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Sample records for erdproben aus dem

  1. Reisen im freien Fall - Teil 2: Das Zwillingsparadoxon aus dem Blickwinkel der ART

    NASA Astrophysics Data System (ADS)

    Sonne, Bernd; Weiß, Reinhard

    2013-07-01

    Nachdem wir uns mit den Prinzipien der ART und einigen Beispielen vertraut gemacht haben, kommen wir nun zur Berechnung des Zwillingsparadoxons aus Sicht des reisenden Zwillings. Dabei spielt das Äquivalenzprinzip eine große Rolle. Deshalb wird die Bewegungssituation noch einmal erläutert, diesmal aus Sicht von Katrin. Sie befindet sich in ihrem System S'in Ruhe. In ihrem System läuft die Zeit t'ab. Nach dem Start fühlt Katrin jedoch eine Kraft, die sie als Gravitationskraft interpretieren kann. Sie merkt es daran, dass sie in den Sitz gedrückt wird. Nach einiger Zeit werden die Triebwerke abgeschaltet, und das Raumschiff fliegt mit konstanter Geschwindigkeit weiter, Phase 2. Anschließend wird der Schub der Triebwerke solange umgekehrt, bis das Raumschiff irgendwo mit der Geschwindigkeit null am Umkehrpunkt U landet, Phase 3 (Abb. 15.1). Die Erde, auf der sich Michael befindet, bewegt sich mit x'(t') aus Sicht von Katrin im freien Fall von ihr weg, s. das Experiment mit dem steigenden Fahrstuhl in Abschn. 13.2.1.

  2. Weichteile von Fossilien aus dem Erdaltertum

    NASA Astrophysics Data System (ADS)

    Müller, Klaus J.

    1982-06-01

    Phosphatisation of small, soft-bodied fossils in the Upper Cambrian of Sweden yielded rich faunal assemblages, mainly of arthropods, which have been isolated from the rock by etching techniques. The highly diverse fossils are uncompressed and constitute the best preserved material known from the Paleozoic era, exposing minute details such as fine bristles, pores of glands, and eyes. Agnostus clearly has biramous appendages and therefore, cannot be regarded as trilobite anymore. The Crustacea are the most widespread components of the phosphatised fauna. The representatives of a separate order of Ostracoda already have been studied in some detail. Other primordial crustaceans include nauplius stages and show a surprising diversity in specialisation. A similar occurrence in Upper Devonian from the Carnic Alps demonstrates that this mode of preservation is not restricted to a single environment, but also can be expected elsewhere.

  3. AusEinetter, 1997.

    ERIC Educational Resources Information Center

    AusEinetter, 1997

    1997-01-01

    This document comprises the two AusEinetter newsletters published in 1997. The first newletter describes the background and structure of Australia's Early Intervention Network for Mental Health in Young People (AusEinet) and discusses the necessity of early intervention for mental health issues in young people 5-25 years of age. The following…

  4. Ostracoden von Hawaii, insbesondere aus dem marinen Interstitial

    NASA Astrophysics Data System (ADS)

    Hartmann, G.

    1991-03-01

    The present paper deals with ostracods collected by H. Kunz during October and November 1979 on the Hawaiian Islands (Big Island, Maui and Kauai). 26 species were found, nine species are described, two were already known to science, 15 remain in open nomenclature. Although some of the new species are represented only by a single specimen, the morphologic characters permit to distinguish them from other species of the genus. The ostracods of the Hawaiian Islands are very imperfectly known.

  5. 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.

  6. 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.

  7. Vollautomatische Segmentierung der Prostata aus 3D-Ultraschallbildern

    NASA Astrophysics Data System (ADS)

    Heimann, Tobias; Simpfendörfer, Tobias; Baumhauer, Matthias; Meinzer, Hans-Peter

    Diese Arbeit beschreibt ein modellbasiertes Verfahren zur Segmentierung der Prostata aus 3D-Ultraschalldaten. Kern der Methode ist ein statistisches Formmodell, das auf Beispieldaten der Prostata trainiert wird. Erster Schritt der Segmentierung ist ein evolutionärer Algorithmus, mit dem das Modell grob im zu segmentierenden Bild positioniert wird. Für die darauf folgende lokale Suche wurden mehrere Varianten des Algorithmus evaluiert, unter anderem Ausreißer-Unterdrückung, freie Deformation und Gewichtung der verwendeten Erscheinungsmodelle nach ihrer Zuverlässigkeit. Alle Varianten wurden auf 35 Ultraschallbildern getestet und mit manuellen Referenzsegmentierungen verglichen. Die beste Variante erreichte eine durchschnittliche Oberflächenabweichung von 1.1 mm.

  8. 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.

  9. 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.

  10. Political Participation of Non-Citzens in Germany and Western Europe. (Beitrage aus dem Fachbereich Padagogik).

    ERIC Educational Resources Information Center

    Reuter, Lutz R.

    This paper compares the present social, economic, and political rights labor immigrants enjoy within the European Community (EC). Its focus is the current debate about the municipal suffrage of permanent residents. The dual relevance of the topic is obvious. EC bodies like the Commission, Council of Ministers, Political Council, and European…

  11. 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.

  12. 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).

  13. Wasserundurchlässige Bauten aus Beton

    NASA Astrophysics Data System (ADS)

    Lohmeyer, Gottfried C. O.

    Für die Dichtigkeit von Bauwerken oder Bauteilen ist außer der Verwendung geeigneter Abdichtungsstoffe auch eine günstige Konstruktion von Bedeutung. Sofern die Abdichtung nicht nach DIN 18195 "Bauwerksabdichtungen“ mit den dort genannten Stoffen erfolgt (z.B. Bitumen- oder Kunststoffdichtungsbahnen) oder Sonderabdichtungen zum Einsatz kommen, ist die Abdichtung mit Beton auszuführen, der einen hohen Wassereindringwiderstand aufweist. Dieser Beton wird auch als wasserundurchlässiger Beton (WU-Beton) bezeichnet. Maßgebend für das Bauen mit wasserundurchlässigem Beton sind die Normen DIN 1045-1 bis 1045-4 "Tragwerke aus Beton, Stahlbeton und Spannbeton“ [10.1, 10.2] und die Richtlinie "Wasserundurchlässige Bauwerke aus Beton (WU-Richtlinie)“ vom Deutschen Ausschuss für Stahlbeton DAfStb [10.19].

  14. 3D-Meshes aus medizinischen Volumendaten

    NASA Astrophysics Data System (ADS)

    Zelzer, Sascha; Meinzer, Hans-Peter

    Diese Arbeit beschreibt eine template-basierte Methode zur Erzeugung von adaptiven Hexaeder-Meshes aus Volumendaten, welche komplizierte konkave Strukturen aufweisen können. Es wird ein vollständiger Satz von Templates generiert der es erlaubt, die Ränder konkaver Regionen feiner zu zerlegen als angrenzende Bereiche und somit die Gesamtzahl an Hexaeder verringert. Der Algorithmus arbeitet mit beliebigen gelabelten Volumendaten und erzeugt ein adaptives, konformes, reines Hexaeder-Mesh.

  15. Wiederbeginn nach dem Zweiten Weltkrieg

    NASA Astrophysics Data System (ADS)

    Strecker, Heinrich; Bassenge-Strecker, Rosemarie

    Dieses Kapitel schildert zunächst die Ausgangslage für die Statistik in Deutschland nach dem Zweiten Weltkrieg: Der statistische Dienst in den Besatzungszonen musste teilweise erst aufgebaut und der statistische Unterricht an den Hochschulen wieder in Gang gebracht werden. In dieser Lage ergriff der Präsident des Bayerischen Statistischen Landesamtes, Karl Wagner, tatkräftig unterstützt von Gerhard Fürst, dem späteren Präsidenten des Statistischen Bundesamtes, die Initiative zur Neugründung der Deutschen Statistischen Gesellschaft (DStatG). Die Gründungsversammlung 1948 im München wurde zu einem Meilenstein in der Geschichte der DStatG. Ziel war es, alle Statistiker zur Zusammenarbeit anzuregen, ihre Qualifikation an das internationale Niveau heranzuführen und die Anwendung neuerer statistischer Methoden in der Praxis zu fördern. Es folgten 24 Jahre fruchtbarer Arbeit unter Karl Wagner (1948-1960) und Gerhard Fürst (1960-1972). Der Beitrag skizziert die Statistischen Wochen, die Tätigkeit der Ausschüsse und die Veröffentlichungen in dieser Zeit.

  16. TanDEM-X high resolution DEMs and their applications to flow modeling

    NASA Astrophysics Data System (ADS)

    Wooten, Kelly M.

    Lava flow modeling can be a powerful tool in hazard assessments; however, the ability to produce accurate models is usually limited by a lack of high resolution, up-to-date Digital Elevation Models (DEMs). This is especially obvious in places such as Kilauea Volcano (Hawaii), where active lava flows frequently alter the terrain. In this study, we use a new technique to create high resolution DEMs on Kilauea using synthetic aperture radar (SAR) data from the TanDEM-X (TDX) satellite. We convert raw TDX SAR data into a geocoded DEM using GAMMA software [Werner et al., 2000]. This process can be completed in several hours and permits creation of updated DEMs as soon as new TDX data are available. To test the DEMs, we use the Harris and Rowland [2001] FLOWGO lava flow model combined with the Favalli et al. [2005] DOWNFLOW model to simulate the 3-15 August 2011 eruption on Kilauea's East Rift Zone. Results were compared with simulations using the older, lower resolution 2000 SRTM DEM of Hawaii. Effusion rates used in the model are derived from MODIS thermal infrared satellite imagery. FLOWGO simulations using the TDX DEM produced a single flow line that matched the August 2011 flow almost perfectly, but could not recreate the entire flow field due to the relatively high DEM noise level. The issues with short model flow lengths can be resolved by filtering noise from the DEM. Model simulations using the outdated SRTM DEM produced a flow field that followed a different trajectory to that observed. Numerous lava flows have been emplaced at Kilauea since the creation of the SRTM DEM, leading the model to project flow lines in areas that have since been covered by fresh lava flows. These results show that DEMs can quickly become outdated on active volcanoes, but our new technique offers the potential to produce accurate, updated DEMs for modeling lava flow hazards.

  17. 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.

  18. An assessment of TanDEM-X GlobalDEM over rural and urban areas

    NASA Astrophysics Data System (ADS)

    Koudogbo, Fifamè N.; Duro, Javier; Huber, Martin; Rudari, Roberto; Eddy, Andrew; Lucas, Richard

    2014-10-01

    Digital Elevation Model (DEM) is a key input for the development of risk management systems. Main limitation of the current available DEM is the low level of resolution. DEMs such as STRM 90m or ASTER are globally available free of charge, but offer limited use, for example, to flood modelers in most geographic areas. TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), the first bistatic SAR can fulfil this gap. The mission objective is the generation of a consistent global digital elevation model with an unprecedented accuracy according to the HRTI-3 (High Resolution Terrain Information) specifications. The mission opens a new era in risk assessment. In the framework of ALTAMIRA INFORMATION research activities, the DIAPASON (Differential Interferometric Automated Process Applied to Survey Of Nature) processing chain has been successfully adapted to TanDEM-X CoSSC (Coregistered Slant Range Single Look Complex) data processing. In this study the capability of CoSSC data for DEM generation is investigated. Within the on-going FP7 RASOR project (Rapid Analysis and Spatialisation and Of Risk), the generated DEM are compared with Intermediate DEM derived from the TanDEM-X first global coverage. The results are presented and discussed.

  19. 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

  20. Quality Test Various Existing dem in Indonesia Toward 10 Meter National dem

    NASA Astrophysics Data System (ADS)

    Amhar, Fahmi

    2016-06-01

    Indonesia has various DEM from many sources and various acquisition date spreaded in the past two decades. There are DEM from spaceborne system (Radarsat, TerraSAR-X, ALOS, ASTER-GDEM, SRTM), airborne system (IFSAR, Lidar, aerial photos) and also terrestrial one. The research objective is the quality test and how to extract best DEM in particular area. The method is using differential GPS levelling using geodetic GPS equipment on places which is ensured not changed during past 20 years. The result has shown that DEM from TerraSAR-X and SRTM30 have the best quality (rmse 3.1 m and 3.5 m respectively). Based on this research, it was inferred that these parameters are still positively correlated with the basic concept, namely that the lower and the higher the spatial resolution of a DEM data, the more imprecise the resulting vertical height.

  1. Auf der Suche nach dem Unendlichen.

    NASA Astrophysics Data System (ADS)

    Fraser, G.; Lillestøl, E.; Sellevåg, I.

    This book is a German translation by C. Ascheron and J. Urbahn, of "The search for infinity: solving the mysteries of the universe", published in 1994. Diese Buch beschreibt anschaulich die Meilensteine, die der Mensch seit der Antike auf der Suche nach dem Unendlichen erreicht und hinter sich gelassen hat. Es enthält Kurzbiographien der wichtigsten Forscher, verständlich geschriebene Texte sowie Erläuterungen der entscheidenen Fachtermini.

