using the commercial photogrammetric package PhotoModeler Scanner, generating threedimensional point clouds consisting of many thousands of XYZ coordinates, each colour-coded. It had been feared that lack of texture in the ice surface combined with differing specular reflections in each image would compromise the DEM generation process. Results were better than expected, although DEM quality proved to be variable depending on ice cleanliness and more significantly, the degree of obliquity of the image pairs. Despite these differences, digital close-range photogrammetry has proven to be a useful technique to reconstruct the glacier's surface to sub-centimeter precision. Moreover, the method is providing glacial scientists with new data to examine the relationship between cryoconite, ice surface roughness and melt processes.

  20. Toward a simple, DEM-based model for linking channel morphology with Atlantic salmon habitat

    NASA Astrophysics Data System (ADS)

    Snyder, N. P.; Wilkins, B. C.; Wright, J. R.

    2008-12-01

    Atlantic salmon require swiftwater gravel-bedded rivers for rearing and spawning. Morphology of the rivers in coastal New England and Atlantic Canada is strongly influenced by glacial and land-use history. Longitudinal profiles are characterized by relatively steep (gradient >0.002) and flat (gradient <0.0005) segments, with length scales of several km. This heterogeneity corresponds to strong variations in channel form (boulder cascades, pools and riffles, plane beds, low-gradient wetlands, mainstem lakes), substrate grain size, and aquatic habitat characteristics. We seek to develop methods to use simple GIS-based measurements to investigate relationships between channel processes and habitat characteristics. The near extirpation of Atlantic salmon from U.S. rivers motivates restoration efforts, including the removal of barriers to migration and instream habitat restoration projects. Resource managers desire GIS-based methods to facilitate rapid identification of potential spawning and rearing habitat within channel networks. We develop methods for predicting channel conditions using traditional (10-30 m pixels) and lidar (1-m pixels) digital elevation models (DEMs). We calibrate and test our methods using field surveys of habitat, channel form and bed grain size in coastal Maine and New Brunswick. A statistical approach uses stream gradient measured over segments defined by channel centerline intersections with contour lines (3-6 m intervals) on digitized topographic maps, contributing area, and physiographic province. This model explains 73% of the variation in field-identified rearing habitat. Commonly available GIS data allows this model to be applied over large areas, making it useful for regional habitat assessments. We present preliminary results from a process- based model that predicts bed grain size using morphologic measurements from lidar DEMs and the Shields equation. We compare these predictions to field grain size and habitat mapping. The lidar-based method has similar predictive capability to the statistical model, and greater spatial resolution (channel gradient is measured over 0.5-m vertical intervals). We suggest that failures in the lidar-based approach likely relate to local variations in channel roughness and sediment size and supply not included in the model. Further, we speculate that these mismatches may present an opportunity to prioritize stream restoration efforts such as removal of small dams or additions of large woody debris by identifying river reaches with potential high- quality habitat.

  1. Influence of the external DEM on PS-InSAR processing and results on Northern Appennine slopes

    NASA Astrophysics Data System (ADS)

    Bayer, B.; Schmidt, D. A.; Simoni, A.

    2014-12-01

    We present an InSAR analysis of slow moving landslide in the Northern Appennines, Italy, and assess the dependencies on the choice of DEM. In recent years, advanced processing techniques for synthetic aperture radar interferometry (InSAR) have been applied to measure slope movements. The persistent scatterers (PS-InSAR) approach is probably the most widely used and some codes are now available in the public domain. The Stanford method of Persistent Scatterers (StamPS) has been successfully used to analyze landslide areas. One problematic step in the processing chain is the choice of an external DEM that is used to model and remove the topographic phase in a series of interferograms in order to obtain the phase contribution caused by surface deformation. The choice is not trivial, because the PS InSAR results differ significantly in terms of PS identification, positioning, and the resulting deformation signal. We use four different DEMs to process a set of 18 ASAR (Envisat) scenes over a mountain area (~350 km2) of the Northern Appennines of Italy, using StamPS. Slow-moving landslides control the evolution of the landscape and cover approximately 30% of the territory. Our focus in this presentation is to evaluate the influence of DEM resolution and accuracy by comparing PS-InSAR results. On an areal basis, we perform a statistical analysis of displacement time-series to make the comparison. We also consider two case studies to illustrate the differences in terms of PS identification, number and estimated displacements. It is clearly shown that DEM accuracy positively influences the number of PS, while line-of-sight rates differ from case to case and can result in deformation signals that are difficult to interpret. We also take advantage of statistical tools to analyze the obtained time-series datasets for the whole study area. Results indicate differences in the style and amount of displacement that can be related to the accuracy of the employed DEM.

  2. Application of CryoSat-2 data product for DEM generation in Dome-A summit area, Antarctica

    NASA Astrophysics Data System (ADS)

    fang, W.; Cheng, X.; Hui, F.

    2012-12-01

    Currently available Digital Elevation Models (DEMs) of Dome A were originally derived from radar altimetry data (ERS-1/2, GLAS/ICESat), and later improved by GPS measurements. The relatively low resolution and coverage poses a problem, especially for the regional research. CryoSat-2 with SIRAL (SAR/Interferometric Altimeter) was launched on 8 April 2010, providing an alternative for high-density and high-accuracy acquisition of terrain point data. The inclination of the satellite's orbit is 92°, and the orbit can approach latitude of 88°. The repeat period of 369 days provides a high orbit crossover density (10 crossovers km-2 year-1 at 87°) with a 30-day sub-cycle. In this study, we collected ten months (March to December 2011) of successive CryoSat-2 Low Rate Mode level 2 (LRM L2) datasets. Two types of filters were applied to remove additional elevation outliers. These filtering procedures excluded 5.95% of the original data. According to the distribution of the point data, terrain modeling of grid DEM, interpolation method of Kriging (ordinary Kriging), and a grid resolution of 200m is chosen for DEM generation in this study. Finally, we used the satellite's monthly revisits with non-repeated coverage and present a novel DEM of 900 km2 in the Dome A region centered at Kunlun Station (80°25‧01″S, 77°06‧58″E). It shows that the topography of the Dome A region is saddle-shaped, with a northern peak and a southern peak. We used a subtraction method to compare the novel DEM with the previous DEM of GPS measurements. The elevation differences exhibit a positive average elevation bias. It may be due to the penetration of the Ku-band radar wave into the soft snow. As a first approximation based on the statistics of the height differences, we estimate that the average penetration depth of the CryoSat-2 Ku-band wave in this area is 1 m. Map of surface topography over the Dome A region generated from CryoSat-2 data. Contours are smoothed. The contour interval is 1 m.

  3. Constructing a Comprehensive Tool for Deriving Drainage Network using Semi-Open Source Tools and Comparision on Different DEM Data Sources

    NASA Astrophysics Data System (ADS)

    Gupta, P. K.; Yadav, P.

    2014-11-01

    Digital elevation model (DEM) provides elevation information in raster format for an area which help in analysis as these phenomena are gravity depended. Hydrological study requires creation of drainage network map. DEM is the primary input for this process. Generally 6 or more processes are required to be completed to get the drainage network. These are available in form of hydrology tools in the ArcGIS software. These processes are manual and time consuming which increases the chances of human error. An automated process is constructed in this paper which aims to create a tool that can handle multiple files in an intelligent manner. The input DEM plays a significant role in hydrological studies. This study attempts to do a comparative study to analyse the variation in the drainage network and the intermediate products with the change in the input DEM. A tool is created using ArcPy site package in Python programming language to integrate all required hydrology tools. The script is then used to create a tool in ArcGIS 10 which takes location as an input parameter and perform the process on all the DEM files inside the directory. The tool creates separate directory for every DEM file and thus reduces the chances of file mismanagement. The proposed tool is tested on two different datasets namely ASTER GDEM and Cartosat DEM. The tool runs efficiently on both the datasets and thus provides results to compare the drainage pattern produced by these different data sources.

  4. Fusion of space-borne multi-baseline and multi-frequency interferometric results based on extended Kalman filter to generate high quality DEMs

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojie; Zeng, Qiming; Jiao, Jian; Zhang, Jingfa

    2016-01-01

    Repeat-pass Interferometric Synthetic Aperture Radar (InSAR) is a technique that can be used to generate DEMs. But the accuracy of InSAR is greatly limited by geometrical distortions, atmospheric effect, and decorrelations, particularly in mountainous areas, such as western China where no high quality DEM has so far been accomplished. Since each of InSAR DEMs generated using data of different frequencies and baselines has their own advantages and disadvantages, it is therefore very potential to overcome some of the limitations of InSAR by fusing Multi-baseline and Multi-frequency Interferometric Results (MMIRs). This paper proposed a fusion method based on Extended Kalman Filter (EKF), which takes the InSAR-derived DEMs as states in prediction step and the flattened interferograms as observations in control step to generate the final fused DEM. Before the fusion, detection of layover and shadow regions, low-coherence regions and regions with large height error is carried out because MMIRs in these regions are believed to be unreliable and thereafter are excluded. The whole processing flow is tested with TerraSAR-X and Envisat ASAR datasets. Finally, the fused DEM is validated with ASTER GDEM and national standard DEM of China. The results demonstrate that the proposed method is effective even in low coherence areas.

  5. Macromolecular Structure Modeling from 3DEM Using VolRover 2.01

    PubMed Central

    Zhang, Qin; Bettadapura, Radhakrishna

    2012-01-01

    We report several tools for 3DEM structure identification and model-based refinement developed by our research group and implemented in our in-house software package, VolRover. For viral density maps with icosahedral symmetry, we segment the capsid, polymeric and monomeric subunits using segmentation techniques based on symmetry detection and fast marching. For large biomolecules without symmetry information, we use a multi-seeded fast-marching method to segment meaningful substructures. In either case, we subject the resulting segmented subunit to secondary structure detection when the EM resolution is sufficiently high, and rigid-body fitting when the corresponding crystal structure is available. Secondary structure elements are identified by our volume- and boundary-based skeletonization methods as well as a new method, currently in development, based on solving the grassfire flow equation. For rigid-body fitting, we use a translational fast Fourier based scheme. We apply our segmentation, secondary structure elements identification, and rigid-body fitting techniques to the PSB 2011 cryo-EM modeling challenge data, and compare our results to those submitted from other research groups. The comparisons show that our software is capable of segmenting relatively accurate subunits from a viral or protein assembly, and that the high segmentation quality leads in turn to high-quality results of secondary structure elements identification and rigid-body fitting. PMID:22696407

  6. DEM simulation of flow of dumbbells on a rough inclined plane

    NASA Astrophysics Data System (ADS)

    Mandal, Sandip; Khakhar, Devang

    2015-11-01

    The rheology of non-spherical granular materials such as food grains, sugar cubes, sand, pharmaceutical pills, among others, is not understood well. We study the flow of non-spherical dumbbells of different aspect ratios on a rough inclined plane by using soft sphere DEM simulations. The dumbbells are generated by fusing two spheres together and a linear spring dashpot model along with Coulombic friction is employed to calculate inter-particle forces. At steady state, a uni-directional shear flow is obtained which allows for a detailed study of the rheology. The effect of aspect ratio and inclination angle on mean velocity, volume fraction, shear rate, shear stress, pressure and viscosity profiles is examined. The effect of aspect ratio on probability distribution of angles, made by the major axes of the dumbbells with the flow direction, average angle and order parameter is analyzed. The dense flow rheology is well explained by Bagnold's law and the constitutive laws of JFP model. The dependencies of first and second normal stress differences on aspect ratio are studied. The probability distributions of translational and rotational velocity are analyzed.

  7. DEM4-26. Deming`s General Least Square Fitting

    SciTech Connect

    Rinard, P.M.; Goldman, A.

    1988-03-01

    DEM4-26 is a generalized least square fitting program based on Deming`s method. Functions built into the program for fitting include linear, quadratic, cubic, power, Howard`s, exponential, and Gaussian; others can easily be added. The program has the following capabilities: (1) entry, editing, and saving of data; (2) fitting of any of the built-in functions or of a user-supplied function; (3) plotting the data and fitted function on the display screen, with error limits if requested, and with the option of copying the plot to the printer; (4) interpolation of x or y values from the fitted curve with error estimates based on error limits selected by the user; and (5) plotting the residuals between the y data values and the fitted curve, with the option of copying the plot to the printer. If the plot is to be copied to a printer, GRAPHICS should be called from the operating system disk before the BASIC interpreter is loaded.

  8. New insights into high resolution DEM structural analysis with Coltop3D software

    NASA Astrophysics Data System (ADS)

    Metzger, R.; Jaboyedoff, M.; Oppikofer, T.

    2009-04-01

    Modern measurement devices such a terrestrial laser scanning (TLS) systems allow for collecting tremendous amount of (x,y,z) points (up to 20 millions) within a few minutes. However, data analysis still may be impaired because of software limitations, which are usually not designed to handle such huge data sets. To overcome this shortcoming, a software - Coltop3D - was written from scratch. Coltop3D aims at providing the geosciences community a powerful tool to visually handle seamlessly large point clouds and large regular grids DEM, at allowing for straightforward visual analysis of the data with different colour scheme, and at providing specific geologist and/or geoscientist treatment methods such as structural analysis. The main features of Coltop3D are as follow: 1) Ability to handle huge data sets (up to 150 millions points); 2) Coloring the surface with a color scheme linking computer graphics HSV wheel and Schmidt-Lambert stereonet projection; 3) Ability to select a subset of a point cloud with complex geometric shapes; 4) Ability to select a subset of a point cloud with dip and dip direction values; 5) Creating density stereonets with selected subset; 6) Easily import from or export point cloud data to third party software. Besides the technical and basic capabilities of Coltop3D, specific case studies such as structural analysis and rock fall analysis will be presented.

  9. Relationships between volcanic patterns and neotectonics in Eastern Anatolia from analysis of satellite images and DEM

    NASA Astrophysics Data System (ADS)

    Adıyaman, Ö.; Chorowicz, J.; Köse, O.

    1998-10-01

    The late Neogene to Quaternary volcanism in Eastern Anatolia is related to the Arabia-Eurasia convergence but a clear deformation pattern has not yet been established in this region. We have used the distribution and shape of volcanoes and fault geometry as indicators of the tectonic regime. Volcanic edifices and related faults were analyzed in vertical view using SAR-ERS, Spot images and a Digital Elevation Model (DEM). In several places, adjacent volcanoes that form linear clusters or elongated volcanoes are clearly rooted on vertical tension fractures. These are compatible with horizontal σ 3 striking 90°N, associated with σ 1 horizontal (strike-slip regime) or vertical (extensional regime). We mapped the recent faults that are directly associated to volcanoes. Volcanic vents are related to tail-crack, horsetail or releasing bend structures. In this work, it has been possible to define the ESE-striking, 270-km-long Tutak-Hamur-Çaldiran fault that forms a releasing bend testifying to right-lateral motion. Extension is well documented for few places but no recent fold has been observed. Since 8 Ma, the tectonic system is principally strike-slip. Most of the tension fractures being 2 to 10 km in length, so we infer that they affect only part of the crust. Most strike-slip fault zones are of several tens to a few hundred kilometers long and thus not of lithospheric scale. Therefore, the channels used by the magma to reach the surface are crustal structures.

  10. A DEM-Based Watershed Model with Spatial Hortonian Infiltration and Run-Off/On

    NASA Astrophysics Data System (ADS)

    Meng, H.; Green, T. R.; Salas, J. D.; Ahuja, L. R.

    2005-12-01

    A physically based, distributed rainfall-runoff-runon model was developed for event-based studies of dynamic watershed processes, including space-time patterns of state variables (e.g., soil profile water storage) and fluxes (e.g., overland flow and infiltration). A routing hierarchy for dynamic runoff and runon is defined over all DEM grid cells using the D-infinity terrain algorithm. Ponding time is computed to handle variable rainfall intensity, the Green-Ampt model is used to calculate infiltration, and the kinematic wave model is used to route Hortonian hillslope runoff and channel flow. The distributed rainfall-runoff model can handle input rainfall, soil parameters, and other watershed properties that vary in space and/or time. The model was first tested against theoretical solutions for idealized overland plane with satisfactory results. After a sensitivity analysis to identify the most significant calibration parameters, the model was calibrated and verified using rainfall and channel streamflow data collected from USDA-ARS Walnut Gulch experimental watershed. Finally, we will demonstrate applications of the model for simulating space-time patterns of fluxes and state variables within a watershed.

  11. CFD-DEM study of effect of bed thickness for bubbling fluidized beds

    SciTech Connect

    Tingwen, Li; Gopalakrishnan, Pradeep; Garg, Rahul; Shahnam, Mehrdad

    2011-10-01

    The effect of bed thickness in rectangular fluidized beds is investigated through the CFD–DEM simulations of small-scale systems. Numerical results are compared for bubbling fluidized beds of various bed thicknesses with respect to particle packing, bed expansion, bubble behavior, solids velocities, and particle kinetic energy. Good two-dimensional (2D) flow behavior is observed in the bed having a thickness of up to 20 particle diameters. However, a strong three-dimensional (3D) flow behavior is observed in beds with a thickness of 40 particle diameters, indicating the transition from 2D flow to 3D flow within the range of 20–40 particle diameters. Comparison of velocity profiles near the walls and at the center of the bed shows significant impact of the front and back walls on the flow hydrodynamics of pseudo-2D fluidized beds. Hence, for quantitative comparison with experiments in pseudo-2D columns, the effect of walls has to be accounted for in numerical simulations.

  12. Satellite-derived Digital Elevation Model (DEM) selection, preparation and correction for hydrodynamic modelling in large, low-gradient and data-sparse catchments

    NASA Astrophysics Data System (ADS)

    Jarihani, Abdollah A.; Callow, John N.; McVicar, Tim R.; Van Niel, Thomas G.; Larsen, Joshua R.

    2015-05-01

    Digital Elevation Models (DEMs) that accurately replicate both landscape form and processes are critical to support modelling of environmental processes. Topographic accuracy, methods of preparation and grid size are all important for hydrodynamic models to efficiently replicate flow processes. In remote and data-scarce regions, high resolution DEMs are often not available and therefore it is necessary to evaluate lower resolution data such as the Shuttle Radar Topography Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) for use within hydrodynamic models. This paper does this in three ways: (i) assessing point accuracy and geometric co-registration error of the original DEMs; (ii) quantifying the effects of DEM preparation methods (vegetation smoothed and hydrologically-corrected) on hydrodynamic modelling relative accuracy; and (iii) quantifying the effect of the hydrodynamic model grid size (30-2000 m) and the associated relative computational costs (run time) on relative accuracy in model outputs. We initially evaluated the accuracy of the original SRTM (∼30 m) seamless C-band DEM (SRTM DEM) and second generation products from the ASTER (ASTER GDEM) against registered survey marks and altimetry data points from the Ice, Cloud, and land Elevation Satellite (ICESat). SRTM DEM (RMSE = 3.25 m,) had higher accuracy than ASTER GDEM (RMSE = 7.43 m). Based on these results, the original version of SRTM DEM, the ASTER GDEM along with vegetation smoothed and hydrologically corrected versions were prepared and used to simulate three flood events along a 200 km stretch of the low-gradient Thompson River, in arid Australia (using five metrics: peak discharge, peak height, travel time, terminal water storage and flood extent). The hydrologically corrected DEMs performed best across these metrics in simulating floods compared with vegetation smoothed DEMs and original DEMs. The response of model performance to grid size was non-linear and while the smaller grid sizes (⩽120 m) improved the hydrodynamic model results, these offered only slight improvements at very significant computational costs compared to grid size of 120 m, with grid sizes 250 m and greater decreasing in model accuracy. This study highlights the important impact that the quality of the underlying DEM has, and in particular how sensitive hydrodynamic models are to preparation methods and how important vegetation smoothing and hydrological correction of the base topographic data for modelling floods in low-gradient and multi-channel environments.

  13. Predicting anthropogenic streambed shifts in Beckley, West Virginia, modeled over 15 years using LANDSAT TM and DEMS

    NASA Astrophysics Data System (ADS)

    Reinhardt, Andrew D.

    Anthropogenic change of streambeds in the Beckley, West Virginia watershed region was modeled using Landsat 5 TM satellite data from 1988 and 2003, and Digital Elevation Model (DEM) data for 1969 and 2005. Comparing the 15 year land cover changes and the 36 year elevation shifts, and using a modified Universal Soil Loss Equation (USLE), in ESRI ArcMap and ERDAS Imagine, a streambed shift model was created. The model predicted land cover and elevation changes for 2018, using inputs from geospatial differencing of 2003 and 1988 land cover as well as 2003 and 1969 DEM data. Further analysis using hydrodynamic differential equations provided in depth information on stream clogging over the 15 year study period.

  14. Precise Determination of the Baseline Between the TerraSAR-X and TanDEM-X Satellites

    NASA Astrophysics Data System (ADS)

    Koenig, Rolf; Rothacher, Markus; Michalak, Grzegorz; Moon, Yongjin

    TerraSAR-X, launched on June 15, 2007, and TanDEM-X, to be launched in September 2009, both carry the Tracking, Occultation and Ranging (TOR) category A payload instrument package. The TOR consists of a high-precision dual-frequency GPS receiver, called Integrated GPS Occultation Receiver (IGOR), for precise orbit determination and atmospheric sounding and a Laser retro-reflector (LRR) serving as target for the global Satellite Laser Ranging (SLR) ground station network. The TOR is supplied by the GeoForschungsZentrum Potsdam (GFZ) Germany, and the Center for Space Research (CSR), Austin, Texas. The objective of the German/US collaboration is twofold: provision of atmospheric profiles for use in numerical weather predictions and climate studies from the occultation data and precision SAR data processing based on precise orbits and atmospheric products. For the scientific objectives of the TanDEM- X mission, i.e., bi-static SAR together with TerraSAR-X, the dual-frequency GPS receiver is of vital importance for the millimeter level determination of the baseline or distance between the two spacecrafts. The paper discusses the feasibility of generating millimeter baselines by the example of GRACE, where for validation the distance between the two GRACE satellites is directly available from the micrometer-level intersatellite link measurements. The distance of the GRACE satellites is some 200 km, the distance of the TerraSAR-X/TanDEM-X formation will be some 200 meters. Therefore the proposed approach is then subject to a simulation of the foreseen TerraSAR-X/TanDEM-X formation. The effect of varying space environmental conditions, of possible phase center variations, multi path, and of varying center of mass of the spacecrafts are evaluated and discussed.

  15. Quantifying Ice-sheet/Ice-shelf Dynamics and Variability with Meter-scale DEM and Velocity Timeseries

    NASA Astrophysics Data System (ADS)

    Shean, D. E.; Joughin, I. R.; Smith, B. E.; Moratto, Z. M.; Porter, C.; Morin, P. J.

    2012-12-01

    Both the Antarctic and Greenland ice sheets are losing mass at an increasing rate, although loss due to accelerating flow and dynamic thinning remains poorly understood. We are using complementary data from repeat satellite and airborne observations to investigate the relationship between ice-sheet/ice-shelf dynamics and geometry on seasonal to interannual timescales. High-resolution along-track stereo imagery from commercial satellite vendors DigitalGlobe and GeoEye provides unprecedented spatial (~0.5 m/px with ~17 km swath width) and temporal (weekly/monthly) resolution for these efforts. We have developed an automated pipeline using open-source software to produce orthoimage, DEM, and surface velocity products from DigitalGlobe imagery. High-contrast surface texture (e.g. sastrugi, crevasses) visible at sub-meter resolution provides near-perfect image correlation (~99% success rate) during DEM and velocity map derivation. Elevation data from IceBridge ATM/LVIS, ICESat GLAS, and GPS campaigns are used to correct DEMs and perform accuracy assessment. Preliminary tests over exposed bedrock provide relative vertical accuracy estimates of <1-2 m for Worldview-1/2 DEMs. Velocity data from TerraSAR-X and GPS campaigns provide validation for surface velocity products, with horizontal error estimates of <10 m. Velocity and elevation change products with 2-4 m/px spatial resolution allow for unprecedented 3D dynamic characterization of sub-km flow transition zones (e.g. grounding lines, shear margins), capturing both local and regional variations due to melting and dynamic thinning. We present timeseries for West Greenland (Jakobshavn front - 20 observations, Jakobshavn south catchment - 10) and West Antarctica (Pine Island and Thwaites - 5 each) from 2009-2012. These observations complement ongoing efforts to measure and model outlet glacier dynamics, with implications for future ice-sheet mass balance estimates.

  16. Direct micromechanics derivation and DEM confirmation of the elastic moduli of isotropic particulate materials: Part I No particle rotation

    NASA Astrophysics Data System (ADS)

    Fleischmann, J. A.; Drugan, W. J.; Plesha, M. E.

    2013-07-01

    We derive the macroscopic elastic moduli of a statistically isotropic particulate aggregate material via the homogenization methods of Voigt (1928) (kinematic hypothesis), Reuss (1929) (static hypothesis), and Hershey (1954) and Kröner (1958) (self-consistent hypothesis), originally developed to treat crystalline materials, from the directionally averaged elastic moduli of three regular cubic packings of uniform spheres. We determine analytical expressions for these macroscopic elastic moduli in terms of the (linearized) elastic inter-particle contact stiffnesses on the microscale under the three homogenization assumptions for the three cubic packings (simple, body-centered, and face-centered), assuming no particle rotation. To test these results and those in the literature, we perform numerical simulations using the discrete element method (DEM) to measure the overall elastic moduli of large samples of randomly packed uniform spheres with constant normal and tangential contact stiffnesses (linear spring model). The beauty of DEM is that simulations can be run with particle rotation either prohibited or unrestrained. In this first part of our two-part series of papers, we perform DEM simulations with particle rotation prohibited, and we compare these results with our theoretical results that assumed no particle rotation. We show that the self-consistent homogenization assumption applied to the locally body-centered cubic (BCC) packing most accurately predicts the measured values of the overall elastic moduli obtained from the DEM simulations, in particular Poisson's ratio. Our new analytical self-consistent results lead to significantly better predictions of Poisson's ratio than all prior published theoretical results. Moreover, our results are based on a direct micromechanics analysis of specific geometrical packings of uniform spheres, in contrast to all prior theoretical analyses, which were based on difficult-to-verify hypotheses involving overall inter-particle contact distributions. We continue the analysis begun in this first part for the case of unrestrained particle rotation in Part II, Fleischmann et al. (2013).

  17. Effect of DEM source on equivalent Horton-Strahler ratio based GIUH for catchments in two Indian river basins

    NASA Astrophysics Data System (ADS)

    Chavan, Sagar Rohidas; Srinivas, V. V.

    2015-09-01

    Horton-Strahler (H-S) concept has been extensively used for quantification of characteristics of a stream network since several decades. The quantified values are often sensitive to threshold area specified for initiation of streams to demarcate the network, and to the position of outlet of a catchment. This implies that inferences drawn based on derived characteristics for a stream network are likely to be inconsistent, which is undesirable. To address this, a strategy based on self-similarity properties of channel network was proposed recently by Moussa (2009), which involves estimation of equivalent H-S ratios using catchment shape descriptors that are independent of threshold area. This study investigates effectiveness of the strategy on 42 catchments of various sizes in two Indian river basins (Cauvery and Mahanadi). Effect of digital elevation model (DEM) source on estimates of equivalent H-S ratios and characteristics of Geomorphologic Instantaneous Unit Hydrograph (GIUH) derived based on the same are examined by considering SRTM and ASTER DEMs. Results indicate that self-similarity assumptions are valid for the Indian catchments. Comparison of equivalent GIUH derived for each of the catchments based on real channel network with that derived using different DEM sources indicated differences that could be attributed to DEM-based uncertainty associated with estimates of: (i) equivalent H-S ratios that are functions of the self-similarity properties of channel network, and (ii) equivalent length of highest order stream that depends on self-similarity properties and configuration/characteristics of stream network. This uncertainty cannot be ignored in hydrological studies.

  18. A Screening Method for Flash Flooding Risk using Instantaneous Unit Hydrographs Derived from High Resolution DEM data

    NASA Astrophysics Data System (ADS)

    Senevirathne, Nalin; Willgoose, Garry

    2015-04-01

    Flash flooding is considered a severe natural hazard and has had significant impact on human and infrastructure throughout the history. Modelling techniques and the understanding of flash flooding are getting improved with the availability of better quality data such as high resolution Digital Elevation Models (DEM). DEMs allow the automated characterization of the influence of geomorphology on the hydrologic response of catchments. They are particularly useful for small ungauged catchments where available hydrologic data (e.g. rainfall, runoff) are sparse and where site specific studies are rarely done unless some evidence of high risk is available. In this paper, we present new risk indicators, derived directly from instantaneous unit hydrographs (IUH), which can be used to identify flash flooding risk areas within catchments. The study area includes 35 major river basins covering a 1700km long by 50km wide coastal strip of Eastern Australia. Standard terrain analysis methods (pit filling, flow direction, local slope, contributing area, flow velocity and travel time) were used to produce IUHs for every pixel in the study area using a high resolution (1 arc second) DEM. When computing the IUHs, each pixel was considered as the outlet of its own catchment bounded by its contributing area. This allows us to characterise the hydrological response at the finest scale possible for a DEM. Risk indicators related to rate of storm rise and catchment lag time were derived from IUHs. Flash flood risk maps were produced at the catchment scale and they are match well with the data of severe flash flooding that occurred around Toowoomba (at the northern end of the coastal strip studied) in January 2011.

  19. Instabilities in a Freely Cooling Granular Gas: A Quantitative Comparison of DEM simulations and Kinetic-Theory-based models

    NASA Astrophysics Data System (ADS)

    Mitrano, Peter; Hilger, Andrew; Hrenya, Christine

    2011-11-01

    Experiments, discrete element method (DEM) simulations, and kinetic-theory-based predictions have demonstrated the existence of clustering instabilities in flows of solid, inelastic grains. Such instabilities have also been studied via stability analyses of the continuum balances for rapid granular flows. Spurred by discrepancies between DSMC-based and kinetic-theory-based transport coefficients in extremely dissipative systems, previous work has shown that a modified Sonine approximation reduces this disagreement. However, the quantitative accuracy of this modified kinetic theory with respect to predicting instabilities has not been addressed. In this work, hard-sphere, event-driven DEM simulations of the homogenous cooling system are used to study instabilities in granular systems. Detection of instabilities is determined via Fourier analysis. The aim is to determine the critical system size at which clustering appears over a wide range of dissipation. By comparing the critical size from DEM with the predictions based on standard (Garz 2005) and modified (Garz 2007) Sonine approximations, this work aims to assess the quantitative ability of each model to predict instabilities for monodisperse granular flows.

  20. Detecting Blind Fault with Fractal and Roughness Factors from High Resolution LiDAR DEM at Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, Y. S.; Yu, T. T.

    2014-12-01

    There is no obvious fault scarp associated with blind fault. The traditional method of mapping this unrevealed geological structure is the cluster of seismicity. Neither the seismic event nor the completeness of cluster could be captured by network to chart the location of the entire possible active blind fault within short period of time. High resolution DEM gathered by LiDAR could denote actual terrain information despite the existence of plantation. 1-meter interval DEM of mountain region at Taiwan is utilized by fractal, entropy and roughness calculating with MATLAB code. By jointing these handing, the regions of non-sediment deposit are charted automatically. Possible blind fault associated with Chia-Sen earthquake at southern Taiwan is served as testing ground. GIS layer help in removing the difference from various geological formation, then multi-resolution fractal index is computed around the target region. The type of fault movement controls distribution of fractal index number. The scale of blind fault governs degree of change in fractal index. Landslide induced by rainfall and/or earthquake possesses larger degree of geomorphology alteration than blind fault; special treatment in removing these phenomena is required. Highly weathered condition at Taiwan should erase the possible trace remained upon DEM from the ruptured of blind fault while reoccurrence interval is higher than hundreds of years. This is one of the obstacle in finding possible blind fault at Taiwan.

  1. Two Different Supply Styles of Crater Outflow Materials on Venus Inferred from Numerical Simulations over DEMs

    NASA Astrophysics Data System (ADS)

    Miyamoto, Hideaki; Sasaki, Sho

    2000-06-01

    The three-dimensional numerical simulation code for nonisothermal Bingham fluid was applied to four typical crater outflows on Venus to estimate emplacement styles of outflow materials. We have succeeded in reproducing emplacement features qualitatively over digital elevation models (DEMs) obtained by the Magellan spacecraft, and we have shown that outflow materials can be formed by melts of basaltic crust. Therefore, the presence of crater outflows may not be evidence of the presence of previously suggested fluid materials, such as komatiite or carbonatite, although we failed to model the very low viscosity flow. Numerically estimated supply rates of flow materials are categorized into two types, a catastrophic style and a gentle style. Markham and Isabella crater outflows are examples of catastrophic styles, and the flow materials required to form them were probably supplied at higher rates than 10 10 m 3/s and the durations of material supply were less than 100 s. This very high supply rate is difficult to attribute to any volcanic process because typical eruption rates of terrestrial volcanic flows are less than 8 or 9 orders of magnitude lower than that. Such a style of emplacement is more plausibly considered as a result of the impact itself, for example, a catastrophic debris flow or a vapor cloud triggered by the impact. On the other hand, supply rates of Willard and Xantippe outflows, which are considered gentle-style flows, were estimated to be about 10 4 m 3/s and the durations were more than 10 5 s. Such a gentle style of outflow emplacement is probably not a direct result of the impact but is rather due to a secondary process, possibly segregation and drainage of impact melt materials from within previously emplaced ejecta materials, or post-impact volcanism.

  2. Influence of H- and OH-adsorbates on the ethanol oxidation reaction--a DEMS study.

    PubMed

    Bach Delpeuch, Antoine; Chatenet, Marian; Rau, Maria Sol; Cremers, Carsten

    2015-04-28

    The ethanol oxidation reaction (EOR) was investigated by potentiodynamic techniques on Pt/C, Rh/C, Pt-Rh/C, Pt-SnO2/C and Pt-Rh-SnO2/C by differential electrochemical mass spectrometry (DEMS) in a flow cell system. Prior to the cyclic voltammetries, adsorption of H- and OH-species was carried out by chronoamperometry at Ead = 0.05 and 1 V vs. RHE, respectively, in order to examine their influence on the EOR on the different electrocatalysts. For the sake of comparison, another adsorption potential was chosen at Ead = 0.3 V vs. RHE, in the double layer region (i.e. in the absence of such adsorbates). For this study, 20 wt% electrocatalysts were synthesized using a modified polyol method and were physically characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). When comparing the first and second cycles of the cyclic voltammograms (CVs) on Pt/C and Pt-SnO2/C, the presence of Had on the electrocatalyst surface seems to hinder the initiation of the ethanol electrooxidation, whereas the reaction onset potential is shifted negatively with the presence of OH-adsorbates. In contrast to them, the EOR on Rh/C is enhanced when the electrocatalyst surface is covered with Had and is inhibited after adsorption at Ead = 0.3 and 1 V vs. RHE. Finally, on Pt-Rh/C and Pt-Rh-SnO2/C, neither the H- nor OH-adsorbates do impact the EOR initiation. The lowest EOR onset was recorded on Pt-SnO2/C and Pt-Rh-SnO2/C electrocatalysts. The CO2 currency efficiency (CCE) was also determined for each electrocatalyst and demonstrated higher values on Pt-Rh-SnO2/C. PMID:25820025

  3. Assessment of potential catastrophic landslides in Taiwan by airborne LiDAR-derived DEM

    NASA Astrophysics Data System (ADS)

    Hou, Chin-Shyong; Hsieh, Yu-Chung; Hu, Jyr-Ching; Chiu, Cheng-Lung; Chen, Hung-Jen; Fei, Li-Yuan

    2013-04-01

    The heavy rainfall of Typhoon Morakot caused severe damage to infrastructures, property and human lives in southern Taiwan in 2009. The most atrocious incident was the Hsiaolin landslide, which buried more than 400 victims. After this catastrophic event, the recognition of localities of deep-seated landslides becomes a critical issue in landslide hazard mitigation induced from extreme climate events. Consequently the airborne LiDAR survey was carried out in first phase from 2010 to 2012 by Central Geological Survey, MOEA in Taiwan in order to assess the potential catastrophic deep-seated landslides in the steep and rocky terrain in south-central Taiwan. The second phase of LiDAR survey is ongoing from 2013 to 2015 for the recognition and the assessment of possible impact area induced by deep-seated landslide in the mountainous area of whole Taiwan. Transitionally, the recognition of potential deep-seated landslide sites is adopted in term of landslide inventories from space-borne images, aerial photographs and field investigation. However, it is difficult to produce robust landslide inventories due to the poor spatial resolution of ground elevation and highly dense vegetation in mountainous area in Taiwan. In this study, the 1 m LiDAR-derived DEM is used to extract key geomorphological features such as crown cracks, minor scarps, toe of surface rupture at meter to sub-meter scale hidden under forests with high degree of accuracy. Preliminary result shows that about 400 potential landslide sites have been recognized to improve the quality of landslide inventories. In addition, detailed contour maps and visualized images are reproduced to outline the shape of potential deep-seated landslides. Further geomorphometric analyses based on hillshade, aspect, slope, eigenvalue ratio (ER) and openness will be integrated to easily create landslide inventories to mitigate landslide disasters in Taiwan mountainous area.

  4. Stereo-derived Topography from the Venus Magellan Dataset: An Assessment of the Quantitative Scientific Value of Sub-km DEM Products

    NASA Astrophysics Data System (ADS)

    Gleason, A. L.; Glaze, L. S.; Herrick, R. R.; Garvin, J. B.

    2009-03-01

    Quantitative information is difficult to extract from sub-km DEMs (derived from stereo SAR images) on surface properties and processes for a range of different landforms on Venus, including tesserae, coronae, lava flows, and lava channels.

  5. Release of a 10-m-resolution DEM for the whole Italian territory: a new, freely available resource for research purposes

    NASA Astrophysics Data System (ADS)

    Tarquini, S.; Nannipieri, L.; Favalli, M.; Fornaciai, A.; Vinci, S.; Doumaz, F.