  2. 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

  3. 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

  4. Spaceborne radar interferometry for coastal DEM construction

    USGS Publications Warehouse

    Hong, S.-H.; Lee, C.-W.; Won, J.-S.; Kwoun, Oh-Ig; Lu, Zhiming

    2005-01-01

    Topographic features in coastal regions including tidal flats change more significantly than landmass, and are characterized by extremely low slopes. High precision DEMs are required to monitor dynamic changes in coastal topography. It is difficult to obtain coherent interferometric SAR pairs especially over tidal flats mainly because of variation of tidal conditions. Here we focus on i) coherence of multi-pass ERS SAR interferometric pairs and ii) DEM construction from ERS-ENVISAT pairs. Coherences of multi-pass ERS interferograms were good enough to construct DEM under favorable tidal conditions. Coherence in sand dominant area was generally higher than that in muddy surface. The coarse grained coastal areas are favorable for multi-pass interferometry. Utilization of ERS-ENVISAT interferometric pairs is taken a growing interest. We carried out investigation using a cross-interferometric pair with a normal baseline of about 1.3 km, a 30 minutes temporal separation and the height sensitivity of about 6 meters. Preliminary results of ERS-ENVISAT interferometry were not successful due to baseline and unfavorable scattering conditions. ?? 2005 IEEE.

  5. Volcanic geomorphology using TanDEM-X

    NASA Astrophysics Data System (ADS)

    Poland, Michael; Kubanek, Julia

    2016-04-01

    Topography is perhaps the most fundamental dataset for any volcano, yet is surprisingly difficult to collect, especially during the course of an eruption. For example, photogrammetry and lidar are time-intensive and often expensive, and they cannot be employed when the surface is obscured by clouds. Ground-based surveys can operate in poor weather but have poor spatial resolution and may expose personnel to hazardous conditions. Repeat passes of synthetic aperture radar (SAR) data provide excellent spatial resolution, but topography in areas of surface change (from vegetation swaying in the wind to physical changes in the landscape) between radar passes cannot be imaged. The German Space Agency's TanDEM-X satellite system, however, solves this issue by simultaneously acquiring SAR data of the surface using a pair of orbiting satellites, thereby removing temporal change as a complicating factor in SAR-based topographic mapping. TanDEM-X measurements have demonstrated exceptional value in mapping the topography of volcanic environments in as-yet limited applications. The data provide excellent resolution (down to ~3-m pixel size) and are useful for updating topographic data at volcanoes where surface change has occurred since the most recent topographic dataset was collected. Such data can be used for applications ranging from correcting radar interferograms for topography, to modeling flow pathways in support of hazards mitigation. The most valuable contributions, however, relate to calculating volume changes related to eruptive activity. For example, limited datasets have provided critical measurements of lava dome growth and collapse at volcanoes including Merapi (Indonesia), Colima (Mexico), and Soufriere Hills (Montserrat), and of basaltic lava flow emplacement at Tolbachik (Kamchatka), Etna (Italy), and Kīlauea (Hawai`i). With topographic data spanning an eruption, it is possible to calculate eruption rates - information that might not otherwise be available

  6. 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.

  7. TanDEM-X DEMs and feature-tracking of Helheim and Kangerdlugssuaq glaciers in south-east Greenland

    NASA Astrophysics Data System (ADS)

    Bevan, Suzanne; Luckman, Adrian; Murray, Tavi

    2013-04-01

    We use sequences of TanDEM-X acquisitions over 'supersites' Helheim and Kangerdlugssuaq glaciers in south-east Greenland to generate interferometric digital elevation models (DEMs) and to feature-track surface displacement between image acquisitions. The high spatial resolution, day/night, and cloud-penetrating capabilities of the X-band SAR system enabled the production of more than 20 DEMs for each glacier with a spatial resolution of 8 m or better. The DEMs span the period June 2011 to March 2012, at 11-day intervals, with a few breaks. Time-lapse animations of Helheim DEMs reveal the development of troughs in surface elevation close to the front. The troughs propagate down flow and develop into the rifts from which calving takes place. On both glaciers, regions of high variance in elevation can be identified caused by the transit of crevasses. In addition, on Helheim, a 1 km wide band of high variance adjacent to the calving front may be interpreted as the response to tidal forcing of a partially floating tongue. In addition to the DEMs we will also present featured tracked high-quality surface velocity fields at a spatial resolution of 2 m coincident with the DEMs. On Helheim these velocity fields indicate a winter deceleration of less than 10% at a point 4 km behind the calving front.

  8. Spotlight COSMO-SkyMed DEM generation and validation

    NASA Astrophysics Data System (ADS)

    Lombardi, N.; Lorusso, R.; Milillo, G.

    2016-10-01

    This paper focuses on the generation of Digital Elevation Models (DEMs) with COSMO SkyMed Spotlight data in providing DEMs. In particular, the peculiarity of Spotlight data (affected from Doppler centroid drift) is investigated, and the use of the processing chain included in the Delft Object-oriented Radar Interferometric Software (DORIS [1]). The effects of not correctly handled Doppler drift is shown. The standard interferometric processing, without Doppler drift handling, has been applied to Spotlight image pairs, resulting in interferometric coherence loss in interferograms as we move away from scene center. So, the standard processing chain has been modified to take in account the Doppler centroid drift affecting Spotlight data and very high resolution and accuracy DEMs have been obtained. Some Spotlight image pairs have been processed and the obtained DEMs have been shown and analyzed proving the high details and product accuracy.

  9. 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

  10. Feasibility Analysis of DEM Differential Method on Tree Height Assessment wit Terra-SAR/TanDEM-X Data

    NASA Astrophysics Data System (ADS)

    Zhang, Wangfei; Chen, Erxue; Li, Zengyuan; Feng, Qi; Zhao, Lei

    2016-08-01

    DEM Differential Method is an effective and efficient way for forest tree height assessment with Polarimetric and interferometric technology, however, the assessment accuracy of it is based on the accuracy of interferometric results and DEM. Terra-SAR/TanDEM-X, which established the first spaceborne bistatic interferometer, can provide highly accurate cross-track interferometric images in the whole global without inherent accuracy limitations like temporal decorrelation and atmospheric disturbance. These characters of Terra-SAR/TandDEM-X give great potential for global or regional tree height assessment, which have been constraint by the temporal decorrelation in traditional repeat-pass interferometry. Currently, in China, it will be costly to collect high accurate DEM with Lidar. At the same time, it is also difficult to get truly representative ground survey samples to test and verify the assessment results. In this paper, we analyzed the feasibility of using TerraSAR/TanDEM-X data to assess forest tree height with current free DEM data like ASTER-GDEM and archived ground in-suit data like forest management inventory data (FMI). At first, the accuracy and of ASTER-GDEM and forest management inventory data had been assessment according to the DEM and canopy height model (CHM) extracted from Lidar data. The results show the average elevation RMSE between ASTER-GEDM and Lidar-DEM is about 13 meters, but they have high correlation with the correlation coefficient of 0.96. With a linear regression model, we can compensate ASTER-GDEM and improve its accuracy nearly to the Lidar-DEM with same scale. The correlation coefficient between FMI and CHM is 0.40. its accuracy is able to be improved by a linear regression model withinconfidence intervals of 95%. After compensation of ASTER-GDEM and FMI, we calculated the tree height in Mengla test site with DEM Differential Method. The results showed that the corrected ASTER-GDEM can effectively improve the assessment accuracy

  11. Die Anfaenge der Melker Bibliothek - Neue Erkenntnisse zu Handschriften und Fragmenten aus der Zeit vor 1200

    NASA Astrophysics Data System (ADS)

    Glaßner, Christine; Haidinger, Alois

    1996-04-01

    Untersuchung der zeitnahen Eintragungen in diese Handschrift gelang es, die Tätigkeit von zumindest drei wichtigen, im 12. Jahrhundert in Melk identifizierbaren, namentlich nicht bekannten Schreibern chronologisch zuzuordnen. Erstmals wurden die nur fragmentarisch als Makulatur in den Bucheinbänden erhaltenen Handschriften in die Untersuchung einbezogen, so dass für die Wende vom 12. zum 13. Jahrhundert ein Bücherbestand von 68 Handschriften erschlossen werden konnte. Besonders hervorzuheben ist, dass in der Sonderausstellung von 1996 und im Begleitband erstmals eingehend die Bedeutung der ältesten Melker Handschrift, Cod. 412 aus dem frühen 9. Jahrhundert mit naturwissenschaftlichen Texten des Beda Venerabilis, als Vorlage für drei weitere Handschriften diente: Vatikan, Cod. Vat. lat. 643, abgeschrieben wahrscheinlich in Melk, davon abhängig Zwettl, Cod. 296, und Klosterneuburg, Cod. 685. Die Abschriften der Melker Beda-Handschrift sind inhaltlich fast identisch, allerdings um den im Mittelalter fälschlicherweise Beda Venerabilis zugeschriebenen Sternbilderkatalog erweitert.

  12. 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.

  13. Local validation of EU-DEM using Least Squares Collocation

    NASA Astrophysics Data System (ADS)

    Ampatzidis, Dimitrios; Mouratidis, Antonios; Gruber, Christian; Kampouris, Vassilios

    2016-04-01

    In the present study we are dealing with the evaluation of the European Digital Elevation Model (EU-DEM) in a limited area, covering few kilometers. We compare EU-DEM derived vertical information against orthometric heights obtained by classical trigonometric leveling for an area located in Northern Greece. We apply several statistical tests and we initially fit a surface model, in order to quantify the existing biases and outliers. Finally, we implement a methodology for orthometric heights prognosis, using the Least Squares Collocation for the remaining residuals of the first step (after the fitted surface application). Our results, taking into account cross validation points, reveal a local consistency between EU-DEM and official heights, which is better than 1.4 meters.

  14. 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.

  15. Utopie: Eine Geschichte aus dem 15. Jahrhundert fur die Siebte Klasse, mit Ubungen (Utopia: A View of the 15th Century for the Seventh Class, with Exercises).

    ERIC Educational Resources Information Center

    Stott, Michael

    This German language textbook is intended for classroom use. The theme of the text relates to the Renaissance, and the narrative is based on Sir Thomas More's "Utopia" (1516) and relates to the experiences of its central character Raphael among the inhabitants of the strange island. Each chapter touches lightly on some thought provoking…

  16. 25 Jahre - Institut fuer Geodaesie, Teil 3: Aus dem Leben des Instituts (25 Years - Institute of Geodesy, Part 3: The Life of the Institute)

    DTIC Science & Technology

    2000-01-01

    seit 1995 Dezernatsleiter fOr digitale Kartographie am Landesvermessungsarnt Thiringen in Erfurt Dipl.-Ing. Chengzu Li * geboren 1946 in Chengdu, VR...UniversitUit Berlin, geleiteten Projekte Dl1, D2 und D6 des DFG-Sonderforschungsbereichs 69 waren Dl: die digitale Bildklassifizierung und -interpretation...Messkampagne bei der Einrichtung eines ganz SUid- amerika Oberdeckenden geodditischen Bezugssystems ( Sistema de Referencia Geocentrico para America del

  17. 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.

  18. CapDEM Exercise Gamma: Results and Discussion

    DTIC Science & Technology

    2011-06-01

    internal team’ using CapDEM towards the reality of external groups using the CapDEM approach to address their own problem by themselves. The results...enable and support different internal and external configurations of the classified CEE requires further study, including both technical and security...qu’épreuve et évaluation tout à fait indépendantes, l’Exercice a moins mis l’accent sur une « équipe interne » utilisant l’approche DIGCap et il a plutôt

  19. 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

  20. 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.

  1. Validation of the Australian Propensity for Angry Driving Scale (Aus-PADS).

    PubMed

    Leal, Nerida L; Pachana, Nancy A

    2009-09-01

    The present study used a university sample to assess the test-retest reliability and validity of the Australian Propensity for Angry Driving Scale (Aus-PADS). The scale has stability over time, and convergent validity was established, as Aus-PADS scores correlated significantly with established anger and impulsivity measures. Discriminant validity was also established, as Aus-PADS scores did not correlate with Venturesomeness scores. The Aus-PADS has demonstrated criterion validity, as scores were correlated with behavioural measures, such as yelling at other drivers, gesturing at other drivers, and feeling angry but not doing anything. Aus-PADS scores reliably predicted the frequency of these behaviours over and above other study variables. No significant relationship between aggressive driving and crash involvement was observed. It was concluded that the Aus-PADS is a reliable and valid tool appropriate for use in Australian research, and that the potential relationship between aggressive driving and crash involvement warrants further investigation with a more representative (and diverse) driver sample.

  2. Improved Fluvial Geomorphic Interpretation Derived From DEM Differencing

    NASA Astrophysics Data System (ADS)

    Wheaton, J. M.; Brasington, J.; Brewer, P. A.; Darby, S.; Pasternack, G. B.; Sear, D.; Vericat, D.; Williams, R.