    2012-04-01

    Digital elevation models (DEMs) are fundamental in any kind of environmental or morphological study. DEMs are obtained from a variety of sources and generated in several ways. Nowadays, a few global-coverage elevation datasets are available for free (e.g., SRTM, http://www.jpl.nasa.gov/srtm; ASTER, http://asterweb.jpl.nasa.gov/). When the matrix of a DEM is used also for computational purposes, the choice of the elevation dataset which better suits the target of the study is crucial. Recently, the increasing use of DEM-based numerical simulation tools (e.g. for gravity driven mass flows), would largely benefit from the use of a higher resolution/higher accuracy topography than those available at planetary scale. Similar elevation datasets are neither easily nor freely available for all countries worldwide. Here we introduce a new web resource which made available for free (for research purposes only) a 10 m-resolution DEM for the whole Italian territory. The creation of this elevation dataset was presented by Tarquini et al. (2007). This DEM was obtained in triangular irregular network (TIN) format starting from heterogeneous vector datasets, mostly consisting in elevation contour lines and elevation points derived from several sources. The input vector database was carefully cleaned up to obtain an improved seamless TIN refined by using the DEST algorithm, thus improving the Delaunay tessellation. The whole TINITALY/01 DEM was converted in grid format (10-m cell size) according to a tiled structure composed of 193, 50-km side square elements. The grid database consists of more than 3 billions of cells and occupies almost 12 GB of disk memory. A web-GIS has been created (http://tinitaly.pi.ingv.it/ ) where a seamless layer of images in full resolution (10 m) obtained from the whole DEM (both in color-shaded and anaglyph mode) is open for browsing. Accredited navigators are allowed to download the elevation dataset.

  6. Mapping hydrological environments in central Amazonia: ground validation and surface model based on SRTM DEM data corrected for deforestation

    NASA Astrophysics Data System (ADS)

    Moulatlet, G. M.; Rennó, C. D.; Costa, F. R. C.; Emilio, T.; Schietti, J.

    2015-03-01

    One of the most important freely available digital elevation models (DEMs) for Amazonia is the one obtained by the Shuttle Radar Topography Mission (SRTM). However, since SRTM tends to represent the vegetation surface instead of the ground surface, the broad use of SRTM DEM as a framework for terrain description in Amazonia is hampered by the presence of deforested areas. We present here two data sets: (1) a deforestation-corrected SRTM DEM for the interfluve between the Purus and Madeira rivers, in central Amazonia, which passed through a careful identification of different environments and has deforestation features corrected by a new method of increasing pixel values of the DEM (Rennó, 2009); and (2) a set of 18 hydrological-topographic descriptors based on the corrected SRTM DEM. Deforestation features are related with the opening of an 800 km road in the central part of the interfluve and occupancy of its vicinity. We used topographic profiles from the pristine forest to the deforested feature to evaluate the recovery of the original canopy coverage by minimizing canopy height variation (corrections ranged from 1 to 38 m). The hydrological-topographic description was obtained by the Height Above the Nearest Drainage (HAND) algorithm, which normalizes the terrain elevation (above sea level) by the elevation of the nearest hydrologically connected drainage. The validation of the HAND data set was done by in situ hydrological description of 110 km of walking trails also available in this data set. The new SRTM DEM expands the applicability of SRTM data for landscape modelling; the data sets of hydrological features based on topographic modelling are undoubtedly appropriate for ecological modelling and an important contribution to environmental mapping of Amazonia. The deforestation-corrected SRTM DEM is available at http://ppbio.inpa.gov.br/knb/metacat/naman.318.3/ppbio; the polygons selected for deforestation correction are available at http://ppbio.inpa.gov.br/knb/metacat/naman.317.3/ppbio; the set of hydrological-topographic descriptors is available at http://ppbio.inpa.gov.br/knb/metacat/naman.544.2/ppbio; the environmental description of access trails is available at http://ppbio.inpa.gov.br/knb/metacat/naman.541.2/ppbio; and the limits of deforestation corrections and drainage validation are available at http://ppbio.inpa.gov.br/knb/metacat/liliandias.38.1/ppbio.

  7. DEM-based model for reconstructing volcano's morphology from primary volcanic landforms

    NASA Astrophysics Data System (ADS)

    Gayer, Eric; Lopez, Philippe; Michon, Laurent

    2014-05-01

    Volumes of magma intruded in and emitted by volcanoes through time can be estimated by reconstruction of volcano's morphology and time sequence. Classical approaches for quantifying magma volumes on active volcanoes are based on the difference between pre- and post-eruption digital elevation models (DEM), but this kind of approach needs the pre-eruptive surfaces to be available. For old and eroded volcanoes these surfaces are poorly constrained. However, because the geometrical form of many volcanic edifices exhibits a remarkable symmetry we propose, here, a new approach using primary volcanic landforms in order to estimate the amount of the both erupted and eroded material and to locate eruptive centers. A large fraction of composite volcanoes have near constant slope on their flanks and a form that is concave upwards near their summits. But many phenomena can lead to non-symetrical edifices and complex morphologies can result, for example from parasitic centers of volcanism on the flanks, from alternation of short effusive and explosive construction phases, from flank or caldera collapses, or from glacial and other types of erosion. In this study we propose that, on the first order approximation, complex morphologies can be modeled by piling regular cones. In this model, cones centers and slopes are derived by fitting primary volcanic landform with a linear function :elevation=f(distance from center). Such an approach allows to estimate both errors on location of the eruptive center and on the volume of the resulting cones. This model can then be used for quantifying volume of erupted and eroded material, and for quantifying catastrophic events as giant landslides or flank collapse. This approach is tested on four different active volcanoes : Mount Mayon (Philippines), Mount Fuji (Japan), Mount Etna (Sicily) and Mount Teide (Canary Island) to estimate errors in volume between modeled and actual edifices. It is then used on volcanoes of La Réunion hotspot to reconstruct the Piton des Neiges and Piton de la Fournaise volcanoes at its different stages of growing.

  8. Coupled LBM-DEM Three-phase Simulation on Gas Flux Seeping from Marine Sediment

    NASA Astrophysics Data System (ADS)

    Kano, Y.; Sato, T.

    2014-12-01

    One of the main issues of the geological storage of CO2 under the seabed is a risk of CO2 leakage. Once CO2seeps into the ocean, it rises in water column dissolving into seawater, which results in the acidification of seawater and/or returning to the air. Its behaviour significantly depends on flow rate and bubble size (Kano et al., 2009; Dewar et al., 2013). As for porous media, bubble size is generally predicted through simple force balance based on flow rate, surface tension and channel size which is estimated by porosity and grain size. However, in shallow marine sediments, grains could be mobilised and displaced by buoyant gas flow, which causes distinctive phenomena such as blow-out or formation of gas flow conduit. As a result, effective gas flux into seawater can be intermissive, and/or concentrated in narrow area (QICS, 2012; Kawada, 2013). Bubble size is also affected by these phenomena. To predict effective gas flux and bubble size into seawater, three-phase behaviour of gas-water-sediment grains should be revealed. In this presentation, we will report the results of gas-liquid-solid three-phase simulations and their comparisons with experimental and observation data. Size of solid particles is based on grain size composing marine sediments at some CCS project sites. Fluid-particle interactions are solved using the lattice Boltzmann method (LBM), while the particle-particle interactions are treated by coupling with the Discrete Element method (DEM). References: Dewar, M., Wei, W., McNeil, D., Chen, B., 2013. Small-scale modelling of the physiochemical impacts of CO2leaked from sub-seabed reservoirs or pipelines within the North Sea and surrounding waters. Marine Pollution Bulletin 73(2), 504-515. Kano, Y., Sato, T., Kita, J., Hirabayashi, S., Tabeta, S., 2009. Model prediction on the rise of pCO2 in uniform flows by leakage of CO2purposefully stored under the seabed. Int. J. Greenhouse Gas Control, Vol. 3(5), 617-625. Kawada, R. 2014. A study on the mechanism which determines the size of bubbles seeping from sand sediment. Graduation thesis. Faculty of Engineering, The University of Tokyo. (in Japanese). QICS, 2012. QICS: Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage. (accessed Aug.06.14)

  9. Forecasting Rainfall Induced Landslide using High Resolution DEM and Simple Water Budget Model

    NASA Astrophysics Data System (ADS)

    Luzon, P. K. D.; Lagmay, A. M. F. A.

    2014-12-01

    Philippines is hit by an average of 20 typhoons per year bringing large amount of rainfall. Monsoon carrying rain coming from the southwest of the country also contributes to the annual total rainfall that causes different hazards. Such is shallow landslide mainly triggered by high saturation of soil due to continuous downpour which could take up from hours to days. Recent event like this happened in Zambales province September of 2013 where torrential rain occurred for 24 hours amounting to half a month of rain. Rainfall intensity measured by the nearest weather station averaged to 21 mm/hr from 10 pm of 22 until 10 am the following day. The monsoon rains was intensified by the presence of Typhoon Usagi positioned north and heading northwest of the country. A number of landslides due to this happened in 3 different municipalities; Subic, San Marcelino and Castillejos. The disaster have taken 30 lives from the province. Monitoring these areas for the entire country is but a big challenge in all aspect of disaster preparedness and management. The approach of this paper is utilizing the available forecast of rainfall amount to monitor highly hazardous area during the rainy seasons and forecasting possible landslide that could happen. A simple water budget model following the equation Perct=Pt-R/Ot-∆STt-AETt (where as the terms are Percolation, Runoff, Change in Storage, and Actual Evapotraspiration) was implemented in quantifying all the water budget component. Computations are in Python scripted grid system utilizing the widely used GIS forms for easy transfer of data and faster calculation. Results of successive runs will let percolation and change in water storage as indicators of possible landslide.. This approach needs three primary sets of data; weather data, topographic data, and soil parameters. This research uses 5 m resolution DEM (IfSAR) to define the topography. Soil parameters are from fieldworks conducted. Weather data are from the Philippine Atmospheric, Geophysical and Astronomical Services Administration. The model is calibrated from stream gauges downsteam corresponding to the calculated runoff. Reliability of the results are as good as the data and is limited by the availability of such, though continuous enhancement of the method is expected as implementation progresses.

  10. Bonded 2D-DEM Models of Pit Craters and Collapse Calderas

    NASA Astrophysics Data System (ADS)

    Holohan, E. P.; Schöpfer, M. P. J.; Walsh, J. J.

    2010-05-01

    Subsidence of the roof of a magma reservoir commonly produces volcanic depressions, which, depending on scale, are termed pit craters or collapse calderas. To identify what geometric and mechanical factors influence the structural evolution of this subsidence, we used Distinct Element Method (DEM) numerical models. The models comprise an assemblage of gravitationally-loaded circular particles that interact at their contacts according to elastic-frictional laws. Cohesion is provided by inter-particle bonds that break once their shear or tensile strength is exceeded. Varying particle and bond micro-properties yields assemblage macro-properties characteristic of natural rock masses (e.g. elasticity, failure, and strain softening), with fracture localization simulated by bond breakage. The magma reservoir is represented as a region of non-bonded, low-fiction particles. Withdrawal of magma is simulated by incrementally reducing the area of the reservoir particles. The resultant gravity-driven failure and subsidence of the overlying reservoir roof is explicitly replicated. We investigated the effect on subsidence of several initial mechanical and geometric properties. Of these, the strength (cohesion) and thickness/diameter ratio (T/D) of the roof exerted strongest influences, whilst the roof's Young's Modulus and the reservoir's ceiling curvature imparted secondary influences. These properties interacted to produce four ‘end-member' subsidence styles, although elements of several styles tended to occur in any one model realization: (1) Predominantly central sagging at low T/D and low strength; (2) hitherto unrecognized ‘central snapping' at low T/D and high strength; (3) predominantly single central block subsidence at low to intermediate strength and at intermediate T/D ratios; (4) multiple central block subsidence at high strength and high T/D ratios. The critical T/D ratio, at which subsidence changes from single central block to multiple central block, was strongly dependent on material strength. Our model results provide a more quantitative understanding of the genesis of subsidence styles observed or inferred in the field: e.g. at Nindiri crater, Nicaragua; Dolomieu caldera, Reunion; and Miyakejima caldera, Japan.

  11. Forecasting of Storm-Surge Floods Using ADCIRC and Optimized DEMs

    NASA Technical Reports Server (NTRS)

    Valenti, Elizabeth; Fitzpatrick, Patrick

    2006-01-01

    Increasing the accuracy of storm-surge flood forecasts is essential for improving preparedness for hurricanes and other severe storms and, in particular, for optimizing evacuation scenarios. An interactive database, developed by WorldWinds, Inc., contains atlases of storm-surge flood levels for the Louisiana/Mississippi gulf coast region. These atlases were developed to improve forecasting of flooding along the coastline and estuaries and in adjacent inland areas. Storm-surge heights depend on a complex interaction of several factors, including: storm size, central minimum pressure, forward speed of motion, bottom topography near the point of landfall, astronomical tides, and, most importantly, maximum wind speed. The information in the atlases was generated in over 100 computational simulations, partly by use of a parallel-processing version of the ADvanced CIRCulation (ADCIRC) model. ADCIRC is a nonlinear computational model of hydrodynamics, developed by the U.S. Army Corps of Engineers and the US Navy, as a family of two- and three-dimensional finite-element-based codes. It affords a capability for simulating tidal circulation and storm-surge propagation over very large computational domains, while simultaneously providing high-resolution output in areas of complex shoreline and bathymetry. The ADCIRC finite-element grid for this project covered the Gulf of Mexico and contiguous basins, extending into the deep Atlantic Ocean with progressively higher resolution approaching the study area. The advantage of using ADCIRC over other storm-surge models, such as SLOSH, is that input conditions can include all or part of wind stress, tides, wave stress, and river discharge, which serve to make the model output more accurate. To keep the computational load manageable, this work was conducted using only the wind stress, calculated by using historical data from Hurricane Camille, as the input condition for the model. Hurricane storm-surge simulations were performed on an eight-node Linux computer cluster. Each node contained dual 2-GHz processors, 2GB of memory, and a 40GB hard drive. The digital elevation model (DEM) for this region was specified using a combination of Navy data (over water), NOAA data (for the coastline), and optimized Interferometric Synthetic Aperture Radar data (over land). This high-resolution topographical data of the Mississippi coastal region provided the ADCIRC model with improved input with which to calculate improved storm-surge forecasts.

  12. Landform change due to soil redistribution by intense tillage based on high-resolution DEMs

    NASA Astrophysics Data System (ADS)

    Su, Z. A.; Zhang, J. H.; Qin, F. C.; Nie, X. J.

    2012-11-01

    Tillage erosion is considered to be one of the most widespread forms of soil erosion on sloping agricultural land, yet little attention has been paid to the impact of tillage erosion on landform change. This study assessed the rates of tillage erosion caused by manual hoeing and evaluated the impacts of medium-term tillage erosion on landform change on slopes with linear and complex forms in the Three Gorges Reservoir region, China. To quantify the tillage erosion rate without the influence of water erosion, a series of tillage experiments were set up and an on-site survey was conducted during the dry season of 2008. The tillage erosion rates on the linear and complex slopes were assessed using high-resolution digital elevation models (DEMs), a step profile method and a tillage erosion model. The erosion rates from the step profile method were 16.8 and 36.6 Mg ha- 1 tillage pass- 1 on the linear and complex slopes, respectively, and those deduced from the tillage erosion model were 17.6 and 41.7 Mg ha- 1 tillage pass- 1. After intense tillage, the most notable changes in soil depth occurred at the summit and toe positions, with a decrease of 100% at the 0-m position (summit) and an increase of 13.1% and 30.9% after 5- and 15-operation tillage, respectively, at the toeslope position on the linear slope. On the complex slope, a 100% reduction in soil depth was observed at the summit; the largest increase in soil depth appeared at the toeslope position after 5- and 15-operation tillage by 23.1% and 48.2%, respectively; and a significant decrease in soil depth at the shoulder slope also occurred. For the linear slope, the slope gradient gradually decreased due to intense tillage, and the landform could be referred to as slow-forming terraces where no severe water erosion occurred at the lower slope positions. Additionally, insignificant changes in the slope gradient occurred at the flat summit slope positions, whereas significant soil accumulation at the toeslope positions caused an obvious reduction of the slope gradients on the complex slope. This indicates that intensive tillage results in a gradual smoothening of the slopes. Furthermore, tillage erosion altered the soil profiles leading to the truncation, the mixing of soil profiles and the formation of new soil profiles at different slope positions. Overall, these results clearly indicate that tillage erosion is one of the important soil redistribution processes, and hoeing tillage plays a dominant role in landform change.

  13. New insights from DEM's into form, process and causality in Distributive Fluvial Systems

    NASA Astrophysics Data System (ADS)

    Scuderi, Louis; Weissmann, Gary; Hartley, Adrian; Kindilien, Peter

    2014-05-01

    Recent developments in platforms and sensors, as well as advances in our ability to access these rich data sources in near real time presents geoscientists with both opportunities and problems. We currently record raster and point cloud data about the physical world at unprecedented rates with extremely high spatial and spectral resolution. Yet the ability to extract scientifically useful knowledge from such immense data sets has lagged considerably. The interrelated fields of database creation, data mining and modern geostatistics all focus on such interdisciplinary data analysis problems. In recent years these fields have made great advances in analyzing the complex real-world data such as that captured in Digital Elevation Models (DEM's) and satellite imagery and by LIDAR and other geospatially referenced data sets. However, even considering the vast increase in the use of these data sets in the past decade these methods have enjoyed only a relatively modest penetration into the geosciences when compared to data analysis in other scientific disciplines. In part, a great deal of the current research weakness is due to the lack of a unifying conceptual approach and the failure to appreciate the value of highly structured and synthesized compilations of data, organized in user-friendly formats. We report on the application of these new technologies and database approaches to global scale parameterization of Distributive Fluvial Systems (DFS) within continental sedimentary basins and illustrate the value of well-constructed databases and tool-rich analysis environments for understanding form, process and causality in these systems. We analyzed the characteristics of aggradational fluvial systems in more than 700 modern continental sedimentary basins and the links between DFS within these systems and their contributing drainage basins. Our studies show that in sedimentary basins, distributive fluvial and alluvial systems dominate the depositional environment. Consequently, we have found that studies of modern tributary drainage systems in degradational settings are likely insufficient for understanding the geomorphology expressed within these basins and ultimately for understanding the basin-scale architecture of dominantly distributive fluvial deposits preserved in the rock record.

  14. Evaluation of ASTER and SRTM DEM data for lahar modeling: A case study on lahars from Popocatépetl Volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Huggel, C.; Schneider, D.; Miranda, P. Julio; Delgado Granados, H.; Kääb, A.

    2008-02-01

    Lahars are among the most serious and far-reaching volcanic hazards. In regions with potential interactions of lahars with populated areas and human structures the assessment of the related hazards is crucial for undertaking appropriate mitigating actions and reduce the associated risks. Modeling of lahars has become an important tool in such assessments, in particular where the geologic record of past events is insufficient. Mass-flow modeling strongly relies on digital terrain data. Availability of digital elevation models (DEMs), however, is often limited and thus an obstacle to lahar modeling. Remote-sensing technology has now opened new perspectives in generating DEMs. In this study, we evaluate the feasibility of DEMs derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) for lahar modeling on Popocatépetl Volcano, Mexico. Two GIS-based models are used for lahar modeling, LAHARZ and a flow-routing-based debris-flow model (modified single-flow direction model, MSF), both predicting areas potentially affected by lahars. Results of the lahar modeling show that both the ASTER and SRTM DEMs are basically suitable for use with LAHARZ and MSF. Flow-path prediction is found to be more reliable with SRTM data, though with a coarser spatial resolution. Errors of the ASTER DEM affecting the prediction of flow paths due to the sensor geometry are associated with deeply incised gorges with north-facing slopes. LAHARZ is more sensitive to errors of the ASTER DEM than the MSF model. Lahar modeling with the ASTER DEM results in a more finely spaced predicted inundation area but does not add any significant information in comparison with the SRTM DEM. Lahars at Popocatépetl are modeled with volumes of 1 × 10 5 to 8 × 10 6 m 3 based on ice-melt scenarios of the glaciers on top of the volcano and data on recent and historical lahar events. As regards recently observed lahars, the travel distance of lahars of corresponding volume modeled with LAHARZ falls short by 2 to 4 km. An important finding is that the travel distance of potential lahar events modeled with LAHARZ may differ by about 2 km when using SRTM or ASTER data because of varying lateral flow-volume distribution. As a consequence, verification and sensitivity analysis of the DEM is fundamental to deriving hazard maps from predicted modeled inundation areas. Because of the global coverage of this type of remote-sensing data, the conclusion that both SRTM and ASTER-derived DEMs are feasible for lahar modeling opens a wide field of application in volcanic-hazards studies.

  15. Dem Assessment Derived from Close Range Photogrammetry: a Case Study from Kadavur Area, Karur District, Tamil Nadu, India

    NASA Astrophysics Data System (ADS)

    Anbarasan, S.; Sakthivel, R.

    2012-07-01

    Close-Range Photogrammetry is an accurate, cost effective technique of collecting measurements of real world objects and conditions, directly from photographs. Photogrammetry utilizes digital images to obtain accurate measurements and geometric data of the object or area of interest, in order to provide spatial information for Engineering design, spatial surveys or 3D modeling. The benefits of close-range Photogrammetry over other field procedures are purported to be: Increased accuracy; complete as-built information; reduced costs; reduced on-site time; and effective for small and large projects. The same basic principle of traditional Aerial Photogrammetry can be applied to stereoscopic pictures taken from lower altitudes or from the ground. Terrestrial, ground-based, and close-range are all descriptive terms that refer to photos taken with an object-to-camera distance less than 300m (1000 feet). (Matthews, N.A, 2008). Close range Photogrammetry is a technique for obtaining the geometric information (e.g. position, distance, size and shape) of any object in 3D space that was imaged on the two dimensional (2D) photos, (Wolf, P.R, et.al, 2000) DEM Generation requires many processing and computation, such as camera calibration, stereo matching, editing, and interpolation. All the mentioned steps contribute to the quality of DEM. Image on close range Photogrammetry can be captured using three kind of camera: metric camera, semi-metric camera, and non-metric camera (Hanke, K., et.al, 2002). In this paper DEM quality assessed at Kadavur area, Karur district, Tamil Naudu, India using Close Range Photogrammetry technique, Commercial Digital Camera and Leica Photogrammetry Suite.

  16. Direct micromechanics derivation and DEM confirmation of the elastic moduli of isotropic particulate materials:. Part II Particle rotation

    NASA Astrophysics Data System (ADS)

    Fleischmann, J. A.; Drugan, W. J.; Plesha, M. E.

    2013-07-01

    In Part I, Fleischmann et al. (2013), we performed theoretical analyses of three cubic packings of uniform spheres (simple, body-centered, and face-centered) assuming no particle rotation, employed these results to derive the effective elastic moduli for a statistically isotropic particulate material, and assessed these results by performing numerical discrete element method (DEM) simulations with particle rotations prohibited. In this second part, we explore the effect that particle rotation has on the overall elastic moduli of a statistically isotropic particulate material. We do this both theoretically, by re-analyzing the elementary cells of the three cubic packings with particle rotation allowed, which leads to the introduction of an internal parameter to measure zero-energy rotations at the local level, and numerically via DEM simulations in which particle rotation is unrestrained. We find that the effects of particle rotation cannot be neglected. For unrestrained particle rotation, we find that the self-consistent homogenization assumption applied to the locally body-centered cubic packing incorporating particle rotation effects most accurately predicts the measured values of the overall elastic moduli obtained from the DEM simulations, in particular Poisson's ratio. Our new self-consistent results and theoretical modeling of particle rotation effects together lead to significantly better theoretical predictions of Poisson's ratio than all prior published results. Moreover, our results are based on a direct micromechanics analysis of specific geometrical packings of uniform spheres, in contrast to prior theoretical analyses based on hypotheses involving overall inter-particle contact distributions. Thus, our results permit a direct assessment of the reasons for the theory-experiment discrepancies noted in the literature with regard to previous theoretical derivations of the macroscopic elastic moduli for particulate materials, and our new theoretical results greatly narrow such discrepancies.

  17. Airborne LiDAR DEMs as a tool for deriving information on past glacier extent and ice flow

    NASA Astrophysics Data System (ADS)

    Seiser, Bernd; Fischer, Andrea

    2014-05-01

    The quantification of ice volumes and the identification of ice flow regimes within historical glacier systems are important steps towards understanding historical phases of glacier advance and disintegration in the context of Holocene climate fluctuation. Topographic LiDAR DEMs provide an excellent tool for gaining various kinds of spatially distributed information. Several case studies have been performed in the Austrian Alps, where LiDAR DEMs are available for almost the entire glacier area. LiDAR DEMs achieve vertical accuracies of few decimetres and can be used to calculate hillshade images with flat incidence angles, so that the surface structures of moraines and other glacial deposits can be identified. These hillshade images were used together with aerial photographs to identify the LIA (Little Ice Age) moraines and the elevation of the lateral moraines, so that, together with information on today's ice volume, a lower limit for the LIA ice volume could be calculated. The resulting LIA glacier areas showed good coincidence with former reconstructions based on field mapping and airborne photogrammetry. In addition to that, historical ice flow directions could be derived from the structure of basal moraines. These data allow an interpretation of the changing contribution of specific tributary glaciers to a joint glacier tongue, which may result in an important switch in ice dynamics leading to fast glacier advances recorded by frontal moraines. The combination of terrestrial long-term observations and LiDAR data documents the genesis of specific geomorphological features in the periglacial area by recording the processes occurring during the disintegration of glacier tongues. For example, the deposition of the material from former medial moraines in the newly formed periglacial area can be identified and quantified from the LiDAR data as well as debris flows or rock falls from the LIA moraines.

  18. A method of detecting land use change of remote sensing images based on texture features and DEM

    NASA Astrophysics Data System (ADS)

    Huang, Dong-ming; Wei, Chun-tao; Yu, Jun-chen; Wang, Jian-lin

    2015-12-01

    In this paper, a combination method, between the neural network and textures information, is proposed to remote sensing images classification. The methodology involves an extraction of texture features using the gray level co-occurrence matrix and image classification with BP artificial neural network. The combination of texture features and the digital elevation model (DEM) as classified bands to neural network were used to recognized different classes. This scheme shows high recognition accuracy in the classification of remote sensing images. In the experiments, the proposed method was successfully applied to remote sensing image classification and Land Use Change Detection, in the meanwhile, the effectiveness of the proposed method was verified.

  19. Extracting Precise and Affordable Dems Despite of the Clouds. Ajax: the Joining of Radar and Optical Strengths

    NASA Astrophysics Data System (ADS)

    Cunin, 1 L.; Nonin, 2 P.; Janoth, 3 J.; Bernard, 4 M.

    2012-07-01

    On the one hand, onboard SPOT 5, the HRS instrument systematically collects stereopairs around the Globe since 2002. Each stereopair can encompass an area up to 600 km x 120 km within a single pass (i.e. 72 000 km² stereoscopic strips). Covering now more than 120 millions sq.km of the Earth landmasses, SPOT 5 stereoscopic imagery has become one of main satellite data sources for accurate DEM extraction, at least where the cloud coverage leaves a chance to do so ! On the other hand, the TerraSAR-X satellite, launched in June 2007, is able to collect radar data through the clouds in several modes. An approach to extract height information by radargrammetry was developed, and the commercial distribution of Digital Elevation Models based on TerraSAR-X StripMap and SpotLight Modes (resp. 3m and 1m resolution) has started in 2010. To improve the overall height accuracy of the DEM, acquisitions from both orbit directions are utilised, each point on the ground being thus imaged at least 4 times by TerraSAR-X. Since 2002, Spot Image and French National Cartographic Institute (IGN) are building a worldwide database called Elevation30/Reference3D™, which includes a Digital Elevation Model at 1-arc-second resolution (DTED level 2) extracted from HRS stereopairs. To answer the wide demand of precise DEMs over Tropical and Northern areas, frequently covered by clouds, a study was performed to integrate StripMap radargrammetric TerraSAR-X data into the Reference3D process, and two prototype products were issued, over Colombia and Congo areas. During this experiment, efforts have been made to stick to technical steps that could be integrated within a standardized production process, in order to keep offering affordable prices while maintaining a high standard of horizontal and vertical accuracy. The DEMs extracted from TerraSAR-X and HRS proved extremely consistent with each other, showing a mean difference of 0.80m. This allows to propose a unified Elevation30 product to the users, with a guaranteed accuracy materialized into the product through a dedicated vertical Accuracy Commitment Mask.

  20. The Discrete Equation Method (DEM) for Fully Compressible Two-Phase Flows in Ducts of Spatially Varying Cross-Section

    SciTech Connect

    Ray A. Berry; Richard Saurel; Tamara Grimmett

    2009-07-01

    Typically, multiphase modeling begins with an averaged (or homogenized) system of partial differential equations (traditionally ill-posed) then discretizes this system to form a numerical scheme. Assuming that the ill-posedness problem is avoided by using a well-posed formulation such as the seven-equation model, this presents problems for the numerical approximation of non-conservative terms at discontinuities (interfaces, shocks) as well as unwieldy treatment of fluxes with seven waves. To solve interface problems without conservation errors and to avoid this questionable determination of average variables and the numerical approximation of the non-conservative terms associated with 2 velocity mixture flows we employ a new homogenization method known as the Discrete Equations Method (DEM). Contrary to conventional methods, the averaged equations for the mixture are not used, and this method directly obtains a (well-posed) discrete equation system from the single-phase system to produce a numerical scheme which accurately computes fluxes for arbitrary numbers of phases and solves non-conservative products. The method effectively uses a sequence of single phase Riemann equation solves. Phase interactions are accounted for by Riemann solvers at each interface. Flow topology can change with changing expressions for the fluxes. Non-conservative terms are correctly approximated. Some of the closure relations missing from the traditional approach are automatically obtained. Lastly, we can often times identify the continuous equation system, resulting from taking the continuous limit with weak wave assumptions, of the discrete equations. This can be very useful from a theoretical standpoint. As a first step toward implict integration of the DEM method in multidimensions, in this paper we construct a DEM model for the flow of two compressible phases in 1-D ducts of spatially varying cross-section to test this approach. To relieve time step size restrictions due to stiffness and to achieve tighter coupling of equations, a fully implicit time integration method is employed. For the first time, we demonstrate on a converging-diverging two-phase nozzle that this well-posed, 2 pressure, 2 velocity DEM model can be integrated to a meaningful steady-state with both phases treated as compressible.

  1. Visualising shear stress distribution inside flow geometries containing pharmaceutical powder excipients using photo stress analysis tomography and DEM simulations

    NASA Astrophysics Data System (ADS)

    Albaraki, Saeed; Antony, S. Joseph.; Arowosola, C. Babatunde

    2013-06-01

    For the first time, photo stress analysis tomography (PSAT) is applied to probe the distribution of maximum shear stress and direction of major principal stress field within `powder' assemblies inside hopper geometries, and further supported by discrete element model (DEM) simulations. The results show that for decrease in hopper angle, the direction of major principle stress aligns with the direction of gravity which could promote flow rate under dynamic conditions. Conversely, the propensity of developing relatively more non-homogeneous distribution of shear resistance zones inside powder assemblies increases with the hopper angle, which could subsequently decrease their macroscopic flow rate.

  2. Sediment budget estimation in a small torrential catchment using DEM of difference approach

    NASA Astrophysics Data System (ADS)

    Bezak, Nejc; Grigillo, Dejan; Rusjan, Simon; Šraj, Mojca; Urbančič, Tilen; Kozmus Trajkovski, Klemen; Petrovič, Dušan; Mikoš, Matjaž

    2015-04-01

    The aim of the study was to estimate the sediment budget (net erosion change) in a small torrential catchment using the DEM of difference (DoD) approach. The Kuzlovec torrent (~ 0.7 km2; in the Gradaščica River catchment) is located approximately 20 km west of the City of Ljubljana and is part of the Sava River basin. The elevation ranges between 394 and 847 m.a.s.l, the mean catchment slope is 27.3°, the mean annual precipitation typically ranges between 1600 to 1800 mm, forest covers more than 85% of the area, and the predominant soil type is Rendzic Leptosol (according to the FAO classification). Using the Terestrical Laser Scanning (TLS) a digital terrain model (DTM) with a 5 cm grid cell was obtained. A smaller (about 25 m wide and 160 m long) specific study site with a mean slope of 37° was selected in order to ensure the high quality of data. A high resolution (several million points) surveys were performed in April 2013 and August 2014. In the night from 4th to 5th of August 2014 an extreme flash flood happened in the investigated area. Three tipping bucket rain gauges and one disdrometer, which are located in the Gradaščica River catchment, measured 110 to 185 mm of rainfall in less than 10 hours. Two rain gauges measured about 110 mm, one rain gauge (the closest to the Kuzloved torrent) recorded approximately 140 mm of rainfall, while the disdrometer measured 185 mm of rainfall. The estimated return period of this rainfall event (based on the rain gauge data) was between 100 and 250 years, however based on the disdrometer observations the return period was larger than 250 years. The Gumbel distribution was used in order to construct the intensity-duration-frequency (IDF) relationship and the data from 1976 to 2008 was used for this purpose. Furthermore, the maximum one minute rainfall intensity measured by the disdrometer was 288 mm/h. This high rainfall intensities triggered several shallow landslides and caused intense soil erosion processes, especially large bedload and suspended load movement along the stream channel network. A DoD approach was used to estimate the net erosion change in the selected section of the Kuzlovec torrent. A mean difference in the elevation between the DTM 2014 (after flash flood) and DTM 2013 (before flash flood) was -0.104 m. Based on the grid cell size (0.05 m) and number of cells (~ 1.93 106) a net erosion of about 500 m3 was calculated. Furthermore, uncertainty estimation is needed to validate the calculated net erosion change between two DTMs.

  3. DEM-based Approaches for the Identification of Flood Prone Areas

    NASA Astrophysics Data System (ADS)

    Samela, Caterina; Manfreda, Salvatore; Nardi, Fernando; Grimaldi, Salvatore; Roth, Giorgio; Sole, Aurelia

    2013-04-01

    The remarkable number of inundations that caused, in the last decades, thousands of deaths and huge economic losses, testifies the extreme vulnerability of many Countries to the flood hazard. As a matter of fact, human activities are often developed in the floodplains, creating conditions of extremely high risk. Terrain morphology plays an important role in understanding, modelling and analyzing the hydraulic behaviour of flood waves. Research during the last 10 years has shown that the delineation of flood prone areas can be carried out using fast methods that relay on basin geomorphologic features. In fact, the availability of new technologies to measure surface elevation (e.g., GPS, SAR, SAR interferometry, RADAR and LASER altimetry) has given a strong impulse to the development of Digital Elevation Models (DEMs) based approaches. The identification of the dominant topographic controls on the flood inundation process is a critical research question that we try to tackle with a comparative analysis of several techniques. We reviewed four different approaches for the morphological characterization of a river basin with the aim to provide a description of their performances and to identify their range of applicability. In particular, we explored the potential of the following tools. 1) The hydrogeomorphic method proposed by Nardi et al. (2006) which defines the flood prone areas according to the water level in the river network through the hydrogeomorphic theory. 2) The linear binary classifier proposed by Degiorgis et al. (2012) which allows distinguishing flood-prone areas using two features related to the location of the site under exam with respect to the nearest hazard source. The two features, proposed in the study, are the length of the path that hydrologically connects the location under exam to the nearest element of the drainage network and the difference in elevation between the cell under exam and the final point of the same path. 3) The method by Manfreda et al. (2011) that suggested a modified Topographic Index (TIm) for the identification of flood prone area. 4) The downslope index proposed by Hjerdt et al. (2004) that quantifies the topographic controls on hydrology by evaluating head differences following the (surface) flow path in the steepest direction. The method does not use the exit point at the stream as reference; instead, the algorithm looks at how far a parcel of water has to travel along its flow path to lose a given head potential, d [m]. This last index was not defined with the aim to describe flood prone areas; in fact it represents an interesting alternative descriptor of morphological features that deserve to be tested. Analyses have been carried out for some Italian catchments. The outcomes of the four methods are presented using, for calibration and validation purposes, flood inundation maps made available by River Basin Authorities. The aim is, therefore, to evaluate the reliability and the relative errors in the detection of the areas subject to the flooding hazard. These techniques should not be considered as an alternative of traditional procedures, but additional tool for the identification of flood-prone areas and hazard graduation over large regions or when a preliminary identification is needed. Reference Degiorgis M., G. Gnecco, S. Gorni, G. Roth, M. Sanguineti, A. C. Taramasso, Classifiers for the detection of flood-prone areas using remote sensed elevation data, J. Hydrol., 470-471, 302-315, 2012. Hjerdt, K. N., J. J. McDonnell, J. Seibert, A. Rodhe, A new topographic index to quantify downslope controls on local drainage, Water Resour. Res., 40, W05602, 2004. Manfreda, S., M. Di Leo, A. Sole, Detection of Flood Prone Areas using Digital Elevation Models, Journal of Hydrologic Engineering, Vol. 16, No. 10, 781-790, 2011. Nardi, F., E. R. Vivoni, S. Grimaldi, Investigating a floodplain scaling relation using a hydrogeomorphic delineation method, Water Resour. Res., 42, W09409, 2006.

  4. SveDem, the Swedish Dementia Registry – A Tool for Improving the Quality of Diagnostics, Treatment and Care of Dementia Patients in Clinical Practice

    PubMed Central

    Religa, Dorota; Fereshtehnejad, Seyed-Mohammad; Cermakova, Pavla; Edlund, Ann-Katrin; Garcia-Ptacek, Sara; Granqvist, Nicklas; Hallbäck, Anne; Kåwe, Kerstin; Farahmand, Bahman; Kilander, Lena; Mattsson, Ulla-Britt; Nägga, Katarina; Nordström, Peter; Wijk, Helle; Wimo, Anders; Winblad, Bengt; Eriksdotter, Maria

    2015-01-01

    Background The Swedish Dementia Registry (SveDem) was developed with the aim to improve the quality of diagnostic work-up, treatment and care of patients with dementia disorders in Sweden. Methods SveDem is an internet based quality registry where several indicators can be followed over time. It includes information about the diagnostic work-up, medical treatment and community support (www.svedem.se). The patients are diagnosed and followed-up yearly in specialist units, primary care centres or in nursing homes. Results The database was initiated in May 2007 and covers almost all of Sweden. There were 28 722 patients registered with a mean age of 79.3 years during 2007–2012. Each participating unit obtains continuous online statistics from its own registrations and they can be compared with regional and national data. A report from SveDem is published yearly to inform medical and care professionals as well as political and administrative decision-makers about the current quality of diagnostics, treatment and care of patients with dementia disorders in Sweden. Conclusion SveDem provides knowledge about current dementia care in Sweden and serves as a framework for ensuring the quality of diagnostics, treatment and care across the country. It also reflects changes in quality dementia care over time. Data from SveDem can be used to further develop the national guidelines for dementia and to generate new research hypotheses. PMID:25695768

  5. SediFoam: A general-purpose, open-source CFD-DEM solver for particle-laden flow with emphasis on sediment transport

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Xiao, Heng

    2016-04-01

    With the growth of available computational resource, CFD-DEM (computational fluid dynamics-discrete element method) becomes an increasingly promising and feasible approach for the study of sediment transport. Several existing CFD-DEM solvers are applied in chemical engineering and mining industry. However, a robust CFD-DEM solver for the simulation of sediment transport is still desirable. In this work, the development of a three-dimensional, massively parallel, and open-source CFD-DEM solver SediFoam is detailed. This solver is built based on open-source solvers OpenFOAM and LAMMPS. OpenFOAM is a CFD toolbox that can perform three-dimensional fluid flow simulations on unstructured meshes; LAMMPS is a massively parallel DEM solver for molecular dynamics. Several validation tests of SediFoam are performed using cases of a wide range of complexities. The results obtained in the present simulations are consistent with those in the literature, which demonstrates the capability of SediFoam for sediment transport applications. In addition to the validation test, the parallel efficiency of SediFoam is studied to test the performance of the code for large-scale and complex simulations. The parallel efficiency tests show that the scalability of SediFoam is satisfactory in the simulations using up to O(107) particles.

  6. Hydrography change detection: the usefulness of surface channels derived From LiDAR DEMs for updating mapped hydrography

    USGS Publications Warehouse

    Poppenga, Sandra K.; Gesch, Dean B.; Worstell, Bruce B.

    2013-01-01

    The 1:24,000-scale high-resolution National Hydrography Dataset (NHD) mapped hydrography flow lines require regular updating because land surface conditions that affect surface channel drainage change over time. Historically, NHD flow lines were created by digitizing surface water information from aerial photography and paper maps. Using these same methods to update nationwide NHD flow lines is costly and inefficient; furthermore, these methods result in hydrography that lacks the horizontal and vertical accuracy needed for fully integrated datasets useful for mapping and scientific investigations. Effective methods for improving mapped hydrography employ change detection analysis of surface channels derived from light detection and ranging (LiDAR) digital elevation models (DEMs) and NHD flow lines. In this article, we describe the usefulness of surface channels derived from LiDAR DEMs for hydrography change detection to derive spatially accurate and time-relevant mapped hydrography. The methods employ analyses of horizontal and vertical differences between LiDAR-derived surface channels and NHD flow lines to define candidate locations of hydrography change. These methods alleviate the need to analyze and update the nationwide NHD for time relevant hydrography, and provide an avenue for updating the dataset where change has occurred.

  7. Effective Thermal Property Estimation of Unitary Pebble Beds Based on a CFD-DEM Coupled Method for a Fusion Blanket

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Chen, Youhua; Huang, Kai; Liu, Songlin

    2015-12-01

    Lithium ceramic pebble beds have been considered in the solid blanket design for fusion reactors. To characterize the fusion solid blanket thermal performance, studies of the effective thermal properties, i.e. the effective thermal conductivity and heat transfer coefficient, of the pebble beds are necessary. In this paper, a 3D computational fluid dynamics discrete element method (CFD-DEM) coupled numerical model was proposed to simulate heat transfer and thereby estimate the effective thermal properties. The DEM was applied to produce a geometric topology of a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. Based on this geometric topology, a CFD model was built to analyze the temperature distribution and obtain the effective thermal properties. The current numerical model was shown to be in good agreement with the existing experimental data for effective thermal conductivity available in the literature. supported by National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2015GB108002, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)

  8. Catchment properties in the Kruger National Park derived from the new TanDEM-X Intermediate Digital Elevation Model (IDEM)

    NASA Astrophysics Data System (ADS)

    Baade, J.; Schmullius, C.

    2015-04-01

    Digital Elevation Models (DEM) represent fundamental data for a wide range of Earth surface process studies. Over the past years the German TanDEM-X mission acquired data for a new, truly global Digital Elevation Model with unpreceded geometric resolution, precision and accuracy. First processed data sets (i. e. IDEM) with a geometric resolution of 0.4 to 3 arcsec have been made available for scientific purposes. This includes four 1° x 1° tiles covering the Kruger National Park in South Africa. Here we document the results of a local scale IDEM validation exercise utilizing RTK-GNSS-based ground survey points from a dried out reservoir basin and its vicinity characterized by pristine open Savanna vegetation. Selected precursor data sets (SRTM1, SRTM90, ASTER-GDEM2) were included in the analysis and highlight the immense progress in satellite-based Earth surface surveying over the past two decades. Surprisingly, the high precision and accuracy of the IDEM data sets have only little impact on the delineation of watersheds and the calculation of catchment size. But, when it comes to the derivation of topographic catchment properties (e.g. mean slope, etc.) the high resolution of the IDEM04 is of crucial importance, if - from a geomorphologist's view - it was not for the disturbing vegetation.

  9. Co-seismic landslide topographic analysis based on multi-temporal DEM-A case study of the Wenchuan earthquake.

    PubMed

    Ren, Zhikun; Zhang, Zhuqi; Dai, Fuchu; Yin, Jinhui; Zhang, Huiping

    2013-01-01

    Hillslope instability has been thought to be one of the most important factors for landslide susceptibility. In this study, we apply geomorphic analysis using multi-temporal DEM data and shake intensity analysis to evaluate the topographic characteristics of the landslide areas. There are many geomorphologic analysis methods such as roughness, slope aspect, which are also as useful as slope analysis. The analyses indicate that most of the co-seismic landslides occurred in regions with roughness, hillslope and slope aspect of >1.2, >30, and between 90 and 270, respectively. However, the intersection regions from the above three methods are more accurate than that derived by applying single topographic analysis method. The ground motion data indicates that the co-seismic landslides mainly occurred on the hanging wall side of Longmen Shan Thrust Belt within the up-down and horizontal peak ground acceleration (PGA) contour of 150 PGA and 200 gal, respectively. The comparisons of pre- and post-earthquake DEM data indicate that the medium roughness and slope increased, the roughest and steepest regions decreased after the Wenchuan earthquake. However, slope aspects did not even change. Our results indicate that co-seismic landslides mainly occurred at specific regions of high roughness, southward and steep sloping areas under strong ground motion. Co-seismic landslides significantly modified the local topography, especially the hillslope and roughness. The roughest relief and steepest slope are significantly smoothed; however, the medium relief and slope become rougher and steeper, respectively. PMID:24171155

  10. The Discrete Equation Method (DEM) for Fully Compressible, Two-Phase Flows in Ducts of Spatially Varying Cross-Section

    SciTech Connect

    R. A. Berry; R. Saurel; O. LeMetayer

    2010-11-01

    For the simulation of light water nuclear reactor coolant flows, general two-phase models (valid for all volume fractions) have been generally used which, while allowing for velocity disequilibrium, normally force pressure equilibrium between the phases (see, for example, the numerous models of this type described in H. Städtke, Gasdynamic Aspects of Two-Phase Flow, Wiley-VCH, 2006). These equations are not hyperbolic, their physical wave dynamics are incorrect, and their solution algorithms rely on dubious truncation error induced artificial viscosity to render them numerically well posed over a portion of the computational spectrum. The inherent problems of the traditional approach to multiphase modeling, which begins with an averaged system of (ill-posed) partial differential equations (PDEs) which are then discretized to form a numerical scheme, are avoided by employing a new homogenization method known as the Discrete Equation Method (DEM) (R. Abgrall and R. Saurel, Discrete Equations for Physical and Numerical Compressible Multiphase Mixtures, J. Comp. Phys. 186, 361-396, 2003). This method results in well-posed hyperbolic systems, this property being important for transient flows. This also allows a clear treatment of non-conservative terms (terms involving interfacial variables and volume fraction gradients) permitting the solution of interface problems without conservation errors, this feature being important for the direct numerical simulation of two-phase flows. Unlike conventional methods, the averaged system of PDEs for the mixture are not used, and the DEM method directly obtains a well-posed discrete equation system from the single-phase conservation laws, producing a numerical scheme which accurately computes fluxes for arbitrary number of phases and solves non-conservative products. The method effectively uses a sequence of single phase Riemann problem solutions. Phase interactions are accounted for by Riemann solvers at each interface. Non-conservative terms are correctly approximated. Some of the closure relations missing from the traditional approach are automatically obtained. Lastly, the continuous equation system resulting from the discrete equations can be identified by taking the continuous limit with weak-wave assumptions. In this work, this approach is tested by constructing a DEM model for the flow of two compressible phases in 1-D ducts of spatially varying cross-section with explicit time integration. An analytical equation of state is included for both water vapor and liquid phases, and a realistic interphase mass transfer model is developed based on interphase heat transfer. A robust compliment of boundary conditions are developed and discussed. Though originally conceived as a first step toward implict time integration of the DEM method (to relieve time step size restrictions due to stiffness and to achieve tighter coupling of equations) in multidimensions, this model offers some unique capabilities for incorporation into next generation light water reactor safety analysis codes. We demonstrate, on a converging-diverging two-phase nozzle, that this well-posed, 2-pressure, 2-velocity DEM model can be integrated to a realistic and meaningful steady-state with both phases treated as compressible.

  11. Low-altitude remote sensing dataset of DEM and RGB mosaic for AB corridor on July 13 2013 and L2 corridor on July 21 2013

    DOE Data Explorer

    Baptiste Dafflon

    2015-04-07

    Low-altitude remote sensing dataset including DEM and RGB mosaic for AB (July 13 2013) and L2 corridor (July 21 2013).Processing flowchart for each corridor:Ground control points (GCP, 20.3 cm square white targets, every 20 m) surveyed with RTK GPS. Acquisition of RGB pictures using a Kite-based platform. Structure from Motion based reconstruction using hundreds of pictures and GCP coordinates. Export of DEM and RGB mosaic in geotiff format (NAD 83, 2012 geoid, UTM zone 4 north) with pixel resolution of about 2 cm, and x,y,z accuracy in centimeter range (less than 10 cm). High-accuracy and high-resolution inside GCPs zone for L2 corridor (500x20m), AB corridor (500x40) DEM will be updated once all GCPs will be measured. Only zones between GCPs are accurate although all the mosaic is provided.

  12. A FEM-DEM technique for studying the motion of particles in non-Newtonian fluids. Application to the transport of drill cuttings in wellbores

    NASA Astrophysics Data System (ADS)

    Celigueta, Miguel Angel; Deshpande, Kedar M.; Latorre, Salvador; Oñate, Eugenio

    2015-11-01

    We present a procedure for coupling the finite element method (FEM) and the discrete element method (DEM) for analysis of the motion of particles in non-Newtonian fluids. Particles are assumed to be spherical and immersed in the fluid mesh. A new method for computing the drag force on the particles in a non-Newtonian fluid is presented. A drag force correction for non-spherical particles is proposed. The FEM-DEM coupling procedure is explained for Eulerian and Lagrangian flows, and the basic expressions of the discretized solution algorithm are given. The usefulness of the FEM-DEM technique is demonstrated in its application to the transport of drill cuttings in wellbores.

  13. A FEM-DEM technique for studying the motion of particles in non-Newtonian fluids. Application to the transport of drill cuttings in wellbores

    NASA Astrophysics Data System (ADS)

    Celigueta, Miguel Angel; Deshpande, Kedar M.; Latorre, Salvador; Oñate, Eugenio

    2016-04-01

    We present a procedure for coupling the finite element method (FEM) and the discrete element method (DEM) for analysis of the motion of particles in non-Newtonian fluids. Particles are assumed to be spherical and immersed in the fluid mesh. A new method for computing the drag force on the particles in a non-Newtonian fluid is presented. A drag force correction for non-spherical particles is proposed. The FEM-DEM coupling procedure is explained for Eulerian and Lagrangian flows, and the basic expressions of the discretized solution algorithm are given. The usefulness of the FEM-DEM technique is demonstrated in its application to the transport of drill cuttings in wellbores.

  14. Landslide-dammed lakes detection via ALOS/PALSAR InSAR DEM: A case study of the Iwate-Miyagi Nairiku earthquake

    NASA Astrophysics Data System (ADS)

    Asaka, Tomohito; Yamamoto, Yoshiyuki; Iwashita, Keishi; Kudou, Katsuteru; Fujii, Hisao; Nishikawa, Hajime; Sensing Specialist Yukihiro Suzuoki, Remote

    On 14th June 2008, the Japan Meteorological Agency recorded a 7.2 magnitude (Richter scale) earthquake with an epicenter depth of 8 km in the southern Iwate prefecture of the Tohoku region of Japan. In the hardest hit prefectures of Iwate and Miyagi, the earthquake produced 15 new landslide-dammed lakes; a phenomenon common when the earthquake hypocenter is within inland areas. In our last study, we demonstrated that interferometric SAR (InSAR) technique can detect surface displacements within centimeter accuracy and create detailed three-dimensional terrain information. In this study, we developed a new methodology to detect landslide-dammed lakes using Digital Drainage Models (DDMs) generated from the DEM's cre-ated with InSAR data. Using our technique, small scale topographical change was detected by comparing pre-earthquake DEM's such as created from the Shuttle Radar Topographic Mission (SRTM) data and post-earthquake DEM's created from the Advanced Land Observing System (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data. Pre-and post-earthquake changes in the drainage networks were detected by comparing DDM features derived from an existing DEM to DDM features derived from a post-earthquake DEM created from ALOS InSAR data. It was verified that landslide-dammed lakes were detected specifically in the area where drainage network with more than three of the river-order computed from DDM's shifted before and after the earthquake. Thus, InSAR DEM generated from ALOS/PALSAR can provide timely and useful spatial information for detecting landslide-dammed lakes.

  15. Modeling the DEM Error effects in InSAR time-series results; with application to inter-seismic ground deformation estimation along the Chaman Fault

    NASA Astrophysics Data System (ADS)

    Fattahi, H.; Amelung, F.

    2011-12-01

    Temporal surface deformation, estimated from InSAR time-series techniques, is affected by various sources of errors, including topographic artifacts, atmospheric delay, orbital errors and noise. Topographic artifacts are the results of the inaccuracy of the DEMs, which are used to remove the topographic signal from the differential interferograms. While the DEM error effect in each interferogram is proportional to it's perpendicular baseline, but this effect was not well known and modeled in InSAR time-series results. We present a mathematical model for the DEM error effects in the estimated phase history, resulted from SBAS time-series inversion of interferometric phases. This model enables us to recognize the DEM error effects in the estimated temporal displacement signal. Using this model, we clarify that while selecting small spatial baseline interferograms minimizes the DEM error effect in the individual interferograms, but it cannot necessarily reduce this effect in the time-series results. We show the results of verification of the proposed model using simulated and real InSAR data sets. Based on this model we present our proposed new algorithm to correct the DEM error effects in InSAR time-series inversion results, as a post-processing method, which is independent of any preliminary assumption about the temporal deformation signal. We discuss the efficiency of the proposed method using the simulated and real data sets. We have used this post processing time-series technique to estimate the inter-seismic ground deformation along the Chaman fault. This fault is the transform boundary of Indian and Eurasian plates; located at the border of Afghanistan and Pakistan. Lack of geodetic data in this seismogenic area has been the main obstacle for accurate strain rate estimation. Here we present our results and interpretations of processing Envisat-ASAR acquisitions from different ascending and descending tracks covering the most parts of the fault from 2004 to 2010, which reveals creeping along some segments of the fault.

  16. Machine vision approach to auto-generation of high resolution, continental-scale geomorphometric map from DEM

    NASA Astrophysics Data System (ADS)

    Jasiewicz, J.; Stepinski, T. F.

    2012-04-01

    Geomorphometric map (GM) is a map of landforms delineated exclusively on the basis of their morphology; it depicts a classification of landscape into its constituent elements. GM is a valuable tool for visual terrain analysis, but more importantly, it's a perfect terrain representation for its further algorithmic analysis. GMs themselves are auto-generated from DEM. We have developed a new technique for auto-generation of GMs that is based on the principle of machine vision. Such approach approximates more closely the mapping process of human analyst and results in an efficient generation of GMs having quality and utility superior to maps generated by a standard technique based on differential geometry. The core of the new technique is a notion of geomorphon. A geomorphon is a relief-invariant, orientation-invariant, and size-flexible abstracted elementary unit of terrain. It is calculated from DEM using simple ternary patterns defined on a neighborhood which size adapts to the character of local terrain. Geomorphons are both terrain attributes and landform types at the same time; they allow for a direct and highly efficient, single-step classification and mapping of landforms. There are 498 unique geomorphons but only a small fraction of them are found in typical natural terrain. The geomorphon-based mapping technique is implemented as a GRASS GIS extension written in ANSI C and will be available in the public domain. In order to showcase the capabilities of geomorphons we have calculated the GM for the entire conterminous United States from the 30m/pixel NED DEM. The map shows ten most abundant landforms: flat, peak, ridge, shoulder, spur, slope, hollow, footslope, valley, and pit; a lookup table was used to assign each of the remaining 488 infrequent forms to a morphologically closest mapped form. The result is a unique, never before seen, type of map that clearly shows multiple geomorphic features and indicates the underlying geologic processes. The auto-generation of GM from this high resolution, continental size raster having 168000x104000 cells took 60 hours on a single processor computer. Future applications of such GM include coupling it with a search tool capable of querying the continental-scale GM in order to identify all instances of a given type of local landscape.

  17. Amundsen Sea sector ice shelf thickness, melt rates, and inland response from annual high-resolution DEM mosaics

    NASA Astrophysics Data System (ADS)

    Shean, D. E.; Joughin, I. R.; Smith, B. E.; Alexandrov, O.; Moratto, Z.; Porter, C. C.; Morin, P. J.

    2014-12-01

    Significant grounding line retreat, acceleration, and thinning have occurred along the Amundsen Sea sector of West Antarctica in recent decades. These changes are driven primarily by ice-ocean interaction beneath ice shelves, but existing observations of the spatial distribution, timing, and magnitude of ice shelf melt are limited. Using the NASA Ames Stereo Pipeline, we generated digital elevation models (DEMs) with ~2 m posting from all ~450 available WorldView-1/2 along-track stereopairs for the Amundsen Sea sector. A novel iterative closest point algorithm was used to coregister DEMs to filtered Operation IceBridge ATM/LVIS data and ICESat-1 GLAS data, offering optimal sub-meter horizontal/vertical accuracy. The corrected DEMs were used to produce annual mosaics for the entire ~500x700 km region with focused, sub-annual products for ice shelves and grounding zones. These mosaics provide spatially-continuous measurements of ice shelf topography with unprecedented detail. Using these data, we derive estimates of ice shelf thickness for regions in hydrostatic equilibrium and map networks of sub-shelf melt channels for the Pine Island (PIG), Thwaites, Crosson, and Dotson ice shelves. We also document the break-up of the Thwaites ice shelf and PIG rift evolution leading up to the 2013 calving event. Eulerian difference maps document 2010-2014 thinning over fast-flowing ice streams and adjacent grounded ice. These data reveal the greatest thinning rates over the Smith Glacier ice plain and slopes beyond the margins of the fast-flowing PIG trunk. Difference maps also highlight the filling of at least two subglacial lakes ~30 km upstream of the PIG grounding line in 2011. Lagrangian difference maps reveal the spatial distribution of ice shelf thinning, which can primarily be attributed to basal melt. Preliminary results show focused ice shelf thinning within troughs and large basal channels, especially along the western margin of the Dotson ice shelf. These new data provide critical observations that will improve our understanding ice-ocean interaction and mass loss for the Amundsen Sea sector on local and regional scales.

  18. Analysis of the seasonal and interannual evolution of Jakobshavn Isbrae from 2010-2013 using high spatial/temporal resolution DEM and velocity data

    NASA Astrophysics Data System (ADS)

    Shean, D. E.; Joughin, I. R.; Smith, B. E.; Moratto, Z. M.; Alexandrov, O.; Floricioiu, D.; Morin, P. J.; Porter, C. C.; Beyer, R. A.; Fong, T.

    2013-12-01

    Greenland's large marine-terminating outlet glaciers have displayed marked retreat, speedup, and thinning in recent decades. Jakobshavn Isbrae, one of Greenland's largest outlet glaciers, has retreated ~15 km, accelerated ~150%, and thinned ~200 m since the early 1990s. Here, we present the first comprehensive analysis of high spatial (~2-5 m/px) and temporal (daily-monthly) resolution elevation and velocity data for Jakobshavn from 7/2010 to 7/2013. We have developed an automated processing pipeline using open-source software (Ames Stereo Pipeline, GDAL/OGR, NumPy/SciPy, etc.) to produce orthoimage, digital elevation model (DEM), and surface velocity products from DigitalGlobe WorldView-1/2 stereo imagery (~0.5 m/px, ~17 km swath width). Our timeseries consists of 35 WV DEMs (~2-4 m/px) covering the lower trunks of the main+north branches and fjord, but also extending >110 km inland. We supplement this record with 7 TanDEM-X DEMs (~5 m/px, ~35 km swath width) between 6/2011-9/2012. Elevation data from IceBridge ATM/LVIS, ICESat GLAS, and GPS campaigns provide absolute control data over fixed surfaces (i.e., exposed bedrock). Observed WV DEM offsets are consistent with DigitalGlobe's published value of 5.0 m CE90/LE90 horizontal/vertical accuracy. After DEM co-registration, we observe sub-meter horizontal and vertical absolute accuracy. Velocity data are derived from TerraSAR-X data with 11 day repeat interval. Supplemental velocity data are derived through correlation of high-resolution WV DEM/image data. The contemporaneous DEM and velocity data provide full 3D displacement vectors for each time interval, allowing for the analysis of both Eulerian and Lagrangian elevation change. The lower trunk of Jakobshavn displays significant seasonal velocity variations, with recent rates of ~8 km/yr during winter to >17 km/yr during summer. DEM data show corresponding elevation changes of -30 to -45 m in summer and +15 to +20 m in winter, corresponding to integrated volumes of -1.0 to -1.5 km3 and +0.3 to +0.6 km3 for the lower ~20 km of the main trunk. Further analysis will characterize the upstream propagation of the seasonal elevation change and the relationship with observed strain rates. Seasonal surface mass balance elevation changes are also observed over adjacent grounded, slow-moving (~100 m/yr) regions. The DEM timeseries shows a net interannual thinning trend of -15-20 m/yr for lower Jakobshavn, with decreasing magnitude upstream. This is consistent with long-term altimetry records. Interannual thinning of ~2 m/yr and lateral retreat is also observed for grounded ice sheet margins. These DEM and velocity data capture the timing, magnitude and evolution of dynamic thinning/thickening with unprecedented spatial and temporal resolution. These results also emphasize the importance of dense temporal elevation data when characterizing ice sheet variability and interpreting deviations from long-term records. Similar high-resolution timeseries are available for all major outlet glaciers and ice streams in Greenland and Antarctica. Ultimately, these observations will improve our understanding of outlet glacier behavior, while complementing ongoing efforts to constrain estimates for ice-sheet mass balance and contribution to present/future sea level rise.

  19. The evaluation of unmanned aerial system-based photogrammetry and terrestrial laser scanning to generate DEMs of agricultural watersheds

    NASA Astrophysics Data System (ADS)

    Ouédraogo, Mohamar Moussa; Degré, Aurore; Debouche, Charles; Lisein, Jonathan

    2014-06-01

    Agricultural watersheds tend to be places of intensive farming activities that permanently modify their microtopography. The surface characteristics of the soil vary depending on the crops that are cultivated in these areas. Agricultural soil microtopography plays an important role in the quantification of runoff and sediment transport because the presence of crops, crop residues, furrows and ridges may impact the direction of water flow. To better assess such phenomena, 3-D reconstructions of high-resolution agricultural watershed topography are essential. Fine-resolution topographic data collection technologies can be used to discern highly detailed elevation variability in these areas. Knowledge of the strengths and weaknesses of existing technologies used for data collection on agricultural watersheds may be helpful in choosing an appropriate technology. This study assesses the suitability of terrestrial laser scanning (TLS) and unmanned aerial system (UAS) photogrammetry for collecting the fine-resolution topographic data required to generate accurate, high-resolution digital elevation models (DEMs) in a small watershed area (12 ha). Because of farming activity, 14 TLS scans (≈ 25 points m- 2) were collected without using high-definition surveying (HDS) targets, which are generally used to mesh adjacent scans. To evaluate the accuracy of the DEMs created from the TLS scan data, 1098 ground control points (GCPs) were surveyed using a real time kinematic global positioning system (RTK-GPS). Linear regressions were then applied to each DEM to remove vertical errors from the TLS point elevations, errors caused by the non-perpendicularity of the scanner's vertical axis to the local horizontal plane, and errors correlated with the distance to the scanner's position. The scans were then meshed to generate a DEMTLS with a 1 × 1 m spatial resolution. The Agisoft PhotoScan and MicMac software packages were used to process the aerial photographs and generate a DEMPSC (Agisoft PhotoScan) and DEMMCM (MicMac), respectively, with spatial resolutions of 1 × 1 m. Comparing the DEMs with the 1098 GCPs showed that the DEMTLS was the most accurate data product, with a root mean square error (RMSE) of 4.5 cm, followed by the DEMMCM and the DEMPSC, which had RMSE values of 9.0 and 13.9 cm, respectively. The DEMPSC had absolute errors along the border of the study area that ranged from 15.0 to 52.0 cm, indicating the presence of systematic errors. Although the derived DEMMCM was accurate, an error analysis along a transect showed that the errors in the DEMMCM data tended to increase in areas of lower elevation. Compared with TLS, UAS is a promising tool for data collection because of its flexibility and low operational cost. However, improvements are needed in the photogrammetric processing of the aerial photographs to remove non-linear distortions.

  20. DEM-PFV analysis of solid-fluid transition in granular sediments under the action of waves

    NASA Astrophysics Data System (ADS)

    Catalano, E.; Chareyre, B.; Barthélémy, E.

    2013-06-01

    Solid-fluid transition is a very active area of investigations. It is linked to many applications in geomechanics and near-shore or off-shore engineering. Micromechanical models can give useful insight into the governing mechanisms of this phenomenon, provided they can reflect the role of pore fluids accurately. We present the application of a new hydromechanical model, combining the Discrete Element Method (DEM) to a flow model based on a pore-scale discretization in finite volumes (PFV) for incompressible pore fluids, to simulate the response of near-shore granular sediments subjected to the action of stationary waves. The model reproduces a wide range of physical processes observed in the experiments, including temporary liquefaction events.

  1. The Effects of the Terrain Variation and Changed Parameters of the Moving Window on the LIDAR DEM Spectrum

    NASA Astrophysics Data System (ADS)

    Vrečko, A.; Kovacs, G.; Podobnikar, T.; Székely, B.

    2012-04-01

    LIDAR (Light Detection And Ranging) data has become a highly used data source for modelling the terrain surface in recent years. In comparison to other surveying techniques, LIDAR measurements provide much denser (and affordable) sampling of the terrain in an automated manner. Higher density of data points results also in the better spatial resolution of DEMs (Digital Elevation Model) generated from these data. Fourier transform (FT) is a technique for transforming the terrain information from the spatial into the frequency domain. Higher spatial resolution of the DEM enables more local approach for analyzing the terrain surface with the FT, since even for a smaller area many (enough) sampling points are given. In this study 2D discrete Fast Fourier Transform (as implemented in MatLab) is applied to LIDAR DEM with a cell size of 0.5 m and therefore with a spatial resolution - in Fourier terminology - of 1.0 m. The chosen study area has different terrain characteristics, such as: different orientation of the lineaments, different aspects, different roughness. Our approach is to analyze the spectrum of the series of subareas ("moving window") of the DEM. This enables studying the response to the changes of different variables in the frequency domain. The changing variables were: (1) the size of the transformed area, (2) the offset between different positions of moving window, and (3) the orientation of the landforms with the respect to the moving window. Changes in all the variables influence the spectral information. We focus more on the results of changing the offset between moving windows, since these analysis are less explored. These offset changes reflect as the changes in the frequency domain due to a new relief structures included in the moving window. Additionally, the possibilities for visualization of spectral information were explored. The purpose was to find an appropriate way to visualize a series of FT, which would raise the understanding of the relations between the changes in spatial domain and the responses in the frequency domain. Good results were achieved for visualizing the amplitude but for the phase information further investigation is suggested. From geomorphometric point of view, the results can be interpreted as inherent properties of the terrain that was shaped by various endogenic and exogenic processes through longer time periods. Faulting and folding typically create quasi-linear or curvilinear features; they can be enhanced further by erosion, forming larger valley patterns. On the other hand, sedimentary processes tend to smooth the surface, by covering negative forms with sediments. Glaciation, as it is reshaping the current surface very rapidly, may modify the spatial spectrum considerably, removing higher frequency components. Post-glacial surface may inherit those properties and maintain them for longer time. Moving window FFT spectra are able to enhance hidden context (e.g., fault patterns), and rotation or deformation of original patterns can also be reflected in the succession of 2D Fourier spectra.

  2. Ship Detection and Motion Parameter Estimation with TanDEM-X in Large Along-Track Baseline Configuration

    NASA Astrophysics Data System (ADS)

    Baumgartner, Stefan V.; Krieger, Gerhard

    2013-03-01

    In the paper ship position and motion parameter estimation results obtained with the German TerraSARX/ TanDEM-X radar satellite formation are presented. For processing a novel ground moving target indication (GMTI) algorithm applicable for dual-platform SAR systems separated by a large along-track baseline is used [1]. This algorithm enables high accurate estimation of the true geographical positions, the velocities and moving directions of the detected ships and land moving targets without the need of a priori knowledge. The algorithm is verified and evaluated using SAR data and ground truth reference data acquired during the commissioning phase of TanDEMX in 2010. We have already presented the first results in [2][3]. The current paper is an extension.

  3. Inter-annual surface evolution of an Antarctic blue-ice moraine using multi-temporal DEMs

    NASA Astrophysics Data System (ADS)

    Westoby, M. J.; Dunning, S. A.; Woodward, J.; Hein, A. S.; Marrero, S. M.; Winter, K.; Sugden, D. E.

    2015-11-01

    Multi-temporal and fine resolution topographic data products are being increasingly used to quantify surface elevation change in glacial environments. In this study, we employ 3-D digital elevation model (DEM) differencing to quantify the topographic evolution of a blue-ice moraine complex in front of Patriot Hills, Heritage Range, Antarctica. Terrestrial laser scanning (TLS) was used to acquire multiple topographic datasets of the moraine surface at the beginning and end of the austral summer season in 2012/2013 and during a resurvey field campaign in 2014. A complementary topographic dataset was acquired at the end of season 1 through the application of Structure-from-Motion (SfM) photogrammetry to a set of aerial photographs taken from an unmanned aerial vehicle (UAV). Three-dimensional cloud-to-cloud differencing was undertaken using the Multiscale Model to Model Cloud Comparison (M3C2) algorithm. DEM differencing revealed net uplift and lateral movement of the moraine crests within season 1 (mean uplift ∼ 0.10 m), with lowering of a similar magnitude in some inter-moraine depressions and close to the current ice margin. Our results indicate net uplift across the site between seasons 1 and 2 (mean 0.07 m). This research demonstrates that it is possible to detect dynamic surface topographical change across glacial moraines over short (annual to intra-annual) timescales through the acquisition and differencing of fine-resolution topographic datasets. Such data offer new opportunities to understand the process linkages between surface ablation, ice flow, and debris supply within moraine ice.

  4. Improvement of Forest Height Retrieval By Integration of Dual-Baseline PolInSAR Data And External DEM Data

    NASA Astrophysics Data System (ADS)

    Xie, Q.; Wang, C.; Zhu, J.; Fu, H.; Wang, C.

    2015-06-01

    In recent years, a lot of studies have shown that polarimetric synthetic aperture radar interferometry (PolInSAR) is a powerful technique for forest height mapping and monitoring. However, few researches address the problem of terrain slope effect, which will be one of the major limitations for forest height inversion in mountain forest area. In this paper, we present a novel forest height retrieval algorithm by integration of dual-baseline PolInSAR data and external DEM data. For the first time, we successfully expand the S-RVoG (Sloped-Random Volume over Ground) model for forest parameters inversion into the case of dual-baseline PolInSAR configuration. In this case, the proposed method not only corrects terrain slope variation effect efficiently, but also involves more observations to improve the accuracy of parameters inversion. In order to demonstrate the performance of the inversion algorithm, a set of quad-pol images acquired at the P-band in interferometric repeat-pass mode by the German Aerospace Center (DLR) with the Experimental SAR (E-SAR) system, in the frame of the BioSAR2008 campaign, has been used for the retrieval of forest height over Krycklan boreal forest in northern Sweden. At the same time, a high accuracy external DEM in the experimental area has been collected for computing terrain slope information, which subsequently is used as an inputting parameter in the S-RVoG model. Finally, in-situ ground truth heights in stand-level have been collected to validate the inversion result. The preliminary results show that the proposed inversion algorithm promises to provide much more accurate estimation of forest height than traditional dualbaseline inversion algorithms.

  5. Numerical slope stability simulations of chasma walls in Valles Marineris/Mars using a distinct element method (dem).

    NASA Astrophysics Data System (ADS)

    Imre, B.

    2003-04-01

    NUMERICAL SLOPE STABILITY SIMULATIONS OF CHASMA WALLS IN VALLES MARINERIS/MARS USING A DISTINCT ELEMENT METHOD (DEM). B. Imre (1) (1) German Aerospace Center, Berlin Adlershof, bernd.imre@gmx.net The 8- to 10-km depths of Valles Marineris (VM) offer excellent views into the upper Martian crust. Layering, fracturing, lithology, stratigraphy and the content of volatiles have influenced the evolution of the Valles Marineris wallslopes. But these parameters also reflect the development of VM and its wall slopes. The scope of this work is to gain understanding in these parameters by back-simulating the development of wall slopes. For that purpose, the two dimensional Particle Flow Code PFC2D has been chosen (ITASCA, version 2.00-103). PFC2D is a distinct element code for numerical modelling of movements and interactions of assemblies of arbitrarily sized circular particles. Particles may be bonded together to represent a solid material. Movements of particles are unlimited. That is of importance because results of open systems with numerous unknown variables are non-unique and therefore highly path dependent. This DEM allows the simulation of whole development paths of VM walls what makes confirmation of the model more complete (e.g. Oreskes et al., Science 263, 1994). To reduce the number of unknown variables a proper (that means as simple as possible) field-site had to be selected. The northern wall of eastern Candor Chasma has been chosen. This wall is up to 8-km high and represents a significant outcrop of the upper Martian crust. It is quite uncomplex, well-aligned and of simple morphology. Currently the work on the model is at the stage of performing the parameter study. Results will be presented via poster by the EGS-Meeting.

  6. Automated classifications of topography from DEMs by an unsupervised nested-means algorithm and a three-part geometric signature

    NASA Astrophysics Data System (ADS)

    Iwahashi, Junko; Pike, Richard J.

    2007-05-01

    An iterative procedure that implements the classification of continuous topography as a problem in digital image-processing automatically divides an area into categories of surface form; three taxonomic criteria-slope gradient, local convexity, and surface texture-are calculated from a square-grid digital elevation model (DEM). The sequence of programmed operations combines twofold-partitioned maps of the three variables converted to greyscale images, using the mean of each variable as the dividing threshold. To subdivide increasingly subtle topography, grid cells sloping at less than mean gradient of the input DEM are classified by designating mean values of successively lower-sloping subsets of the study area (nested means) as taxonomic thresholds, thereby increasing the number of output categories from the minimum 8 to 12 or 16. Program output is exemplified by 16 topographic types for the world at 1-km spatial resolution (SRTM30 data), the Japanese Islands at 270 m, and part of Hokkaido at 55 m. Because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre-set criteria, the resulting classes are undefined and must be calibrated empirically by subsequent analysis. Maps of the example classifications reflect physiographic regions, geological structure, and landform as well as slope materials and processes; fine-textured terrain categories tend to correlate with erosional topography or older surfaces, coarse-textured classes with areas of little dissection. In Japan the resulting classes approximate landform types mapped from airphoto analysis, while in the Americas they create map patterns resembling Hammond's terrain types or surface-form classes; SRTM30 output for the United States compares favorably with Fenneman's physical divisions. Experiments are suggested for further developing the method; the Arc/Info AML and the map of terrain classes for the world are available as online downloads.

  7. A hierarchical pyramid method for managing large-scale high-resolution drainage networks extracted from DEM

    NASA Astrophysics Data System (ADS)

    Bai, Rui; Tiejian, Li; Huang, Yuefei; Jiaye, Li; Wang, Guangqian; Yin, Dongqin

    2015-12-01

    The increasing resolution of Digital Elevation Models (DEMs) and the development of drainage network extraction algorithms make it possible to develop high-resolution drainage networks for large river basins. These vector networks contain massive numbers of river reaches with associated geographical features, including topological connections and topographical parameters. These features create challenges for efficient map display and data management. Of particular interest are the requirements of data management for multi-scale hydrological simulations using multi-resolution river networks. In this paper, a hierarchical pyramid method is proposed, which generates coarsened vector drainage networks from the originals iteratively. The method is based on the Horton-Strahler's (H-S) order schema. At each coarsening step, the river reaches with the lowest H-S order are pruned, and their related sub-basins are merged. At the same time, the topological connections and topographical parameters of each coarsened drainage network are inherited from the former level using formulas that are presented in this study. The method was applied to the original drainage networks of a watershed in the Huangfuchuan River basin extracted from a 1-m-resolution airborne LiDAR DEM and applied to the full Yangtze River basin in China, which was extracted from a 30-m-resolution ASTER GDEM. In addition, a map-display and parameter-query web service was published for the Mississippi River basin, and its data were extracted from the 30-m-resolution ASTER GDEM. The results presented in this study indicate that the developed method can effectively manage and display massive amounts of drainage network data and can facilitate multi-scale hydrological simulations.