    2007-12-01

    Technological advances over the past two decades in remotely-sensed and ground-based topographic surveying technologies have made the rapid acquisition of topographic data in the fluvial environment possible at spatial resolutions and extents previously unimaginable. Consequently, monitoring geomorphic changes and estimating fluvial sediment budgets through comparing repeat topographic surveys (DEM differencing) has now become a tractable, affordable approach for both research purposes and long-term monitoring associated with river restoration. However, meaningful quantitative geomorphic interpretation of repeat topographic surveys has received little attention from either researchers or practitioners. Previous research has shown that quantitative estimates of erosion and deposition from DEM differencing are highly sensitive to DEM uncertainty, with minimum level of detection techniques typically discarding between 40% and 90% of the predicted changes. A series of new methods for segregating reach-scale sediment budgets into their specific process components, while accounting for the influence of DEM uncertainty, were developed and explored to highlight distinctive geomorphic signatures between different styles of change. To illustrate the interpretive power of the techniques in different settings, results are presented from analyses across a range of gravel-bed river types: a) the braided River Feshie, Scotland, UK; b) the formerly gravel-mined, wandering Sulphur Creek, California, USA; c) a heavily regulated reach of the Mokelumne River, California, USA that has been subjected to over 5 years of spawning habitat rehabilitation; and d) a restored meandering channel and floodplain of the Highland Water, New Forest, UK. Despite fundamentally different process suites between the study sites, the budget segregation technique is in each case able to aid in more reliable and meaningful geomorphic interpretations of DEM differences.

  3. DEM generated from InSAR in mountainous terrain and its accuracy analysis

    NASA Astrophysics Data System (ADS)

    Hu, Hongbing; Zhan, Yulan

    2011-02-01

    Digital Elevation Model (DEM) derived from survey data is accurate but it is very expensive and time-consuming. In recent years, remote sensing techniques including Synthetic Apenture Radar Interferometry (InSAR) had been developed as a powerful method to derive high precision DEM, especially in mountainous or deep forest areas. The purpose of this paper is to illustrate the principle of InSAR and show the result of a case study in Gejiu city, Yunnan province, China. The accuracy of DEM derived from InSAR (abbreviation as InSAR-DEM) is also evaluated by comparing it with DEM generated from topographic map at the scale of 1:50000 (abbreviation as TOP-DEM). The result shows that: (1)The general precision of the whole selected area acquired by subtracting InSAR-DEM from TOP-DEM is that the maximum, the minimum, the RMSE, and the mean of difference of the two DEMs are 203m, -188m, 26.9m and 5.7m respectively. (2)The topographic trend represented by the two DEMs is coincident, even though TOP-DEM is finer than InSAR-DEM, especial at the valley. (3) Contour maps with the interval of 100m and 50m converted from InSAR-DEM and TOP-DEM respectively show accordant relief trend. Contour from TOP-DEM is smoother than that of from InSAR-DEM, while Contour from InSAR-DEM has more islands than that of from TOP-DEM.(4) Coherence has great influence on the precision of InSAR-DEM, the precision of low-coherence area approaches 100 m while that of high-coherence area can up to m level. (5) The relief trend of 6 profiles represented by InSAR-DEM and TOP-DEM is accordant with tiny difference in partial minutiae. InSAR-DEM displays hypsographies at relative flat areas including surface of water, which reflects the influence of flat earth on InSAR to a certain extent.

  4. 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

  5. Lineare und verzweigte Blockcopolymere aus Polypeptiden und synthetischen Polymeren

    NASA Astrophysics Data System (ADS)

    Kukula, Hildegard

    2001-07-01

    Die vorliegende Arbeit beschäftigt sich mit der Synthese und den Eigenschaften von linearen und verzweigten amphiphilen Polypeptid-Blockcopolymeren. Die Frage nach dem Einfluss der Topologie und Konformation der Blockcopolymere auf die supramolekularen und kolloidalen Eigenschaften bildete einen wichtigen Aspekt bei den Untersuchungen. Die Blockcopolymere wurden nach einem mehrstufigen Reaktionsschema durch Kombination von anionischer und ringöffnender Polymerisation von Aminosäuren-N-Carboxyanhydriden (NCA) synthetisiert. Die Untersuchung der Polypeptid-Blockcopolymere hinsichtlich ihres Aggregationsverhaltens in fester Phase sowie in verdünnter wässriger Lösung erfolgte mittels Streumethoden (SAXS, WAXS, DLS) sowie abbildender Methoden (TEM). Durch Einsatz der Blockcopolymere als polymere Stabilisatoren in der Emulsionspolymerisation wurden Oberflächen funktionalisierte Latizes erhalten. Als Beispiel für eine pharmazeutische Anwendung wurden bioverträgliche Polypeptid-Blockcopolymere als Wirkstoff-Trägersysteme in der Krebstherapie eingesetzt. This work describes the synthesis and characterization of linear and branched polypeptide block copolymers having amphiphilic character. The studies focused on the impact of the block copolymers' conformation and architecture on the supramolecular and colloidal properties. The polypeptide block copolymers were prepared in a multi-step process involving the anionic synthesis of (poly)amino-functional polymers (polystyrene and polybutadiene) which where used as macroinitiators for the ring-opening polymerization of N-carboxyanhydrides (NCA) of protected a-aminoacids. Supramolecular structures of the block copolymers in the solid state as well as in diluted aqueous solution were investigated using scattering (SAXS, WAXS, DLS) and microscopic (TEM) methods. Both linear and branched polypeptide block copolymers were used as polymeric stabilizers in the emulsion polymerization of styrene to yield polypeptide

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Mapping debris-flow hazard in Honolulu using a DEM

    USGS Publications Warehouse

    Ellen, Stephen D.; Mark, Robert K.; ,

    1993-01-01

    A method for mapping hazard posed by debris flows has been developed and applied to an area near Honolulu, Hawaii. The method uses studies of past debris flows to characterize sites of initiation, volume at initiation, and volume-change behavior during flow. Digital simulations of debris flows based on these characteristics are then routed through a digital elevation model (DEM) to estimate degree of hazard over the area.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Segmentierung des Femurs aus MRT-Daten mit Shape-Based Level-Sets

    NASA Astrophysics Data System (ADS)

    Dekomien, Claudia; Busch, Martin; Teske, Wolfram; Winter, Susanne

    Inhalt dieser Arbeit ist die Segmentierung des Femurs aus MRT-Datensätzen mit einem Shape-based Level-Set-Ansatz. Der Algorithmus besteht aus zwei Phasen, der Modellerstellung und der Segmentierungsphase. In der Segmentierungsphase wurde ein kantenbasiertes und ein auf Intensitäten basierendes Optimierungskriterium mit einander kombiniert. Für eine lokale Verbesserung des Ergebnisses wurde zusätzlich ein Laplacian Level-Set-Verfahren angewendet. Der Femur konnte mit diesem Ansatz in drei verschiedenen MRT-Sequenzen und einem Fusionsdatensatz gut segmentiert werden.

  16. 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

  17. Research on the method of extracting DEM based on GBInSAR

    NASA Astrophysics Data System (ADS)

    Yue, Jianping; Yue, Shun; Qiu, Zhiwei; Wang, Xueqin; Guo, Leping

    2016-05-01

    Precise topographical information has a very important role in geology, hydrology, natural resources survey and deformation monitoring. The extracting DEM technology based on synthetic aperture radar interferometry (InSAR) obtains the three-dimensional elevation of the target area through the phase information of the radar image data. The technology has large-scale, high-precision, all-weather features. By changing track in the location of the ground radar system up and down, it can form spatial baseline. Then we can achieve the DEM of the target area by acquiring image data from different angles. Three-dimensional laser scanning technology can quickly, efficiently and accurately obtain DEM of target area, which can verify the accuracy of DEM extracted by GBInSAR. But research on GBInSAR in extracting DEM of the target area is a little. For lack of theory and lower accuracy problems in extracting DEM based on GBInSAR now, this article conducted research and analysis on its principle deeply. The article extracted the DEM of the target area, combined with GBInSAR data. Then it compared the DEM obtained by GBInSAR with the DEM obtained by three-dimensional laser scan data and made statistical analysis and normal distribution test. The results showed the DEM obtained by GBInSAR was broadly consistent with the DEM obtained by three-dimensional laser scanning. And its accuracy is high. The difference of both DEM approximately obeys normal distribution. It indicated that extracting the DEM of target area based on GBInSAR is feasible and provided the foundation for the promotion and application of GBInSAR.

  18. 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

  19. An Overview of the CapDEM Integrated Engineering Environment

    DTIC Science & Technology

    2005-07-01

    cours d’un exercice d’élaboration et d’expérimentation de concepts (EEC) du DIGCap. On utilisera lors de cet exercice d’EEC les mêmes outils pour...utilize the existing IEE. First, the IEE will be used to provide engineering data management for the CapDEM Concept Development and Experimentation (CD...E) exercise. This CD&E exercise will employ the same set of tools to demonstrate the application of capability engineering concepts to support CD&E

  20. Processing, validating, and comparing DEMs for geomorphic application on the Puna de Atacama Plateau, northwest Argentina

    NASA Astrophysics Data System (ADS)

    Purinton, Benjamin; Bookhagen, Bodo

    2016-04-01

    This study analyzes multiple topographic datasets derived from various remote-sensing methods from the Pocitos Basin of the central Puna Plateau in northwest Argentina at the border to Chile. Here, the arid climate and clear atmospheric conditions and lack of vegetation provide ideal conditions for remote sensing and Digital Elevation Model (DEM) comparison. We compare the following freely available DEMs: SRTM-X (spatial resolution of ~30 m), SRTM-C v4.1 (90 m), and ASTER GDEM2 (30 m). Additional DEMs for comparison are generated from optical and radar datasets acquired freely (ASTER Level 1B stereo pairs and Sentinal-1A radar), through research agreements (RapidEye Level 1B scenes, ALOS radar, and ENVISAT radar), and through commercial sources (TerraSAR-X / TanDEM-X radar). DEMs from ASTER (spatial resolution of 15 m) and RapidEye (~5-10 m) optical datasets are produced by standard photogrammetric techniques and have been post-processed for validation and alignment purposes. Because RapidEye scenes are captured at a low incidence angle (<20°) and stereo pairs are unavailable, merging and averaging methods of two to four overlapping scenes is explored for effective DEM generation. Sentinal-1A, TerraSAR-X / TanDEM-X, ALOS, and ENVISAT radar data is processed through interferometry resulting in DEMs with spatial resolutions ranging from 5 to 30 meters. The SRTM-X dataset serves as a control in the creation of further DEMs, as it is widely used in the geosciences and represents the highest-quality DEM currently available. All DEMs are validated against over 400,000 differential GPS (dGPS) measurements gathered during four field campaigns in 2012 and 2014 to 2016. Of these points, more than 250,000 lie within the Pocitos Basin with average vertical and horizontal accuracies of 0.95 m and 0.69 m, respectively. Dataset accuracy is judged by the lowest standard deviations of elevation compared with the dGPS data and with the SRTM-X control DEM. Of particular interest in

  1. Effects of lidar point density on bare earth extraction and DEM creation

    NASA Astrophysics Data System (ADS)

    Puetz, Angela M.; Olsen, R. Chris; Anderson, Brian

    2009-05-01

    Data density has a crucial impact on the accuracy of Digital Elevation Models (DEMs). In this study, DEMs were created from a high point-density LIDAR dataset using the bare earth extraction module in Quick Terrain Modeler. Lower point-density LIDAR collects were simulated by randomly selecting points from the original dataset at a series of decreasing percentages. The DEMs created from the lower resolution datasets are compared to the original DEM. Results show a decrease in DEM accuracy as the resolution of the LIDAR dataset is reduced. Some analysis is made of the types of errors encountered in the lower resolution DEMs. It is also noted that the percentage of points classified as bare earth decreases as the resolution of the LIDAR dataset is reduced.

  2. High-Precision DEM Generation Using Satellite-Borne InSAR Technology

    NASA Astrophysics Data System (ADS)

    Li, Tao; Tang, Xinming; Gao, Xiaoming; Chen, Weinan; Chen, Qianfu; Wu, Danqin

    2016-08-01

    Satellite-borne InSAR is useful in generating DEM globally. Especially after TanDEM-X interferometer started its mission in 2010. In this paper, we analyze the interferometric geometry in surveying and mapping application. And we locate main error sources, i.e., phase error and baseline error, using the parameters extracted from TanDEM-X interferometer. The phase error is suppressed using multi-look iteration. The rich textures as well as the high phase accuracy are both maintained through this method. The baseline error is reduced by using the long-and-short baseline combination method. Finally, we propose to mosaic the ascending and descending DEM according to coherence values to reduce the low coherent areas. Experiments in flat ground, hill and mountain land are conducted to test the feasibility of the proposed methods. Results demonstrate that TanDEM-X may be used in high-precision DEM generation.