  8. Automated classifications of topography from DEMs by an unsupervised nested-means algorithm and a three-part geometric signature

    USGS Publications Warehouse

    Iwahashi, J.; Pike, R.J.

    2007-01-01

    An iterative procedure that implements the classification of continuous topography as a problem in digital image-processing automatically divides an area into categories of surface form; three taxonomic criteria-slope gradient, local convexity, and surface texture-are calculated from a square-grid digital elevation model (DEM). The sequence of programmed operations combines twofold-partitioned maps of the three variables converted to greyscale images, using the mean of each variable as the dividing threshold. To subdivide increasingly subtle topography, grid cells sloping at less than mean gradient of the input DEM are classified by designating mean values of successively lower-sloping subsets of the study area (nested means) as taxonomic thresholds, thereby increasing the number of output categories from the minimum 8 to 12 or 16. Program output is exemplified by 16 topographic types for the world at 1-km spatial resolution (SRTM30 data), the Japanese Islands at 270??m, and part of Hokkaido at 55??m. Because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre-set criteria, the resulting classes are undefined and must be calibrated empirically by subsequent analysis. Maps of the example classifications reflect physiographic regions, geological structure, and landform as well as slope materials and processes; fine-textured terrain categories tend to correlate with erosional topography or older surfaces, coarse-textured classes with areas of little dissection. In Japan the resulting classes approximate landform types mapped from airphoto analysis, while in the Americas they create map patterns resembling Hammond's terrain types or surface-form classes; SRTM30 output for the United States compares favorably with Fenneman's physical divisions. Experiments are suggested for further developing the method; the Arc/Info AML and the map of terrain classes for the world are available as online downloads. ?? 2006 Elsevier B.V. All rights reserved.

  9. Evaluation of adequacy of DEM level-1 as an alternative to level-2: in a context of a case study for radiometric normalization of desert bare soil in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Alomran, Ali. I.; McCullagh, M. J.

    2008-10-01

    The Kingdom of Saudi Arabia has not yet had a full (national) land cover mapping survey. The very limited areas in Saudi Arabia covered by the 30m resolution DEM level-2 that is compatible with the fine and medium resolution (SPOT and TM) imagery makes it unreliable as a topographic source. The validity of the lower spatial resolution (100m) DEM level- 1 of full coverage of the Kingdom as a substitute is tested for that purpose. Two approaches to assessment were considered for this purpose. The first approach, implemented in this paper, involved a comparison between the two DEMs data with the aid of reference data, whereas in the second, not published yet, the assessment was performed on the radiometrically corrected image data using the two DEMs data. Visual and statistical analyses have revealed that differences (discrepancies) between the two DEMs increase with increase of terrain slope, indicating that possibility of DEM level-1 to replace level-2 decreases with increase in terrain slope. The possibility of DEM level-1 to be an adequate alternative to level-2 would apply in flat to moderate terrain (0° - 5°) only, and is expected to decrease as terrain orientation turns away from north (highest differences at 271° - 360°). The differences between the two DEMs for west facing slopes (i.e., 181° - 360°) are significantly higher than those for east oriented slopes (i.e., 0° - 180°).

  10. MARE2DEM: an open-source code for anisotropic inversion of controlled-source electromagnetic and magnetotelluric data using parallel adaptive 2D finite elements (Invited)

    NASA Astrophysics Data System (ADS)

    Key, K.

    2013-12-01

    This work announces the public release of an open-source inversion code named MARE2DEM (Modeling with Adaptively Refined Elements for 2D Electromagnetics). Although initially designed for the rapid inversion of marine electromagnetic data, MARE2DEM now supports a wide variety of acquisition configurations for both offshore and onshore surveys that utilize electric and magnetic dipole transmitters or magnetotelluric plane waves. The model domain is flexibly parameterized using a grid of arbitrarily shaped polygonal regions, allowing for complicated structures such as topography or seismically imaged horizons to be easily assimilated. MARE2DEM efficiently solves the forward problem in parallel by dividing the input data parameters into smaller subsets using a parallel data decomposition algorithm. The data subsets are then solved in parallel using an automatic adaptive finite element method that iterative solves the forward problem on successively refined finite element meshes until a specified accuracy tolerance is met, thus freeing the end user from the burden of designing an accurate numerical modeling grid. Regularized non-linear inversion for isotropic or anisotropic conductivity is accomplished with a new implementation of Occam's method referred to as fast-Occam, which is able to minimize the objective function in much fewer forward evaluations than the required by the original method. This presentation will review the theoretical considerations behind MARE2DEM and use a few recent offshore EM data sets to demonstrate its capabilities and to showcase the software interface tools that streamline model building and data inversion.

  11. An automated, open-source pipeline for mass production of digital elevation models (DEMs) from very-high-resolution commercial stereo satellite imagery

    NASA Astrophysics Data System (ADS)

    Shean, David E.; Alexandrov, Oleg; Moratto, Zachary M.; Smith, Benjamin E.; Joughin, Ian R.; Porter, Claire; Morin, Paul

    2016-06-01

    We adapted the automated, open source NASA Ames Stereo Pipeline (ASP) to generate digital elevation models (DEMs) and orthoimages from very-high-resolution (VHR) commercial imagery of the Earth. These modifications include support for rigorous and rational polynomial coefficient (RPC) sensor models, sensor geometry correction, bundle adjustment, point cloud co-registration, and significant improvements to the ASP code base. We outline a processing workflow for ∼0.5 m ground sample distance (GSD) DigitalGlobe WorldView-1 and WorldView-2 along-track stereo image data, with an overview of ASP capabilities, an evaluation of ASP correlator options, benchmark test results, and two case studies of DEM accuracy. Output DEM products are posted at ∼2 m with direct geolocation accuracy of <5.0 m CE90/LE90. An automated iterative closest-point (ICP) co-registration tool reduces absolute vertical and horizontal error to <0.5 m where appropriate ground-control data are available, with observed standard deviation of ∼0.1-0.5 m for overlapping, co-registered DEMs (n = 14, 17). While ASP can be used to process individual stereo pairs on a local workstation, the methods presented here were developed for large-scale batch processing in a high-performance computing environment. We are leveraging these resources to produce dense time series and regional mosaics for the Earth's polar regions.

  12. Assessment of a Near-Global 30-meter Resolution DEM Derived from the Publicly Available SRTM Data Set for Use in Orthorectification of Satellite SAR Imagery

    NASA Astrophysics Data System (ADS)

    McDonald, K. C.; Chapman, B.; Podest, E.; Jimenez, A.

    2007-12-01

    The Shuttle Radar Topography Mission (SRTM) utilized an interferometric synthetic aperture radar (InSAR) flown onboard the space shuttle Endeavour to obtain high resolution elevation data of Earth's land surface. Virtually all land surface between +/- 60 degrees latitude was mapped. Regions within these bounds contain some data gaps but this represents less than 0.2 % of the coverage. Standard publicly-available data sets from SRTM include a 3 arc-second (~90 meter) resolution Digital Elevation Model (DEM) with absolute average global vertical accuracy of approximately 4 to 5 meters. A 1 arc-second (~30 meter) resolution DEM has also been developed, but only the portion of the data set covering the United States is publicly available. The finished version of these products has been edited for pixel-level errors and delineation of coastlines and water bodies, although some data voids are still present. Utilizing such DEMs of appropriate resolution in a common framework with satellite synthetic aperture radar (SAR) data allows robust ortho-rectification and geo-referencing of the SAR data sets. We have derived a 1 arc-second resolution DEM over the entire domain of the SRTM coverage using a 3- dimensional interpolation scheme applied to the 3 arc-second SRTM DEM. Development of this product involves (1) translation of SRTM products into the WGS84 datum, (2) interpolation of the lower resolution DEMs to 1 arc- second, and (3) assembly of the global-scale 1 arc-second DEM. We assess effectiveness of this interpolation scheme through comparative statistical analysis of the 3 arc-second finished product, the 1 arc-second finished product, and the 1 arc-second interpolated product over selected test regions within the USA where all products are available. Comparisons are also made to standard GTOPO30 products for regions inside and outside of the USA. Comparisons are presented for regions representative of gentle and complex terrain. Ortho-rectification of SAR data such as those obtained from the Japanese Earth Resources Satellite (JERS) and ALOS PALSAR allows for an accurate representation of these data, providing crucial information accounting for effects of topography on geophysical retrievals. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

  13. Estimation of mass change rates of surge-type glaciers in the Karakoram derived from TanDEM-X and SRTM Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Rankl, Melanie; Braun, Matthias; Vijay, Saurabh

    2014-05-01

    Glaciers in the Karakoram region exhibit stable and advancing termini positions accompanied by less negative or even positive surface mass balances in comparison to the adjacent Greater Himalaya Range and the Hindu Kush mountains. Moreover, a large number of surge-type glaciers is found in the Karakoram. During the active phase of a surge, ice masses are shifted from the reservoir area towards the receiving area of a glacier. Remote sensing based methods provide various possibilities to identify surge-type glaciers (termini position changes, surface velocity variations, mass changes), where in-situ measurements are hardly available. The present study focuses on glacier mass changes in the Karakoram between 2000 and 2013 derived from DEM differencing. We used the C-band SRTM DEM (February, 2000) and high resolution TanDEM-X data (2011-2013). Due to quasi bi-static image acquisitions, TanDEM-X data is very suitable for interferometric elevation generation minimizing decorrelation impacts. However, influences of different penetration depths of X- and C-band have to be considered. We quantified glacier volume and mass changes for the central part of the Karakoram for a twelve year period. For a surge-type glacier in the Shimshal Valley we observed a mass relocation of 2.96±2.52 m/a w.e. close to its snout between 2000 and 2012. Further case studies will be presented including annual mass changes (2011-2013) determined using repeat TanDEM-X acquisitions. In addition to interannual surface velocity changes, mass change observations can help to obverse the propagation of the surge front down-glacier and quantify the relocation of mass during an active surge phase.

  14. Site-specific assessment of the rockfall and the rock block volume distribution relations, using a LIDAR generated DEM

    NASA Astrophysics Data System (ADS)

    Mavrouli, Olga; Corominas, Jordi; Jaboyedoff, Michel

    2014-05-01

    The quantification of the rockfall hazard and, in particular of the rockfall propagation, requires information on the expected probability or frequency of rockfalls of a given magnitude (size), usually in the form of magnitude-frequency M-F relations. Two kinds of relations are needed. The first one characterises the rockfall masses that can be potentially detached from the slope face giving information on the volume distribution of rockfalls. From now on, this will be referred to as potential rockfall volume distribution VDR. For fragmental rockfalls, the evaluation of the VDR can be a first step towards the temporal M-F, The second one characterises the volume distribution of the rock blocks that result from the disintegration of the previous rockfall masses due to impact with the ground. This one will be referred to as rock block volume distribution VDB. In this work we present two analytical procedures which are independent from the existence of empirical data, for: (i) The calculation of the potential VDR that refers to big volumes with low probability of occurrence. This is realised by detection of the kinematically unstable surfaces on a DEM and on orthophotos, and calculation of the volumes that correspond to them. The basic assumptions here describing a conservative scenario of very low probability are: (a) the rockfall mass is detached entirely at a single rockfall event, without taking into account that smaller successive failures are possible instead; (b) all discontinuity sets are present everywhere in the slope and have infinite persistence; and (c) big stepped-path failures are possible. (ii) The assessment of the in-situ rock blocks volume distribution on the slope face, VDB, by calculation of the volume of the prisms which are formed by the intersection of the existing discontinuity sets and are kinematically unstable. This is also based on data obtained by DEM analysis. A high-resolution DEM obtained by Lidar is used. Both procedures are presented though an application example at the country of Andorra and in particular at the chute of Forat Negre. The results from the first procedure indicate that it is kinematically possible to have mobilised volumes of some thousands of cubic meters although the probability of generating large volumes is low. The VDR for big volume events was well fitted by a power-law equal to -0.5. The VDB from the second procedure, assuming three intersection types within the discontinuity network and two extreme cases of discontinuity persistence, was also found to follow a power-law, with exponent -1.3. The comparison with field data collected by past studies in the same area indicates that in reality, the discontinuities have a very high persistence and that considering only their visible trace length is very conservative.

  15. Elevation Change of Greenland's Jakobshavn Glacier from ICESat, IceBridge Altimetry and TerraSAR-X DEMs

    NASA Astrophysics Data System (ADS)

    Qi, W.; Braun, A.

    2012-12-01

    The recent accelerated ice mass loss of the Greenland ice sheet, and its outlet glacier in particular, has been widely documented. The Jakobshavn Isbrae/Glacier is one of the fastest melting and retreating glaciers in Greenland. Recent observations from the laser altimetry mission ICESat (2003-2009) and the airborne campaigns of the IceBridge project (2009-2011) were used to determine Jakobshavn's total elevation change for those time periods as well as annual elevation change rates. TerraSAR-X data acquired in 2009 were processed to form 3 m horizontal resolution digital elevation models (DEM), which were constrained using ICESat measurements. The elevation change results confirm previously determined rates of several decimeters per year of elevation loss. More specifically, while the outlet glacier shows elevation loss of up to several meters per year, the higher elevation areas of the ice sheet exhibit only a few decimeters per year loss and even elevation gain for some years. The study area below 1500 m elevation shows elevation change rates between -0.5 to -2.5 m/yr, the higher elevation area exhibits a much decreased rate between +0.34 and -0.55 m/yr. The Jakobshavn outlet glacier showed a consistently increasing elevation change rate of -3.0 to -5.0 m/yr between 2003 and 2011. It demonstrates that both ICESat and IceBridge observations allow for the accurate estimation of elevation change rates with uncertainties of less than 0.5 m/yr standard deviation. The major contributor to the uncertainty is the slope correction needed to project two footprints at different epochs onto a common location. The slope correction was applied based on the DEMs from ICESat and TerraSAR-X data or the IceBridge slope measurements. Both ICESat and IceBridge observations are able to demonstrate the variations in annual and seasonal elevation change rates exceeding 0.5 m/yr, a rate which is by far exceeded for low-elevation areas below 1500 m. By having an improved understanding of annual and seasonal variability of elevation change, the mass balance of the Jakobshavn glacier can be better assessed towards quantifying its contribution to sea level change.otal elevation change between early-summer 2009 and early-summer 2011 from IceBridge data along the flight tracks.

  16. Terrain Classification of Aster gDEM for Seismic Microzonation of Port-Au Haiti, Using - and - Based Analytic Methods

    NASA Astrophysics Data System (ADS)

    Yong, A.; Hough, S. E.; Cox, B. R.; Rathje, E. M.; Bachhuber, J.; Hulslander, D.; Christiansen, L.; Abrams, M.

    2010-12-01

    The aftermath of the M7.0 Haiti earthquake of 12 January 2010 witnessed an impressive scientific response from the international community. In addition to conventional post-earthquake investigations, there was also an unprecedented reliance on remote-sensing technologies for scientific investigation and damage assessment. These technologies include sensors from both aerial and space-borne observational platforms. As part of the Haiti earthquake response and recovery effort, we develop a seismic zonation map of Port-au-Prince based on high-resolution satellite imagery as well as data from traditional seismographic monitoring stations and geotechnical site characterizations. Our imagery consists of a global digital elevation model (gDEM) of Hispaniola derived from data recorded by NASA-JPL's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument onboard the multi-platform satellite Terra. To develop our model we also consider recorded waveforms from portable seismographic stations (Hough et al., in review) and 36 geotechnical shear-wave velocity surveys (Cox et al., in review). Following a similar approach developed by Yong et al. (2008; Bull. Seism Soc. Am.), we use both pixel- and object- based imaging analytic methods to systematically identify and extract local terrain features that are expected to amplify seismic ground motion. Using histogram-stretching techniques applied to the rDEM values, followed by multi-resolution, segmentations of the imagery into terrain types, we systematically classify the terrains of Hispaniola. By associating available Vs30 (average shear-wave velocity in the upper 30 meter depth) calculated from the MASW (Multi-channel Analysis of Surface Wave) survey method, we develop a first-order site characterization map. Our results indicate that the terrain-based Vs30 estimates are significantly associated with amplitudes recorded at station sites. We also find that the damage distribution inferred from UNOSAT (UNITAR Operational Satellite Applications Program) data matches our estimates. However, the strongest amplifications are observed at two stations on a foothill ridge, where Vs30 values indicate that amplification should be relatively lower. Hough et al. (2010, this session) conclude that the observations can be explained by topographic amplification along a steep, narrow ridge. On the basis of these preliminary results, we conclude that the terrain-based framework, which characterizes topographic amplification as well as sediment-induced amplification, is needed to develop a microzonation map for Port-au-Prince.

  17. Implications of Geomorphic Change on Salmonid Habitat Using a Narrow-Beam Terrestrial-Aquatic Lidar and DEM Uncertainty Accounting

    NASA Astrophysics Data System (ADS)

    Wheaton, J. M.; McKean, J. A.; Tonina, D.; Garrard, C.

    2009-12-01

    The high-density of airborne LiDaR data has paved the way for a wide range of multi-scalar analyses of watersheds, some of which elegantly highlight abiotic-faunal interactions. However, most LiDaR sensors do not penetrate the water surface, and in-channel habitat in the fluvial environment cannot typically be characterized with traditional LiDaR. Airborne-LiDaR has also been touted for its potential in monitoring change through time, but to date, very few studies have explicitly used repeat LiDaR surveys for monitoring geomorphic change (i.e. morphological sediment budgeting) nor established that the changes of interest are above minimum level of detection thresholds, given the uncertainty in the data. Two new technological advances are helping to address these shortcomings and may highlight its utility at monitoring change in fluvial environments. The first is the emergence of green-LiDaR, which is capable of penetrating the water surface of many rivers and providing returns off the bed, which can be used to model bathymetry and in-channel habitat. The second is the development of new methods and software for characterizing the spatial variability of uncertainty in digital elevation models (DEMs) derived from this new terrestrial/aquatic green-LiDaR and propagating that through to DEMs of difference to differentiate between changes due to noise and actual geomorphic changes. In this study, we report the application of these two technologies to looking at changes in physical habitat for salmonids between 2004 and 2007 on Bear Creek in the headwaters of the Salmon River Watershed in Idaho. The analyses show that although the individual terrestrial-aquatic LiDaR surveys provide a broad coverage and enable a rich characterization of in-channel habitat, that uncertainties in the data limit the spatial coverage of areas where we can be confident about the magnitude of geomorphic change. However, due to the incorporation of a spatially-variable establishment of minimum levels of change detection, the analyses clearly segregate areas of questionable change from areas of likely change. Moreover, a series of spatial masking tools based on habitat characterization allow meaningful interpretations of the geomorphic changes in terms of their ecological significance to salmonids.

  18. Analysis of landslide development using aerial photographs and DEMs comparison, along part of the Chacoura River valley, Quebec, Canada.

    NASA Astrophysics Data System (ADS)

    Lévy, S.; Locat, J.; Jaboyedoff, M.; Demers, D.; Loye, A.

    2009-04-01

    The large plains of Eastern Canada sensitive clays are cut by numerous rivers, in a way that their slopes have been and are still affected by landslides. They play an important role in the modelling of the landscape of these regions. Hence, the role of erosion as a trigger of landslides is important. On the Chacoura River, north of Louiseville (Quebec), several large landslides scars, more or less recent, are visible. A first inventory of areas of erosion, slides and landslides clay was carried out by Locat et al. (1984) on some series of aerial photographs covering a period from 1948 to 1979. This study is based on a detailed analysis of aerial photographs, dating from 1948 to 1997 and an airborne LiDAR digital elevation model (DEM-LiDAR), dating from 2007, in a GIS environment, using two different approaches: (1) a map of the phenomena was drawn by identifying various elements such as land movements, limits of the slope, position of the river, the area covered by forest and agricultural drainage structures, e.g., and (2) the comparison of DEMs was performed to estimate slipped and eroded volumes, the rate of erosion on a section of the river (about 6 km) and the spatial distribution of movements. The results show that the location of landslides is directly linked to the presence of some characteristic topographical features, such as (1) the shape of the meandering river, (2) the flow of agricultural drainage, or (3) the erosion at the toe of the slope. Finally, the study of landslides over a period of 60 years shows that the major landslide scars in this area could be in fact the sum of several events of lesser importance. For example, a large landslide (around 13'000 m2) occurred in 1976 at the same place where a first landslide of 1500 m2 in 1964. Locat, J., Demers, D., Lebuis, J. and Rissmann, P. (1984), Prédiction des Glissements de Terrain; Application aux Argiles Sensibles, Rivière Chacoura, Québec, Canada, the IV International Symposium on Landslides Toronto 1984 Proceedings, Volume II, pp 549-555.

  19. Developing sub 5-m LiDAR DEMs for forested sections of the Alpine and Hope faults, South Island, New Zealand: Implications for structural interpretations

    NASA Astrophysics Data System (ADS)

    Langridge, R. M.; Ries, W. F.; Farrier, T.; Barth, N. C.; Khajavi, N.; De Pascale, G. P.

    2014-07-01

    Kilometre-wide airborne light detection and ranging (LiDAR) surveys were collected along portions of the Alpine and Hope faults in New Zealand to assess the potential for generating sub 5-m bare earth digital elevation models (DEMs) from ground return data in areas of dense rainforest (bush) cover as an aid to mapping these faults. The 34-km long Franz-Whataroa LiDAR survey was flown along the densely-vegetated central-most portion of the transpressive Alpine Fault. Six closely spaced flight lines (200 m apart) yielded survey coverage with double overlap of swath collection, which was considered necessary due to the low density of ground returns (0.16 m-2 or a point every 6 m2) under mature West Coast podocarp-broadleaf rainforest. This average point spacing (˜2.5 m) allowed for the generation of a robust, high quality 3-m bare earth DEM. The DEM confirmed the zigzagged form of the surface trace of the Alpine Fault in this area, originally recognised by Norris and Cooper (1995, 1997) and highlights that the surface strike variations are more variant than previously mapped. The 29-km long Hurunui-Hope LiDAR survey was flown east of the Main Divide of the Southern Alps along the dextral-slip Hope Fault, where the terrain is characterised by lower rainfall and more open beech forest. Flight line spacings of ˜275 m were used to generate a DEM from the ground return data. The average ground return values under beech forest were 0.27 m-2 and yielded an estimated cell size suitable for a 2-m DEM. In both cases the LiDAR revealed unprecedented views of the surface geomorphology of these active faults. Lessons learned from our survey methodologies can be employed to plan cost-effective, high-gain airborne surveys to yield bare earth DEMs underneath vegetated terrain and multi-storeyed canopies from densely forested environments across New Zealand and worldwide.

  20. DEM analyses of the whole failure process of shallow foundation in plate load test on dense sand

    NASA Astrophysics Data System (ADS)

    Li, L.; Jiang, M. J.; Li, T.; Chen, S. L.

    2015-09-01

    Shallow foundations are widely used in civil engineering practice, but the instability mechanism is still unclear yet. Previously, the Finite Element Method (FEM) was commonly used to analyze the failure process of shallow foundations, but it meets difficulty in properly simulating the whole failure process of shallow foundation on the strain-softening material. Hence, the Discrete Element Method (DEM) is employed in this paper to study the instability mechanism of the shallow foundation via numerical plate load test with focus on the microscopic features evolution during vertical loading. In the simulation, an amplified gravity was applied to a dense granular ground to reproduce a gravity stress state at a large scale. Then, a plate was put on the granular ground to simulate the plate load test. Deformation pattern, particle velocity and distribution of void ratio in the ground were examined to illustrate the microscopic features in the whole failure process of the granular ground. The results show that: 1) There are a marked peak value and a settlement softening branch in the stress-settlement relationship. 2) The grids close to the edge of the plate are peculiarly extended and twisted. 3) Four particle motion patterns were observed in the velocity fields and the percentage of each motion pattern changes during loading. 4) The void ratio field varies during loading, and the distinguishing interface tends to be similar to Terzaghi's shear failure surface.

  1. Investigation of Landslide from Deformation - Comparison of High Resolution DEM, Aero Photos Using Long Wave Length DInSAR

    NASA Astrophysics Data System (ADS)

    Wang, Kuo-Lung; Lin, Jun-Tin; Lin, Meei-Ling; Lin, Ching-Wee; Chen, Tien-Chien; Tseng, Chih-Ming; Chen, Hongey; Lin, Sheng-Chi

    2013-04-01

    Landslide is one of the common natural hazards in Taiwan, especially in central Taiwan with high elevation and steep terrain. Rainfall is increasing both in accumulation and intensity after 2000. Severe landslide events after Chi Chi earthquake are including typhoon Toraj, typhoon Mindulle, 69 heavy rainfall, typhoon Sinlaku, and typhoon Morakot. However, these landslides could be unstable or deformed after rainfall and sliding in next events. The major purpose of this study is to find these deformed but not slide out slopes but slip in following events. For this objective, differential interferometry synthetic aperture radar (DInSAR) is adopted and an event after 69 heavy rainfall is selected for this research. The vegetation in Taiwan is very well thus wave length of SAR needs as long as possible to penetrate vegetation to reach ground surface. ALOS PALSAR HH image is used in this research to derive fringe in study area. The Study area ranges from Puli in south and Wulin in north, including May River basin, Lushan hot spring area, Chingjing area, and Tsuiluan area. The result shows appropriate relationship between the founded deformed slope from DInSAR and landslip in following event. Also high resolution DEM and aero photos are used to derive topography and landslide identification. The results also show that the process can be reference to produce landslide susceptibility map.

  2. Empirical relationships among triangular facet slope, facet height and slip rates along active normal faults from ASTER DEM data

    NASA Astrophysics Data System (ADS)

    Tsimi, Christina; Ganas, Athanassios

    2015-04-01

    ASTER DEM data (30-m pixel size) are used to derive empirical relationships between triangular facet attributes and slip rates along active normal faults. We sampled 232 triangular facets along 10 normal faults in Greece and Bulgaria that slip with rates from 0.1 mm/yr up to 1.3 mm/yr. The studied normal faults accumulate Quaternary tectonic strain in well-known extensional provinces, such as central Greece, Crete and SW Bulgaria. The normal fault footwalls analysed herein have been developed under similar long-term climatic conditions. It is suggested that two key geometrical features of the youngest generation of triangular facets (slope angle and height) can provide useful metrics to assess rates of deformation when seismological and geodetic data are lacking or not found in sufficient quantity to make reasonable assessments. Our derived empirical relation between slip rate and facet slope angle is: Y=0.057•X-1 where Y is fault slip rate (mm/yr) and X is facet slope angle (degrees), with an R² = 0.728. It is envisaged that our analysis may be helpful in assessing seismic hazard along normal faults with similar facet characteristics in other extensional settings. Note: This research was funded by The Rapid Analysis and Spatialisation Of Risk (RASOR) project http://www.rasor-project.eu/

  3. Numerical Modelling of the Anisotropic Mechanical Behaviour of Opalinus Clay at the Laboratory-Scale Using FEM/DEM

    NASA Astrophysics Data System (ADS)

    Lisjak, Andrea; Tatone, Bryan S. A.; Grasselli, Giovanni; Vietor, Tim

    2014-01-01

    The Opalinus Clay (OPA) is an argillaceous rock formation selected to host a deep geologic repository for high-level nuclear waste in Switzerland. It has been shown that the excavation damaged zone (EDZ) in this formation is heavily affected by the anisotropic mechanical response of the material related to the presence of bedding planes. In this context, the purpose of this study is twofold: (i) to illustrate the new developments that have been introduced into the combined finite-discrete element method (FEM/DEM) to model layered materials and (ii) to demonstrate the effectiveness of this new modelling approach in simulating the short-term mechanical response of OPA at the laboratory-scale. A transversely isotropic elastic constitutive law is implemented to account for the anisotropic elastic modulus, while a procedure to incorporate a distribution of preferentially oriented defects is devised to capture the anisotropic strength. Laboratory results of indirect tensile tests and uniaxial compression tests are used to calibrate the numerical model. Emergent strength and deformation properties, together with the simulated damage mechanisms, are shown to be in strong agreement with experimental observations. Subsequently, the calibrated model is validated by investigating the effect of confinement and the influence of the loading angle with respect to the specimen anisotropy. Simulated fracture patterns are discussed in the context of the theory of brittle rock failure and analyzed with reference to the EDZ formation mechanisms observed at the Mont Terri Underground Research Laboratory.

  4. An iterative LiDAR DEM-aided algorithm for GNSS positioning in obstructed/rapidly undulating environments

    NASA Astrophysics Data System (ADS)

    Danezis, Chris; Gikas, Vassilis

    2013-09-01

    This paper describes a new algorithm to aid stand-alone GNSS positioning in areas of bad signal reception using a Digital Elevation Model (DEM). Traditional Height-Aiding (HA) algorithms assume either a preset (fixed) value for the receiver elevation or rely on the elevation value that corresponds to the nearest available position fix. This may lead in erroneous receiver elevation estimates that, under circumstances, are inefficient to aid effectively GNSS positioning. In this study, the receiver elevation is updated at every iteration step of the navigation solution through dynamic interpolation of the elevation model. The algorithm, because of its ability to extract and fully exploit the elevation information derived from a digital model, it can prove particularly useful in forested areas with steep-sloped terrain. Extended test runs were undertaken to validate the correctness of the mathematical model and the feasibility of the algorithm and associated software. Particularly, analysis of a dataset acquired in a forested, rapidly undulating environment reveals significant average improvement in all performance metrics of positioning, namely the GNSS position availability (50%), accuracy (56%) and external reliability (86%) compared to the Standard Point Positioning (SPP) solution. Moreover, it was found that the method can cope successfully in marginal operating conditions with situations of bad satellite geometry and satellite signals affected by interference due to tree canopy.

  5. An efficient and comprehensive method for drainage network extraction from DEM with billions of pixels using a size-balanced binary search tree

    NASA Astrophysics Data System (ADS)

    Bai, Rui; Li, Tiejian; Huang, Yuefei; Li, Jiaye; Wang, Guangqian

    2015-06-01

    With the increasing resolution of digital elevation models (DEMs), computational efficiency problems have been encountered when extracting the drainage network of a large river basin at billion-pixel scales. The efficiency of the most time-consuming depression-filling pretreatment has been improved by using the O(NlogN) complexity least-cost path search method, but the complete extraction steps following this method have not been proposed and tested. In this paper, an improved O(NlogN) algorithm was proposed by introducing a size-balanced binary search tree (BST) to improve the efficiency of the depression-filling pretreatment further. The following extraction steps, including the flow direction determination and the upslope area accumulation, were also redesigned to benefit from this improvement. Therefore, an efficient and comprehensive method was developed. The method was tested to extract drainage networks of 31 river basins with areas greater than 500,000 km2 from the 30-m-resolution ASTER GDEM and two sub-basins with areas of approximately 1000 km2 from the 1-m-resolution airborne LiDAR DEM. Complete drainage networks with both vector features and topographic parameters were obtained with time consumptions in O(NlogN) complexity. The results indicate that the developed method can be used to extract entire drainage networks from DEMs with billions of pixels with high efficiency.

  6. Mapping SOC content and bulk density of a disturbed peatland relict with electromagnetic induction and DEM data

    NASA Astrophysics Data System (ADS)

    Altdorff, Daniel; Bechtold, Michel; van der Kruk, Jan; Tiemeyer, Bärbel; von Hebel, Christian; Huisman, Johan Alexander

    2014-05-01

    Peatlands represent a huge storage of soil organic carbon (SOC), and there is considerable interest to assess the total amount of carbon stored in these ecosystems. However, reliable field-scale information about peat properties, particularly SOC content and bulk density (BD) necessary to estimate C stocks, remains difficult to obtain. A potential way to acquire information on these properties and its spatial variation is the non-invasive mapping of easily recordable physical variables that correlate with peat properties, such as bulk electrical conductivity (ECa) measured with electromagnetic induction (EMI). However, ECa depends on a range of soil properties, including BD, soil and water chemistry, and water content, and thus results often show complex and site-specific relationships. Therefore, a reliable prediction of SOC and BD from ECa data is not necessarily given. In this study, we aim to explore the usefulness of Multiple Linear Regression (MLR) models to predict the peat soil properties SOC and BD from multi-offset EMI and high-resolution DEM data. The quality of the MLR models is assessed by cross-validation. We use data from a medium-scale disturbed peat relict (approximately 35ha) in Northern Germany. The potential explanatory variables considered in MLR were: EMI data of six different integral depths (approximately 0.25, 0.5, 0.6, 0.9, 1, and 1.80 m), their vertical heterogeneity, as well as several topographical variables extracted from the DEM. Ground truth information for SOC, BD content and peat layer thickness was obtained from 34 soil cores of 1 m depth. Each core was divided into several 5 to 20 cm thick layers so that integral information of the upper 0.25, 0.5, and 1 m as well as from the total peat layer was obtained. For cross-validation of results, we clustered the 34 soil cores into 4 classes using K-means clustering and selected 8 cores for validation from the clusters with a probability that depended on the size of the cluster. With the remaining 26 samples, we performed a stepwise MLR and generated separate models for each depth and soil property. Preliminary results indicate reliable model predictions for SOC and BD (R² = 0.83- 0.95). The RMSE values of the validation ranged between 3.5 and 7.2 vol. % for SOC and 0.13 and 0.37 g/cm³ for BD for the independent samples. This equates roughly the quality of SOC predictions obtained by field application of vis-NIR (visible-near infrared) presented in literature for a similar peatland setting. However, the EMI approach offers the potential to derive information from deeper depths and allows non-invasive mapping of BD variability, which is not possible with vis-NIR. Therefore, this new approach potentially provides a more useful tool for total carbon stock assessment in peatlands.

  7. Seasonal effects on the estimation of height of boreal and deciduous forests from interferometric TanDEM-X coherence data

    NASA Astrophysics Data System (ADS)

    Olesk, Aire; Voormansik, Kaupo; Tamm, Tanel; Noorma, Mart; Praks, Jaan

    2015-10-01

    The aim of this study is to assess the performance of single-pass X-band bistatic SAR interferometric forest height estimation of boreal and temperate deciduous forests under variable seasonal conditions. For this, twelve acquisitions of single- and dual-polarized TanDEM-X coherence images over 118 forest stands were analyzed and compared against LiDAR forest height maps. Strong correlations were found between interferometric coherence magnitude and LiDAR derived forest stand height for pine forests (r2=0.94) and spruce forest (r2=0.87) as well as for deciduous trees (r2=0.94) during leaf-off conditions with temperatures below 0°C. It was found that coherence magnitude based forest height estimation is influenced by leaf-on and leaf-off conditions as well as daily temperature fluctuations, height of ambiguity and effective baseline. These factors alter the correlation and should be taken into account for accurate coherence-based height retrieval. Despite the influence of the mentioned factors, generally a strong relationship in regression analysis between X-band SAR coherence and LiDAR derived forest stand height can be found. Moreover, a simple semi empirical model, derived from Random Volume over Ground model, is presented. The model takes into account all imaging geometry dependent parameters and allows to derive tree height estimate without a priori knowledge. Our results show that X-band SAR interferometry can be used to estimate forest canopy height for boreal and deciduous forests in both summer and winter, but the conditions should be stable.

  8. Lineament Mapping for Hydrogeological Characterization of Volcanic Terrains Using Products Derived from DEMs, Radar, Landsat and Aster Imagery

    NASA Astrophysics Data System (ADS)

    Rios-Sanchez, M.; Gierke, J. S.; Muñoz-Martínez, T.

    2010-12-01

    Remote sensing techniques can be used in the characterization of landscapes for assessing groundwater resources. Expressions of the subsurface geological conditions, such as faulting, qualitative proximity of the groundwater table to the surface, and changes in bedrock geology, can be inferred from satellite imagery. Products obtained from satellite imagery can identify areas of higher potential for more detailed water resources exploration activities, such as surface geophysics, hydrochemistry and hydraulic analysis to be focus on these priority areas. Lineament mapping has been the most common application of remotely sensed imagery to delineate places for geophysical studies and well drilling. A remote sensing-based protocol is presented for characterizing fracture networks, discontinuities and boundaries of local and regional aquifer systems, and to evaluate their control on natural hydrological behavior and well yields in volcanic aquifers. The protocol is tested using satellite imagery (RADARSAT-1, Landsat TM and ETM+, Aster) and two DEMs (30- and 90-m spatial resolutions) applied to the Quito Aquifer System (QAS). The aquifer is located in the Central Inter-Andean Valley of Ecuador, a region affected by active volcanism and faulting and characterized by basins filled with series of volcanic deposits and primary and reworked sedimentary rocks. Coincidence analysis was applied after initial processing and interpretation to obtain a lineament map of the study areas. By combining our results with those from previous geological studies and hydrogeological data, a pattern of fracturing that is affecting the hydrogeology of the QAS can be distinguished and an improved understanding of the regional flow systems was gained.

  9. Coastal flood risk analysis using landsat-7 ETM+ imagery and SRTM DEM: a case study of Izmir, Turkey.

    PubMed

    Demirkesen, A C; Evrendilek, F; Berberoglu, S; Kilic, S

    2007-08-01

    The Intergovernmental Panel on Climate Change (IPCC) reports an acceleration of the global mean sea-level rise (MSLR) in the twentieth century in response to global climate change. If this acceleration remains constant, then some coastal areas are most likely to be inundated by the year 2100. The ability to identify the differential vulnerability of coastlines to future inundation hazards as result of global climate change is necessary for timely actions to be taken. Yildiz et al. (Journal of Mapping, 17, 1-75, 2003) reported that the local MSLR in the city of Izmir rose at a rate of 6.8 +/- 0.9 mm year(-1) between 1984 and 2002. In this study, the spatial distribution of the coastal inundation hazards of Izmir region was determined using not only land-use and land-cover (LULC) types derived from the maximum likelihood classification of Landsat-7 Enhanced Thematic Mapper Plus (ETM+) multi-spectral image set but also the classification of the digital elevation model (DEM) acquired by the shuttle radar topography mission (SRTM). Coastal areas with elevations of 2 and 5 m above mean sea-level vulnerable to inundation were found to cover 2.1 and 3.7% of the study region (6,107 km(2)), respectively. Our findings revealed that Menemen plain along Gediz river, and the settlements of Karsiyaka, Alacati, Aliaga, Candarli and Selcuk are at high risk in order of decreasing vulnerability to permanent and episodic inundation by 2100 under the high MSLR scenarios of 20 to 50 mm year(-1). PMID:17171268

  10. DEM Particle Fracture Model

    SciTech Connect

    Zhang, Boning; Herbold, Eric B.; Homel, Michael A.; Regueiro, Richard A.

    2015-12-01

    An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density and packings o the samples are also studied in numerical examples.

  11. Yaquina Bay Topobathy DEM

    EPA Science Inventory

    The U.S.EPA contracted with the U.S.ACE to obtain intertidal and subtidal bathymetric soundings of Yaquina Bay between Poole Slough and the South Beach Marina in 2002. These data were compiled with U.S.ACE subtidal soundings from 1999, 1998, 2000 and National Ocean Service soundi...

  12. Intercomparison of DEM-based approaches for the identification of flood-prone areas in different geomorphologic and climatic conditions

    NASA Astrophysics Data System (ADS)

    Samela, Caterina; Nardi, Fernando; Grimaldi, Salvatore; De Paola, Francesco; Sole, Aurelia; Manfreda, Salvatore

    2014-05-01

    Floods represent the most critical natural hazard for many countries and their frequency appears to be increasing in recent times. The legal constraints of public administrators and the growing interest of private companies (e.g., insurance companies) in identifying the areas exposed to the flood risk, is determining the necessity of developing new tools for the risk classification over large areas. Nowadays, among the numerous hydrologic and hydraulic methods regularly used for practical applications, 2-D hydraulic modeling represents the most accurate approach for deriving detailed inundation maps. Nevertheless, data requirement for these modeling approaches is certainly onerous, limiting their applicability over large areas. On this issue, the terrain morphology may provide an extraordinary amount of information useful to detect areas that are particularly prone to serious flooding. In the present work, we compare the reliability of different DEM-derived quantitative morphologic descriptors in characterizing the relationships between geomorphic attributes and flood exposure. The tests are carried out using techniques of pattern classification, such as linear binary classifiers (Degiorgis et al., 2012), whose ability is evaluated through performance measures. Simple and composed morphologic features are taken into account. The morphological features are: the upslope contributing area (A), the local slope (S), the length of the path that hydrologically connects the location under exam to the nearest element of the drainage network (D), the difference in elevation between the cell under exam and the final point of the same path (H), the curvature (downtriangle2H). In addition to the mentioned features, the study takes into consideration a number of composed indices, such as: the modified topographic index (Manfreda et al., 2011), the downslope index (DI) proposed by Hjerdt et al. (2004), the ratio between the elevation difference H and the distance to the network D, and other indices. Each binary classifier is applied in several catchments in order to verify the reproducibility of the procedures in different geomorphologic, climatic and hydrologic conditions. The study explores the use of these procedures in gauged river basins located in Italy and in an ungauged basin located in Africa. References Degiorgis, M., G. Gnecco, S. Gorni, G. Roth, M. Sanguineti, A.C. Taramasso, 2012. Classifiers for the detection of flood-prone areas using remote sensed elevation data, J. Hydrol., 470-471, 302-315. Hjerdt, K. N., J.J. McDonnell, J. Seibert, A. Rodhe, A new topographic index to quantify downslope controls on local drainage, Water Resour. Res., 40, W05602, 2004. Manfreda, S., M. Di Leo, A. Sole, Detection of Flood Prone Areas using Digital Elevation Models, J. Hydrol. Eng., 16(10), 781-790, 2011.

  13. Photogrammetric Processing of IceBridge DMS Imagery into High-Resolution Digital Surface Models (DEM and Visible Overlay)

    NASA Astrophysics Data System (ADS)

    Arvesen, J. C.; Dotson, R. C.

    2014-12-01

    The DMS (Digital Mapping System) has been a sensor component of all DC-8 and P-3 IceBridge flights since 2009 and has acquired over 3 million JPEG images over Arctic and Antarctic land and sea ice. The DMS imagery is primarily used for identifying and locating open leads for LiDAR sea-ice freeboard measurements and documenting snow and ice surface conditions. The DMS is a COTS Canon SLR camera utilizing a 28mm focal length lens, resulting in a 10cm GSD and swath of ~400 meters from a nominal flight altitude of 500 meters. Exterior orientation is provided by an Applanix IMU/GPS which records a TTL pulse coincident with image acquisition. Notable for virtually all IceBridge flights is that parallel grids are not flown and thus there is no ability to photogrammetrically tie any imagery to adjacent flight lines. Approximately 800,000 Level-3 DMS Surface Model data products have been delivered to NSIDC, each consisting of a Digital Elevation Model (GeoTIFF DEM) and a co-registered Visible Overlay (GeoJPEG). Absolute elevation accuracy for each individual Elevation Model is adjusted to concurrent Airborne Topographic Mapper (ATM) Lidar data, resulting in higher elevation accuracy than can be achieved by photogrammetry alone. The adjustment methodology forces a zero mean difference to the corresponding ATM point cloud integrated over each DMS frame. Statistics are calculated for each DMS Elevation Model frame and show RMS differences are within +/- 10 cm with respect to the ATM point cloud. The DMS Surface Model possesses similar elevation accuracy to the ATM point cloud, but with the following advantages: · Higher and uniform spatial resolution: 40 cm GSD · 45% wider swath: 435 meters vs. 300 meters at 500 meter flight altitude · Visible RGB co-registered overlay at 10 cm GSD · Enhanced visualization through 3-dimensional virtual reality (i.e. video fly-through) Examples will be presented of the utility of these advantages and a novel use of a cell phone camera for aerial photogrammetry will also be presented.

  14. Mapping the topography and cone morphology of the Dalinor volcanic swarm in Inner Mongolia with remote sensing and DEM data

    NASA Astrophysics Data System (ADS)

    Gong, Liwen; Li, Ni; Fan, Qicheng; Zhao, Yongwei; Zhang, Liuyi; Zhang, Chuanjie

    2016-01-01

    The Dalinor volcanic swarm, located south of Xilinhot, Inner Mongolia of China, was a result of multistage eruptions that occurred since the Neogene period. This swarm is mainly composed of volcanic cones and lava tablelands. The objective of this study is to map the topography and morphology of this volcanic swarm. It is based on a variety of data collected from various sources, such as the digital elevation model (DEM), Landsat images, and a 1:50,000 topographic map, in addition to various software platforms, including ArcGIS, Envi4.8, Global Mapper, and Google Earth for data processing and interpretation. The results show that the overall topography of the volcanic swarm is a platform with a central swell having great undulation, sizable gradient variations, a rough surface, and small terrain relief. According to the undulating characteristics of the line profile, the volcanic swarm can be divided into four stairs with heights of 1,280 m, 1,360 m, 1,440 m, and 1,500 m. The analysis of the swath profile characterizes the two clusters of volcanoes with different height ranges and evolution. The lava tablelands and volcanic cones are distributed in nearly EW-trending belts, where tableland coverage was delineated with superposed layers of gradients and degrees of relief. According to the morphology, the volcanic cones were classified into four types: conical, composite, dome, and shield. The formation causes and classification basis for each type of volcanic cone were analyzed and their parameters were extracted. The H/D ratios of all types of volcanic cones were then statistically determined and projected to create a map of volcanic density distribution. Based on the relationship between distribution and time sequence of the formation of different volcanic cones, it can be inferred that the volcanic eruptions migrated from the margins to the center of the lava plateau. The central area was formed through superposition of multi-stage eruptive materials. In addition, a large number of early shield volcanoes were distributed on the margins. The morphological analysis of volcanic cones reveals the evolutionary stages of different types of cones. From the interpreted geomorphological indicators of faults, such as surface scarps, the pattern of volcanic cones, and the arrangement of crater major axes, it can be inferred that NE-trending and nearly EW-trending faults are present in this area, which are closely related to the formation and distribution of the volcanoes.

  15. Activity of Nyiragongo and Nyamulagira Volcanoes (Dem. Rep. of Congo) Revealed Using Geological, Geophysical and InSAR data

    NASA Astrophysics Data System (ADS)

    Wauthier, C.; Cayol, V.; Hooper, A.; Kervyn, F.; Marinkovic, P.; D'Oreye, N.; Poland, M. P.

    2010-12-01

    Ground-based monitoring of active volcanoes in Africa can be problematic due to political instabilities, safety issues and poor accessibility. Remote-sensing techniques such as Differential Interferometric Synthetic Aperture Radar (DInSAR, more commonly InSAR), are therefore very useful and provide robust observational tools for natural hazard assessment, regardless of local conditions. Nyiragongo and Nyamulagira volcanoes (which experienced nine eruptions from December 1996 to January 2010) are located in the western branch of the East African Rift (Virunga Volcanic Province, North Kivu, Dem. Rep. of Congo). InSAR has recorded ground displacements related to most of the tectonic and volcanic events that have occurred since 1996 using SAR images from the JERS, ERS-1/2, ENVISAT, RADARSAT-1, RADARSAT-2 and ALOS satellites. This database provides excellent spatial and temporal resolution of deformation, leading to insights into tectonic and volcanic processes. Loss of coherence within the SAR signal due to rapid-changing equatorial vegetation hampers the use of InSAR as a volcano-tectonic monitoring tool. We partially overcome this limitation using 1) a large number of SAR images, including about 150 ENVISAT and more than 100 RADARSAT-1 images, 2) short repeat times of 24 and 35 days for RADARSAT-1 and ENVISAT, respectively, and 3) satellites with longer wavelengths, such as JERS and ALOS. Using a large dataset combining short revisit time SAR images significantly increases the chances of producing interferograms with good coherence. A longer wavelength radar signal better penetrates vegetation cover, also increasing coherence. Furthermore, useful data were retrieved in low-coherence areas by applying the “StaMPS” (Stanford Method for Persistent Scatterers) method, which combines a small baseline and persistent scatterers approach, to our largest SAR datasets. Using several look angles from both ascending and descending orbital tracks, we were able to characterize the 3D ground displacement field. A 3D Mixed Boundary Element Method is used to infer geometry and physical characteristics of the sources controlling volcanic unrest and tectonic activity. In addition, we combined our InSAR database with other available data, such as seismicity from a network maintained since 2002 and results from geological and geophysical surveys from the volcanoes, to better constrain source processes. The improved understanding and constraints on volcanic processes in the North Kivu area made possible by this multidisciplinary approach will be highlighted with a few case studies of recent volcanic activity.

  16. Determination of the hydrological properties of a small-scale catchment area in Northern Greece from ASTER and SRTM DEMs and accuracy assessment with a local DTM

    NASA Astrophysics Data System (ADS)

    Tzanou, E. A.; Vergos, G. S.

    2012-04-01

    The combined use of Geographic Information Systems and recent high-resolution Digital Elevation Models (DEMs) from Remote Sensing imagery offers a unique opportunity to study the hydrological properties of basin and catchment dynamics and derive the hydrological features of specific regions of various spatial scales. Until recently, the availability of global DEMs was restricted to low-resolution and accuracy models, e.g., ETOPO5, ETOPO2 and GTOPO30, compared to local Digital Terrain Models (DTMs) derived from photogrammetric methods and offered usually in the form of topographic maps of various scales. The advent of the SRTM and ASTER missions, offer some new tools and opportunities in order to use their data within a GIS to study the hydrological properties of basins and consequently validate their performance both amongst each other, as well as in terms of the results derived from a local DTM. The present work focuses on the use of the recent SRTM v2 90 m and ASTER v2 30 m DEMs along with the national 500 m DTM generated by the Hellenic Military Geographic Service (HMGS), within a GIS in order to assess their performance in determining the hydrological properties of basins. To this respect, the ArcHydro extension tool of ArcGIS v9.3 and HEC-GeoRAS v4.3 have been exploited to determine the hydrographic data of the basins under study which are located in Northern Greece. The hydrological characteristics refer to stream geometry, curve number, flooding areas, etc. as well as the topographic characteristics of the basin itself, such as aspect, hillshade, slope e.t.c..

  17. Tracking and evolution of irrigation triggered active landslides by multi-source high resolution DEM: The Jiaojiacun landslide group of Heifangtai (Northwest of China)

    NASA Astrophysics Data System (ADS)

    Zeng, Runqiang; Meng, Xingmin; Wang, Siyuan; Chen, Guan; Lee, Yajun; Zhang, Yi

    2014-05-01

    The construction of three large hydropower stations, i.e. Liujia, Yanguo and Bapan, resulted in the immigration of the impacted people to Heifangtai from 1960s. To support the living and farming of the immigrated people, a large amount of water has been pumped from the Yellow River to Heifangtai, which has changed the former underground water budget and led to 111 landslides from 1968 in this area. To reveal the deformation process of landslides in Heifangtai, a quantitative deformation analysis model of landslide based on multi-source DEM data is established using four periods of topographic maps obtained in 1970, 2001, 2010 and 2013 respectively, including two 1:10000 topographic maps and two 1:1000 data acquired from 3D Laser Scanner. The whole study area was divided into two sections based on the two distinct kinds of landslide patterns. The selected morphometric parameters, residual topographic surface and surface roughness, extracted from three typical landslides, and the statistical analysis (Box-plot diagrams) of the temporal variations of these parameters, allowed the reconstruction and tracking of these landslides. We monitored the changing of landslide boundaries, average vertical and horizontal displacement rates and zones of uplift and subsidence. The volumes of removed and/or accumulated material were estimated as well. We can then demonstrate the kinematics of landslides based on information from high-resolution DEM, and the changing table of underground water, ring-shear test and soil-water characteristic curve referenced from other researchers. The results provide a new insight on the use of multi-source high resolution DEM in the monitoring of irrigation-triggered landslides.

  18. Mass changes of glaciers over the Central Karakoram derived from TanDEM-X and SRTM/X-SAR Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Rankl, Melanie; Braun, Matthias

    2015-04-01

    Snow cover and glaciers in the Karakoram region are important freshwater resources for many downriver communities as they provide water for irrigation and hydro power. A better understanding of current glacier changes is hence an important baseline information. Glaciers in the Karakoram have shown stable and positive glacier mass balances during recent years as well as stable and advancing termini positions. The Karakoram is also known for a large number of surge-type glaciers. Here, we present geodetic glacier elevation and mass changes using TanDEM-X and SRTM/X-SAR Digital Elevation Models between 2000 and 2012. Based on previous glacier inventories for the Karakoram, we show elevation changes and glacier mass balances for glaciers with advancing and stable termini between 2000 and 2012 as well as surge-type glaciers separately. In order to convert volume changes to mass changes, we applied different density scenarios (i.e., constant densities for ice and snow or zonally variable densities). Our findings show average glacier thickening of +0.01 ± 0.02 m a-1 or mass gain of +0.0099 ± 2.8x10-5 Gt a-1(using a density of 850 kg m-3) between 2000 and 2012 for parts of the Central Karakoram. Surge-type glaciers and advancing glaciers indicated slight surface lowering, while the majority of the studied glaciers showed stable termini and surface thickening. Our measurements are independent from varying penetration depths of the radar signal or temporal decorrelation between image acquisitions. Both datasets were acquired in the X-band frequency under assumed similar surface conditions. The bistatic TanDEM-X mission is highly suitable for interferometric processing due to high spatial resolutions and only 3 sec time lag between TanDEM-X and TerraSAR-X overpasses. We want to stress the enormous potential of the TanDEM-X mission to estimate geodetic glacier mass balances, in particular when compared to elevation data sets acquired in a similar frequency and comparable observation period.

  19. Neural correlates of the DemTect in Alzheimer's disease and frontotemporal lobar degeneration – A combined MRI & FDG-PET study☆

    PubMed Central

    Woost, Timo B.; Dukart, Juergen; Frisch, Stefan; Barthel, Henryk; Sabri, Osama; Mueller, Karsten; Schroeter, Matthias L.

    2013-01-01

    Valid screening devices are critical for an early diagnosis of dementia. The DemTect is such an internationally accepted tool. We aimed to characterize the neural networks associated with performance on the DemTect's subtests in two frequent dementia syndromes: early Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). Voxel-based group comparisons of cerebral glucose utilization (as measured by F-18-fluorodeoxyglucose positron emission tomography) and gray matter atrophy (as measured by structural magnetic resonance imaging) were performed on data from 48 subjects with AD (n = 21), FTLD (n = 14) or subjective cognitive impairment (n = 13) as a control group. We performed group comparisons and correlation analyses between multimodal imaging data and performance on the DemTect's subtests. Group comparisons showed regional patterns consistent with previous findings for AD and FTLD. Interestingly, atrophy dominated in FTLD, whereas hypometabolism in AD. Across diagnostic groups performance on the “wordlist” subtest was positively correlated with glucose metabolism in the left temporal lobe. The “number transcoding” subtest was significantly associated with glucose metabolism in both a predominantly left lateralized frontotemporal network and a parietooccipital network including parts of the basal ganglia. Moreover, this subtest was associated with gray matter density in an extensive network including frontal, temporal, parietal and occipital areas. No significant correlates were observed for the “supermarket task” subtest. Scores on the “digit span reverse” subtest correlated with glucose metabolism in the left frontal cortex, the bilateral putamen, the head of caudate nucleus and the anterior insula. Disease-specific correlation analyses could partly verify or extend the correlates shown in the analyses across diagnostic groups. Correlates of gray matter density were found in FTLD for the “number transcoding” subtest and the “digit span reverse” subtest. Correlates of glucose metabolism were found in AD for the “wordlist” subtest and in FTLD for the “digit span reverse” subtest. Our study contributes to the understanding of the neural correlates of cognitive deficits in AD and FTLD and supports an external validation of the DemTect providing preliminary conclusions about disease-specific correlates. PMID:24179826

  20. Performance Evaluation of Four DEM-Based Fluvial Terrace Mapping Methods Across Variable Geomorphic Settings: Application to the Sheepscot River Watershed, Maine

    NASA Astrophysics Data System (ADS)

    Hopkins, A. J.; Snyder, N. P.

    2014-12-01

    Fluvial terraces are utilized in geomorphic studies as recorders of land-use, climate, and tectonic history. Advances in digital topographic data, such as high-resolution digital elevation models (DEMs) derived from airborne lidar surveys, has promoted the development of several methods used to extract terraces from DEMs based on their characteristic morphology. The post-glacial landscape of the Sheepscot River watershed, Maine, where strath and fill terraces are present and record Pleistocene deglaciation, Holocene eustatic forcing, and Anthropocene land-use change, was selected to implement a comparison between terrace mapping methodologies. At four study sites within the watershed, terraces were manually mapped to facilitate the comparison between fully and semi-automated DEM-based mapping procedures, including: (1) edge detection functions in Matlab, (2) feature classification algorithms developed by Wood (1996), (3) spatial relationships between interpreted terraces and surrounding topography (Walter et al., 2007), and (4) the TerEx terrace mapping toolbox developed by Stout and Belmont (2014). Each method was evaluated based on its accuracy and ease of implementation. The four study sites have varying longitudinal slope (0.1% - 5%), channel width (<5 m - 30 m), relief in surrounding landscape (15 m - 75 m), type and density of surrounding land use, and mapped surficial geologic units. In general, all methods overestimate terrace areas (average predicted area 136% of the manually defined area). Surrounding topographic relief appears to exert the greatest control on mapping accuracy, with the most accurate results (92% of terrace area mapped by Walter et al., 2007 method) achieved where the river valley was most confined by adjacent hillslopes. Accuracy decreased for study sites surrounded by a low-relief landscape, with the most accurate results achieved by the TerEx toolbox (Stout and Belmont, 2014; predicted areas were 45% and 89% of manual delineations). Our work informs future studies by highlighting the strengths and drawbacks of each method tested and by making recommendations for the types of geomorphic settings where each is most appropriate. The tested algorithms represent powerful new ways to analyze landscape history over large regions using high-resolution, lidar DEMs.

  1. Seasonal variabilty of surface velocities and ice discharge of Columbia Glacier, Alaska using high-resolution TanDEM-X satellite time series and NASA IceBridge data

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2014-05-01

    Columbia Glacier is a grounded tidewater glacier located on the south coast of Alaska. It has lost half of its volume during 1957-2007, more rapidly after 1980. It is now split into two branches, known as Main/East and West branch due to the dramatic retreat of ~ 23 km and calving of iceberg from its terminus in past few decades. In Alaska, a majority of the mass loss from glaciers is due to rapid ice flow and calving icebergs into tidewater and lacustrine environments. In addition, submarine melting and change in the frontal position can accelerate the ice flow and calving rate. We use time series of high-resolution TanDEM-X stripmap satellite imagery during 2011-2013. The active image of the bistatic TanDEM-X acquisitions, acquired over 11 or 22 day repeat intervals, are utilized to derive surface velocity fields using SAR intensity offset tracking. Due to the short temporal baselines, the precise orbit control and the high-resolution of the data, the accuracies of the velocity products are high. We observe a pronounce seasonal signal in flow velocities close to the glacier front of East/Main branch of Columbia Glacier. Maximum values at the glacier front reach up to 14 m/day were recorded in May 2012 and 12 m/day in June 2013. Minimum velocities at the glacier front are generally observed in September and October with lowest values below 2 m/day in October 2012. Months in between those dates show corresponding increase or deceleration resulting a kind of sinusoidal annual course of the surface velocity at the glacier front. The seasonal signal is consistently decreasing with the distance from the glacier front. At a distance of 17.5 km from the ice front, velocities are reduced to 2 m/day and almost no seasonal variability can be observed. We attribute these temporal and spatial variability to changes in the basal hydrology and lubrification of the glacier bed. Closure of the basal drainage system in early winter leads to maximum speeds while during a fully developed basal drainage system speeds are at their minimum. We also analyze the variation in conjunction with the prevailing meteorological conditions as well as changes in calving front position in order to exclude other potential influencing factors. In a second step, we also exploit TanDEM-X data to generate various digital elevation models (DEMs) at different time steps. The multi-temporal DEMs are used to estimate the difference in surface elevation and respective ice thickness changes. All TanDEM-X DEMs are well tied with a SPOT reference DEM. Errors are estimated over ice free moraines and rocky areas. The quality of the TanDEM-X DEMs on snow and ice covered areas are further assessed by a comparison to laser scanning data from NASA Icebridge campaigns. The time wise closest TanDEM-X DEMs were compared to the Icebridge tracks from winter and summer surveys in order to judge errors resulting from the radar penetration of the x/band radar signal into snow, ice and firn. The average differences between laser scanning and TanDEM-X in August, 2011 and March, 2012 are observed to be 8.48 m and 14.35 m respectively. Retreat rates of the glacier front are derived manually by digitizing the terminus position. By combining the data sets of ice velocity, ice thickness and the retreat rates at different time steps, we estimate the seasonal variability of the ice discharge of Columbia Glacier.

  2. Application of the inundation area—lake level rating curves constructed from the SRTM DEM to retrieving lake levels from satellite measured inundation areas

    NASA Astrophysics Data System (ADS)

    Pan, Feifei; Liao, Jingjuan; Li, Xinwu; Guo, Huadong

    2013-03-01

    Remote sensing technology has great potential for measuring lake inundation areas and lake levels, and providing important lake water quantity and quality information which can be used for improving our understanding of climate change impacts on the global water cycle, and assessing the influence of the projected future climate change on the global water resources. One remote sensing approach is to estimate lake level from satellite measured inundation area based on the inundation area—lake level rating (IALLR) curves. However, this approach is not easy to implement because of a lack of data for constructing the IALLR curves. In this study, an innovative and robust approach to construct the IALLR curves from the digital elevation model (DEM) data collected during the Shuttle Radar Topography Mission (SRTM) was developed and tested. It was shown that the IALLR curves derived from the SRTM DEM data could be used to retrieve lake level from satellite measured inundation area. Applying the constructed IALLR curve to the estimated inundation areas from 16 Landsat Thematic Mapper (TM) images, 16 lake levels of Lake Champlain in Vermont were obtained. The root mean square error (RMSE) of the estimated lake levels compared to the observed water levels at the U.S. Geological Survey (USGS) gauging station (04294500) at Burlington, Vermont is about 0.12 m.

  3. Semi-automatic recognition and mapping of event-induced landslides by exploiting multispectral satellite images and DEM in a Bayesian framework

    NASA Astrophysics Data System (ADS)

    Mondini, Alessandro C.; Chang, Kang-tsung; Rossi, Mauro; Marchesini, Ivan; Guzzetti, Fausto

    2012-10-01

    Landslides occur every year in many areas of the world, causing casualties, economic and environmental losses. Landslide inventory maps are important to document the extent of the landslide phenomena in a region, for risk estimation and management, and to study landscape evolution. We present a method to facilitate the semi-automatic recognition and mapping of event induced shallow landslides. The method is based on the combination in a Bayesian framework of information extracted from High Resolution optical multispectral satellite images and Digital Elevation Models (DEM). The landslide membership probability is estimated from post-event satellite images using a supervised image classification method. The likelihood of landslide occurrence is obtained adopting a "data-driven" approach, intersecting existing landslide inventories with maps of morphometric parameters (slope and curvature) calculated from the DEM. We tested the method in the Huaguoshan basin, Taiwan, where it proved capable of detecting and mapping landslides triggered by Typhoon Morakot in August 2009. Compared to other pixel-based approaches, the method reduces significantly the typical "salt-and-pepper" effect of landslide classifications, and allows the internal classification of landslide areas in landslide source areas and landslide travel and depositional ("run out") areas.

  4. Co-seismic vertical displacements from a single post-seismic lidar DEM: example from the 2010 El Mayor-Cucapah earthquake

    NASA Astrophysics Data System (ADS)

    Barišin, Ivana; Hinojosa-Corona, Alejandro; Parsons, Barry

    2015-07-01

    A method is outlined by means of which it is possible to estimate high-resolution vertical displacements due to an earthquake even in the case where high-resolution topography is lacking before the earthquake. This result can be achieved by combining a highly accurate, post-event digital elevation model (DEM), for example lidar, with archived satellite imagery. The method is illustrated by calculating vertical displacements for the 2010 El Mayor-Cucapah earthquake. For this earthquake, there are both pre- and post-event lidar DEMs from which vertical displacements may also be estimated after correcting for the lateral advection of topography due to horizontal displacements. A comparison between the two means of deriving vertical displacements shows generally good agreement, with the displacements obtained using satellite imagery performing better in high relief areas. As a result of this property, we are able to trace the vertical offsets due to the El Mayor-Cucapah earthquake as the rupture jumped from the Pescadores fault to the Borrego fault in propagating through the high relief of the Sierra Cucapah.

  5. Application of Positron Emission Particle Tracking (PEPT) to validate a Discrete Element Method (DEM) model of granular flow and mixing in the Turbula mixer.

    PubMed

    Marigo, M; Davies, M; Leadbeater, T; Cairns, D L; Ingram, A; Stitt, E H

    2013-03-25

    The laboratory-scale Turbula mixer comprises a simple cylindrical vessel that moves with a complex, yet periodic 3D motion comprising of rotation, translation and inversion. Arising from this complexity, relatively few studies to obtain fundamental understanding of particle motion and mixing mechanisms have been reported. Particle motion within a cylindrical vessel of a Turbula mixer has been measured for 2mm glass spheres using Positron Emission Particle Tracking (PEPT) in a 2l blending mixing vessel at 50% fill level. These data are compared to results from Discrete Element Method (DEM) simulations previously published by the authors. PEPT mixing experiments, using a single particle tracer, gave qualitatively similar trends to the DEM predictions for axial and radial dispersion as well as for the axial displacement statistics at different operational speeds. Both experimental and simulation results indicate a minimum mixing efficiency at ca. 46 rpm. The occupancy plots also show a non-linear relationship with the operating speed. These results add further evidence to a transition between two flow and mixing regimes. Despite the similarity in overall flow and mixing behaviour measured and predicted, including the mixing speed at which the flow behaviour transition occurs, a systematic offset between measured and predicted result is observed. PMID:23376506

  6. Surface lowering and flow speed decrease of Khumbu Glacier detected from GPS survey and ASTER-DEM, in Nepal Himalayas between 1995 and 2004.

    NASA Astrophysics Data System (ADS)

    Nuimura, T.; Fukui, K.; Asahi, K.; Fujita, K.; Ageta, Y.

    2006-12-01

    Four characteristic areas in the debris-covered ablation zone have been surveyed intermittently on Khumbu Glacier, Nepal Himalayas since 1978. We carried out ground survey by differential GPS (DGPS) in 2004 to clarify changes in surface elevation and flow speeds of the glacier. Surface lowerings are obtained by comparison of digital elevation model (DEM, 60 m grid size), which are generated from the survey data in 1978, 1995, 1999 and 2004. Since it was too dangerous to access to the other two areas, middle parts of the ablation zone, due to surface roughness we use ASTER DEM, which was verified by the ground survey. Flow speeds are also obtained in comparison with position of ice pinnacles at the upper area. We clarify the lowerings of the glacier surface. The surface lowering was not significant at the lowest area (4900 m.a.s.l). Remarkable acceleration of surface lowering was found at the middle area (about 5100 m.a.s.l.), where, glacier surface is undulating in comparison to other areas. The topographic feature might affect to the surface lowering. In the most upper area (about 5300 m.a.s.l.), surface lowering is continued. Surface flow speeds between 1995 and 2004, decreased in comparison with that between 1956 and 1995. Our results suggest that the recent decrease of ice flux from the accumulation zone might enhance the surface lowering of glacier.

  7. A GIS modeled DEM-based hydrologic watershed network of the Greenland Ice Sheet and non-ice land surface areas

    NASA Astrophysics Data System (ADS)

    Pitcher, L. H.; Smith, L. C.; Chu, V. W.; Wang, J.

    2011-12-01

    Increased mass loss of the Greenland Ice Sheet and subsequent global sea level rise has amplified the need to understand Greenland's hydrology and melt patterns. Drainage basins for Greenland's land surface and ice sheet were produced using the GLAS/IceSat 1km surface DEM and a hydrostatic surface pressure grid over the ice sheet. The pressure grid was modeled using the surface DEM and a 5km bedrock elevation grid (Bamber et al., 2001), assuming hydrostatic pressure and no conduit flow within the ice sheet as per Lewis & Smith (2009). Pour points were generated using an 8-pixel pour point derivation algorithm (Jenson & Domingue, 1988) and were used to model watersheds and flow networks. This work provides a complete watershed, flow and drainage network dataset for the entirety of Greenland - both land and ice surface regions. Potential applications include ice sheet melt water routing to the ocean, supraglacial melt water patterns, and the separation of specific ice melt drainage networks from snow melt networks. These basins act as a base for the incorporation of finer resolution IceBridge and GLAS/IceSat data products.

  8. Delineation of subglacial bedrock structure in glaciated regions using DEMs derived from stereoscopic satellite imagery: An example of the Land Glacier catchment, West Antarctica

    NASA Astrophysics Data System (ADS)

    Robertson, A. M.; Contreras, A.; Siddoway, C. S.; Gottfried, M.; Porter, C.

    2012-12-01

    The Land Glacier of coastal Marie Byrd Land is proximal to the inferred tectonic boundary between the Ross and Amundsen provinces of the Marie Byrd Land terrane in West Antarctica. Its asymmetrical upper catchment draws ice from the volcanic peaks of the western Flood Range, a linear mountain change that is thought to be fault-controlled. A north-flowing ice stream with velocities >1200m/yr, Land Glacier occupies a narrow outlet flanked by sparse rock exposures along the remote Hobbs Coast. The narrow configuration and high flow velocity of the ice stream, together with the contrast in rock types on either side, suggest that the locus of Land Glacier is controlled by bedrock structures, however no faults have been mapped in this remote region on the basis of traditional ground-based methods nor airborne geophysics. We employ a new approach to mapping of subglacial bedrock faults and geological contacts in this region that entails quantitative analysis of high resolution DEMs computed from high resolution WorldView stereographic imagery. DEMs are computed using ERDAS Imagine's LPS eATE algorithm, followed by MATLAB-based routines to interpolate and remove artifacts in the terrain model. The resolution of the ice sheet DEM is 3 to 5 m, providing sufficient resolution for identification of geometrically regular features in the ice surface topography that may be attributable to bedrock faults and lithological contacts. The first phase of our ongoing work focuses upon lineaments that form a systematic array with regular geometry and spacing, that may be fault-controlled. A procedure involving use of hillshade applied from multiple sun angles, slope aspect, and slope gradient analysis of the high resolution DEMs was carried out in ArcGIS for characterization of the surface lineaments. We used the following criteria to distinguish bedrock-controlled lineaments from ice flow lineations: 1) laterally continuous for a minimum distance of 3 km, 2) vertical relief of ≥ 50m across a lineament, and 3) a minimum gradient of 5°. Raster layers of computed slope and aspect were cross-referenced to DEMs to confirm the location and geometry of lineaments that were identified. For the Land Glacier region, we discern two dominant sets of km-scale lineaments oriented ~E-W (~270-285°) and NW-SE (315-330°). The E-W trending lineaments are the most abundant and laterally continuous, with lengths up to 20 km and relief as high as 150 m. This trend is parallel to that of the Flood Range volcanoes that are ≤ 6 Ma in age. The NW-SE trending lineations range up to 14 km in length and attain 180 m of relief; they are coparallel to the alignment in the Ames Range (volcano ages 6 to 15 Ma). Potentially the regionally extensive Land Glacier lineament array is controlled by bedrock structures formed or reactivated during two Neogene stress states (e.g. Paulson & Wilson (2010, JGSL v167). Structural inheritance is a likelihood due to protracted tectonism and lithospheric thinning in West Antarctica since Cretaceous time.

  9. Testing the influence of vertical, pre-existing joints on normal faulting using analogue and 3D discrete element models (DEM)

    NASA Astrophysics Data System (ADS)

    Kettermann, Michael; von Hagke, Christoph; Virgo, Simon; Urai, Janos L.

    2015-04-01

    Brittle rocks are often affected by different generations of fractures that influence each other. We study pre-existing vertical joints followed by a faulting event. Understanding the effect of these interactions on fracture/fault geometries as well as the development of dilatancy and the formation of cavities as potential fluid pathways is crucial for reservoir quality prediction and production. Our approach combines scaled analogue and numerical modeling. Using cohesive hemihydrate powder allows us to create open fractures prior to faulting. The physical models are reproduced using the ESyS-Particle discrete element Modeling Software (DEM), and different parameters are investigated. Analogue models were carried out in a manually driven deformation box (30x28x20 cm) with a 60° dipping pre-defined basement fault and 4.5 cm of displacement. To produce open joints prior to faulting, sheets of paper were mounted in the box to a depth of 5 cm at a spacing of 2.5 cm. Powder was then sieved into the box, embedding the paper almost entirely (column height of 19 cm), and the paper was removed. We tested the influence of different angles between the strike of the basement fault and the joint set (0°, 4°, 8°, 12°, 16°, 20°, and 25°). During deformation we captured structural information by time-lapse photography that allows particle imaging velocimetry analyses (PIV) to detect localized deformation at every increment of displacement. Post-mortem photogrammetry preserves the final 3-dimensional structure of the fault zone. We observe that no faults or fractures occur parallel to basement-fault strike. Secondary fractures are mostly oriented normal to primary joints. At the final stage of the experiments we analyzed semi-quantitatively the number of connected joints, number of secondary fractures, degree of segmentation (i.e. number of joints accommodating strain), damage zone width, and the map-view area fraction of open gaps. Whereas the area fraction does not change distinctly, the number of secondary fractures and connected joints increases strongly with increasing angles between basement fault and joint strike. Integrating these models with a 3-dimensional DEM code using the ESyS-Particle software allows for retrieving 4D information from the models, as well as for testing other parameters such as joint spacing or joint depth. Our DEM models are capable of robustly reproducing all characteristic features observed in the analogue models, and will provide a quantitative measure of the influence of joint-fault angle on permeability of cohesive rocks that have experienced more than one brittle deformation phase.

  10. A new set of MATLAB functions (TecDEM toolbox) to analyze erosional stages in landscapes and base-level changes in river profiles

    NASA Astrophysics Data System (ADS)

    Andreani, Louis; Gloaguen, Richard; Shahzad, Faisal

    2014-05-01

    We implemented three new functions in the MATLAB-based TecDEM toolbox [1,2]: surface index, topographic position index, and the analysis of base-levels in river longitudinal profiles. These tools provide useful ways to understand the effects of base-level changes on topography such as stream captures, erosion or rejuvenation of pre-existing topographic features and anomalies in river longitudinal profiles. We developed a new index (referred as "surface index") which provides a quick way to map simultaneously preserved and eroded portions of an elevated landscape. This index classifies landscapes according to their erosional stages using the combination of the hypsometric integral, which efficiently highlights flat surfaces, and the surface roughness, which substantially increases with incision. We also implemented the commonly used "topographic position index". This index provides a simple way to classify the landscapes as valleys, ridges and flat areas. However, its application in tectonic geomorphology can go far beyond as it discriminates valleys shapes and reveals other important features such as wind gaps and knickpoints when associated to the extracted river system. Finally, we implemented a tool allowing the estimation of base-level changes using the reconstruction of river longitudinal profiles. River profiles can be decomposed in concave or convex segments. Relict base-levels are typically associated to gently concave segments in river profiles. By restoring the initial shape of these segments we are able to estimate the amount of incision between the present day base-level and the relict base-level. All these tools were successfully tested in different settings such as Central America, Central Europe and Pamir. In addition to the description of these tools we provide examples from these different areas. [1] Shahzad, F., & Gloaguen, R. (2011). TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 1: Drainage network preprocessing and stream profile analysis. Computers & Geosciences, 37, 250-260. [2] Shahzad, F., & Gloaguen, R. (2011). TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 2: Surface dynamics and basin analysis. Computers & Geosciences, 37, 261-271.

  11. Late-stage volcano geomorphic evolution of the Pleistocene San Francisco Mountain, Arizona (USA), based on high-resolution DEM analysis and 40Ar/39Ar chronology

    NASA Astrophysics Data System (ADS)

    Karátson, Dávid; Telbisz, Tamás; Singer, Brad S.