  3. The Importance of Precise Digital Elevation Models (DEM) in Modelling Floods

    NASA Astrophysics Data System (ADS)

    Demir, Gokben; Akyurek, Zuhal

    2016-04-01

    Digital elevation Models (DEM) are important inputs for topography for the accurate modelling of floodplain hydrodynamics. Floodplains have a key role as natural retarding pools which attenuate flood waves and suppress flood peaks. GPS, LIDAR and bathymetric surveys are well known surveying methods to acquire topographic data. It is not only time consuming and expensive to obtain topographic data through surveying but also sometimes impossible for remote areas. In this study it is aimed to present the importance of accurate modelling of topography for flood modelling. The flood modelling for Samsun-Terme in Blacksea region of Turkey is done. One of the DEM is obtained from the point observations retrieved from 1/5000 scaled orthophotos and 1/1000 scaled point elevation data from field surveys at x-sections. The river banks are corrected by using the orthophotos and elevation values. This DEM is named as scaled DEM. The other DEM is obtained from bathymetric surveys. 296 538 number of points and the left/right bank slopes were used to construct the DEM having 1 m spatial resolution and this DEM is named as base DEM. Two DEMs were compared by using 27 x-sections. The maximum difference at thalweg of the river bed is 2m and the minimum difference is 20 cm between two DEMs. The channel conveyance capacity in base DEM is larger than the one in scaled DEM and floodplain is modelled in detail in base DEM. MIKE21 with flexible grid is used in 2- dimensional shallow water flow modelling. The model by using two DEMs were calibrated for a flood event (July 9, 2012). The roughness is considered as the calibration parameter. From comparison of input hydrograph at the upstream of the river and output hydrograph at the downstream of the river, the attenuation is obtained as 91% and 84% for the base DEM and scaled DEM, respectively. The time lag in hydrographs does not show any difference for two DEMs and it is obtained as 3 hours. Maximum flood extents differ for the two DEMs

  4. 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.

  5. Numerical Simulation of High Velocity Impact Phenomenon by the Distinct Element Method (dem)

    NASA Astrophysics Data System (ADS)

    Tsukahara, Y.; Matsuo, A.; Tanaka, K.

    2007-12-01

    Continuous-DEM (Distinct Element Method) for impact analysis is proposed in this paper. Continuous-DEM is based on DEM (Distinct Element Method) and the idea of the continuum theory. Numerical simulations of impacts between SUS 304 projectile and concrete target has been performed using the proposed method. The results agreed quantitatively with the impedance matching method. Experimental elastic-plastic behavior with compression and rarefaction wave under plate impact was also qualitatively reproduced, matching the result by AUTODYN®.

  6. Simulation of triaxial response of granular materials by modified DEM

    NASA Astrophysics Data System (ADS)

    Wang, XiaoLiang; Li, JiaChun

    2014-12-01

    A modified discrete element method (DEM) with rolling effect taken into consideration is developed to examine macroscopic behavior of granular materials in this study. Dimensional analysis is firstly performed to establish the relationship between macroscopic mechanical behavior, mesoscale contact parameters at particle level and external loading rate. It is found that only four dimensionless parameters may govern the macroscopic mechanical behavior in bulk. The numerical triaxial apparatus was used to study their influence on the mechanical behavior of granular materials. The parametric study indicates that Poisson's ratio only varies with stiffness ratio, while Young's modulus is proportional to contact modulus and grows with stiffness ratio, both of which agree with the micromechanical model. The peak friction angle is dependent on both inter-particle friction angle and rolling resistance. The dilatancy angle relies on inter-particle friction angle if rolling stiffness coefficient is sufficiently large. Finally, we have recommended a calibration procedure for cohesionless soil, which was at once applied to the simulation of Chende sand using a series of triaxial compression tests. The responses of DEM model are shown in quantitative agreement with experiments. In addition, stress-strain response of triaxial extension was also obtained by numerical triaxial extension tests.

  7. An efficient method for DEM-based overland flow routing

    NASA Astrophysics Data System (ADS)

    Huang, Pin-Chun; Lee, Kwan Tun

    2013-05-01

    The digital elevation model (DEM) is frequently used to represent watershed topographic features based on a raster or a vector data format. It has been widely linked with flow routing equations for watershed runoff simulation. In this study, a recursive formulation was encoded into the conventional kinematic- and diffusion-wave routing algorithms to permit a larger time increment, despite the Courant-Friedrich-Lewy condition having been violated. To meet the requirement of recursive formulation, a novel routing sequence was developed to determine the cell-to-cell computational procedure for the DEM database. The routing sequence can be set either according to the grid elevation in descending order for the kinematic-wave routing or according to the water stage of the grid in descending order for the diffusion-wave routing. The recursive formulation for 1D runoff routing was first applied to a conceptual overland plane to demonstrate the precision of the formulation using an analytical solution for verification. The proposed novel routing sequence with the recursive formulation was then applied to two mountain watersheds for 2D runoff simulations. The results showed that the efficiency of the proposed method was significantly superior to that of the conventional algorithm, especially when applied to a steep watershed.

  8. DEM modeling of flexible structures against granular material avalanches

    NASA Astrophysics Data System (ADS)

    Lambert, Stéphane; Albaba, Adel; Nicot, François; Chareyre, Bruno

    2016-04-01

    This article presents the numerical modeling of flexible structures intended to contain avalanches of granular and coarse material (e.g. rock slide, a debris slide). The numerical model is based on a discrete element method (YADE-Dem). The DEM modeling of both the flowing granular material and the flexible structure are detailed before presenting some results. The flowing material consists of a dry polydisperse granular material accounting for the non-sphericity of real materials. The flexible structure consists in a metallic net hanged on main cables, connected to the ground via anchors, on both sides of the channel, including dissipators. All these components were modeled as flexible beams or wires, with mechanical parameters defined from literature data. The simulation results are presented with the aim of investigating the variability of the structure response depending on different parameters related to the structure (inclination of the fence, with/without brakes, mesh size opening), but also to the channel (inclination). Results are then compared with existing recommendations in similar fields.

  9. 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.

  10. 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.

  11. a Near-Global Bare-Earth dem from Srtm

    NASA Astrophysics Data System (ADS)

    Gallant, J. C.; Read, A. M.

    2016-06-01

    The near-global elevation product from NASA's Shuttle Radar Topographic Mission (SRTM) has been widely used since its release in 2005 at 3 arcsecond resolution and the release of the 1 arcsecond version in late 2014 means that the full potential of the SRTM DEM can now be realised. However the routine use of SRTM for analytical purposes such as catchment hydrology, flood inundation, habitat mapping and soil mapping is still seriously impeded by the presence of artefacts in the data, primarily the offsets due to tree cover and the random noise. This paper describes the algorithms being developed to remove those offsets, based on the methods developed to produce the Australian national elevation model from SRTM data. The offsets due to trees are estimated using the GlobeLand30 (National Geomatics Center of China) and Global Forest Change (University of Maryland) products derived from Landsat, along with the ALOS PALSAR radar image data (JAXA) and the global forest canopy height map (NASA). The offsets are estimated using several processes and combined to produce a single continuous tree offset layer that is subtracted from the SRTM data. The DEM products will be made freely available on completion of the first draft product, and the assessment of that product is expected to drive further improvements to the methods.

  12. A New DEM Generalization Method Based on Watershed and Tree Structure

    PubMed Central

    Chen, Yonggang; Ma, Tianwu; Chen, Xiaoyin; Chen, Zhende; Yang, Chunju; Lin, Chenzhi; Shan, Ligang

    2016-01-01

    The DEM generalization is the basis of multi-dimensional observation, the basis of expressing and analyzing the terrain. DEM is also the core of building the Multi-Scale Geographic Database. Thus, many researchers have studied both the theory and the method of DEM generalization. This paper proposed a new method of generalizing terrain, which extracts feature points based on the tree model construction which considering the nested relationship of watershed characteristics. The paper used the 5 m resolution DEM of the Jiuyuan gully watersheds in the Loess Plateau as the original data and extracted the feature points in every single watershed to reconstruct the DEM. The paper has achieved generalization from 1:10000 DEM to 1:50000 DEM by computing the best threshold. The best threshold is 0.06. In the last part of the paper, the height accuracy of the generalized DEM is analyzed by comparing it with some other classic methods, such as aggregation, resample, and VIP based on the original 1:50000 DEM. The outcome shows that the method performed well. The method can choose the best threshold according to the target generalization scale to decide the density of the feature points in the watershed. Meanwhile, this method can reserve the skeleton of the terrain, which can meet the needs of different levels of generalization. Additionally, through overlapped contour contrast, elevation statistical parameters and slope and aspect analysis, we found out that the W8D algorithm performed well and effectively in terrain representation. PMID:27517296

  13. 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.

  14. 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

  15. Shuttle radar DEM hydrological correction for erosion modelling in small catchments

    NASA Astrophysics Data System (ADS)

    Jarihani, Ben; Sidle, Roy; Bartley, Rebecca

    2016-04-01

    Digital Elevation Models (DEMs) that accurately replicate both landscape form and processes are critical to support modelling of environmental processes. Catchment and hillslope scale runoff and sediment processes (i.e., patterns of overland flow, infiltration, subsurface stormflow and erosion) are all topographically mediated. In remote and data-scarce regions, high resolution DEMs (LiDAR) are often not available, and moderate to course resolution digital elevation models (e.g., SRTM) have difficulty replicating detailed hydrological patterns, especially in relatively flat landscapes. Several surface reconditioning algorithms (e.g., Smoothing) and "Stream burning" techniques (e.g., Agree or ANUDEM), in conjunction with representation of the known stream networks, have been used to improve DEM performance in replicating known hydrology. Detailed stream network data are not available at regional and national scales, but can be derived at local scales from remotely-sensed data. This research explores the implication of high resolution stream network data derived from Google Earth images for DEM hydrological correction, instead of using course resolution stream networks derived from topographic maps. The accuracy of implemented method in producing hydrological-efficient DEMs were assessed by comparing the hydrological parameters derived from modified DEMs and limited high-resolution airborne LiDAR DEMs. The degree of modification is dominated by the method used and availability of the stream network data. Although stream burning techniques improve DEMs hydrologically, these techniques alter DEM characteristics that may affect catchment boundaries, stream position and length, as well as secondary terrain derivatives (e.g., slope, aspect). 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.

  16. Two Preliminary SRTM DEMs Within the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Alsdorf, D.; Hess, L.; Melack, J.; Dunne, T.; Mertes, L.; Ballantine, A.; Biggs, T.; Holmes, K.; Sheng, Y.; Hendricks, G.

    2002-12-01

    Digital topography provides important measures, such as hillslope lengths and flow path networks, for understanding hydrologic and geomorphic processes (e.g., runoff response to land use change and floodplain inundation volume). Two preliminary Shuttle Radar Topography Mission digital elevation models of Manaus (1S to 5S and 59W to 63W) and Rondonia (9S to 12S and 61W to 64W) were received from NASA JPL in August 2002. The "PI Processor" produced these initial DEM segments and we are using them to assess the initial accuracy of the interferometrically derived heights and for hydrologic research. The preliminary SRTM derived absolute elevations across the Amazon floodplain in the Cabaliana region generally range from 5 to 15 m with reported errors of 1 to 3 m. This region also includes some preliminary elevations that are erroneously negative. However, topographic contours on 1:100,000 scale quadrangles of 1978 to 1980 vintage indicate elevations of 20 to 30 m. Because double-bounce travel paths are possible over the sparsely vegetated and very-flat 2400 sq-km water surface of the Balbina reservoir near Manaus, it serves to identify the relative accuracy of the SRTM heights. Here, cell-to-cell height changes are generally 0 to 1 m and changes across a ~100 km transect rarely exceed 3 m. Reported errors throughout the transect range from 1 to 2 m with some errors up to 5 m. Deforestation in Rondonia is remarkably clear in the C-band DEM where elevations are recorded from the canopy rather than bare earth. Here, elevation changes are ~30 m (with reported 1 to 2 m errors) across clear-cut areas. Field derived canopy heights are in agreement with this change. Presently, we are deriving stream networks in the Amazon floodplain for comparison with our previous network extraction from JERS-1 SAR mosaics and for hydrologic modeling.

  17. Influence of dem in Watershed Management as Flood Zonation Mapping

    NASA Astrophysics Data System (ADS)

    Alrajhi, Muhamad; Khan, Mudasir; Afroz Khan, Mohammad; Alobeid, Abdalla

    2016-06-01

    Despite of valuable efforts from working groups and research organizations towards flood hazard reduction through its program, still minimal diminution from these hazards has been realized. This is mainly due to the fact that with rapid increase in population and urbanization coupled with climate change, flood hazards are becoming increasingly catastrophic. Therefore there is a need to understand and access flood hazards and develop means to deal with it through proper preparations, and preventive measures. To achieve this aim, Geographical Information System (GIS), geospatial and hydrological models were used as tools to tackle with influence of flash floods in the Kingdom of Saudi Arabia due to existence of large valleys (Wadis) which is a matter of great concern. In this research paper, Digital Elevation Models (DEMs) of different resolution (30m, 20m,10m and 5m) have been used, which have proven to be valuable tool for the topographic parameterization of hydrological models which are the basis for any flood modelling process. The DEM was used as input for performing spatial analysis and obtaining derivative products and delineate watershed characteristics of the study area using ArcGIS desktop and its Arc Hydro extension tools to check comparability of different elevation models for flood Zonation mapping. The derived drainage patterns have been overlaid over aerial imagery of study area, to check influence of greater amount of precipitation which can turn into massive destructions. The flow accumulation maps derived provide zones of highest accumulation and possible flow directions. This approach provide simplified means of predicting extent of inundation during flood events for emergency action especially for large areas because of large coverage area of the remotely sensed data.