    2010-09-01

    The cone-building volcanic activity and subsequent erosion of San Francisco Mountain, AZ, USA, were studied by using high-resolution digital elevation model (DEM) analysis and new 40Ar/39Ar dating. By defining remnants or planèzes of the volcano flanks in DEM-derived images, the original edifice can be reconstructed. We propose a two-cone model with adjacent summit vents which were active in different times. The reconstructed cones were 4,460 and 4,350 m high a.s.l., corresponding to ˜2,160 and 2,050 m relative height, respectively. New 40Ar/39Ar data allow us to decipher the chronological details of the cone-building activity. We dated the Older and Younger Andesites of the volcano that, according to previous mapping, built the stage 2 and stage 3 stratocones, respectively. The new 40Ar/39Ar plateau ages yielded 589-556 ka for the Older and 514-505 ka for the Younger Andesites, supporting their distinct nature with a possible dormant period between. The obtained ages imply an intense final (≤100 ka long) cone-building activity, terminating ˜100 ka earlier than indicated by previous K-Ar ages. Moreover, 40Ar/39Ar dating constrains the formation of the Inner Basin, an elliptical depression in the center of the volcano initially created by flank collapse. A 530 ka age (with a ±58.4 ka 2σ error) for a post-depression dacite suggests that the collapse event is geochronologically indistinguishable from the termination of the andesitic cone-building activity. According to our DEM analysis, the original cone of San Francisco Mountain had a volume of about 80 km3. Of this volume, ˜7.5 km3 was removed by the flank collapse and subsequent glacial erosion, creating the present-day enlarged Inner Basin, and ˜2 km3 was removed from the outer valleys by erosion. Based on volumetric analysis and previous and new radiometric ages, the average long-term eruption rate of San Francisco Mountain was ˜0.2 km3/ka, which is a medium rate for long-lived stratovolcanoes. However, according to the new 40Ar/39Ar dates for the last ≤100 ka period, the final stratovolcanic activity was characterized by a greater ˜0.3 km3/ka rate.

  12. Grundwassermonitoring im Zusammenhang mit der hydraulischen Stimulation einer Erdölbohrung

    NASA Astrophysics Data System (ADS)

    Bönsch, Carola; Basan, Swantje

    2016-02-01

    The petroleum well Barth-11 in Mecklenburg-Western Pommerania (2700 m deep) is the first well in eastern Germany to use horizontal directional drilling. Hydraulic stimulation was performed in June 2014, connecting the oil reservoir and borehole. Five Pleistocene aquifers lie within the investigation area, with aquifer depths ranging between 5 and 90 m below surface. Three observation wells were installed for groundwater monitoring. Two weeks before hydraulic stimulation, reference measurements were conducted and a data logger was installed for measurements of water level, temperature and electrical conductivity. To detect any possible influence of hydraulic stimulation on groundwater quality, groundwater samples were analysed for several organic and inorganic parameters. The investigation area is located in a natural saline water discharge zone. Hence, it was necessary to develop methods to distinguish hydraulic stimulation water from Triassic and Permian formation saline water in order to uniquely identify any trace of the injected fluid in the natural groundwater. These methods and the monitoring system design are presented and discussed.

  13. Full-waveform and discrete-return lidar in salt marsh environments: An assessment of biophysical parameters, vertical uncertatinty, and nonparametric dem correction

    NASA Astrophysics Data System (ADS)

    Rogers, Jeffrey N.

    High-resolution and high-accuracy elevation data sets of coastal salt marsh environments are necessary to support restoration and other management initiatives, such as adaptation to sea level rise. Lidar (light detection and ranging) data may serve this need by enabling efficient acquisition of detailed elevation data from an airborne platform. However, previous research has revealed that lidar data tend to have lower vertical accuracy (i.e., greater uncertainty) in salt marshes than in other environments. The increase in vertical uncertainty in lidar data of salt marshes can be attributed primarily to low, dense-growing salt marsh vegetation. Unfortunately, this increased vertical uncertainty often renders lidar-derived digital elevation models (DEM) ineffective for analysis of topographic features controlling tidal inundation frequency and ecology. This study aims to address these challenges by providing a detailed assessment of the factors influencing lidar-derived elevation uncertainty in marshes. The information gained from this assessment is then used to: 1) test the ability to predict marsh vegetation biophysical parameters from lidar-derived metrics, and 2) develop a method for improving salt marsh DEM accuracy. Discrete-return and full-waveform lidar, along with RTK GNSS (Real-time Kinematic Global Navigation Satellite System) reference data, were acquired for four salt marsh systems characterized by four major taxa (Spartina alterniflora, Spartina patens, Distichlis spicata, and Salicornia spp.) on Cape Cod, Massachusetts. These data were used to: 1) develop an innovative combination of full-waveform lidar and field methods to assess the vertical distribution of aboveground biomass as well as its light blocking properties; 2) investigate lidar elevation bias and standard deviation using varying interpolation and filtering methods; 3) evaluate the effects of seasonality (temporal differences between peak growth and senescent conditions) using lidar data flown in summer and spring; 4) create new products, called Relative Uncertainty Surfaces (RUS), from lidar waveform-derived metrics and determine their utility; and 5) develop and test five nonparametric regression model algorithms (MARS -- Multivariate Adaptive Regression, CART -- Classification and Regression Trees, TreeNet, Random Forests, and GPSM -- Generalized Path Seeker) with 13 predictor variables derived from both discrete and full waveform lidar sources in order to develop a method of improving lidar DEM quality. Results of this study indicate strong correlations for Spartina alterniflora (r > 0.9) between vertical biomass (VB), the distribution of vegetation biomass by height, and vertical obscuration (VO), the measure of the vertical distribution of the ratio of vegetation to airspace. It was determined that simple, feature-based lidar waveform metrics, such as waveform width, can provide new information to estimate salt marsh vegetation biophysical parameters such as vegetation height. The results also clearly illustrate the importance of seasonality, species, and lidar interpolation and filtering methods on elevation uncertainty in salt marshes. Relative uncertainty surfaces generated from lidar waveform features were determined useful in qualitative/visual assessment of lidar elevation uncertainty and correlate well with vegetation height and presence of Spartina alterniflora. Finally, DEMs generated using full-waveform predictor models produced corrections (compared to ground based RTK GNSS elevations) with R2 values of up to 0.98 and slopes within 4% of a perfect 1:1 correlation. The findings from this research have strong potential to advance tidal marsh mapping, research and management initiatives.

  14. Development of Flood Inundation Libraries using Historical Satellite Data and DEM for Part of Godavari Basin: An Approach Towards Better Flood Management

    NASA Astrophysics Data System (ADS)

    Bhatt, C. M.; Rao, G. S.; Patro, B.

    2014-12-01

    Conventional method of identifying areas to be inundated for issuing flood alert require inputs like discharge data, fine resolution digital elevation model (DEM), software for modelling and technically trained manpower to interpret the results meaningfully. Due to poor availability of these inputs, including good network of historical hydrological observations and limitation of time, quick flood early warning becomes a difficult task. Presently, based on the daily river water level and forecasted water level for major river systems in India, flood alerts are provided which are non-spatial in nature and does not help in understanding the inundation (spatial dimension) which may be caused at various water levels. In the present paper a concept for developing a series of flood-inundation map libraries two approaches are adopted one by correlating inundation extent derived from historical satellite data analysis with the corresponding water level recorded by the gauge station and the other simulation of inundation using digital elevation model (DEM's) is demonstrated for a part of Godavari Basin. The approach explained can be one of quick and cost-effective method for building a library of flood inundation extents, which can be utilized during flood disaster for alerting population and taking the relief and rescue operations. This layer can be visualized from a spatial dimension together with other spatial information like administrative boundaries, transport network, land use and land cover, digital elevation data and satellite images for better understanding and visualization of areas to be inundated spatially on free web based earth visualization portals like ISRO's Bhuvan portal (http://bhuvan.nrsc.gov.in). This can help decision makers in taking quick appropriate measures for warning, planning relief and rescue operations for the population to get affected under that river stage.

  15. Topographic precursors and geological structures of deep-seated catastrophic landslides caused by typhoon Talas, determined from the analysis of high-resolution DEMs

    NASA Astrophysics Data System (ADS)

    Chigira, Masahiro; Tsou, Ching-Ying; Matsushi, Yuki

    2013-04-01

    Typhoon Talas crossed the Japanese Islands between 2 and 5 September 2011, causing more than 70 deep-seated catastrophic landslides in a Jurassic to Paleogene-Early Miocene accretion complex. Detailed examination of the topographic features of 10 large landslides before the event, recorded on DEMs with a resolution of 1 m (based on airborne laser scanner surveys), showed that all of the landslides had small scarplets near their future crowns prior to the slide, and one landslide had linear depressions along its future crown as precursor topographic features. These scarplets and linear depressions were caused by gravitational slope deformation that preceded the catastrophic failure. Strains, defined by the ratio of the length of a scarplet to the length of the whole slope (as measured along the slope line), ranged from 5% to 21%, and are the first reliable numerical data relating to the topographic precursor features of large and catastrophic landslides. Careful examination of aerial photographs from another four large landslides, for which no high-resolution DEMs were available, suggested that they also developed scarplets at their heads beforehand, which are not precisely quantified. Twelve of the 14 landslides we surveyed in the field had sliding surfaces with wedge-shaped discontinuities that consisted of faults, shear surfaces that formed during accretion, and bedding, suggesting that the buildup of pore pressure occurs readily in a gravitationally deformed rock body containing wedge-shaped discontinuities. Other types of gravitational deformation were also active; e.g., flexural toppling and buckling were each observed to have preceded one landslide.

  16. Measuring the quality of life of people with dementia in nursing homes in Germany – the study protocol for the Qol-Dem Project

    PubMed Central

    Dichter, Martin Nikolaus; Halek, Margareta; Dortmann, Olga; Meyer, Gabriele; Bartholomeyczik, Sabine

    2013-01-01

    Background: QUALIDEM is a standardized dementia-specific quality of life (Qol) measurement, which was developed and validated in the Netherlands. A German version has been available since 2008. This study protocol describes the design and methodology for the quality of life of people with dementia (Qol-Dem) project. Objective: This project aims to evaluate the reliability and validity of the German version of the QUALIDEM. Method: Due to the lack of both a universal definition of Qol and of standards to verify the validity of Qol measurements, this study is divided into three phases. The aim of the first theoretical phase is the development of a dementia-specific Qol model as a result of a meta-synthesis of qualitative studies. The second empirical phase consists of the three following steps: (a) an investigation of the scalability and internal consistency of the measure, (b) an evaluation of the interrater and intrarater reliability, and (c) an extensive evaluation of the validity of the QUALIDEM. The resulting Qol model (phase 1) will be used for the selection of appropriate comparators for validity testing. In the third phase, the QUALIDEM will be adapted, if necessary, based on the knowledge generated in the first two phases. Conclusion: The findings of the Qol-Dem project should deliver an accurate assessment of the psychometric properties of the German version of the QUALIDEM. The results will contribute to the further development of the instrument. Furthermore, the results will contribute to the theoretical development of the concept of Qol among people with dementia. PMID:23922616

  17. Detection of seasonal erosion processes at the scale of an elementary black marl gully from time series of Hi-Resolution DEMs

    NASA Astrophysics Data System (ADS)

    Bechet, J.; Duc, J.; Loye, A.; Jaboyedoff, M.; Mathys, N.; Malet, J.-P.; Klotz, S.; Le Bouteiller, C.; Rudaz, B.; Travelletti, J.

    2015-12-01

    The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to weathering processes. Since 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope erosion processes at the scale of elementary gullies. Since 2007, a monitoring of surface changes has been performed by comparing of high-resolution digital elevation models (HR-DEMs) produced from Terrestrial Laser Scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the DEM at the centimetre scale. The topographic changes over a time span of 4 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes contributing to the recharge of tributary gullies and rills are presented. According to the transport capacity generated by runoff, loose regolith soil sources are eroded at different periods of the year. These are forming transient deposits in the main reach when routed downstream, evolving from a transport-limited to a supply-limited regime through the year. The monitoring allows a better understanding of the seasonal pattern of erosion processes for black marls badland-type slopes and illustrates the mode of sediment production and the temporal storage/entrainment in similar slopes. The observed surface changes caused by erosion (ablation/deposition) are quantified for the complete TLS time-series, and sediment budget maps are presented for each season. Comparisons of the TLS sediment budget map with the in situ sediment monitoring (limnigraph and sedigraph) in the stream are discussed. Intense and long duration rainfall events are the triggering factor of the major erosive events.

  18. Time-averaged discharge rate of subaerial lava at Kīlauea Volcano, Hawai‘i, measured from TanDEM-X interferometry: Implications for magma supply and storage during 2011-2013

    USGS Publications Warehouse

    Poland, Michael P.

    2014-01-01

    Differencing digital elevation models (DEMs) derived from TerraSAR add-on for Digital Elevation Measurements (TanDEM-X) synthetic aperture radar imagery provides a measurement of elevation change over time. On the East Rift Zone (EZR) of Kīlauea Volcano, Hawai‘i, the effusion of lava causes changes in topography. When these elevation changes are summed over the area of an active lava flow, it is possible to quantify the volume of lava emplaced at the surface during the time spanned by the TanDEM-X data—a parameter that can be difficult to measure across the entirety of an ~100 km2 lava flow field using ground-based techniques or optical remote sensing data. Based on the differences between multiple TanDEM-X-derived DEMs collected days to weeks apart, the mean dense-rock equivalent time-averaged discharge rate of lava at Kīlauea between mid-2011 and mid-2013 was approximately 2 m3/s, which is about half the long-term average rate over the course of Kīlauea's 1983–present ERZ eruption. This result implies that there was an increase in the proportion of lava stored versus erupted, a decrease in the rate of magma supply to the volcano, or some combination of both during this time period. In addition to constraining the time-averaged discharge rate of lava and the rates of magma supply and storage, topographic change maps derived from space-based TanDEM-X data provide insights into the four-dimensional evolution of Kīlauea's ERZ lava flow field. TanDEM-X data are a valuable complement to other space-, air-, and ground-based observations of eruptive activity at Kīlauea and offer great promise at locations around the world for aiding with monitoring not just volcanic eruptions but any hazardous activity that results in surface change, including landslides, floods, earthquakes, and other natural and anthropogenic processes.

  19. Time-averaged discharge rate of subaerial lava at Kīlauea Volcano, Hawai`i, measured from TanDEM-X interferometry: Implications for magma supply and storage during 2011-2013

    NASA Astrophysics Data System (ADS)

    Poland, Michael P.

    2014-07-01

    Differencing digital elevation models (DEMs) derived from TerraSAR add-on for Digital Elevation Measurements (TanDEM-X) synthetic aperture radar imagery provides a measurement of elevation change over time. On the East Rift Zone (EZR) of Kīlauea Volcano, Hawai`i, the effusion of lava causes changes in topography. When these elevation changes are summed over the area of an active lava flow, it is possible to quantify the volume of lava emplaced at the surface during the time spanned by the TanDEM-X data—a parameter that can be difficult to measure across the entirety of an ~100 km2 lava flow field using ground-based techniques or optical remote sensing data. Based on the differences between multiple TanDEM-X-derived DEMs collected days to weeks apart, the mean dense-rock equivalent time-averaged discharge rate of lava at Kīlauea between mid-2011 and mid-2013 was approximately 2 m3/s, which is about half the long-term average rate over the course of Kīlauea's 1983-present ERZ eruption. This result implies that there was an increase in the proportion of lava stored versus erupted, a decrease in the rate of magma supply to the volcano, or some combination of both during this time period. In addition to constraining the time-averaged discharge rate of lava and the rates of magma supply and storage, topographic change maps derived from space-based TanDEM-X data provide insights into the four-dimensional evolution of Kīlauea's ERZ lava flow field. TanDEM-X data are a valuable complement to other space-, air-, and ground-based observations of eruptive activity at Kīlauea and offer great promise at locations around the world for aiding with monitoring not just volcanic eruptions but any hazardous activity that results in surface change, including landslides, floods, earthquakes, and other natural and anthropogenic processes.

  20. Geomorphic change detection using repetitive topographic surveys and DEMs of Differences: Implementation for short-term transformation of the ice-cored moraines in the Petuniabukta, Svalbard

    NASA Astrophysics Data System (ADS)

    Tomczyk, Aleksandra; Ewertowski, Marek

    2015-04-01

    The exposed glacial forelands are supposed to be intensively transformed by geomorphological processes due to the paraglacial adjustment of the topography. To recognize how high is the activity of such processes, we monitored the transformation rates of ice-cored moraines on the forelands of two glaciers, Ebbabreen and Ragnarbreen, both of which are located near the Petuniabukta at the northern end of the Billefjorden. The main objectives were to: (1) analyse the spatial and temporal aspects of debris flow activity in cm-scale, (2) quantify the short-term (seasonal and intra-seasonal) rate of volume changes, (3) compare transformations of the ice-cored moraine surfaces due to active geomorphic processes (including dead-ice backwasting and debris mass movements) with transformations caused by dead-ice downwasting only. The short-term (yearly and weekly) dynamics of mass-wasting processes were studied in a cm-scale using repetitive topographic scanning. In total, four different locations were scanned, containing seven active debris flows or other mass wasting processes, and including non-active surfaces. Sites were chosen to ensure representation from different parts of the end moraine, different types of dominant processes (debris flows, debris falls, etc.) as well as different types of morphology (exposed ice cliffs, steep debris slope, gentle debris flows lobes, etc.). Altogether, the total scanned area was about 14,200 m2, of which 5,500 m2 were transformed by the active mass movement processes. Ten measurement sessions were carried out: three in summer of 2012, three in summer of 2013, and four in summer of 2014, which allowed for assessing the seasonal (annual) and intra-seasonal (weekly) variations. The results of the surveys in the form of cloud points were used to generate digital elevation models (DEMs) with cell size 0.05 m. Subtracting DEMs from subsequent time periods created DEMs of Differences - DoDs, which enabled us to investigate the volume of and spatial patterns of transformations. The surveys indicate high dynamic rates of landforms' transformations. The mean annual volume loss of sediments and dead-ice for the most active parts of the moraines was up to 1.8 m a-1. However, most of the transformation occurred during summer, with the short-term values of mean elevation changes as high as -104 mm/day. In comparison, the dynamics of the other (i.e. non-active) parts of the ice-cored moraines were much lower, namely, the mean annual lowering (attributed mainly to dead-ice downwasting) was up to 0.3 m a-1, whereas lowering during summer was up to 8 mm/day. Our results indicate that in the case of the studied glaciers, backwasting was much more effective than downwasting in terms of landscape transformation in the glacier forelands. However, despite the high activity of localised mass movement processes, the overall short-term dynamic of ice-cored moraines for the studied glaciers was relatively low. We suggest that as long as debris cover is sufficiently thick (thicker than the permafrost's active layer depths), the mass movement activity would occur only under specific topographic conditions and/or due to occurrence of external meltwater sources and slope undercutting. In the other areas, ice-cored moraines remain a stable landsystem component in a yearly to decadal time-scale. Our results support the hypothesis of a spatio-temporal switching between stable and active conditions within an ice-marginal environment. The project was funded by the Polish National Science Centre as granted by decision number DEC-2011/01/D/ST10/06494.

  1. On the investigation of the performances of a DEM-based hydrogeomorphic floodplain identification method in a large urbanized river basin: the Tiber river case study in Italy

    NASA Astrophysics Data System (ADS)

    Nardi, Fernando; Biscarini, Chiara; Di Francesco, Silvia; Manciola, Piergiorgio

    2013-04-01

    Floodplains are critical landscape features for their importance in both ecohydrological and socio-economic terms. River valleys are, in fact, the domain where the interdependence of the complex human-environmental interface is more significant. Riparian zones, along perennial channels, where the frequency of saturation is high and most flooding occurs, are also the areas where urban areas and infrastructures (e.g. highways, bridges, railways, etc) are more present. This is mainly due to geomorphologic conditions since those areas are predominantly flat and easier to develop. One of the more challenging issues under changing climatic, environmental and human drivers for implementing efficient current and future urban plans is to accurately and timely identify, map and characterize the potential flooding scenarios of floodplains. This is currently achieved by implementing detailed topographic, hydrologic and hydraulic studies for flood modeling and mapping for different frequencies (i.e. return time), but those activities are rarely implemented at the large (river basin) scale for their economic cost and time of implementation. In addition to that, flood map updating is not as frequent as needed for following the rapid changing land use conditions. As a result, it is very often the case that urban plans are based on heterogeneous and discontinuous flood map information. Nevertheless, several recent researches demonstrated the potential for the use of high resolution digital elevation models (DEMs) to define the floodplain feature by means of automated hydrogeomorphic methods. This means identifying the flood prone area by filtering potentially inundated cells by implementing proper morphological and hydrological analyses. In this work we implemented the flooplain identification model proposed by Nardi et al. (WRR, 2006) which automatically extract the river network and estimate flood water levels according to a predefined scaling Leopold law. Inundated areas are consequently identified as those river buffers, draining towards the channel, with an elevation that is less than the maximum flow depth of the corresponding outlet. Keeping in mind that this hydrogeomorhic model performances are strictly related to the quality and properties of the input DEM and that the intent of this kind of methodology is not to substitute standard flood modeling and mapping methods, in this work the performances of this approach are qualitatively evaluated by comparing results with standard flood maps. The Tiber river basin was selected as case study, one of the main river basins in Italy covering a drainage area of approximately 17.000 km2. This comparison is interesting for understanding the performance of the model in a large and complex domain where the impact of the urbanization matrix is significant. Results of this investigation confirm the potential of such DEM-based floodplain mapping models for providing a fast timely homogeneous and continuous inundation scenario to urban planners and decision makers, but also the drawbacks of using such methodology where the humans are significantly and rapidly modifying the surface properties.

  2. Morphotectonics inferred from the analysis of topographic lineaments auto-detected from DEMs: Application and validation for the Sinai Peninsula, Egypt

    NASA Astrophysics Data System (ADS)

    Masoud, Alaa A.; Koike, Katsuaki

    2011-10-01

    Morphotectonic lineaments observed on the Sinai Peninsula in Egypt were auto-detected from Shuttle Radar Topography Mission 90-m digital elevation model (DEM) and gravity grid data and then analyzed to characterize the tectonic trends that dominated the geologic evolution of this area. The approach employed consists of DEM shading, segment tracing, grouping, statistical analysis of the distribution and orientation of the lineaments, fault plane characterization, and smooth representation techniques. Statistical quantification of counts, mean lengths, densities, and orientations was used to infer the relative severity of the tectonic regimes, to unravel the prominent structural trends, and to demarcate the contribution of various faulting styles that prevailed through time. Restored to the present-day geographic position, prominent N50°-60°W, N20°-40°W, N50°-60°E, and N20°-30°E and less prominent N-S, E-W, and ENE trends were common. The prominence of these trends varied through time. The NW and NE trends showed relatively equal abundances in the Precambrian and the Cambrian whereas the prominence of the NW trends prevailed from the Carboniferous to the Holocene. Lineaments in all formations were near vertical and on average, about 65% showed as strike-slip, 22% as reverse, and 13% as normal faulting styles. Statistics from the detected linear features and the reference geological data reveal the relative severity of five dominant tectonic regimes: Precambrian compression followed by extension at its end, Cretaceous compression, Eocene compression, Miocene extension, and finally Holocene compression. Auto-detected lineaments and the severity of the characterized tectonic periods correspond well with reference data on the geologic structure, geodynamic framework, and the gravity anomaly. Furthermore, the recent significance of the broad structural zones was confirmed by the foci of the earthquake epicenters along and at the intra-plate intersections of the broad lineament zones and at the plate boundaries. The spatial distribution of trends with varying styles of faulting distinguished four main tectonic provinces of marked geodynamics variances.

  3. Constraining the DEM and the kinematics of an unstable slope in the Maurienne Valley (French Alps) from remote and ground optical techniques

    NASA Astrophysics Data System (ADS)

    Valentin, Johann; Donze, Frédéric; Jongmans, Denis; Yvart, Sébastien; Lacroix, Pascal; Brenguier, Ombeline; Baillet, Laurent; Lescurier, Anne; Muller, Nicolas; Larose, Eric

    2015-04-01

    Clay-rich rocks are abundant in the Alps where they make a significant part of the sedimentary cover. When they are exposed, these rocks may form reliefs that are affected by rock falls. The failed material quickly transform into rock debris with a fine-grained matrix, which accumulates on slope and in gullies. Historical chronicles show that devastating debris flows can be triggered in the Alpine valleys in case of heavy rain falls. An unstable slope located in the Flysch zone (of Eocene age) has been chosen in the Maurienne valley (French Alps), which is 1 km wide at this location. The study area (0.3 km2) exhibits a rough topography with a slope varying between 20° at the bottom and 90° at the top, for a difference in elevation of about 500 m. The site has been affected by three rock falls (with a volume of about 30,000 m3) in the last fifteen years. The fallen material has filled two gullies. A debris flow occurred in one of this gully in January 2012 and covered a road on a thickness of 4 m. Seismic prospecting was carried out in this 400 long gully and at the cliff top. The results showed that the rock is strongly fractured and deconsolidated over a thickness of at least 10 m and could be affected by further collapses in the near future. A displacement measurement strategy, based on low-cost remote sensing techniques, has been developed in order to obtain spatially-distributed information on the kinematics of the slope and to better understand the double mechanism (fall-flow). Different remote sensing optical techniques using various platforms (satellite, helicopter, drone, and ground) have been first applied in order to obtain DEMs of the site at various scales. The resolution ranges from 1 cm (close range terrestrial optical photogrammetry) to 2 m (Pleiades images), with 50 cm for the helicopter. The DEMs accuracies were estimated from the results of a differential GPS survey. We discuss the optimum strategy to monitor both the flow and the cliff.

  4. Coupled DEM and FEM Models: an Approach to Bridge the gap Between Large-Scale Geodynamic and High-Resolution Tectonic Modeling

    NASA Astrophysics Data System (ADS)

    Seyferth, M.; Andreas, H.

    2002-12-01

    During the past decade, improved modeling techniques have heralded an era of visualization and quantification in tectonophysics. However, there is still a broad gap between lithosphere-scale geodynamic models mainly addressing ductile deformation and high-resolution models of distinct tectonic structures picturing the brittle domain. Since the first is best managed by numerical continuum methods and the second is a figurehead of analogue (sand-box) modeling, an interconnection of both domains is difficult to handle. Therefore, a numerical approach suited to simulate brittle fracturing and, thus, to act as a ?virtual sand-box?, represents an essential tool to study the interplay of shallow tectonics and deeper-seated geodynamic processes. This can be achieved using PFC2D, a special implementation of the discrete-element method (DEM) based on circular particles. High-resolution DE models offer a number of advantages over sand-box models: material properties can be determined more adequately; lithostatic pressure influences frictional sliding at different crustal levels; the evolution of stress and strain through time can be monitored at any point of the model. Additionally, DE models can easily be coupled with computer simulations of exogenic processes. However, the principal advantage of high-resolution DE models is their capability to be coupled with continuum models describing the lower, ductile part of the lithosphere. Thermomechanically coupled finite-element models (FEM, ANSYS) allow to consider temperature- and strain rate-dependent material behavior. Therefore, they are well suited to simulate ductile kinematics and, thus, to determine boundary conditions, that can applied to the base of the DE model. Vice versa, current reaction forces of the DE model can be used as input data for the FE model. Half-grabens forming above detachment faults are used as an example to illustrate the capabilities of high-resolution DE models. A lot of analogue modeling has been done on this topic, providing the chance to compare the results and to validate the new method. Thereby, special focus is laid on the fault pattern which evolves in the pre- and syn-rift strata of the hanging wall block. As a second step, the mechanically limited boundary conditions of sand-box models can be left behind by using the coupled DEM-FEM technique. Thereby, the asymmetry induced by the upper crustal detachment results in an asymmetric distribution of strain in the lower part of the lithosphere, which, in turn, leads to vertical movements along the detachment plane.

  5. Modeling the evolution of loess-covered landforms in the Loess Plateau of China using a DEM of underground bedrock surface

    NASA Astrophysics Data System (ADS)

    Xiong, Li-Yang; Tang, Guo-An; Li, Fa-Yuan; Yuan, Bao-Yin; Lu, Zhong-Chen

    2014-03-01

    The evolution of loess-covered landforms is largely controlled by the pre-Quaternary underlying bedrock terrain, which is one of the most important factors in understanding the formation mechanism of the landforms. This study used multiple data sources to detect 1729 outcropping points of underlying terrain, in order to construct a digital elevation model (DEM) of the paleotopography of an area of the Loess Plateau subject to severe soil erosion. Four terrain characteristics, including terrain texture, slope gradient, the hypsometric curve, and slope aspect, were used to quantify topographic differences and reveal the loess-deposition process during the Quaternary. A loess thickness map was then created to show the spatial distribution of loess deposits in the test area. Finally, the geomorphological inheritance characteristics of the loess-covered landforms were evaluated in different landform divisions. The results showed the significant inheritance of modern topography from the underlying topography with a similar general relief trends. The average thickness of loess deposits was computed to be 104.6 m, with the thickest part located in the Xifeng loess tableland area. In addition, the slope aspects of the North and Northwest seem to have favored Quaternary loess deposition, which supported the hypothesis of an eolian origin for loess in China. The modern surface has lower topographic relief compared to the underlying terrain due to loess deposition.

  6. Scale-dependency of stream gradients derived from LiDAR DEM and its relationship to watershed morphology in the Southern Japanese Alps

    NASA Astrophysics Data System (ADS)

    Hayakawa, Y. S.; Imaizumi, F.; Hattanji, T.

    2008-12-01

    Bedrock erosion in streams is a key element in determining topography of mountain watershed. Failures in steep slopes can often be controlled by riverbed incision with regard to base level changes, where knickzone propagation often has a significant impact on such stream incision. Here we analyze longitudinal morphology of bedrock rivers in a steep mountain watershed in terms of stream gradient, using a high-resolution (1 m) LiDAR DEM in a steep mountain watershed at Ikawa, central Japan. By computing stream gradients with different measure lengths, scale-dependent changes in the gradient are revealed. Relative steepness of riverbed is then quantified using the scaling gradients. Spatial distribution of relative steepness in the watershed indicates that longitudinal riverbed morphology often correspond to morphological condition of slopes with differing types of channel head. Streams in subwatersheds with gentle slopes have less steepness while those in subwatersheds with steep slopes in which failures are frequent. These differences are not likely derived from lithological or tectonic factors, but from geomorphic history in the watershed. The steepness index can also be used for detection of knickzones comprising small knickpoints and waterfalls, whereas location of knickzones has rarely been identified quantitatively in such an uppermost steep mountainous watersheds. The distribution of relative steepness and knickzones possibly reflect incision waves occurring in the watershed: late- or post-glacial base level lowering could have caused formation of knickzones, and some of the propagating knickzones reached upper portions in the watershed while the uppermost area seems to be preserved.

  7. Investigating the definition of flood maps using a 2D hydraulic routing model forced by a DEM-based fully continuous rainfall-runoff algorithm

    NASA Astrophysics Data System (ADS)

    Nardi, Fernando; Petroselli, Andrea; Grimaldi, Salvatore

    2013-04-01

    Ongoing efforts of remote sensing technologies to provide more accurate digital elevation models (DEMs) at the global scale are supporting the use of terrain analysis and hydrologic and hydraulic modelling algorithms for flood mapping in ungauged basins. In this work we implement a fully continuous hydrologic-hydraulic model feeded by a rainfall synthetic time series for providing river hydrographs that are routed along the channel using a bidimensional hydraulic model for the detailed physically-based characterization of the inundation process. In this way the whole physical process is represented, from the net rainfall to the flow time series, avoiding any conceptual sub-method (design hyetograph and hydrograph) commonly needed to apply standard flood modelling and mapping procedures. Nevertheless, the floodplain information is no longer deterministic as the result of the evaluation of the impact on the river valley of a single design hydrologic scenario (event-based approach,EBA), but the final result is composed of a combination of data derived by the application of a fully-continuous approach (FCA). Indeed FCA provides a flow depth time series for each single cell of the inundated domain. The final flood map should be, thus, the result of a proper analysis of this dataset in statistical, qualitative and quantitative terms. Otherwise this would lead to an undefined flooding scenario that could be useless for flood risk management and decision making in urban plans.

  8. Ethanol electro-oxidation on carbon-supported Pt, PtRu and Pt 3Sn catalysts: A quantitative DEMS study

    NASA Astrophysics Data System (ADS)

    Wang, H.; Jusys, Z.; Behm, R. J.

    The electrocatalytic activity of commercial carbon supported PtRu/Vulcan and Pt 3Sn/Vulcan bimetallic catalysts (E-TEK, Inc.) for ethanol oxidation under well defined electrolyte transport conditions and their selectivity for complete oxidation were evaluated using cyclic voltammetry combined with on-line differential electrochemistry mass spectrometry (DEMS) measurements and compared to the activity/selectivity of standard Pt/Vulcan catalysts. The main reaction products CO 2, acetaldehyde and acetic acid were determined quantitatively, by appropriate calibration procedures, current efficiencies and product yields were calculated. Addition of Ru or Sn in binary Pt catalysts lowers the onset potential for ethanol electro-oxidation and leads to a subtle increase of the total activity of the Pt 3Sn/Vulcan catalyst. It does not improve, however, the selectivity for complete oxidation to CO 2, which is about 1% for all three catalysts under present reaction conditions—incomplete ethanol oxidation to acetaldehyde and acetic acid prevails on all three catalysts. The results demonstrate that the performance of the respective catalysts is limited by their ability for C-C bond breaking rather than by their activity for the oxidation of poisoning adsorbed intermediates such as CO ad or CH x,ad species.

  9. Evaluation of the influence of metabolic processes and body composition on cognitive functions: Nutrition and Dementia Project (NutrDem Project).

    PubMed

    Magierski, R; Kłoszewska, I; Sobow, T

    2014-11-01

    The global increase in the prevalence of dementia and its associated comorbidities and consequences has stimulated intensive research focused on better understanding of the basic mechanisms and the possibilities to prevent and/or treat cognitive decline or dementia. The etiology of cognitive decline and dementia is very complex and is based upon the interplay of genetic and environmental factors. A growing body of epidemiological evidence has suggested that metabolic syndrome and its components may be important in the development of cognitive decline. Furthermore, an abnormal body mass index in middle age has been considered as a predictor for the development of dementia. The Nutrition and Dementia Project (NutrDem Project) was started at the Department of Old Age Psychiatry and Psychotic Disorders with close cooperation with Department of Medical Psychology. The aim of this study is to determine the effect of dietary patterns, nutritional status, body composition (with evaluation of visceral fat) and basic regulatory mechanisms of metabolism in elderly patients on cognitive functions and the risk of cognitive impairment (mild cognitive impairment and/or dementia). PMID:25139556

  10. Three-dimensional DEM-CFD analysis of air-flow-induced detachment of API particles from carrier particles in dry powder inhalers.

    PubMed

    Yang, Jiecheng; Wu, Chuan-Yu; Adams, Michael

    2014-02-01

    Air flow and particle-particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs). Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM-CFD (discrete element method-computational fluid dynamics) is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier) increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force. PMID:26579364

  11. DemTect, PANDA, EASY, and MUSIC: cognitive screening tools with age correction and weighting of subtests according to their sensitivity and specificity.

    PubMed

    Kalbe, Elke; Calabrese, Pasquale; Fengler, Sophie; Kessler, Josef

    2013-01-01

    Many cognitive screening instruments have been developed during the last decades to detect mild cognitive dysfunction and dementia, and there is an ongoing discussion as to which tool should be used in which setting and which challenges have to be considered. Among other aspects, dependence on age is a recognized problem in screening tools which still has not found its way into common scoring procedures. Another aspect which has been handled very heterogeneously is which domain is represented in which proportion in the total score. Furthermore, screening ethnic minority patients has been identified as an important but so far widely unresolved matter. In this review, four cognitive screening tools that all follow a common, stringent concept and pay regard to some critical aspects are described: the DemTect, a "generic" tool; the PANDA for Parkinson's disease patients; the EASY, a non-verbal, culture-fair screening test for patients with migration background; and the MUSIC for patients with multiple sclerosis. All of these screening instruments have an age-correction, provide a total score in which the different subtests are weighted according to their individual sensitivity and specificity, and include tasks that are specifically aligned to the cognitive profile of the target group, including the EASY with non-verbal, culture-fair tasks to overcome language and cultural barriers. The development, main characteristics, data, and limitations of these tools are presented and discussed against the background of the current landscape of cognitive screening tools. PMID:23313929

  12. Failure and frictional sliding envelopes in three-dimensional stress space: Insights from Distinct Element Method (DEM) models and implications for the brittle-ductile transition of rock

    NASA Astrophysics Data System (ADS)

    Schöpfer, Martin; Childs, Conrad; Manzocchi, Tom

    2013-04-01

    Rocks deformed at low confining pressure are brittle, meaning that after peak stress the strength decreases to a residual value determined by frictional sliding. The difference between the peak and residual value is the stress drop. At high confining pressure, however, no stress drop occurs. The transition pressure at which no loss in strength occurs is a possible definition of the brittle-ductile transition. The Distinct Element Method (DEM) is used to illustrate how this type of brittle-ductile transition emerges from a simple model in which rock is idealised as an assemblage of cemented spherical unbreakable grains. These bonded particle models are subjected to loading under constant mean stress and stress ratio conditions using distortional periodic space, which eliminates possible boundary effects arising from the usage of rigid loading platens. Systematic variation of both mean stress and stress ratio allowed determination of the complete three dimensional yield, peak stress and residual strength envelopes. The models suggest that the brittle-ductile transition is a mean stress and stress ratio dependent space curve, which cannot be adequately described by commonly used failure criteria (e.g., Mohr-Coulomb, Drucker-Prager). The model peak strength data exhibit an intermediate principal stress dependency which is, at least qualitatively, similar to that observed for natural rocks deformed under polyaxial laboratory conditions. Comparison of failure envelopes determined for bonded particle models with and without bond shear failure suggests that the non-linear pressure dependence of strength (concave failure envelopes) is, at high mean stress, the result of microscopic shear failure, a result consistent with earlier two-dimensional numerical multiple-crack simulations [D. A. Lockner & T. R. Madden, JGR, Vol. 96, No. B12, 1991]. Our results may have implications for a wide range of geophysical research areas, including the strength of the crust, the seismogenic zone and slip-tendency analysis.

  13. Landscape response to recent tectonic deformation in the SW Pannonian Basin: Evidence from DEM-based morphometric analysis of the Bilogora Mt. area, NE Croatia

    NASA Astrophysics Data System (ADS)

    Matoš, Bojan; Pérez-Peña, José Vicente; Tomljenović, Bruno

    2016-06-01

    Bilogora Mt. area is a transpressional structure located in the NE of Croatia, linked with the tectonic evolution of the Drava Depression. The structure formed during Pliocene and Quaternary from the inversion of NW-striking Drava Depression Boundary Fault, which originated as a normal fault and was reactivated as a dextral strike-slip fault. During Pliocene and Quaternary time, Bilogora Mt. area underwent more than 400 m of differential uplift, while still ongoing tectonic deformation is documented by historical and instrumental seismicity (3.5 ≤ ML ≤ 5.6). In this geomorphic study, the recent deformation in the Bilogora Mt. area, although obscured by landscape evolution variables, was assessed using DEM-based landscape morphometry and a set of morphometric indexes. Local relief and slope angle variability distributions were combined with morphometric indexes computed at the scale of the drainage basin. We analyzed hypsometric curves with the hypsometric integral (HI), basin asymmetry (AF) and parameters of longitudinal stream profiles (Cf, Cmax, Δl/L, θ, and ksn). Analyzed morphometric parameters were combined into a cumulative index of relative tectonic activity (RTA). This index summarizes drainage basin response to the possible recent tectonic activity. Results suggest that most of the tectonic activity is probably located along the NE front of the Bilogora Mt. area, in its NW and central part. This activity could be likely related to recent tectonic activity along the Kalnik Mt. Fault zone and Drava Depression Boundary Fault zones, respectively. A subordinate area characterized by recent tectonic activity could be suggested within the southernmost part of the study area. Quaternary activity in this area is probably related to NE-striking faults in vicinity of the town Daruvar that continue towards the northeast into the study area. Though methodology presented here represents a good identification tool of possible ongoing deformation, this study will be followed by detailed fieldwork and paleoseismological investigations at the identified locations.

  14. Classification and mapping of anthropogenic landforms on cultivated hillslopes using DEMs and soil thickness data Example from the SW Parisian Basin, France

    NASA Astrophysics Data System (ADS)

    Chartin, C.; Bourennane, H.; Salvador-Blanes, S.; Hinschberger, F.; Macaire, J.-J.

    2011-12-01

    This study focuses on linear anthropogenic landforms of decametric width on cultivated hillslopes and their relations to soil thickness variability. The 16 ha study area shows a rolling topography supported by Cretaceous chalk of the SW Parisian Basin, France. Two types of landforms were identified: lynchets, similar to those described as soil terraces occurring on downslope field parts in other contexts, and undulations, linear, convex landforms that cut across fields. Accurate DEM construction and a detailed soil thickness survey were performed all over the study area. Soil samples were classified considering their location on specific types of anthropogenic landforms. The Classification Tree (CT) method was applied to assess whether lynchets and undulations can be discriminated through morphometric attributes (slope, curvature, profile curvature and planform curvature) and soil thickness (CT soil) or through morphometric attributes only (CT topo). The CT application establishes predictive classification models to map the spatial distribution of lynchets and undulations over the whole study area. The validation results of the CT soil and CT topo applications show model efficiencies of 83% and 67%, respectively. Both models performed well for lynchets. Errors arise mainly from difficulties in unequivocally discriminating gently convex undulations and undifferentiated surfaces, especially when soil thickness is not accounted for. Mean values of soil thickness are 1.08, 0.62 and 0.45 m in lynchets, undulations and undifferentiated areas, respectively. The general shape of the thickened soil is characteristic to each type of anthropogenic landform. Multi-temporal mapping of field border networks shows that undulations are linked to borders that were removed during the latest land consolidation. Lynchets are associated with current field borders. Lynchets and undulations, which cover 39% of the study area, define topographic indicators of human-induced soil accumulations. The method involves perspectives for efficiently mapping and quantifying the anthropogenically modified spatial variability of soil thickness on agricultural hillsides.

  15. Improving the identification of hydrologically sensitive areas using LiDAR DEMs for the delineation and mitigation of critical source areas of diffuse pollution.

    PubMed

    Thomas, I A; Jordan, P; Mellander, P-E; Fenton, O; Shine, O; Ó hUallacháin, D; Creamer, R; McDonald, N T; Dunlop, P; Murphy, P N C

    2016-06-15

    Identifying critical source areas (CSAs) of diffuse pollution in agricultural catchments requires the accurate identification of hydrologically sensitive areas (HSAs) at highest propensity for generating surface runoff and transporting pollutants. A new GIS-based HSA Index is presented that improves the identification of HSAs at the sub-field scale by accounting for microtopographic controls. The Index is based on high resolution LiDAR data and a soil topographic index (STI) and also considers the hydrological disconnection of overland flow via topographic impediment from flow sinks. The HSA Index was applied to four intensive agricultural catchments (~7.5-12km(2)) with contrasting topography and soil types, and validated using rainfall-quickflow measurements during saturated winter storm events in 2009-2014. Total flow sink volume capacities ranged from 8298 to 59,584m(3) and caused 8.5-24.2% of overland-flow-generating-areas and 16.8-33.4% of catchment areas to become hydrologically disconnected from the open drainage channel network. HSA maps identified 'breakthrough points' and 'delivery points' along surface runoff pathways as vulnerable points where diffuse pollutants could be transported between fields or delivered to the open drainage network, respectively. Using these as proposed locations for targeting mitigation measures such as riparian buffer strips reduced potential costs compared to blanket implementation within an example agri-environment scheme by 66% and 91% over 1 and 5years respectively, which included LiDAR DEM acquisition costs. The HSA Index can be used as a hydrologically realistic transport component within a fully evolved sub-field scale CSA model, and can also be used to guide the implementation of 'treatment-train' mitigation strategies concurrent with sustainable agricultural intensification. PMID:26974575

  16. Kanban - der Weg ist das Ziel

    NASA Astrophysics Data System (ADS)

    Aull, Florian; Berlak, Joachim; Dickmann, Eva; Dickmann, Philipp; Fischäder, Holm; Gerlach, Joachim; Henneberg, Jens; Kapalla, Klaus; Kress, Oliver; Kuttler, Robert; Schneider, Herfried M.; Schürle, Philipp; Stellpflug, Franz-Josef; Wannenwetsch, Ralph; Wulz, Johannes; Zäh, Michael F.

    Wenn man aktuell Produktionsbereiche in Deutschland und Europa besucht, fallen im Zusammenhang mit modernen Produktionsmethoden immer öfter die Begriffe Kanban (jap. Karte, Signal) und Pull-Produktion, und dies nicht ohne Stolz, da diese mit dem schillernden Vorbild des Toyota Produktionssystems in Zusammenhang stehen. Tatsächlich ist Kanban ein integraler Bestandteil moderner Produktionssysteme. Blickt man aber im Rahmen von Prozessanalysen hinter die Fassaden", d. h. in die tägliche Praxis der Arbeitsprozesse, wird man schnell desillusioniert - die viel gepriesenen klassischen Kanban-Regeln werden im Tagesgeschäft nicht eingehalten.

  17. Remote-sensing of Riverine Environments Utilized by Spawning Pallid Sturgeon Using a Suite of Hydroacoustic Tools and High-resolution DEMs

    NASA Astrophysics Data System (ADS)

    Elliott, C. M.; Jacobson, R. B.; DeLonay, A. J.; Braaten, P. J.

    2013-12-01

    The pallid sturgeon (Scaphirynchus albus) inhabits sandy-bedded rivers in the Mississippi River basin including the Missouri and Lower Yellowstone Rivers and has experienced decline generally associated with the fragmentation and alteration of these river systems. Knowledge gaps in the life history of the pallid sturgeon include lack of an understanding of conditions needed for successful reproduction and recruitment. We employed hydroacoustic tools to investigate habitats utilized by spawning pallid sturgeon in the Missouri River in Missouri, Kansas, Iowa, and Nebraska, and the Yellowstone River in Montana and North Dakota USA from 2008-2013. Reproductive pallid sturgeon were tracked to suspected spawning locations by field crews using either acoustic or radio telemetry, a custom mobile mapping application, and differential global positioning systems (DGPS). Female pallid sturgeon were recaptured soon after spawning events to validate that eggs had been released. Habitats were mapped at presumed spawning and embryo incubation sites using a multibeam echosounder system (MBES), sidescan sonar, acoustic Doppler current profiler, an acoustic camera and either a real-time kinematic global positioning system (RTK GPS) or DGPS. High-resolution DEM's and velocimetric maps were gridded from at a variety of scales from 0.10 to 5 meters for characterization and visualization at spawning and presumed embryo incubation sites. Pallid sturgeon spawning sites on the Missouri River are deep (6-8 meters) and have high current velocities (>1.5 meters per second). These sites are also characterized by high turbidity and high rates of bedload sediment transport in the form of migrating sand dunes. Spawning on the channelized Lower Missouri River occurs on or adjacent to coarse angular bank revetment or bedrock. Collecting biophysical information in these environmental conditions is challenging, and there is a need to characterize the substrate and substrate condition at a scale relevant to spawning fish and developing embryos (< 1 meter). The Yellowstone River in Montana and North Dakota provides the closest analog to a reference condition for pallid sturgeon spawning habitat with a natural flow regime and relatively natural channel geomorphology. Recent documented suspected spawning on the Yellowstone River occurs in a a sand-bedded reach with patches of gravel deposits, in zones of higher velocity (1.0-1.5 meters per second) compared to the ranges of velocities available in an adjacent reach and over a range of depths (2-5 meters). Results from substrate assessments at pallid sturgeon spawning sites on the Missouri and Yellowstone Rivers may have implications for sediment and flow management as well as provide guidance for potential habitat manipulation in support of the recovery of the pallid sturgeon.

  18. Estimating Mangrove Canopy Height and Above-Ground Biomass in Everglades National Park with Airbone LiDAR and TanDEM-X Data.

    NASA Astrophysics Data System (ADS)

    Feliciano, E. A.; Wdowinski, S.; Potts, M. D.; Fatoyinbo, T. E.; Lee, S. K.

    2014-12-01

    The coastal mangroves forests of Everglades National Park (ENP) are well protected from development. Nevertheless, climate change, hurricanes and other anthropogenic disturbances have affected these intertidal ecosystems. Understanding and monitoring forest structural parameters such as canopy height and above-ground biomass (AGB) are important for the establishment of an historical database for past, present and future ecosystem comparison. Forest canopy height has a well understood and directly proportional correlation with AGB. It is possible to derive it using (1) airborne LiDAR/Laser Scanning (ALS) or (2) space-borne radar systems such as Shuttle Radar Topography Mission (SRTM) and TanDEM-X (TDX). A previous study of the mangrove canopy height and AGB in the ENP was conducted a decade ago based on ALS data acquired in 2004 in conjunction with SRTM data, which were acquired in 2000 (Simard et al. 2006). In this study we estimated canopy height and AGB using an ALS dataset acquired in 2012 and TDX data acquired during the years 2012-2014. The ALS dataset was acquired along a 16.5 x 1.5 km swath of mangrove forest with variable canopy height. The sampled areas were representative of mangrove stature and structure in the whole ENP. Analysis of the ALS dataset showed that mangrove canopy height can reach up to ~25 meters close to the coastal ENP waters. Additionally, by comparing our ALS results with those of a previous study by Simard et al. (2006) we identified areas where mangrove height changes greater than ± 3 meters occurred. To expand the study area to the full ENP mangrove ecosystem we processed single-polarization TDX data to obtain a Digital Canopy Model (DCM) that represents the mangrove canopy height. In order to obtain the true canopy height we calibrated the TDX phase center height with ALS true canopy height. Preliminary results of a corrected single-polarized (HH) TDX scene show that mangrove canopy height can reach up to ~25 meters in the western region of the ENP.

  19. Long-term erosion rates of Neogene to Quaternary volcanoes of the Altiplano-Puna plateau, Central Andes: an SRTM DEM study

    NASA Astrophysics Data System (ADS)

    Karátson, Dávid; Telbisz, Tamás.; Wörner, Gerhard

    2010-05-01

    Neogene to Quaternary volcanism of the Central Andes offers a unique opportunity to study long-term erosion of stratovolcanoes. On the basis of SRTM DEM data, we invesigated 35 stratovolcanoes of the 3,800-4,000 m high, arid-hyperarid Altiplano-Puna plateau (from 14oS, 64oW to 27oS, 74oW). The volcanoes have been selected on geomorphological criteria such as (1) a single, "mature" cone-shape with considerable size, (2) location on a relatively flat basement, (3) no overlap with other volcanic centres, and (4) lack of calderas or sector collapse scars. Volcanoes of various age (Mid-Miocene to Quaternary based on sporadic radiometric dates) and various degradation stage have been included in order to infer long-term erosion rates. The method we follow is to quantitatively compare the existing topography with the present-day active volcanoes, e.g. Parinacota (Northern Chile). By applying an advanced computational method, we fit the relief of the undissected, almost perfect reference cone over the degraded volcanic edifice. This way, we can precisely calculate (a) the degree of denudation by difference between the computed initial volume from the fit and the observed volume, and (b) for volcanoes with radiometric age constraint the erosion rate (m/Ma) as the areal mean of denudation divided by age. Our results show that (a) the studied volcanoes are degraded to various extent up to ~40% (denudation ratio) of the paleo-volume. In accordance, their relative height which is progressively lower shows a moderately good correlation with denudation (r2 = 0.70). Using the available age constraints, we obtained a stronger correlation between age and denudation (r2 = 0.82 for all volcanoes, and r2 = 0.95 without the southernmost hyperarid and northernmost semihumid volcanoes). (b) Therefore, calculating erosion rates gives highly reliable results. The youngest volcanoes (e.g. Ollagüe, Tacora) shows 50-100 m/Ma erosion rates which fits well to the initially rapid degradation of active volcanic edifices without vegetation cover. Long-term erosion rates of the Pliocene to Miocene volcanoes, in constrast, are much lower and more uniform (7-17 m/Ma), in agreement with other, similarly low erosion rates obtained by other methods (e.g. cosmogenic nuclides) for the Altiplano-Puna highland. Our rates show the smallest values for the hyperarid Puna and the southern Altiplano (e.g. Maricunga volcano), and the greatest values for the semihumid Southern Peru (e.g. Ccarhuaraso, Jatunpuco volcanoes). Moreover, using the very good age vs denudation correlation as a geomorphological dating tool, we are able to estimate ages for undated volcanoes of the Central Andes or for other regions under similar climate conditions.

  20. Pit Craters and Collapse Calderas: Structural Influences of Initial Mechanical and Geometric Properties as revealed by 2D Distinct Element Method (DEM) Models

    NASA Astrophysics Data System (ADS)

    Holohan, E. P.; Schöpfer, M. P.; Walsh, J. J.

    2009-12-01

    Pit craters and collapse calderas are volcanic depressions produced by subsidence of the roof of a magma reservoir. They are near-ubiquitous features of volcanic fields or edifices on Earth and other terrestrial planets. Pit crater and caldera subsidence may occur by diverse structural mechanisms, each previously linked with various initial controlling factors. We present Distinct Element Method (DEM) numerical models of this subsidence process to shed new light on such mechanisms and the factors controlling them. Our models comprise an assemblage of gravitationally-loaded circular particles that interact at their contacts according to elastic-frictional laws. Cohesion is provided by inter-particle bonds that break once their shear or tensile strength is exceeded. Varying particle and bond micro-properties yielded assemblage macro-properties and rheological responses characteristic of natural rock masses (e.g. elasticity, failure, and strain softening), with fracture localization simulated by bond breakage. The magma reservoir is represented as a region of non-bonded, low-friction particles. Withdrawal of magma is simulated by incrementally reducing the area of the reservoir particles. The resultant gravity-driven failure and subsidence of the overlying reservoir roof is explicitly replicated. We have investigated the effect on subsidence of initial mechanical and geometric properties. The former included Young’s Modulus and strength (cohesion), whilst the latter included the thickness/diameter ratio (T/D) of the roof and the ceiling curvature imparted by the shape of the underlying reservoir. These initial mechanical and geometric properties interacted to produce several ‘end-member’ subsidence mechanisms: (1) Predominantly central sagging at low strength and low T/D; (2) predominantly single central block subsidence at low to intermediate strength and at intermediate T/D; (3) multiple central block subsidence at high strength and high T/D; (4) a hitherto unrecognized ‘central snapping’ mechanism at high strength, low T/D, and with a low ceiling curvature. In terms of material properties, the occurrence of these mechanisms was weakly dependent on Young’s Modulus, but strongly dependent on material strength. In terms of geometric properties, a moderate dependency on reservoir shape at low T/D diminished at intermediate and high T/D. One important outcome of the interaction of mechanical and geometric properties is that the critical T/D ratio, above which the single central block mechanism changes to the multiple central block mechanism, decreases from > 1 to < 0.6 with increasing material strength. Our model results agree well with those of analogue studies of pit crater and caldera subsidence, and provide a more quantitative understanding of the genesis of different mechanisms observed in the field - e.g. at Nindiri crater, Nicaragua and Miyakejima caldera, Japan.

  1. Gestaltung von Mensch-Maschine-Schnittstellen

    NASA Astrophysics Data System (ADS)

    Bruder, Ralph; Didier, Muriel

    Die Interaktion zwischen Mensch und Maschine erfolgt über Schnittstellen, die dem Fahrer Informationen liefern und ihm behilfich sein sollen, die Fahraufgabe sicher, effektiv und effzient zu bewältigen. Wie die Gestaltung von Anzeigen und Bedienelementen vorgenommen werden muss und worauf während des Entwicklungsprozesses in Bezug auf die Interaktion zwischen Mensch und Maschine Rücksicht genommen werden muss, soll hier geklärt werden.

  2. Black Hawk Down: Film Zwischen Reflektion und Konstruktion Gesellschaftlicher Wirklichkeit

    NASA Astrophysics Data System (ADS)

    Ptzsch, Holger

    2009-05-01

    BLACK HAWK DOWN: FILM BETWEEN THE REFLECTION AND CONSTRUCTION OF SOCIAL REALITY - In this article, Ridley Scott's film Black Hawk Down (USA 2001) is read in the context of contemporary theories concerning cultural memory (Jan and Aleida Assmann) and media culture (Douglas Kellner). It is argued that film (and representation in general) does not merely reflect a preceding reality; it also actively serves to construct it. It is shown how Scott's film privileges one particular perspective on an actual event and how this point of view is objectified and installed in the memory of Western media culture. What potential implications does an increased blurring of fact and fiction in the representation of war have? What are the consequences for political and pedagogical practice? What role can cultural studies play in these processes?

  3. Kostenvergleich zwischen weißer, schwarzer und brauner Wanne

    NASA Astrophysics Data System (ADS)

    Schlicht, Jürgen

    Bei Gebäuden, deren Kellergeschosse im Grundwasser stehen, ist je nach Nutzung und Tragsystem zu entscheiden, welches der folgenden Dichtungssysteme für Kellerwände und Gebäudesohle eine optimale Funktion bei gleichzeitiger Wertung der Kosten erfüllt.

  4. New insights into palaeoglaciological processes in northeastern Germany by analysis of a LiDAR DEM: using high-resolution elevation data to reassess the geomorphology of the Barnim till plain

    NASA Astrophysics Data System (ADS)

    Hardt, Jacob; Böse, Margot; Hebenstreit, Robert; Lüthgens, Christopher

    2014-05-01

    We used airborne LiDAR DEM data to reassess the current state of research of an intensively studied "classical" glacial landscape, the Barnim till plain northeast of Berlin. To gain new insights into palaeoglaciological dynamics, we examined a high-resolution DEM for geomorphic features that either prove or negate previous research. The study area was last glaciated in the Weichselian, and its landforms are associated with the W1B- (Brandenburg phase) and W1F-advances (Frankfurt phase), except for the eastern Barnim where a push moraine complex was compressed during the Saalian. The course and the timing of the W1F ice marginal position, which is assigned to the Barnim area, are contradictorily discussed in literature. Hence, landscape analysis with a high resolution DEM appears to be a promising tool. The LiDAR data used here has a ground resolution of 1 m and a height accuracy of 30 - 50 cm. In an ArcGIS 10 environment a database was created that contains spatial information about the study area collected from different sources. These include digitized geological and geomorphological maps as well as geochronological data from different authors. Owing to the size of the Barnim (~1900 km²), three subsets with a size of 10 x 15 km were selected for advanced analysis (western, middle and eastern Barnim). Each subset represents one of the most characteristic landscapes of the study area. For each subset we performed a qualitative analysis of landscape features. The results were compared with each other and connected to the whole Barnim area as well as the current state of research. The most remarkable discovery was made in the middle Barnim. Here we identified a set of consecutive arcuate ridges. Their widths (NE-SW) are around 1000 - 1500 m, and their lengths are around 10 - 15 km; they rise some 10 m above their surroundings. According to geological maps and our own fieldwork, they are covered by till. A sandy or peaty substrate lies between the ridges. The inner sides of the ridges are northeast-oriented and rather steep, and the outer sides face southwest with a dip at a flatter angle. The ridges are incised radially. Their lobe-like form and the distribution of the substrates suggest a glacial origin. We propose a genetic model of recessional moraines that were deposited in front of an oscillating glacier lobe; however, other possibilities are also discussed. Similar forms were recently found around the ice margin of piedmont glaciers, e.g. the Malaspina glacier in southwest Alaska. The timing of their formation still has to be investigated. Fine gravel analyses from other studies imply that they consist of a till that can probably be associated with a Weichselian ice advance. Understanding the genesis of the newly described ridges may be a key to solve the contradictory "Frankfurt phase problem" in terms of glaciodynamics and stratigraphy Our study shows that even in intensively researched areas high-resolution DEM data can reveal landscape features that shed a new light on landscape genesis. Nevertheless, further fieldwork and geochronological data are necessary to obtain a complete picture of palaeoglaciological processes in the northeastern German lowland.

  5. Aerial imagery and structure-from-motion based DEM reconstruction of region-sized areas (Sierra Arana, Spain and Namur Province, Belgium) using an high-altitude drifting balloon platform.

    NASA Astrophysics Data System (ADS)

    Burlet, Christian; María Mateos, Rosa; Azañón, Jose Miguel; Perez, José Vicente; Vanbrabant, Yves

    2015-04-01

    A new type of untethered balloon based mapping platform allows affordable remote sensing applications from higher altitudes and with a greater range and payload capacity than common motorized UAV's. The airborne device, called "Stratochip", is based on a dual helium balloons configuration. At a defined altitude (comprised between 1000 and 30000m), the first balloon is released, drastically reducing the platform climbing rate. The payload (up to 10kg) can then drift in a sub-horizontal trajectory until it leaves a pre-defined area of interest. Leaving the pre-defined area, the second balloon is released and the payload is recovered after a parachute landing. The predicted flight path of the Stratochip, launch site and surveyed area are calculated using both forecasted (NOAA model) and real-time (inborne instruments) meteorological data, along with the physical parameters of the balloons and parachute. The predicted recovery area can also be refined in real-time to secure and facilitate equipment retrieval. In this study, we present the results of two cartographic campaigns made in Belgium (Famennian outcrops near Beauraing, Namur Province) and Spain (karstic field in the Eastern part of Sierra Arana, Granada region). Those campaigns aimed to test the usability of the Stratochip to survey a large area at medium altitudes (3000m-8000m) and produced an updated Digital Elevation Model and orthophoto mosaic of those regions. For that purpose, the instrument installed in the Stratochip payload was constituted of a digital camera stabilized with two IMU's and two brushless motors. An automated routine then tilted the camera at predefined angles while taking pictures of the ground. This technique allowed to maximize the photogrammetric information collected on a single pass flight, and improved the DEM reconstruction quality, using structure-from-motion algorithms. Three sets of data (DEM + orthophoto) were created from those campaigns, using pictures sets collected a different elevations. A 1m/pixel ground resolution set covering an area of about 200km² and mapping the eastern part of the Sierra Arana (Andalucía, Spain) includes a kartsic field directly to the south-east of the ridge and the cliffs of the "Riscos del Moro". A 4m/pixel ground resolution set covering an area of about 900km² includes the landslide active Diezma region (Andalucía, Spain) and the water reserve of Francisco Abellan lake. The third set has a 3m/pixel ground resolution, covers about 100km² and maps the Famennian rocks formations, known as part of "La Calestienne", outcropping near Beauraing and Rochefort in the Namur Province (Belgium). The DEM and orthophoto's have been referenced using ground control points from satellite imagery (Spain, Belgium) and DPGS (Belgium). The quality of produced DEM were then evaluated by comparing the level and accuracy of details and surface artefacts between available topographic data (SRTM- 30m/pixel, topographic maps) and the three Stratochip sets. This evaluation showed that the models were in good correlation with existing data, and can be readily be used in geomorphology, structural and natural hazard studies.

  6. Internet-Einzelhandel bei Multi-Channel-Unternehmen

    NASA Astrophysics Data System (ADS)

    Breidenbach, Petra; Rauh, Jürgen

    Die unterschiedliche Bedeutung des Internets zu Informations- und Kaufzwecken konnte anhand von quantitativen Online-Befragungen von Konsumenten bei Multi-Channel-Anbietern verschiedener Bedarfsfristigkeitsstufen aufgezeigt werden. Insbesondere der Wechsel zwischen verschiedenen Vertriebskanälen (Multi-Channel-Verhalten) ist sowohl mit verkehrsubstituierenden als auch verkehrgenerierenden Effekten verbunden.Dabei können von der reinen Virtualisierung von Konsumtätigkeiten durch das Internet bei Informationsprozessen Einsparungspotenziale von Informations-(such-)-Verkehr abgeleitet werden. Einsparungseffekte aufgrund von Online-Käufen stehen in Zusammenhang mit den Wechselwirkungen zwischen unternehmerischen Maßnahmen sowie vertriebskanal- und produktspezifische Akzeptanz der Konsumenten zur Nutzung des Internets. Die siedlungsstrukturelle Einordnung der Wohnorte der Konsumenten sowie unternehmerische Vertriebsnetzstrukturensind bei der Bewertung verkehrlicher Wirkung von hoher Relevanz.

  7. An Automated System of Knickpoint Definition and Extraction from a Digital Elevation Model (DEM): Implications for Efficient Large-Scale Mapping and Statistical Analyses of Knickpoint Distributions in Fluvial Networks

    NASA Astrophysics Data System (ADS)

    Neely, A. B.; Bookhagen, B.; Burbank, D. W.

    2014-12-01

    Knickpoints, or convexities in a stream's longitudinal profile, often delineate boundaries in stream networks that separate reaches eroding at different rates resulting from sharp temporal or spatial changes in uplift rate, contributing drainage area, precipitation, or bedrock lithology. We explicitly defined the geometry of a knickpoint in a manner that can be identified using an algorithm which operates in accordance with the stream power incision model, using a chi-plot analysis approach. This method allows for comparison between the real stream profile extracted from a DEM, and a linear best-fit line profile in chi-elevation space, representing a steady state theoretical stream functioning in accordance to uniform temporal and spatial conditions listed above. Assessing where the stream of interest is "under-steepened" and "over-steepened" with respect to a theoretical linear profile reveals knickpoints as certain points of slope inflection, extractable by our algorithm. We tested our algorithm on a 1m resolution LiDAR DEM of Santa Cruz Island (SCI), a tectonically active island 25km south of Santa Barbara, CA with an estimated uplift rate between 0.5 and 1.2mm/yr calculated from uplifted paleoshorelines. We have identified 1025 knickpoints using our algorithm and compared the position of these knickpoints to a similarly-sized dataset of knickpoints manually selected from distance-elevation longitudinal stream profiles for the same region. Our algorithm reduced mapping time by 99.3% and agreed with knickpoint positions from the manually selected knickpoint map for 85% of the 1025 knickpoints. Discrepancies can arise from inconsistencies in manual knickpoint selection that are not present in an automated computation. Additionally, the algorithm measures useful characteristics for each knickpoint allowing for quick statistical analyses. Histograms of knickpoint elevation and chi coordinate have a 3 peaked distribution, possibly expressing 3 levels of uplifted marine terrace platforms on SCI. Few knickpoints exist with a contributing drainage area >200,000m2, demonstrating a cutoff drainage area where knickpoint migration has stalled. We intend to use this tool to further explore the significance, evolution, and dynamics of knickpoint features on SCI.

  8. Dynamic observations of the 8 January 2010 pyroclastic flow from the Soufriere Hills Volcano, Montserrat ascertained by high-definition and FLIR video analysis, as well as geometric analysis of the DEM

    NASA Astrophysics Data System (ADS)

    Molle, A.; Ogburn, S. E.; Calder, E. S.; Roche, O.; Harris, A. J.

    2012-12-01

    On January 8th 2010, Soufriere Hills Volcano (Montserrat) experienced a collapse of the northwestern part of its andesitic lava dome. The ensuing explosive event lead to a 8.3 km high eruption column and generated a pyroclastic density current (PDC) that propagated down the northern flank of the volcano, moving down the Belham valley. This PDC was recorded from the Montserrat Volcano Observatory using both normal High- Definition and Forward Looking Infrared (FLIR) video cameras. The flow front velocity profile, plus the vertical motion of discrete buoyant thermals ascending above the PDC, were measured by combining the video data with a deposit map and a high spatial-resolution DEM. A theoretical treatment was then applied to extract key parameters that describe the buoyant motion of thermals ascending above the current (including density, particle mass volume fraction, and temperature). Interaction of the PDC with topographic features corresponded to important changes in the dynamics of the PDC as well as the ascent of the buoyant ash-clouds These interactions included an increase of the ascent rate of buoyant thermals when the PDC encountered topographic barriers, and deceleration of the flow front velocity due of high degrees of valley sinuosity. Additionally, a major change in flow dynamics was visible in our data 2 - 3 km from the dome. To investigate this further, channel slope, sinuosity, and cross-sectional area were measured from high-resolution DEMs using GIS software; and were compared to geometric parameters of the mapped ash-cloud surge deposits. The data illustrate three surge generation regimes: a proximal area of rapid lateral expansion; a medial deflation zone; and a steadier distal surge 'fringe'. These surge regimes relate directly the dramatic change in buoyant thermal flow dynamics observed 2-3 km from the dome and are also correlated with velocity and inversely correlated with valley cross-sectional area. Several possible origins can be proposed to explain this change, including changes in internal factors (i.e. degree of fluidization, sedimentation rate, and ash generation from block fragmentation) and/or external factors (influence of topographic barriers, changes in slope, sinuosity, valley-holding capacity). Complementary laboratory and dynamical observation would better constrain variations in the dynamics. Areas of topography-induced increases in velocity and inter-granular collisions are interpreted to result in more pervasive fluidization and thus enhanced surge generation. Distally, surge deposits appear as fringes with decaying extents, indicative of more passive expansion and decreasing velocity. The results indicate that surge mobility and detachment are a complex product of flow mass flux and topography and that future efforts to model dense-dilute coupled flows will need to account for and integrate several mechanisms acting on different parts of the flow.

  9. Channel planform geometry and slopes from freely available high-spatial resolution imagery and DEM fusion: Implications for channel width scalings, erosion proxies, and fluvial signatures in tectonically active landscapes

    NASA Astrophysics Data System (ADS)

    Fisher, G. Burch; Bookhagen, Bodo; Amos, Colin B.

    2013-07-01

    The rapid expansion of high-spatial resolution optical sensors and imagery over the last decade presents exceptional opportunities for quantifying visible attributes of geomorphic systems. In this study, we detail a simple, robust methodology (ChanGeom) to extract continuous channel width and centerline datasets for single-thread channels using freely available high-spatial resolution imagery currently available in Google Earth and Bing Maps. Comparisons with a global dataset of field and lidar-derived channel widths indicate minimal errors associated with the imagery and ChanGeom methodology (< 1% overall), while examples from the Goriganga River (Indian Himalaya) and the Yakima River (WA, USA) emphasize the benefit of empirical width values over established channel width scalings in deciphering fluvial responses to complex landscape forcings in tectonically active regions. Additionally, accurate centerline delineation from the ChanGeom methodology provides improved sinuosity measurements, and when fused with coarse resolution digital elevation models (DEMs), removes along-profile shortening and coincident increases in reach-scale channel slope. Lastly, comparisons of ASTER GDEM V2, SRTM V4.1, and lidar channel profiles extracted in moderate to high-relief regions demonstrate the inferiority of the ASTER GDEM for channel slope calculations, despite the apparent spatial resolution advantages (9 ×). The methodology presented here will facilitate new discoveries in the fluvial environment that have historically been difficult due to access and imagery resolution issues, and provide greater perspective on channel signatures and responses to a host of landscape forcings, especially in tectonically active bedrock and lower order drainage systems.

  10. Jagd nach dem O'Conell-Effekt

    NASA Astrophysics Data System (ADS)

    Reichmann, Norbert

    2013-03-01

    In the present paper, I focus on the O'Connell effect of the WUMa variable V502 Cyg, with the main aim of showing it in the lightcurve. 166 observations were collected in V and B band (100 and 66 measurements, respectively) from my private observatory in Kästenberg, Austria, Ossiacher Tauern, at an elevation of 890 m. All data were acquired with an Apo 130/1200 and an Apogee Alta U16M CCD camera. Photometric colour band and narrowband data were collected simultaneously and evaluated. The combination of photometric data with data for deep-sky imaging I have termed "pretty-picture-photometry". This combination of photometric measurements with colour and narrowband data is presented here in the case of V502 Cyg in its surrounding deep-sky field. Norbert Reichman is member of the BAV.

  11. Dem Bones: Forensic Resurrection of a Skeleton.

    ERIC Educational Resources Information Center

    Bruce, Alease

    2001-01-01

    Presents an activity for students to determine the sex and age of an individual from a collection of bones. Simulates some of the actual procedures conducted in a forensic anthropologist's lab, examining and identifying bones through a series of lab activities. (Author/ASK)

  12. Dem Generation with WORLDVIEW-2 Images

    NASA Astrophysics Data System (ADS)

    Büyüksalih, G.; Baz, I.; Alkan, M.; Jacobsen, K.

    2012-07-01

    For planning purposes 42 km coast line of the Black Sea, starting at the Bosporus going in West direction, with a width of approximately 5 km, was imaged by WorldView-2. Three stereo scenes have been oriented at first by 3D-affine transformation and later by bias corrected RPC solution. The result is nearly the same, but it is limited by identification of the control points in the images. Nevertheless after blunder elimination by data snooping root mean square discrepancies below 1 pixel have been reached. The root mean square discrepancy at control point height reached 0.5 m up to 1.3 m with a base to height relation between 1:1.26 and 1:1.80. Digital Surface models (DSM) with 4 m spacing have been generated by least squares matching with region growing, supported by image pyramids. A higher percentage of the mountainous area is covered by forest, requiring the approximation based on image pyramids. In the forest area the approximation just by region growing leads to larger gaps in the DSM. Caused by the good image quality of WorldView-2 the correlation coefficients reached by least squares matching are high and even in most forest areas a satisfying density of accepted points was reached. Two stereo models have an overlapping area of 1.6 km times 6.7 km allowing an accuracy evaluation. Small, but nevertheless significant differences in scene orientation have been eliminated by least squares shift of both overlapping height models to each other. The root mean square differences of both independent DSM are 1.06m or as a function of terrain inclination 0.74 m + 0.55 m  tangent (slope). The terrain inclination in the average is 7° with 12% exceeding 17°. The frequency distribution of height discrepancies is not far away from normal distribution, but as usual, larger discrepancies are more often available as corresponding to normal distribution. This also can be seen by the normalized medium absolute deviation (NMAS) related to 68% probability level of 0.83m being significant smaller as the root mean square differences. Nevertheless the results indicate a standard deviation of the single height models of 0.75 m or 0.52 m + 0.39* tangent (slope), corresponding to approximately 0.6 pixels for the x-parallax in flat terrain, being very satisfying for the available land cover. An interpolation over 10 m enlarged the root mean square differences of both height models nearly by 50%.

  13. DEM simulation of growth normal fault slip

    NASA Astrophysics Data System (ADS)

    Chu, Sheng-Shin; Lin, Ming-Lang; Nien, Wie-Tung; Chan, Pei-Chen

    2014-05-01

    Slip of the fault can cause deformation of shallower soil layers and lead to the destruction of infrastructures. Shanchiao fault on the west side of the Taipei basin is categorized. The activities of Shanchiao fault will cause the quaternary sediments underneath the Taipei basin to become deformed. This will cause damage to structures, traffic construction, and utility lines within the area. It is determined from data of geological drilling and dating, Shanchiao fault has growth fault. In experiment, a sand box model was built with non-cohesive sand soil to simulate the existence of growth fault in Shanchiao Fault and forecast the effect on scope of shear band development and ground differential deformation. The results of the experiment showed that when a normal fault containing growth fault, at the offset of base rock the shear band will develop upward along with the weak side of shear band of the original topped soil layer, and this shear band will develop to surface much faster than that of single top layer. The offset ratio (basement slip / lower top soil thickness) required is only about 1/3 of that of single cover soil layer. In this research, it is tried to conduct numerical simulation of sand box experiment with a Discrete Element Method program, PFC2D, to simulate the upper covering sand layer shear band development pace and scope of normal growth fault slip. Results of simulation indicated, it is very close to the outcome of sand box experiment. It can be extended to application in water pipeline project design around fault zone in the future. Keywords: Taipei Basin, Shanchiao fault, growth fault, PFC2D

  14. Auf dem Weg zum universellen Quantencomputer

    NASA Astrophysics Data System (ADS)

    Jaksch, Dieter; Calarco, Tommaso; Zoller, Peter

    2000-11-01

    Die Quantenmechanik eröffnet faszinierende Perspektiven für die Kommunikation und die Informationsverarbeitung. Um universell programmierbare Quantenrechner realisieren zu können bedarf es der Implementierung von Konzepten zur Quanteninformationsverarbeitung die sich auf eine große Anzahl von Qubits anwenden lassen.

  15. Future earthquake source faults on deep sea-floor around the Boso triple plate junction revealed by tectonic geomorphology using 3D images produced from 150 meter grid DEM

    NASA Astrophysics Data System (ADS)

    Goto, H.; Nakata, T.; Watanabe, M.; Suzuki, Y.; Izumi, N.; Nishizawa, A.; Horiuchi, D.; Kido, Y. N.