  18. Evaluating Error of LIDAR Derived dem Interpolation for Vegetation Area

    NASA Astrophysics Data System (ADS)

    Ismail, Z.; Khanan, M. F. Abdul; Omar, F. Z.; Rahman, M. Z. Abdul; Mohd Salleh, M. R.

    2016-09-01

    Light Detection and Ranging or LiDAR data is a data source for deriving digital terrain model while Digital Elevation Model or DEM is usable within Geographical Information System or GIS. The aim of this study is to evaluate the accuracy of LiDAR derived DEM generated based on different interpolation methods and slope classes. Initially, the study area is divided into three slope classes: (a) slope class one (0° - 5°), (b) slope class two (6° - 10°) and (c) slope class three (11° - 15°). Secondly, each slope class is tested using three distinctive interpolation methods: (a) Kriging, (b) Inverse Distance Weighting (IDW) and (c) Spline. Next, accuracy assessment is done based on field survey tachymetry data. The finding reveals that the overall Root Mean Square Error or RMSE for Kriging provided the lowest value of 0.727 m for both 0.5 m and 1 m spatial resolutions of oil palm area, followed by Spline with values of 0.734 m for 0.5 m spatial resolution and 0.747 m for spatial resolution of 1 m. Concurrently, IDW provided the highest RMSE value of 0.784 m for both spatial resolutions of 0.5 and 1 m. For rubber area, Spline provided the lowest RMSE value of 0.746 m for 0.5 m spatial resolution and 0.760 m for 1 m spatial resolution. The highest value of RMSE for rubber area is IDW with the value of 1.061 m for both spatial resolutions. Finally, Kriging gave the RMSE value of 0.790m for both spatial resolutions.

  19. 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.

  20. Icesat Validation of Tandem-X I-Dems Over the UK

    NASA Astrophysics Data System (ADS)

    Feng, L.; Muller, J.-P.

    2016-06-01

    From the latest TanDEM-X mission (bistatic X-Band interferometric SAR), globally consistent Digital Elevation Model (DEM) will be available from 2017, but their accuracy has not yet been fully characterised. This paper presents the methods and implementation of statistical procedures for the validation of the vertical accuracy of TanDEM-X iDEMs at grid-spacing of approximately 12.5 m, 30 m and 90 m based on processed ICESat data over the UK in order to assess their potential extrapolation across the globe. The accuracy of the TanDEM-X iDEM in UK was obtained as follows: against ICESat GLA14 elevation data, TanDEM-X iDEM has -0.028±3.654 m over England and Wales and 0.316 ± 5.286 m over Scotland for 12 m, -0.073 ± 6.575 m for 30 m, and 0.0225 ± 9.251 m at 90 m. Moreover, 90 % of all results at the three resolutions of TanDEM-X iDEM data (with a linear error at 90 % confidence level) are below 16.2 m. These validation results also indicate that derivative topographic parameters (slope, aspect and relief) have a strong effect on the vertical accuracy of the TanDEM-X iDEMs. In high-relief and large slope terrain, large errors and data voids are frequent, and their location is strongly influenced by topography, whilst in the low- to medium-relief and low slope sites, errors are smaller. ICESat derived elevations are heavily influenced by surface slope within the 70 m footprint as well as there being slope dependent errors in the TanDEM-X iDEMs.

  1. Global Maps from Interferometeric TanDEM-X Data: Applications and Potentials

    NASA Astrophysics Data System (ADS)

    Rizzoli, Paola; Martone, Michele; Brautigam, Benjamin; Zink, Manfred

    2015-05-01

    TanDEM-X is a spaceborne Synthetic Aperture Radar (SAR) mission, whose goal is the generation of a global Digital Elevation Model (DEM) with unprecedented accuracy, by using interferometric SAR (InSAR) techniques (InSAR). TanDEM-X offers a huge global data set of bistatic InSAR acquisitions, each of them supplemented by quick look images of different SAR quantities, such as amplitude, coherence, and DEM. Global quick look mosaics of the interferometric coherence and of the relative height error can be considered for mission performance monitoring and acquisition strategy optimization. The aim of this paper is to present the use of such mosaics within the TanDEM-X mission and to show their potentials for future scientific applications for example in the fields of glaciology and forestry.

  2. 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.

  3. Open-Source Digital Elevation Model (DEMs) Evaluation with GPS and LiDAR Data

    NASA Astrophysics Data System (ADS)

    Khalid, N. F.; Din, A. H. M.; Omar, K. M.; Khanan, M. F. A.; Omar, A. H.; Hamid, A. I. A.; Pa'suya, M. F.

    2016-09-01

    Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM), Shuttle Radar Topography Mission (SRTM), and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) are freely available Digital Elevation Model (DEM) datasets for environmental modeling and studies. The quality of spatial resolution and vertical accuracy of the DEM data source has a great influence particularly on the accuracy specifically for inundation mapping. Most of the coastal inundation risk studies used the publicly available DEM to estimated the coastal inundation and associated damaged especially to human population based on the increment of sea level. In this study, the comparison between ground truth data from Global Positioning System (GPS) observation and DEM is done to evaluate the accuracy of each DEM. The vertical accuracy of SRTM shows better result against ASTER and GMTED10 with an RMSE of 6.054 m. On top of the accuracy, the correlation of DEM is identified with the high determination of coefficient of 0.912 for SRTM. For coastal zone area, DEMs based on airborne light detection and ranging (LiDAR) dataset was used as ground truth data relating to terrain height. In this case, the LiDAR DEM is compared against the new SRTM DEM after applying the scale factor. From the findings, the accuracy of the new DEM model from SRTM can be improved by applying scale factor. The result clearly shows that the value of RMSE exhibit slightly different when it reached 0.503 m. Hence, this new model is the most suitable and meets the accuracy requirement for coastal inundation risk assessment using open source data. The suitability of these datasets for further analysis on coastal management studies is vital to assess the potentially vulnerable areas caused by coastal inundation.

  4. Impacts of DEM uncertainties on critical source areas identification for non-point source pollution control based on SWAT model

    NASA Astrophysics Data System (ADS)

    Xu, Fei; Dong, Guangxia; Wang, Qingrui; Liu, Lumeng; Yu, Wenwen; Men, Cong; Liu, Ruimin

    2016-09-01

    The impacts of different digital elevation model (DEM) resolutions, sources and resampling techniques on nutrient simulations using the Soil and Water Assessment Tool (SWAT) model have not been well studied. The objective of this study was to evaluate the sensitivities of DEM resolutions (from 30 m to 1000 m), sources (ASTER GDEM2, SRTM and Topo-DEM) and resampling techniques (nearest neighbor, bilinear interpolation, cubic convolution and majority) to identification of non-point source (NPS) critical source area (CSA) based on nutrient loads using the SWAT model. The Xiangxi River, one of the main tributaries of Three Gorges Reservoir in China, was selected as the study area. The following findings were obtained: (1) Elevation and slope extracted from the DEMs were more sensitive to DEM resolution changes. Compared with the results of the 30 m DEM, 1000 m DEM underestimated the elevation and slope by 104 m and 41.57°, respectively; (2) The numbers of subwatersheds and hydrologic response units (HRUs) were considerably influenced by DEM resolutions, but the total nitrogen (TN) and total phosphorus (TP) loads of each subwatershed showed higher correlations with different DEM sources; (3) DEM resolutions and sources had larger effects on CSAs identifications, while TN and TP CSAs showed different response to DEM uncertainties. TN CSAs were more sensitive to resolution changes, exhibiting six distribution patterns at all DEM resolutions. TP CSAs were sensitive to source and resampling technique changes, exhibiting three distribution patterns for DEM sources and two distribution patterns for DEM resampling techniques. DEM resolutions and sources are the two most sensitive SWAT model DEM parameters that must be considered when nutrient CSAs are identified.

  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

  6. How Strong and Weak Readers Perform on the Developmental Eye Movement Test (DEM): Norms for Latvian School-Aged Children

    ERIC Educational Resources Information Center

    Serdjukova, Jelena; Ekimane, Lasma; Valeinis, Janis; Skilters, Jurgis; Krumina, Gunta

    2017-01-01

    The aim of our study was to determine DEM test performance norms for school-aged children in Latvia, assess how DEM test results correlate with children's reading rates, compare test performance between strong and weak readers. A modified DEM test and a newly developed reading test were administered to 1487 children during a screening survey. Our…

  7. 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.

  8. 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.

  9. 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).

  10. Dem Retrieval And Ground Motion Monitoring In China

    NASA Astrophysics Data System (ADS)

    Gatti, Guido; Perissin, Daniele; Wang, Teng; Rocca, Fabio

    2010-10-01

    This paper considers the topographic measurement and analysis basing on multi-baseline Synthetic Aperture Radar data. In 2009, the ongoing works were focused on taking advantage of Permanent Scatterers (PS) Interferometry to estimate the terrain elevation and ground motion in not urban contexts. An adapted version of the method, namely Quasi-PS (QPS) technique, has been used in order to exploit the distributed target information. One of the analyzed datasets concerns the mountainous area around Zhangbei, Hebei Province, from which a geocoded Digital Elevation Model (DEM) has been retrieved. Regarding ground motion monitoring, our attention was focalized on two different areas. The first is a small area near the Three Gorges Dam, in which ground deformations have been identified and measured. The second area regards the west part of the municipality of Shanghai, centered on a straight railway. The subsidence in that zone has been measured and the interferometric coherence of the railway has been studied, according to the hypothesis of spatial and temporal stability of this kind of target.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  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

    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. 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

  18. The topographic grain concept in DEM-based geomorphometric mapping

    NASA Astrophysics Data System (ADS)

    Józsa, Edina

    2016-04-01

    A common drawback of geomorphological analyses based on digital elevation datasets is the definition of search window size for the derivation of morphometric variables. The fixed-size neighbourhood determines the scale of the analysis and mapping, which can lead to the generalization of smaller surface details or the elimination of larger landform elements. The methods of DEM-based geomorphometric mapping are constantly developing into the direction of multi-scale landform delineation, but the optimal threshold for search window size is still a limiting factor. A possible way to determine the suitable value for the parameter is to consider the topographic grain principle (Wood, W. F. - Snell, J. B. 1960, Pike, R. J. et al. 1989). The calculation is implemented as a bash shell script for GRASS GIS to determine the optimal threshold for the r.geomorphon module. The approach relies on the potential of the topographic grain to detect the characteristic local ridgeline-to-channel spacing. By calculating the relative relief values with nested neighbourhood matrices it is possible to define a break-point where the increase rate of local relief encountered by the sample is significantly reducing. The geomorphons approach (Jasiewicz, J. - Stepinski, T. F. 2013) is a cell-based DEM classification method for the identification of landform elements at a broad range of scales by using line-of-sight technique. The landforms larger than the maximum lookup distance are broken down to smaller elements therefore the threshold needs to be set for a relatively large value. On the contrary, the computational requirements and the size of the study sites determine the upper limit for the value. Therefore the aim was to create a tool that would help to determine the optimal parameter for r.geomorphon tool. As a result it would be possible to produce more objective and consistent maps with achieving the full efficiency of this mapping technique. For the thorough analysis on the

  19. Assessing the long-term species composition predicted by PrognAus

    PubMed Central

    Huber, Markus O.

    2010-01-01

    Tree growth models are supposed to contain stand growth laws as so called “emergent properties” which derive from interactions of individual-tree growth and mortality functions. This study investigates whether the evolving tree species composition in a long term simulation by the distance-independent tree growth model PrognAus matches the species composition of the potential natural vegetation type which is expected to occur if one refrains from further management interventions and major disturbances, climate change, and changes in site conditions can be excluded. For this purpose the development of 6933 sample plots of the Austrian National Forest Inventory was predicted for 2500 years. The resulting species proportions, derived from volume per hectare of 15 tree species or species groups, were used to classify every sample plot according to potential natural forest types, following a classification scheme based on expert knowledge. These simulated potential natural vegetation types were compared with expert reconstructions of the sample plots of the Austrian National Forest Inventory. A total of 5789 plots were actually classified with the scheme; in 33% of the cases the classification on the basis of the PrognAus-simulations was identical with the classification by the Austrian National Forest Inventory. A predominantly correct classification was achieved for the subalpine Picea abies-type and the Fagus sylvatica-type although PrognAus showed a tendency to overestimate the proportion of F. sylvatica and P. abies. Weaknesses in the ability to simulate forest types dominated by Quercus spp., Acer spp., and Pinus sylvestris were identified. This shortcoming might be caused by the mortality model which allows a larger diameter at breast height for F. sylvatica or by the ingrowth model whose terms for the consideration of inter-specific competition may lead to a disadvantage of Quercus spp., P. sylvestris, and Abies alba. Moreover, the ingrowth model might be

  20. 2D DEM model of sand transport with wind interaction

    NASA Astrophysics Data System (ADS)

    Oger, L.; Valance, A.

    2013-06-01

    The advance of the dunes in the desert is a threat to the life of the local people. The dunes invade houses, agricultural land and perturb the circulation on the roads. It is therefore very important to understand the mechanism of sand transport in order to fight against desertification. Saltation in which sand grains are propelled by the wind along the surface in short hops, is the primary mode of blown sand movement [1]. The saltating grains are very energetic and when impact a sand surface, they rebound and consequently eject other particles from the sand bed. The ejected grains, called reptating grains, contribute to the augmentation of the sand flux. Some of them can be promoted to the saltation motion. We use a mechanical model based on the Discrete Element Method to study successive collisions of incident energetic beads with granular packing in the context of Aeolian saltation transport. We investigate the collision process for the case where the incident bead and those from the packing have identical mechanical properties. We analyze the features of the consecutive collision processes made by the transport of the saltating disks by a wind in which its profile is obtained from the counter-interaction between air flow and grain flows. We used a molecular dynamics method known as DEM (soft Discrete Element Method) with a initial static packing of 20000 2D particles. The dilation of the upper surface due to the consecutive collisions is responsible for maintaining the flow at a given energy input due to the wind.

  1. Glacier Volume Change Estimation Using Time Series of Improved Aster Dems

    NASA Astrophysics Data System (ADS)

    Girod, Luc; Nuth, Christopher; Kääb, Andreas

    2016-06-01

    Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter seems not to be

  2. 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.

  3. 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.

  4. 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.

  5. Shape and Albedo from Shading (SAfS) for Pixel-Level dem Generation from Monocular Images Constrained by Low-Resolution dem

    NASA Astrophysics Data System (ADS)

    Wu, Bo; Chung Liu, Wai; Grumpe, Arne; Wöhler, Christian

    2016-06-01

    Lunar topographic information, e.g., lunar DEM (Digital Elevation Model), is very important for lunar exploration missions and scientific research. Lunar DEMs are typically generated from photogrammetric image processing or laser altimetry, of which photogrammetric methods require multiple stereo images of an area. DEMs generated from these methods are usually achieved by various interpolation techniques, leading to interpolation artifacts in the resulting DEM. On the other hand, photometric shape reconstruction, e.g., SfS (Shape from Shading), extensively studied in the field of Computer Vision has been introduced to pixel-level resolution DEM refinement. SfS methods have the ability to reconstruct pixel-wise terrain details that explain a given image of the terrain. If the terrain and its corresponding pixel-wise albedo were to be estimated simultaneously, this is a SAfS (Shape and Albedo from Shading) problem and it will be under-determined without additional information. Previous works show strong statistical regularities in albedo of natural objects, and this is even more logically valid in the case of lunar surface due to its lower surface albedo complexity than the Earth. In this paper we suggest a method that refines a lower-resolution DEM to pixel-level resolution given a monocular image of the coverage with known light source, at the same time we also estimate the corresponding pixel-wise albedo map. We regulate the behaviour of albedo and shape such that the optimized terrain and albedo are the likely solutions that explain the corresponding image. The parameters in the approach are optimized through a kernel-based relaxation framework to gain computational advantages. In this research we experimentally employ the Lunar-Lambertian model for reflectance modelling; the framework of the algorithm is expected to be independent of a specific reflectance model. Experiments are carried out using the monocular images from Lunar Reconnaissance Orbiter (LRO

  6. 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

  7. Bathymetric survey of water reservoirs in north-eastern Brazil based on TanDEM-X satellite data.

    PubMed

    Zhang, Shuping; Foerster, Saskia; Medeiros, Pedro; de Araújo, José Carlos; Motagh, Mahdi; Waske, Bjoern

    2016-11-15

    Water scarcity in the dry season is a vital problem in dryland regions such as northeastern Brazil. Water supplies in these areas often come from numerous reservoirs of various sizes. However, inventory data for these reservoirs is often limited due to the expense and time required for their acquisition via field surveys, particularly in remote areas. Remote sensing techniques provide a valuable alternative to conventional reservoir bathymetric surveys for water resource management. In this study single pass TanDEM-X data acquired in bistatic mode were used to generate digital elevation models (DEMs) in the Madalena catchment, northeastern Brazil. Validation with differential global positioning system (DGPS) data from field measurements indicated an absolute elevation accuracy of approximately 1m for the TanDEM-X derived DEMs (TDX DEMs). The DEMs derived from TanDEM-X data acquired at low water levels show significant advantages over bathymetric maps derived from field survey, particularly with regard to coverage, evenly distributed measurements and replication of reservoir shape. Furthermore, by mapping the dry reservoir bottoms with TanDEM-X data, TDX DEMs are free of emergent and submerged macrophytes, independent of water depth (e.g. >10m), water quality and even weather conditions. Thus, the method is superior to other existing bathymetric mapping approaches, particularly for inland water bodies. The proposed approach relies on (nearly) dry reservoir conditions at times of image acquisition and is thus restricted to areas that show considerable water levels variations. However, comparisons between TDX DEM and the bathymetric map derived from field surveys show that the amount of water retained during the dry phase has only marginal impact on the total water volume derivation from TDX DEM. Overall, DEMs generated from bistatic TanDEM-X data acquired in low water periods constitute a useful and efficient data source for deriving reservoir bathymetry and show

  8. Effects of LiDAR Derived DEM Resolution on Hydrographic Feature Extraction

    NASA Astrophysics Data System (ADS)

    Yang, P.; Ames, D. P.; Glenn, N. F.; Anderson, D.

    2010-12-01

    This paper examines the effect of LiDAR-derived digital elevation model (DEM) resolution on digitally extracted stream networks with respect to known stream channel locations. Two study sites, Reynolds Creek Experimental Watershed (RCEW) and Dry Creek Experimental Watershed (DCEW), which represent terrain characteristics for lower and intermediate elevation mountainous watersheds in the Intermountain West, were selected as study areas for this research. DEMs reflecting bare earth ground were created from the LiDAR observations at a series of raster cell sizes (from 1 m to 60 m) using spatial interpolation techniques. The effect of DEM resolution on resulting hydrographic feature (specifically stream channel) derivation was studied. Stream length, watershed area, and sinuosity were explored at each of the raster cell sizes. Also, variation from known channel location as estimated by root mean square error (RMSE) between surveyed channel location and extracted channel was computed for each of the DEMs and extracted stream networks. As expected, the results indicate that the DEM based hydrographic extraction process provides more detailed hydrographic features at a finer resolution. RMSE between the known channel location and modeled locations generally increased with larger cell size DEM with a greater effect in the larger RCEW. Sensitivity analyses on sinuosity demonstrated that the resulting shape of streams obtained from LiDAR data matched best with the reference data at an intermediate cell size instead of highest resolution, which is at a range of cell size from 5 to 10 m likely due to original point spacing, terrain characteristics, and LiDAR noise influence. More importantly, the absolute sinuosity deviation displayed a smallest value at the cell size of 10 m in both experimental watersheds, which suggests that optimal cell size for LiDAR-derived DEMs used for hydrographic feature extraction is 10 m.

  9. CFD-DEM simulations of current-induced dune formation and morphological evolution

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Xiao, Heng

    2016-06-01

    Understanding the fundamental mechanisms of sediment transport, particularly those during the formation and evolution of bedforms, is of critical scientific importance and has engineering relevance. Traditional approaches of sediment transport simulations heavily rely on empirical models, which are not able to capture the physics-rich, regime-dependent behaviors of the process. With the increase of available computational resources in the past decade, CFD-DEM (computational fluid dynamics-discrete element method) has emerged as a viable high-fidelity method for the study of sediment transport. However, a comprehensive, quantitative study of the generation and migration of different sediment bed patterns using CFD-DEM is still lacking. In this work, current-induced sediment transport problems in a wide range of regimes are simulated, including 'flat bed in motion', 'small dune', 'vortex dune' and suspended transport. Simulations are performed by using SediFoam, an open-source, massively parallel CFD-DEM solver developed by the authors. This is a general-purpose solver for particle-laden flows tailed for particle transport problems. Validation tests are performed to demonstrate the capability of CFD-DEM in the full range of sediment transport regimes. Comparison of simulation results with experimental and numerical benchmark data demonstrates the merits of CFD-DEM approach. In addition, the improvements of the present simulations over existing studies using CFD-DEM are presented. The present solver gives more accurate prediction of sediment transport rate by properly accounting for the influence of particle volume fraction on the fluid flow. In summary, this work demonstrates that CFD-DEM is a promising particle-resolving approach for probing the physics of current-induced sediment transport.

  10. 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.

  11. Optimizing grid computing configuration and scheduling for geospatial analysis: An example with interpolating DEM

    NASA Astrophysics Data System (ADS)

    Huang, Qunying; Yang, Chaowei

    2011-02-01

    Many geographic analyses are very time-consuming and do not scale well when large datasets are involved. For example, the interpolation of DEMs (digital evaluation model) for large geographic areas could become a problem in practical application, especially for web applications such as terrain visualization, where a fast response is required and computational demands exceed the capacity of a traditional single processing unit conducting serial processing. Therefore, high performance and parallel computing approaches, such as grid computing, were investigated to speed up the geographic analysis algorithms, such as DEM interpolation. The key for grid computing is to configure an optimized grid computing platform for the geospatial analysis and optimally schedule the geospatial tasks within a grid platform. However, there is no research focused on this. Using DEM interoperation as an example, we report our systematic research on configuring and scheduling a high performance grid computing platform to improve the performance of geographic analyses through a systematic study on how the number of cores, processors, grid nodes, different network connections and concurrent request impact the speedup of geospatial analyses. Condor, a grid middleware, is used to schedule the DEM interpolation tasks for different grid configurations. A Kansas raster-based DEM is used for a case study and an inverse distance weighting (IDW) algorithm is used in interpolation experiments.

  12. 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).

  13. 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.

  14. Establishing the Aus-ROC Australian and New Zealand out-of-hospital cardiac arrest Epistry

    PubMed Central

    Bray, Janet; Smith, Karen; Walker, Tony; Grantham, Hugh; Hein, Cindy; Thorrowgood, Melanie; Smith, Anthony; Smith, Tony; Dicker, Bridget; Swain, Andy; Bailey, Mark; Bosley, Emma; Pemberton, Katherine; Cameron, Peter; Nichol, Graham; Finn, Judith

    2016-01-01

    Introduction Out-of-hospital cardiac arrest (OHCA) is a global health problem with low survival. Regional variation in survival has heightened interest in combining cardiac arrest registries to understand and improve OHCA outcomes. While individual OHCA registries exist in Australian and New Zealand ambulance services, until recently these registries have not been combined. The aim of this protocol paper is to describe the rationale and methods of the Australian Resuscitation Outcomes Consortium (Aus-ROC) OHCA epidemiological registry (Epistry). Methods and analysis The Aus-ROC Epistry is designed as a population-based cohort study. Data collection started in 2014. Six ambulance services in Australia (Ambulance Victoria, SA Ambulance Service, St John Ambulance Western Australia and Queensland Ambulance Service) and New Zealand (St John New Zealand and Wellington Free Ambulance) currently contribute data. All OHCA attended by ambulance, regardless of aetiology or patient age, are included in the Epistry. The catchment population is approximately 19.3 million persons, representing 63% of the Australian population and 100% of the New Zealand population. Data are collected using Utstein-style definitions. Information incorporated into the Epistry includes demographics, arrest features, ambulance response times, treatment and patient outcomes. The primary outcome is ‘survival to hospital discharge’, with ‘return of spontaneous circulation’ as a key secondary outcome. Ethics and dissemination Ethics approval was independently sought by each of the contributing registries. Overarching ethics for the Epistry was provided by Monash University HREC (Approval No. CF12/3938—2012001888). A population-based OHCA registry capturing the majority of Australia and New Zealand will allow risk-adjusted outcomes to be determined, to enable benchmarking across ambulance providers, facilitate the identification of system-wide strategies associated with survival from OHCA, and

  15. 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.

  16. Blaze-DEMGPU: Modular high performance DEM framework for the GPU architecture

    NASA Astrophysics Data System (ADS)

    Govender, Nicolin; Wilke, Daniel N.; Kok, Schalk

    Blaze-DEMGPU is a modular GPU based discrete element method (DEM) framework that supports polyhedral shaped particles. The high level performance is attributed to the light weight and Single Instruction Multiple Data (SIMD) that the GPU architecture offers. Blaze-DEMGPU offers suitable algorithms to conduct DEM simulations on the GPU and these algorithms can be extended and modified. Since a large number of scientific simulations are particle based, many of the algorithms and strategies for GPU implementation present in Blaze-DEMGPU can be applied to other fields. Blaze-DEMGPU will make it easier for new researchers to use high performance GPU computing as well as stimulate wider GPU research efforts by the DEM community.

  17. A Detailed Observation of a LMC SNR, DEM L241, with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Bamba, Aya; Ueno, Masaru; Nakajima, Hiroshi; Mori, Koji; Koyama, Katsuji

    We report on an XMM-Newton observation of the supernova remnant (SNR) DEM L241 in the Large Magellanic Cloud. In the soft band image, the emission shows an elongated structure, like a killifish (Head and Tail), with a central point source, named as XMMU J053559.3-673509 (Eye). The Eye's spectrum is well reproduced with a power-law model. The source has neither significant coherent pulsations nor time variabilities. Its luminosity and spectrum remind us that the source might be a pulsar and/or pulsar wind nebula in DEM L241. The spectra of Head and Tail are well reproduced by a non-equilibrium ionization plasma model with over-abundant Ne and under-abundant Fe, suggesting that the progenitor of DEM L241 is a very massive star.