    2013-12-01

    Boso triple junction, which is the only example of a triple trench junction on earth, is located off the southeast of Boso peninsula, where the Izu-Bonin trench meets with the Japan trench and the Sagami trench. Boso submarine canyon, which is extended to Katsuuma basin about 7000m deep, forms an incised meander along the north side of Sagami trough. Taito spur separate Katsuuma basin from Bando abyssal basin about 9000m deep, where Japan trench meet with Isu-Bonin trench. In this paper, we present detailed stereo-paired topographic images produced from 0.002 degree (about 150m) DBEM (Digital Bathymetry Model), which processed from the depth sounding data obtained by Japan Coast Guard and JAMSTEC around Boso triple junction. It enables us to observe submarine geomorphology easily and precisely. We identified submarine active faults and other tectonic features related to subduction by using the similar standard for air-photo interpretation of inland active faults. We made more precise submarine active tectonic geomorphological map around Boso triple junction than that by previous workers. Numerous distinct faults on the so-called outer rise associated with subduction of Pacific plate are regarded as normal faulting as widely accepted. While the normal faults on the outer rise are parallel to the trench in the southern part of the Japan trench and the northern part of the Izu-Bonin trench, these normal faults around the east of the triple junction with NNW-SSE extend slightly oblique to the trench. The western margin of Bando abyssal basin is bounded by the thrust faults, which form east-facing 200-500m-high convex scarps associated with raised basin floor to the west of the scarp. These faults also deform Mogi submarine fan surface and uplift to the west along the extension of the scarp. The antecedent valley is extended for about 10km across Taito spur that is an active anticlinal ridge about 1000m high. Katsuura basin is surrounded by terraced former basin floor that is tilted to the west, indicating up-growing of Taito spur. Northeastern part of Izu bar on Philippine Sea plate is characterized by rather smooth extensive convex slope between 1500m-7500m for over 200km long along the trench. On the lower part of the slope below 6000m, several gullies such as Mikura canyon and Kita-Hachijo canyon dissecting the slope forms rapids, probably due to continuous up-warping by subsurface thrusting dipping to the west under the slope. It is noteworthy that we can identify prominent active tectonic features on even very deep sea-floor along the plate boundaries, by using 3D images produced from 150 meter grid DEM.

  16. Phenology in Germany in the 20th century : methods, analyses and models

    NASA Astrophysics Data System (ADS)

    Schaber, Jörg

    2002-07-01

    The length of the vegetation period (VP) plays a central role for the interannual variation of carbon fixation of terrestrial ecosystems. Observational data analysis has indicated that the length of the VP has increased in the last decades in the northern latitudes mainly due to an advancement of bud burst (BB). This phenomenon has been widely discussed in the context of Global Warming because phenology is correlated to temperatures. Analyzing the patterns of spring phenology over the last century in Southern Germany provided two main findings: - The strong advancement of spring phases especially in the decade before 1999 is not a singular event in the course of the 20th century. Similar trends were also observed in earlier decades. Distinct periods of varying trend behavior for important spring phases could be distinguished. - Marked differences in trend behavior between the early and late spring phases were detected. Early spring phases changed as regards the magnitude of their negative trends from strong negative trends between 1931 and 1948 to moderate negative trends between 1948 and 1984 and back to strong negative trends between 1984 and 1999. Late spring phases showed a different behavior. Negative trends between 1931 and 1948 are followed by marked positive trends between 1948 and 1984 and then strong negative trends between 1984 and 1999. This marked difference in trend development between early and late spring phases was also found all over Germany for the two periods 1951 to 1984 and 1984 to 1999. The dominating influence of temperature on spring phenology and its modifying effect on autumn phenology was confirmed in this thesis. However, - temperature functions determining spring phenology were not significantly correlated with a global annual CO2 signal which was taken as a proxy for a Global Warming pattern. - an index for large scale regional circulation patterns (NAO index) could only to a small part explain the observed phenological variability in spring. The observed different trend behavior of early and late spring phases is explained by the differing behavior of mean March and April temperatures. Mean March temperatures have increased on average over the 20th century accompanied by an increasing variation in the last 50 years. April temperatures, however, decreased between the end of the 1940s and the mid-1980s, followed by a marked warming after the mid-1980s. It can be concluded that the advancement of spring phenology in recent decades are part of multi-decadal fluctuations over the 20th century that vary with the species and the relevant seasonal temperatures. Because of these fluctuations a correlation with an observed Global Warming signal could not be found. On average all investigated spring phases advanced between 5 and 20 days between 1951 and 1999 for all Natural Regions in Germany. A marked difference be! tween late and early spring phases is due to the above mentioned differing behavior before and after the mid-1980s. Leaf coloring (LC) was delayed between 1951 and 1984 for all tree species. However, after 1984 LC was advanced. Length of the VP increased between 1951 and 1999 for all considered tree species by an average of ten days throughout Germany. It is predominately the change in spring phases which contributes to a change in the potentially absorbed radiation. Additionally, it is the late spring species that are relatively more favored by an advanced BB because they can additionally exploit longer days and higher temperatures per day advancement. To assess the relative change in potentially absorbed radiation among species, changes in both spring and autumn phenology have to be considered as well as where these changes are located in the year. For the detection of the marked difference between early and late spring phenology a new time series construction method was developed. This method allowed the derivation of reliable time series that spanned over 100 years and the construction of locally combined time series increasing the available data for model development. Apart from analyzed protocolling errors, microclimatic site influences, genetic variation and the observers were identified as sources of uncertainty of phenological observational data. It was concluded that 99% of all phenological observations at a certain site will vary within approximately 24 days around the parametric mean. This supports to the proposed 30-day rule to detect outliers. New phenology models that predict local BB from daily temperature time series were developed. These models were based on simple interactions between inhibitory and promotory agents that are assumed to control the developmental status of a plant. Apart from the fact that, in general, the new models fitted and predicted the observations better than classical models, the main modeling results were: - The bias of the classical models, i.e. overestimation of early observations and underestimation of late observations, could be reduced but not completely removed. - The different favored model structures for each species indicated that for the late spring phases photoperiod played a more dominant role than for early spring phases. - Chilling only plays a subordinate role for spring BB compared to temperatures directly preceding BB. Die Länge der Vegetationsperiode (VP) spielt eine zentrale Rolle für die interannuelle Variation der Kohlenstoffspeicherung terrestrischer Ökosysteme. Die Analyse von Beobachtungsdaten hat gezeigt, dass sich die VP in den letzten Jahrzehnten in den nördlichen Breiten verlängert hat. Dieses Phänomen wurde oft im Zusammenhang mit der globalen Erwärmung diskutiert, da die Phänologie von der Temperatur beeinflusst wird. Die Analyse der Pflanzenphänologie in Süddeutschland im 20. Jahrhundert zeigte: - Die starke Verfrühung der Frühjahrsphasen in dem Jahrzehnt vor 1999 war kein singuläres Ereignis im 20. Jahrhundert. Schon in früheren Dekaden gab es ähnliche Trends. Es konnten Perioden mit unterschiedlichem Trendverhalten identifiziert werden. - Es gab deutliche Unterschiede in den Trends von frühen und späten Frühjahrsphasen. Die frühen Frühjahrsphasen haben sich stetig verfrüht, mit deutlicher Verfrühung zwischen 1931 und 1948, moderater Verfrühung zwischen 1948 und 1984 und starker Verfrühung zwischen 1984 und 1999. Die späten Frühjahrsphasen hingegen, wechselten ihr Trendverhalten in diesen Perioden von einer Verfrühung zu einer deutlichen Verspätung wieder zu einer starken Verfrühung. Dieser Unterschied in der Trendentwicklung zwischen frühen und späten Frühjahrsphasen konnte auch für ganz Deutschland in den Perioden 1951 bis 1984 und 1984 bis 1999 beobachtet werden. Der bestimmende Einfluss der Temperatur auf die Frühjahrsphasen und ihr modifizierender Einfluss auf die Herbstphasen konnte bestätigt werden. Es zeigt sich jedoch, dass - die Phänologie bestimmende Funktionen der Temperatur nicht mit einem globalen jährlichen CO2 Signal korreliert waren, welches als Index für die globale Erwärmung verwendet wurde - ein Index für grossräumige regionale Zirkulationsmuster (NAO-Index) nur zu einem kleinen Teil die beobachtete phänologischen Variabilität erklären konnte. Das beobachtete unterschiedliche Trendverhalten zwischen frühen und späten Frühjahrsphasen konnte auf die unterschiedliche Entwicklung von März- und Apriltemperaturen zurückgeführt werden. Während sich die Märztemperaturen im Laufe des 20. Jahrhunderts mit einer zunehmenden Variabilität in den letzten 50 Jahren stetig erhöht haben, haben sich die Apriltemperaturen zwischen dem Ende der 1940er und Mitte der 1980er merklich abgekühlt und dann wieder deutlich erwärmt. Es wurde geschlussfolgert, dass die Verfrühungen in der Frühjahrsphänologie in den letzten Dekaden Teile multi-dekadischer Fluktuationen sind, welche sich nach Spezies und relevanter saisonaler Temperatur unterscheiden. Aufgrund dieser Fluktuationen konnte kein Zusammenhang mit einem globalen Erwärmungsignal gefunden werden. Im Durchschnitt haben sich alle betrachteten Frühjahrsphasen zwischen 1951 und 1999 in Naturräumen in Deutschland zwischen 5 und 20 Tagen verfrüht. Ein starker Unterschied in der Verfrühung zwischen frühen und späten Frühjahrsphasen liegt an deren erwähntem unterschiedlichen Verhalten. Die Blattverfärbung hat sich zwischen 1951 und 1999 für alle Spezies verspätet, aber nach 1984 im Durchschnitt verfrüht. Die VP hat sich in Deutschland zwischen 1951 und 1999 um ca. 10 Tage verlängert. Es ist hauptsächlich die Änderung in den Frühjahrphasen, die zu einer Änderung in der potentiell absorbierten Strahlung (PAS) führt. Darüber hinaus sind es die späten Frühjahrsphasen, die pro Tag Verfrühung stärker profitieren, da die zusätzlichen Tage länger undwärmer sind als dies für die frühen Phasen der Fall ist. Um die relative Änderung in PAS im Vergleich der Spezies abzuschätzen, müssen allerdings auch die Veränderungen in den Herbstphasen berücksichtigt werden. Der deutliche Unterschied zwischen frühen und späten Frühjahrsphasen konnte durch die Anwendung einer neuen Methode zur Konstruktion von Zeitreihen herausgearbeitet werden. Der neue methodische Ansatz erlaubte die Ableitung verlässlicher 100-jähriger Zeitreihen und die Konstruktion von lokalen kombinierten Zeitreihen, welche die Datenverfügbarkeit für die Modellentwicklung erhöhten. Ausser analysierten Protokollierungsfehlern wurden mikroklimatische, genetische und Beobachtereinflüsse als Quellen von Unsicherheit in phänologischen Daten identifiziert. Phänologischen Beobachtungen eines Ortes können schätzungsweise 24 Tage um das parametrische Mittel schwanken.Dies unterstützt die 30-Tage Regel für die Detektion von Ausreissern. Neue Phänologiemodelle, die den Blattaustrieb aus täglichen Temperaturreihen simulieren, wurden entwickelt. Diese Modelle basieren auf einfachen Interaktionen zwischen aktivierenden und hemmenden Substanzen, welche die Entwicklungsstadien einer Pflanze bestimmen. Im Allgemeinen konnten die neuen Modelle die Beobachtungsdaten besser simulieren als die klassischen Modelle. Weitere Hauptresultate waren: - Der Bias der klassischen Modelle, d.h. Überschätzung von frühen und Unterschätzung von späten Beobachtungen, konnte reduziert, aber nicht vollständig eliminiert werden. - Die besten Modellvarianten für verschiedene Spezies wiesen darauf hin, dass für die späten Frühjahrsphasen die Tageslänge eine wichtigere Rolle spielt als für die frühen Phasen. - Die Vernalisation spielte gegenüber den Temperaturen kurz vor dem Blattaustrieb nur eine untergeordnete Rolle.

  17. Unfälle mit Schienenfahrzeugen

    NASA Astrophysics Data System (ADS)

    Burg, Heinz

    Auf einer viel befahrenen Kreuzung ereignete sich in der Winterzeit und gegen Mitternacht eine Kollision zwischen einer Straßenbahn (roter Pfeil) und einem Polizeifahrzeug (blauer Pfeil). Die Straßenbahn hat als schienengebundenes Fahrzeug gegenüber dem sonstigen Verkehr ein Vorrecht. Das Polizeifahrzeug war auf einer Einsatzfahrt zu einem Wohnungsbrand und hatte insoweit auch ein Vorrecht, da unstreitig Blaulicht und Signalhorn eingeschaltet waren. Das Gutachten war in einem Zivilprozess zu erstatten. Nach dem Gerichtsauftrag sollte zu folgenden Parteibehauptungen Stellung genommen werden:

  18. Equations of Motion for Test Particles with Internal Structure

    NASA Astrophysics Data System (ADS)

    Fuchs, Helmut

    The general structure of equations of motion for test particles is considered with the help of a Lagrangian principle postulating a minimal coupling between internal and external variables. As an example the case of the Lorentz group as the basic internal group is considered in more detail. The connection with the Mathisson-Papapetrou equations is established.Translated AbstractBewegungsgleichungen für Test-Teilchen mit innerer StrukturWir untersuchen die allgemeine Struktur von Bewegungsgleichungen mit Hilfe eines Lagrange-Prinzips mit minimaler Kopplung zwischen inneren und äußeren Variablen. Der Fall, für den die zugrunde liegende innere Gruppe die Lorentz-Gruppe ist, wird genauer betrachtet und der Zusammenhang mit den Gleichungen von Mathisson und Papapetrou dargestellt.

  19. Einstellung und Wissen von Lehramtsstudierenden zur Evolution - ein Vergleich zwischen Deutschland und der Türkei

    NASA Astrophysics Data System (ADS)

    Graf, Dittmar; Soran, Haluk

    Es wird eine Untersuchung vorgestellt, in der Wissen und Überzeugungen von Lehramtsstudierenden aller Fächer zum Thema Evolution an zwei Universitäten in Deutschland und der Türkei erhoben worden sind. Die Befragung wurde in Dortmund und in Ankara durchgeführt. Es stellte sich heraus, dass ausgeprägte Defizite im Verständnis der Evolutionsmechanismen herrschen. Viele Studierende, insbesondere aus der Türkei, sind nicht von der Faktizität der Evolution überzeugt. Dies gilt sowohl für Studierende mit Fach Biologie als auch für Studierende mit anderen Fächern. Näher untersucht worden sind die Faktoren, die die Überzeugungen zur Evolution beeinflussen können, was ja in Anbetracht der hohen Ablehnungsrate der Evolution von besonderem Interesse ist. Das Vertrauen in die Wissenschaft spielt hierbei eine besondere Rolle: Wer der Wissenschaft vertraut, ist auch eher von der Evolution überzeugt, als diejenigen, die skeptisch gegenüber der Wissenschaft sind.

  20. Diskrepanzen und Kongruenzen: Das Dilemma des afrikanischen Kindes zwischen Familie und Schule

    NASA Astrophysics Data System (ADS)

    Bauer, Annemarie

    1986-03-01

    This article expounds the theory that the failure of school is due to the incompatibility of the educational goals of school and traditional upbringing in Africa. The thesis is put forward by adherents of the psychoanalytical model of child development and seeks to emphasize the discrepancies between the childhood where children are not frustrated and where their needs are cared for and the school education which represses the drives and its socialization of children. Finding a number of anthropological studies are discussed and reinterpretations of the ethno-psychoanalytical materials attempted. Neither the evaluation of childhood in Africa nor the theory that with school come wholly new expectations of behaviour (e.g., a performance requirement) can no longer be maintained. In conclusion, other explanations for the difficulties encountered by school in Africa are offered.

  1. Der Haupthistokompatibilitätskomplex und die Unterscheidung zwischen Selbst und Fremd durch das Immunsystem

    NASA Astrophysics Data System (ADS)

    Klein, Jan; Rammensee, Hans-Georg; Nagy, Zoltan A.

    1983-06-01

    The major histocompatibility complex (Mhc) is a cluster of closely linked genes which are involved in the distinction between self and non-self. The genes fall into two classes, I and II, which are evolutionarily related but specialized to performing somewhat different functions. The Mhc genes code for proteins which are seen together with foreign substances by the thymus-derived lymphocytes. These lymphocytes thus recognize simultaneously self (Mhc molecules) and non-self (foreign antigen). Some of the Mhc genes are highly polymorphic and this polymorphism probably represents a compensation for the fact that certain combinations of Mhc molecules and antigen fail to be recognized by the T lymphocyte.

  2. Christoph Scheiner's life between 1633 and 1650. (German Title: Christoph Scheiners Lebensjahre zwischen 1633 und 1650)

    NASA Astrophysics Data System (ADS)

    Daxecker, Franz

    In 1636, Christoph Scheiner left Rome where the trial of Galilei had taken place, and went to Vienna. The financing of his main work ``Rosa Ursina'' had to be clarified. Until 1636, Scheiner was not in office From 1636 onward, he was alternatively living in Neiße -- today Nysa (Silesia, Poland) -- and Vienna, from 1637 onward, he took his permanent residence in Neiße. Here, Scheiner worked as an advisor of the rector and as father confessor, in addition he gave religious lectures and looked after the garden.

  3. Zwischen Commonsense und Wissenschaft Mathematik in der Erziehungsphilosophie A. N. Whiteheads

    NASA Astrophysics Data System (ADS)

    Slch, Dennis

    Obwohl Whitehead heute wie selbstverstndlich als Philosoph rezipiert wird, so hat er seine wissenschaftliche Laufbahn doch als Mathematiker begonnen. Lange Zeit war er gemeinsam mit Bertrand Russell als Autor der Principia Mathematica unter Mathematikern und mathematischen Logikern deutlich besser bekannt als unter Philosophen. Doch selbst von denjenigen, die sich mit Whiteheads berlegungen zur Metaphysik, zur Wissenschaftsgeschichte und zur Theologie befassen, werden seine Schriften zur Philosophie von Erziehung und Bildung hufig kaum beachtet. So entgeht es leicht, dass Whitehead nicht nur ein auf theoretischem Gebiet brillanter Mathematiker war, sondern sein theoretisches Fachwissen im Hinblick auf pdagogische und didaktische Relevanz fortwhrend reflektiert hat.

  4. Wechselwirkungen zwischen Grundwasser und Oberflächenwasser an einem Tieflandfluss (Spree)

    NASA Astrophysics Data System (ADS)

    Nützmann, G.; Lewandowski, J.

    2009-09-01

    Water exchange processes in the floodplain of a lowland groundwater-surface water system are studied on the basis of a study site near Freienbrink, NE Germany. The boundaries of this site are formed by an oxbow and the current bed of the river Spree, section Müggelspree. Surface and ground water levels were collected in 12 piezometers and at two recording stage gauges of a 300 m long transect throughout a one-year-period. Due to water level fluctuations, alternating periods of infiltration and exfiltration have been observed. However, most of the time groundwater flux is directed into the river Spree and river water infiltration events into the aquifer are usually short and of minor importance. Due to clogging of the oxbow bed, the hydraulic contact between the oxbow and the adjacent aquifer is marginal. These features are modelled quantitatively using MODFLOW in order to simulate ground water flow in the local aquifer.

  5. Die Amtliche Sammlung von Untersuchungsverfahren nach § 64 LFGB, § 35 Vorläufiges Tabakgesetz und § 28b Gentechnikgesetz - ein Instrument der amtlichen Lebensmittelüberwachung

    NASA Astrophysics Data System (ADS)

    Renger, Silke; Stachel, Carolin

    Immer wieder werden Skandale in Zusammenhang mit Lebensmitteln bekannt. Schlagworte wie BSE, Gammelfleisch, Acrylamid, Cumarin oder auch Melamin, Dioxin sind den Verbrauchern geläufig und erschüttern das Vertrauen in ein gesundes und ernährungsphysiologisch wertvolles Lebensmittel. Das Bewusstsein des Verbrauchers hinsichtlich der Ernährung und der Auswahl beim Kauf der Lebensmittel hat sich in den vergangenen Jahren deutlich verändert. Bei der Auswahl seiner Lebensmittel liegt sein Augenmerk verstärkt auf gesunden, qualitativ hochwertigen und vor allem sicheren Lebensmitteln. Dies wurde insbesondere bei dem verhaltenen Kauf von Fleisch und Fleischerzeugnissen während der BSE-Krise oder auch dem kürzlich aufgetretenen Gammelfleischskandal deutlich.

  6. Gestresste Haut? - Aktueller Stand molekularer psychosomatischer Zusammenhänge und ihr Beitrag zu Ursachen und Folgen dermatologischer Erkrankungen.

    PubMed

    Peters, Eva M J

    2016-03-01

    In den 70er Jahren des vergangenen Jahrhunderts wurde zum ersten Mal ein pathogenetisch relevanter Zusammenhang zwischen Stress, im Sinne von psychosozialem Stress, und Krankheit am Beispiel von viralen Erkrankungen der Schleimhäute (wie Rhinovirus-, Coxsackie-Infektion) nachgewiesen. Seither nehmen Publikationen, die diese Zusammenhänge bis auf die molekulare Ebene erforschen, jährlich zu. Dennoch sind die Evidenzen für einen Einfluss von psychosozialer Belastung auf chronisch-entzündliche Hauterkrankungen und auf Hauttumoren wenig bekannt. In diesem Beitrag fassen wir die aktuellen Erkenntnisse aus Epidemiologie, Psychoneuroimmunologie und molekularer Psychosomatik narrativ zusammen. Sie belegen die vielfältigen krankheitsrelevanten Interaktionen zwischen endokrinem System, Nervensystem und Immunsystem. Im Fokus stehen stressinduzierte Verschiebungen in der Immunbalance bei ausgewählten Erkrankungen wie Neurodermitis, Psoriasis oder malignem Melanom. Ziel dieses Beitrages ist die Vermittlung psychosomatischen Grundlagenwissens bei chronischen Dermatosen. Dies reicht von der Ätiologie über die Symptomatik bis zu den therapeutischen Optionen. Besonderes Augenmerk liegt dabei auf den zugrunde liegenden molekularen Zusammenhängen sowohl aus der somatopsychischen als auch aus der psychosomatischen Perspektive. PMID:26972186

  7. "Dem Wod Mo Saf": Materials for Reading Creole English.

    ERIC Educational Resources Information Center

    Kephart, Ronald

    As part of a study that sought ways to improve the language arts educational experience for Grenadian children, an anthropologist investigated how Carriacou Creole English (CCE) reading materials could be provided and how these children would react to them. CCE is the native language of the inhabitants of Carriacou, a sister island of Grenada. The…

  8. A DEM contact model for history-dependent powder flows

    NASA Astrophysics Data System (ADS)

    Hashibon, Adham; Schubert, Raphael; Breinlinger, Thomas; Kraft, Torsten

    2016-01-01

    Die filling is an important part of the powder handling process chain that greatly influences the characteristic structure and properties of the final part. Predictive modelling and simulation of the die-filling process can greatly contribute to the optimization of the part and the whole production procedure, e.g. by predicting the resulting powder compaction structure as a function of filling process parameters. The rheology of powders can be very difficult to model especially if heterogeneous agglomeration or time-dependent consolidation effects occur. We present a new discrete element contact force model that enables modelling complex powder flow characteristics including direct time-dependent consolidation effects and load history-dependent cohesion to describe the filling process of complex, difficult to handle powders. The model is demonstrated for simple flow and an industrial powder flow.

  9. Forecasting of Storm Surge Floods Using ADCIRC and Optimized DEMs

    NASA Technical Reports Server (NTRS)

    Valenti, Elizabeth; Fitzpatrick, Patrick

    2005-01-01

    Increasing the accuracy of storm surge flood forecasts is essential for improving preparedness for hurricanes and other severe storms and, in particular, for optimizing evacuation scenarios. An interactive database, developed by WorldWinds, Inc., contains atlases of storm surge flood levels for the Louisiana/Mississippi gulf coast region. These atlases were developed to improve forecasting of flooding along the coastline and estuaries and in adjacent inland areas. Storm surge heights depend on a complex interaction of several factors, including: storm size, central minimum pressure, forward speed of motion, bottom topography near the point of landfall, astronomical tides, and most importantly, maximum wind speed. The information in the atlases was generated in over 100 computational simulations, partly by use of a parallel-processing version of the ADvanced CIRCulation (ADCIRC) model. ADCIRC is a nonlinear computational model of hydrodynamics, developed by the U.S. Army Corps of Engineers and the US Navy, as a family of two- and three-dimensional finite element based codes. It affords a capability for simulating tidal circulation and storm surge propagation over very large computational domains, while simultaneously providing high-resolution output in areas of complex shoreline and bathymetry. The ADCIRC finite-element grid for this project covered the Gulf of Mexico and contiguous basins, extending into the deep Atlantic Ocean with progressively higher resolution approaching the study area. The advantage of using ADCIRC over other storm surge models, such as SLOSH, is that input conditions can include all or part of wind stress, tides, wave stress, and river discharge, which serve to make the model output more accurate.

  10. Kafka's "Vor dem Gesetz": The Case for an Integrated Approach

    ERIC Educational Resources Information Center

    Pickar, Gertrud Bauer

    1975-01-01

    Uses a parable from a Kafka novel to illustrate and support the premise that language and literature study should be integrated, even in the early stages. Reading short literary works can explain involved language problems better than long explanations, and can also stimulate further literary study. (CHK)

  11. DEM Solutions Develops Answers to Modeling Lunar Dust and Regolith

    NASA Technical Reports Server (NTRS)

    Dunn, Carol Anne; Calle, Carlos; LaRoche, Richard D.

    2010-01-01

    With the proposed return to the Moon, scientists like NASA-KSC's Dr. Calle are concerned for a number of reasons. We will be staying longer on the planet's surface, future missions may include dust-raising activities, such as excavation and handling of lunar soil and rock, and we will be sending robotic instruments to do much of the work for us. Understanding more about the chemical and physical properties of lunar dust, how dust particles interact with each other and with equipment surfaces and the role of static electricity build-up on dust particles in the low-humidity lunar environment is imperative to the development of technologies for removing and preventing dust accumulation, and successfully handling lunar regolith. Dr. Calle is currently working on the problems of the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces, particularly to those of Mars and the Moon, and is heavily involved in developing instrumentation for future planetary missions. With this end in view, the NASA Kennedy Space Center's Innovative Partnerships Program Office partnered with OEM Solutions, Inc. OEM Solutions is a global leader in particle dynamics simulation software, providing custom solutions for use in tackling tough design and process problems related to bulk solids handling. Customers in industries such as pharmaceutical, chemical, mineral, and materials processing as well as oil and gas production, agricultural and construction, and geo-technical engineering use OEM Solutions' EDEM(TradeMark) software to improve the design and operation of their equipment while reducing development costs, time-to-market and operational risk. EDEM is the world's first general-purpose computer-aided engineering (CAE) tool to use state-of-the-art discrete element modeling technology for the simulation and analysis of particle handling and manufacturing operations. With EDEM you'can quickly and easily create a parameterized model of your granular solids system. Computer-aided design (CAD) models of real particles can be imported to obtain an accurate representation of their shape. EDEM(TradeMark) uses particle-scale behavior models to simulate bulk solids behavior. In addition to particle size and shape, the models can account for physical properties of particles along with interaction between particles and with equipment surfaces and surrounding media, as needed to define the physics of a particular process.

  12. Ratchet models of molecular motors

    NASA Astrophysics Data System (ADS)

    Jaster, Nicole

    2003-09-01

    Transport processes in and of cells are of major importance for the survival of the organism. Muscles have to be able to contract, chromosomes have to be moved to opposing ends of the cell during mitosis, and organelles, which are compartments enclosed by membranes, have to be transported along molecular tracks. Molecular motors are proteins whose main task is moving other molecules.For that purpose they transform the chemical energy released in the hydrolysis of ATP into mechanical work. The motors of the cytoskeleton belong to the three super families myosin, kinesin and dynein. Their tracks are filaments of the cytoskeleton, namely actin and the microtubuli. Here, we examine stochastic models which are used for describing the movements of these linear molecular motors. The scale of the movements comprises the regime of single steps of a motor protein up to the directed walk along a filament. A single step bridges around 10 nm, depending on the protein, and takes about 10 ms, if there is enough ATP available. Our models comprise M states or conformations the motor can attain during its movement along a one-dimensional track. At K locations along the track transitions between the states are possible. The velocity of the protein depending on the transition rates between the single states can be determined analytically. We calculate this velocity for systems of up to four states and locations and are able to derive a number of rules which are helpful in estimating the behaviour of an arbitrary given system. Beyond that we have a look at decoupled subsystems, i.e., one or a couple of states which have no connection to the remaining system. With a certain probability a motor undergoes a cycle of conformational changes, with another probability an independent other cycle. Active elements in real transport processes by molecular motors will not be limited to the transitions between the states. In distorted networks or starting from the discrete Master equation of the system, it is possible to specify horizontal rates, too, which furthermore no longer have to fulfill the conditions of detailed balance. Doing so, we obtain unique, complete paths through the respective network and rules for the dependence of the total current on all the rates of the system. Besides, we view the time evolutions for given initial distributions. In enzymatic reactions there is the idea of a main pathway these reactions follow preferably. We determine optimal paths and the maximal flow for given networks. In order to specify the dependence of the motor's velocity on its fuel ATP, we have a look at possible reaction kinetics determining the connection between unbalanced transitions rates and ATP-concentration. Depending on the type of reaction kinetics and the number of unbalanced rates, we obtain qualitatively different curves connecting the velocity to the ATP-concentration. The molecular interaction potentials the motor experiences on its way along its track are unknown. We compare different simple potentials and the effects the localization of the vertical rates in the network model has on the transport coefficients in comparison to other models. Transportvorgänge in und von Zellen sind von herausragender Bedeutung für das Überleben des Organismus. Muskeln müssen sich kontrahieren können, Chromosomen während der Mitose an entgegengesetzte Enden der Zelle bewegt und Organellen, das sind von Membranen umschlossene Kompartimente, entlang molekularer Schienen transportiert werden. Molekulare Motoren sind Proteine, deren Hauptaufgabe es ist, andere Moleküle zu bewegen. Dazu wandeln sie die bei der ATP-Hydrolyse freiwerdende chemische Energie in mechanische Arbeit um. Die Motoren des Zellskeletts gehören zu den drei Superfamilien Myosin, Kinesin und Dynein. Ihre Schienen sind Filamente des Zellskeletts, Actin und die Microtubuli. In dieser Arbeit werden stochastische Modelle untersucht, welche dazu dienen, die Fortbewegung dieser linearen molekularen Motoren zu beschreiben. Die Skala, auf der wir die Bewegung betrachten, reicht von einzelnen Schritten eines Motorproteins bis in den Bereich der gerichteten Bewegung entlang eines Filaments. Ein Einzelschritt überbrückt je nach Protein etwa 10 nm und wird in ungefähr 10 ms zurückgelegt. Unsere Modelle umfassen M Zustände oder Konformationen, die der Motor annehmen kann, während er sich entlang einer eindimensionalen Schiene bewegt. An K Orten dieser Schiene sind Übergänge zwischen den Zuständen möglich. Die Geschwindigkeit des Proteins lässt sich in Abhängigkeit von den vertikalen Übergangsraten zwischen den einzelnen Zuständen analytisch bestimmen. Wir berechnen diese Geschwindigkeit für Systeme mit bis zu vier Zuständen und Orten und können weiterhin eine Reihe von Regeln ableiten, die uns einschätzen helfen, wie sich ein beliebiges vorgegebenes System verhalten wird. Darüber hinaus betrachten wir entkoppelte Subsysteme, also einen oder mehrere Zustände, die keine Verbindung zum übrigen System haben. Mit einer bestimmten Wahrscheinlichkeit kann ein Motor einen Zyklus von Konformationen durchlaufen, mit einer anderen Wahrscheinlichkeit einen davon unabhängigen anderen. Aktive Elemente werden in realen Transportvorgängen durch Motorproteine nicht auf die Übergänge zwischen den Zuständen beschränkt sein. In verzerrten Netzwerken oder ausgehend von der diskreten Mastergleichung des Systems können auch horizontale Raten spezifiziert werden und müssen weiterhin nicht mehr die Bedingungen der detaillierten Balance erfüllen. Damit ergeben sich eindeutige, komplette Pfade durch das jeweilige Netzwerk und Regeln für die Abhängigkeit des Gesamtstroms von allen Raten des Systems. Außerdem betrachten wir die zeitliche Entwicklung für vorgegebene Anfangsverteilungen. Bei Enzymreaktionen gibt es die Idee des Hauptpfades, dem diese bevorzugt folgen. Wir bestimmen optimale Pfade und den maximalen Fluss durch vorgegebene Netzwerke. Um darüber hinaus die Geschwindigkeit des Motors in Abhängigkeit von seinem Treibstoff ATP angeben zu können, betrachten wir mögliche Reaktionskinetiken, die den Zusammenhang zwischen den unbalancierten Übergangsraten und der ATP-Konzentration bestimmen. Je nach Typ der Reaktionskinetik und Anzahl unbalancierter Raten ergeben sich qualitativ unterschiedliche Verläufe der Geschwindigkeitskurven in Abhängigkeit von der ATP-Konzentration. Die molekularen Wechselwirkungspotentiale, die der Motor entlang seiner Schiene erfährt, sind unbekannt.Wir vergleichen unterschiedliche einfache Potentiale und die Auswirkungen auf die Transportkoeffizienten, die sich durch die Lokalisation der vertikalen Übergänge im Netzwerkmodell im Vergleich zu anderen Ansätzen ergeben.

  13. „Überholen ohne einzuholen“ Die Entwicklung von Technologien für übermorgen in Kernenergie und Mikroelektronik der DDR

    NASA Astrophysics Data System (ADS)

    Barkleit, Gerhard

    Dem nuklearen Patt zwischen Ostblock und westlichem Staatenbündnis ist es nach weitgehend übereinstimmender Auffassung von Politik und Wissenschaft zu danken, dass der "Kalte Krieg" in der zweiten Hälfte des 20. Jahrhunderts nicht zum weltumfassenden Flächenbrand eskalierte. An der raschen Herstellung dieses Patts waren zwei Dresdner Physiker maßgeblich beteiligt, deren einer im Manhattan-Projekt in den USA gearbeitet hatte und später in England der Spionage für die Sowjetunion und des Verrats des Know-how der Atombombe überführt wurde.

  14. Aufbau von organisationsübergreifenden Fehlermanagementprozessen im Projekt IntegraTUM

    NASA Astrophysics Data System (ADS)

    Hommel, Wolfgang; Knittl, Silvia

    Das Projekt IntegraTUM wird in enger Kooperation zwischen der Technischen Universität München (TUM) und dem Leibniz-Rechenzentrum (LRZ) durchgeführt. In diesem Projekt werden Dienste gemeinsam entwickelt, die nachhaltig vom LRZ betrieben werden sollen. Die damit verbundene Rezentralisierung erfordert auch eine enge Kooperation im Falle von technischen Störungen und Fehlern im Betriebsablauf bei diesen Diensten über die Organisationsgrenzen hinweg. Unsere Aktivitäten in diesem organisationsübergreifenden Fehlermanagement werden hier beschrieben.

  15. Between handicraft and science: Friedrich Schwab (1858 - 1931). (German Title: Zwischen Handwerk und Wissenschaft: Friedrich Schwab (1858 - 1931))

    NASA Astrophysics Data System (ADS)

    Brosche, Peter; Zsoldos, Endre

    So far only fragments are known of the biography of Friedrich Schwab. Now that we were able to clear up the essentials of his life, it exhibits an exemplary character between handicraft and science. He tried to apply his talents if possible at scientific expeditions and at higher teaching institutions but did not hesitate to change positions and countries if the circumstances were unacceptable. He served astronomy in his youth as mechanic of the German Venus transit expedition 1882 to the straits of Magellan, later and preponderantly as a long standing observer of variable stars. The inspection of the literature proves that his work was received as serious by the contemporaneous professionals.

  16. Schadstoffmassenströme zwischen Grundwasser, Flussbettsedimenten und Oberflächenwasser am regional kontaminierten Standort Bitterfeld

    NASA Astrophysics Data System (ADS)

    Schmidt, C.; Kalbus, E.; Krieg, R.; Bayer-Raich, M.; Leschik, S.; Reinstorf, F.; Martienssen, M.; Schirmer, M.

    2008-09-01

    As a result of intensive industrial, mining, and urban development, numerous large-scale contaminated areas exist in Germany. These so-called megasites represent a challenge to risk assessment and remediation strategies. At the Bitterfeld megasite, the contaminated groundwater interacts with the local streams. Along a stream reach 280 m long, the mass flow rates of chlorinated benzenes were estimated by combining integral pumping tests, streambed temperature mapping, and analyses of contaminant concentrations in the streambed sediments. On average, a total mass flow rate of 617 mg d-1 monochlorobenzene (MCB) and 157 mg d-1 dichlorobenzene (DCB) is released from the adjoining aquifer into the stream along the investigated reach. Further, the streambed sediment acts as the dominant contaminant source. Considering the streambed sediments, the contaminant mass flow rate to the river increases to values between 2,355 and 4,323 mg d-1 MCB and between 892 and 3,587 mg d-1 DCB.

  17. Zwischen Web 2.0, virtuellen Welten und Game-based Learning - Einsatzszenarien und Prototypen im Hochschulumfeld

    NASA Astrophysics Data System (ADS)

    Pongratz, Hans

    Web 2.0, virtuelle Welten und Game-based Learning werden als Allheilmittel moderner Wissensvermittlung an Hochschulen genannt. Dieser Artikel beschreibt nach einer Einführung in die Thematik Einsatzszenarien und Prototypen im Hochschulumfeld anhand ausgewählter Web 2.0-Dienste, der virtuellen Welt Second Life, eines an der TUM entwickelten Frameworks für Gamebased Learning Applikationen und eines Lernspiels. Diese werden anhand von konkreten Lehr- und Lernszenarien vorgestellt und anhand der bisherigen Erfahrungen in diesem Bereich kritisch beleuchtet.