  18. GPS-Based Precision Baseline Reconstruction for the TanDEM-X SAR-Formation

    NASA Technical Reports Server (NTRS)

    Montenbruck, O.; vanBarneveld, P. W. L.; Yoon, Y.; Visser, P. N. A. M.

    2007-01-01

    The TanDEM-X formation employs two separate spacecraft to collect interferometric Synthetic Aperture Radar (SAR) measurements over baselines of about 1 km. These will allow the generation ofa global Digital Elevation Model (DEM) with an relative vertical accuracy of 2-4 m and a 10 m ground resolution. As part of the ground processing, the separation of the SAR antennas at the time of each data take must be reconstructed with a 1 mm accuracy using measurements from two geodetic grade GPS receivers. The paper discusses the TanDEM-X mission as well as the methods employed for determining the interferometric baseline with utmost precision. Measurements collected during the close fly-by of the two GRACE satellites serve as a reference case to illustrate the processing concept, expected accuracy and quality control strategies.

  19. 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.

  20. 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.

  1. The Effect of DEM Quality on Sea Level Rise Exposure Analysis

    NASA Astrophysics Data System (ADS)

    Kulp, S. A.; Strauss, B.

    2015-12-01

    Sea level rise (SLR) caused by climate change could cause significant disruptions in coastal communities across the world. Current projections estimate that we may see in the vicinity of 1 meter of SLR by the end of the century, and due to collapsing ice sheets in West Antarctica, more than 3 meters of global SLR appear very likely in the long run. It is therefore crucial that we begin to accurately understand both the short- and long-term effects this level of flooding could have on each country's land area and population. However, while we have high-resolution digital elevation models (DEMs) publicly available for some parts of the world, such as the coastal lidar datasets distributed by NOAA for the US, most of the rest of the world is only covered by much poorer-quality data, such as data from SRTM (3 arcsec, or roughly 90m, horizontal resolution). In this work, we perform SLR analysis using both NOAA lidar- and SRTM-derived DEMs in the United States, in order to understand how using low-quality DEMs affect the final analysis results. We find that in many states, the computed population exposure at 1 meter SLR is over 2x higher when using the Lidar DEM, compared to the results computed from SRTM. In addition to the clear differences in horizontal resolution, this very large difference in computed exposure could likely be explained by the fact that SRTM is based on surface elevation, while the Lidar DEM is based on bare earth elevation. We therefore conclude that any worldwide SLR analysis using SRTM would produce exposure estimates that are far too low, and higher-quality global DEMs are necessary in order to generate exposure analysis of reasonable accuracy.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. San Francisco Bay-Delta bathymetric/topographic digital elevation model (DEM)

    USGS Publications Warehouse

    Fregoso, Theresa; Wang, Rueen-Fang; Ateljevich, Eli; Jaffe, Bruce E.

    2017-01-01

    A high-resolution (10-meter per pixel) digital elevation model (DEM) was created for the Sacramento-San Joaquin Delta using both bathymetry and topography data. This DEM is the result of collaborative efforts of the U.S. Geological Survey (USGS) and the California Department of Water Resources (DWR). The base of the DEM is from a 10-m DEM released in 2004 and updated in 2005 (Foxgrover and others, 2005) that used Environmental Systems Research Institute (ESRI), ArcGIS Topo to Raster module to interpolate grids from single beam bathymetric surveys collected by DWR, the Army Corp of Engineers (COE), the National Oceanic and Atmospheric Administration (NOAA), and the USGS, into a continuous surface. The Topo to Raster interpolation method was specifically designed to create hydrologically correct DEMs from point, line, and polygon data (Environmental Systems Research Institute, Inc., 2015). Elevation contour lines were digitized based on the single beam point data for control of channel morphology during the interpolation process. Checks were performed to ensure that the interpolated surfaces honored the source bathymetry, and additional contours and (or) point data were added as needed to help constrain the data. The original data were collected in the tidal datum Mean Lower or Low Water (MLLW) or the National Geodetic Vertical Datum of 1929 (NGVD29). All data were converted to NGVD29.The 2005 USGS DEM was updated by DWR, first by converting the DEM to the current modern datum of North American Vertical Datum of 1988 (NAVD88) and then by following the methodology of the USGS DEM, established for the 2005 DEM (Foxgrover and others, 2005) for adding newly collected single and multibeam bathymetric data. They then included topographic data from lidar surveys, providing the first DEM that included the land/water interface (Wang and Ateljevich, 2012).The USGS further updated and expanded the DWR DEM with the inclusion of USGS interpolated sections of single beam

  8. 388. D.E.M., Delineator December 1932 STATE OF CALIFORNIA; DEPARTMENT OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    388. D.E.M., Delineator December 1932 STATE OF CALIFORNIA; DEPARTMENT OF PUBLIC WORKS; SAN FRANCISCO - OAKLAND BAY BRIDGE; SUPERSTRUCTURE - WEST BAY CROSSING; SUSPENDED STRUCTURE; SIDE SPAN TRUSSES AT ANCHORAGES; CONTRACT NO. 6; DRAWING NO. 40 - San Francisco Oakland Bay Bridge, Spanning San Francisco Bay, San Francisco, San Francisco County, CA

  9. 387. D.E.M., Delineator December 1932 STATE OF CALIFORNIA; DEPARTMENT OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    387. D.E.M., Delineator December 1932 STATE OF CALIFORNIA; DEPARTMENT OF PUBLIC WORKS; SAN FRANCISCO - OAKLAND BAY BRIDGE; SUPERSTRUCTURE - WEST BAY CROSSING; TOWERS 2, 3, 5 & 6; BRACING DETAILS - LOWER DECK; CONTRACT NO. 6; DRAWING NO. 27 - San Francisco Oakland Bay Bridge, Spanning San Francisco Bay, San Francisco, San Francisco County, CA

  10. Rockslide and Impulse Wave Modelling in the Vajont Reservoir by DEM-CFD Analyses

    NASA Astrophysics Data System (ADS)

    Zhao, T.; Utili, S.; Crosta, G. B.

    2016-06-01

    This paper investigates the generation of hydrodynamic water waves due to rockslides plunging into a water reservoir. Quasi-3D DEM analyses in plane strain by a coupled DEM-CFD code are adopted to simulate the rockslide from its onset to the impact with the still water and the subsequent generation of the wave. The employed numerical tools and upscaling of hydraulic properties allow predicting a physical response in broad agreement with the observations notwithstanding the assumptions and characteristics of the adopted methods. The results obtained by the DEM-CFD coupled approach are compared to those published in the literature and those presented by Crosta et al. (Landslide spreading, impulse waves and modelling of the Vajont rockslide. Rock mechanics, 2014) in a companion paper obtained through an ALE-FEM method. Analyses performed along two cross sections are representative of the limit conditions of the eastern and western slope sectors. The max rockslide average velocity and the water wave velocity reach ca. 22 and 20 m/s, respectively. The maximum computed run up amounts to ca. 120 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 and 190 m, respectively). Therefore, the overall study lays out a possible DEM-CFD framework for the modelling of the generation of the hydrodynamic wave due to the impact of a rapid moving rockslide or rock-debris avalanche.

  11. A quick algorithm of counting flow accumulation matrix for deriving drainage networks from a DEM

    NASA Astrophysics Data System (ADS)

    Wang, Yanping; Liu, Yonghe; Xie, Hongbo; Xiang, ZhongLin

    2011-06-01

    Computerized auto-extraction of drainage networks from Digital Elevation Model (DEM) has been widely used in hydrological modeling and relevant studies. Several essential procedures need to be implemented in eight-directional(D8) watershed delineation method, among which a problem need to be resolved is the lack of a high efficiency algorithm for quick and accurate computation of flow accumulation matrix involved in river network delineations. For the problem of depression filling, the algorithm presented by Oliver Planchon has resolved it. This study was aimed to develop a simple and quick algorithm for flow accumulation matrix computations. For this purpose, a simple and high efficiency algorithm of the time complexity of O(n) compared to the commonly used code of the time complexity of O(n2) orO(nlogn) , has been developed. Performance tests on this newly developed algorithm were conducted for different size of DEMs, and the results suggested that the algorithm has a linear time complexity with increasing sizes of DEM. The computation efficiency of this newly developed algorithm is many times higher than the commonly used code, and for a DEM of size 1000*1000, flow accumulation matrix computation can be completed within only several seconds compared with about few minutes needed by common used algorithms.

  12. 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.

  13. DEM-based Watershed Delineation - Comparison of Different Methods and applications

    NASA Astrophysics Data System (ADS)

    Chu, X.; Zhang, J.; Tahmasebi Nasab, M.

    2015-12-01

    Digital elevation models (DEMs) are commonly used for large-scale watershed hydrologic and water quality modeling. With aid of the latest LiDAR technology, submeter scale DEM data are often available for many areas in the United States. Precise characterization of the detailed variations in surface microtopography using such high-resolution DEMs is crucial to the related watershed modeling. Various methods have been developed to delineate a watershed, including determination of flow directions and accumulations, identification of subbasin boundaries, and calculation of the relevant topographic parameters. The objective of this study is to examine different DEM-based watershed delineation methods by comparing their unique features and the discrepancies in their results. Not only does this study cover the traditional watershed delineation methods, but also a new puddle-based unit (PBU) delineation method. The specific topics and issues to be presented involve flow directions (D8 single flow direction vs. multi-direction methods), segmentation of stream channels, drainage systems (single "depressionless" drainage network vs. hierarchical depression-dominated drainage system), and hydrologic connectivity (static structural connectivity vs. dynamic functional connectivity). A variety of real topographic surfaces are selected and delineated by using the selected methods. Comparisons of their delineation results emphasize the importance of selection of the methods and highlight their applicability and potential impacts on watershed modeling.

  14. Rhode Island DEM to Receive $129,000 EPA Pollution Prevention Grant

    EPA Pesticide Factsheets

    The RI Dept. of Environmental Management (RI DEM) has been selected to receive $129,000 over two years as one of five Pollution Prevention grants being awarded by EPA’s New England Regional Office for the FY2016-FY2017 Pollution Prevention Grants cycle.

  15. 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.

  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. An innovative approach to improve SRTM DEM using multispectral imagery and artificial neural network

    NASA Astrophysics Data System (ADS)

    Wendi, Dadiyorto; Liong, Shie-Yui; Sun, Yabin; doan, Chi Dung

    2016-06-01

    Although the Shuttle Radar Topography Mission [SRTM) data are a publicly accessible Digital Elevation Model [DEM) provided at no cost, its accuracy especially at forested area is known to be limited with root mean square error (RMSE) of approx. 14 m in Singapore's forested area. Such inaccuracy is attributed to the 5.6 cm wavelength used by SRTM that does not penetrate vegetation well. This paper considers forested areas of central catchment of Singapore as a proof of concept of an approach to improve the SRTM data set. The approach makes full use of (1) the introduction of multispectral imagery (Landsat 8), of 30 m resolution, into SRTM data; (2) the Artificial Neural Network (ANN) to flex its known strengths in pattern recognition and; (3) a reference DEM of high accuracy (1 m) derived through the integration of stereo imaging of worldview-1 and extensive ground survey points. The study shows a series of significant improvements of the SRTM when assessed with the reference DEM of 2 different areas, with RMSE reduction of ˜68% (from 13.9 m to 4.4 m) and ˜52% (from 14.2 m to 6.7 m). In addition, the assessment of the resulting DEM also includes comparisons with simple denoising methodology (Low Pass Filter) and commercially available product called NEXTMap® World 30™.

  18. Evaluating DEM conditioning techniques, elevation source data, and grid resolution for field-scale hydrological parameter extraction

    NASA Astrophysics Data System (ADS)

    Woodrow, Kathryn; Lindsay, John B.; Berg, Aaron A.

    2016-09-01

    Although digital elevation models (DEMs) prove useful for a number of hydrological applications, they are often the end result of numerous processing steps that each contains uncertainty. These uncertainties have the potential to greatly influence DEM quality and to further propagate to DEM-derived attributes including derived surface and near-surface drainage patterns. This research examines the impacts of DEM grid resolution, elevation source data, and conditioning techniques on the spatial and statistical distribution of field-scale hydrological attributes for a 12,000 ha watershed of an agricultural area within southwestern Ontario, Canada. Three conditioning techniques, including depression filling (DF), depression breaching (DB), and stream burning (SB), were examined. The catchments draining to each boundary of 7933 agricultural fields were delineated using the surface drainage patterns modeled from LiDAR data, interpolated to a 1 m, 5 m, and 10 m resolution DEMs, and from a 10 m resolution photogrammetric DEM. The results showed that variation in DEM grid resolution resulted in significant differences in the spatial and statistical distributions of contributing areas and the distributions of downslope flowpath length. Degrading the grid resolution of the LiDAR data from 1 m to 10 m resulted in a disagreement in mapped contributing areas of between 29.4% and 37.3% of the study area, depending on the DEM conditioning technique. The disagreements among the field-scale contributing areas mapped from the 10 m LiDAR DEM and photogrammetric DEM were large, with nearly half of the study area draining to alternate field boundaries. Differences in derived contributing areas and flowpaths among various conditioning techniques increased substantially at finer grid resolutions, with the largest disagreement among mapped contributing areas occurring between the 1 m resolution DB DEM and the SB DEM (37% disagreement) and the DB-DF comparison (36.5% disagreement in mapped

  19. DEM sourcing guidelines for computing 1 Eö accurate terrain corrections for airborne gravity gradiometry

    NASA Astrophysics Data System (ADS)

    Annecchione, Maria; Hatch, David; Hefford, Shane W.

    2017-01-01

    In this paper we investigate digital elevation model (DEM) sourcing requirements to compute gravity gradiometry terrain corrections accurate to 1 Eötvös (Eö) at observation heights of 80 m or more above ground. Such survey heights are typical in fixed-wing airborne surveying for resource exploration where the maximum signal-to-noise ratio is sought. We consider the accuracy of terrain corrections relevant for recent commercial airborne gravity gradiometry systems operating at the 10 Eö noise level and for future systems with a target noise level of 1 Eö. We focus on the requirements for the vertical gradient of the vertical component of gravity (Gdd) because this element of the gradient tensor is most commonly interpreted qualitatively and quantitatively. Terrain correction accuracy depends on the bare-earth DEM accuracy and spatial resolution. The bare-earth DEM accuracy and spatial resolution depends on its source. Two possible sources are considered: airborne LiDAR and Shuttle Radar Topography Mission (SRTM). The accuracy of an SRTM DEM is affected by vegetation height. The SRTM footprint is also larger and the DEM resolution is thus lower. However, resolution requirements relax as relief decreases. Publicly available LiDAR data and 1 arc-second and 3 arc-second SRTM data were selected over four study areas representing end member cases of vegetation cover and relief. The four study areas are presented as reference material for processing airborne gravity gradiometry data at the 1 Eö noise level with 50 m spatial resolution. From this investigation we find that to achieve 1 Eö accuracy in the terrain correction at 80 m height airborne LiDAR data are required even when terrain relief is a few tens of meters and the vegetation is sparse. However, as satellite ranging technologies progress bare-earth DEMs of sufficient accuracy and resolution may be sourced at lesser cost. We found that a bare-earth DEM of 10 m resolution and 2 m accuracy are sufficient for

  20. Effect of DEM resolution and comparison between different weighting factors for hydrologic connectivity index

    NASA Astrophysics Data System (ADS)

    Cantreul, Vincent; Cavalli, Marco; Degré, Aurore

    2016-04-01

    The emerging concept of hydrological connectivity is difficult to quantify. Some indices have been proposed. The most cited is Borselli's one. It mainly uses the DEM as input. The pixel size may strongly impacts the result of the calculation. It has not been studied yet in silty areas. Another important aspect is the choice of the weighting factor which strongly influences the index value. The objective of this poster is so to compare 8 different DEM's resolutions (12, 24, 48, 72, 96, 204, 504 and 996cm) and 3 different weighting factors (factor C of Wischmeier, Manning's factor and rugosity index) in the Borselli's index calculation. The IC was calculated in a 124ha catchment (Hevillers), in the loess belt, in Belgium. The DEM used is coming from a UAV with a maximum resolution of 12 cm. Permanent covered surfaces are not considered in order to avoid artefact due to the vegetation (2% of the surface). Regarding the DEM pixel size, the IC increases for a given pixel when the pixel size decreases. That confirms some results observed in the Alpine region by Cavalli (2014). The mean difference between 12 cm and 10 m resolution is 35% with higher values up to 100% for higher connectivity zones (flow paths). Another result is the lower impact of connections in the watershed (grass strips…) at lower pixel sizes. This is linked to the small width of some connections which are sometimes comparing to cell size. Furthermore, a great loss of precision is observed from the 500 cm pixel size and upper. That remark is quite intuitive. Finally, some very well disconnected zones appear for the highest resolutions. Regarding the weighting factor, IC values calculated using C factor are lower than with the rugosity index which is only a topographic factor. With very high resolution DEM, it permits to represent the fine topography. For the C factor, the zones up to very well disconnected areas (grass strips, wood…) are well represented with lower index values than downstream

  1. Enhancements to TauDEM to support Rapid Watershed Delineation Services

    NASA Astrophysics Data System (ADS)

    Sazib, N. S.; Tarboton, D. G.

    2015-12-01

    Watersheds are widely recognized as the basic functional unit for water resources management studies and are important for a variety of problems in hydrology, ecology, and geomorphology. Nevertheless, delineating a watershed spread across a large region is still cumbersome due to the processing burden of working with large Digital Elevation Model. Terrain Analysis Using Digital Elevation Models (TauDEM) software supports the delineation of watersheds and stream networks from within desktop Geographic Information Systems. A rich set of watershed and stream network attributes are computed. However limitations of the TauDEM desktop tools are (1) it supports only one type of raster (tiff format) data (2) requires installation of software for parallel processing, and (3) data have to be in projected coordinate system. This paper presents enhancements to TauDEM that have been developed to extend its generality and support web based watershed delineation services. The enhancements of TauDEM include (1) reading and writing raster data with the open-source geospatial data abstraction library (GDAL) not limited to the tiff data format and (2) support for both geographic and projected coordinates. To support web services for rapid watershed delineation a procedure has been developed for sub setting the domain based on sub-catchments, with preprocessed data prepared for each catchment stored. This allows the watershed delineation to function locally, while extending to the full extent of watersheds using preprocessed information. Additional capabilities of this program includes computation of average watershed properties and geomorphic and channel network variables such as drainage density, shape factor, relief ratio and stream ordering. The updated version of TauDEM increases the practical applicability of it in terms of raster data type, size and coordinate system. The watershed delineation web service functionality is useful for web based software as service deployments

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Jäggi, A.; Montenbruck, O.; Moon, Y.; Wermuth, M.; König, 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.

  4. Detailed geomorphological mapping from high resolution DEM data (LiDAR, TanDEM-X): two case studies from Germany and SE Tibet

    NASA Astrophysics Data System (ADS)

    Loibl, D.

    2012-04-01

    Two major obstacles are hampering the production of high resolution geomorphological maps: the complexity of the subject that should be depicted and the enormous efforts necessary to obtain data by field work. The first factor prevented the establishment of a generally accepted map legend; the second hampered efforts to collect comprehensive sets of geomorphological data. This left geomorphologists to produce applied maps, focusing on very few layers of information and often not sticking to any of the numerous standards proposed in the second half of the 20th century. Technological progress of the recent years, especially in the fields of digital elevation models, GIS environments, and computational hardware, today offers promising opportunities to overcome the obstacles and to produce detailed geomorphological maps even for remote or inhospitable regions. The feasibility of detailed geomorphological mapping from two new sets of digital elevation data, the 1 m LiDAR DTM provided by Germany's State Surveying Authority and the upcoming TanDEM-X DEM, has been evaluated in two case studies from a low mountain range in Germany and a high mountain range in SE Tibet. The results indicate that most layers of information of classical geomorphological maps (e.g. the German GMK) can be extracted from this data at appropriate scales but that significant differences occur concerning the quality and the grades of certainty of key contents. Generally, an enhancement of the geomorphographical, especially the geomorphometrical, and a weakening of geomorphogenetical contents was observed. From these findings, theoretical, methodological, and cartographical remarks on detailed geomorphological mapping from DEM data in GIS environments were educed. As GIS environments decouple data and design and enable the geomorphologist to choose information layer combinations freely to fit research topics, a general purpose legend becomes obsolete. Yet, a unified data structure is demanded to

  5. Generation of a precise DEM by interactive synthesis of multi-temporal elevation datasets: a case study of Schirmacher Oasis, East Antarctica

    NASA Astrophysics Data System (ADS)

    Jawak, Shridhar D.; Luis, Alvarinho J.

    2016-05-01

    Digital elevation model (DEM) is indispensable for analysis such as topographic feature extraction, ice sheet melting, slope stability analysis, landscape analysis and so on. Such analysis requires a highly accurate DEM. Available DEMs of Antarctic region compiled by using radar altimetry and the Antarctic digital database indicate elevation variations of up to hundreds of meters, which necessitates the generation of local improved DEM. An improved DEM of the Schirmacher Oasis, East Antarctica has been generated by synergistically fusing satellite-derived laser altimetry data from Geoscience Laser Altimetry System (GLAS), Radarsat Antarctic Mapping Project (RAMP) elevation data and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) global elevation data (GDEM). This is a characteristic attempt to generate a DEM of any part of Antarctica by fusing multiple elevation datasets, which is essential to model the ice elevation change and address the ice mass balance. We analyzed a suite of interpolation techniques for constructing a DEM from GLAS, RAMP and ASTER DEM-based point elevation datasets, in order to determine the level of confidence with which the interpolation techniques can generate a better interpolated continuous surface, and eventually improve the elevation accuracy of DEM from synergistically fused RAMP, GLAS and ASTER point elevation datasets. The DEM presented in this work has a vertical accuracy (≈ 23 m) better than RAMP DEM (≈ 57 m) and ASTER DEM (≈ 64 m) individually. The RAMP DEM and ASTER DEM elevations were corrected using differential GPS elevations as ground reference data, and the accuracy obtained after fusing multitemporal datasets is found to be improved than that of existing DEMs constructed by using RAMP or ASTER alone. This is our second attempt of fusing multitemporal, multisensory and multisource elevation data to generate a DEM of Antarctica, in order to address the ice elevation change and address the ice mass

  6. Central obesity as a precursor to the metabolic syndrome in the AusDiab study and Mauritius.

    PubMed

    Cameron, Adrian J; Boyko, Edward J; Sicree, Richard A; Zimmet, Paul Z; Söderberg, Stefan; Alberti, K George M M; Tuomilehto, Jaakko; Chitson, Pierrot; Shaw, Jonathan E

    2008-12-01

    Evidence from epidemiologic studies that central obesity precedes future metabolic change and does not occur concurrently with the appearance of the blood pressure, glucose, and lipid abnormalities that characterize the metabolic syndrome (MetS) has been lacking. Longitudinal surveys were conducted in Mauritius in 1987, 1992, and 1998, and in Australia in 2000 and 2005 (AusDiab). This analysis included men and women (aged > or = 25 years) in three cohorts: AusDiab 2000-2005 (n = 5,039), Mauritius 1987-1992 (n = 2,849), and Mauritius 1987-1998 (n = 1,999). MetS components included waist circumference, systolic blood pressure, fasting and 2-h postload plasma glucose, high-density lipoprotein (HDL) cholesterol, triglycerides, and homeostasis model assessment of insulin sensitivity (HOMA-S) (representing insulin sensitivity). Linear regression was used to determine which baseline components predicted deterioration in other MetS components over 5 years in AusDiab and 5 and 11 years in Mauritius, adjusted for age, sex, and ethnic group. Baseline waist circumference predicted deterioration (P < 0.01) in four of the other six MetS variables tested in AusDiab, five of six in Mauritius 1987-1992, and four of six in Mauritius 1987-1998. In contrast, an increase in waist circumference between baseline and follow-up was only predicted by insulin sensitivity (HOMA-S) at baseline, and only in one of the three cohorts. These results suggest that central obesity plays a central role in the development of the MetS and appears to precede the appearance of the other MetS components.

  7. Using NOAA/AVHRR based remote sensing data and PCR method for estimation of Aus rice yield in Bangladesh

    NASA Astrophysics Data System (ADS)

    Nizamuddin, Mohammad; Akhand, Kawsar; Roytman, Leonid; Kogan, Felix; Goldberg, Mitch

    2015-06-01

    Rice is a dominant food crop of Bangladesh accounting about 75 percent of agricultural land use for rice cultivation and currently Bangladesh is the world's fourth largest rice producing country. Rice provides about two-third of total calorie supply and about one-half of the agricultural GDP and one-sixth of the national income in Bangladesh. Aus is one of the main rice varieties in Bangladesh. Crop production, especially rice, the main food staple, is the most susceptible to climate change and variability. Any change in climate will, thus, increase uncertainty regarding rice production as climate is major cause year-to-year variability in rice productivity. This paper shows the application of remote sensing data for estimating Aus rice yield in Bangladesh using official statistics of rice yield with real time acquired satellite data from Advanced Very High Resolution Radiometer (AVHRR) sensor and Principal Component Regression (PCR) method was used to construct a model. The simulated result was compared with official agricultural statistics showing that the error of estimation of Aus rice yield was less than 10%. Remote sensing, therefore, is a valuable tool for estimating crop yields well in advance of harvest, and at a low cost.

  8. 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.

  9. 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

  10. Methodologies for watershed modeling with GIS and DEMs for the parameterization of the WEPP model

    NASA Astrophysics Data System (ADS)

    Cochrane, Thomas Arey

    Two methods called the Hillslope and Flowpath methods were developed that use geographical information systems (GIS) and digital elevation models (DEMs) to assess water erosion in small watersheds with the Water Erosion Prediction Project (WEPP) model. The Hillslope method is an automated method for the application of WEPP through the extraction of hillslopes and channels from DEMs. Each hillslope is represented as a rectangular area with a representative slope profile that drains to the top or sides of a single channel. The Hillslope method was further divided into the Calcleng and Chanleng methods, which are similar in every way except on how the hillslope lengths are calculated. The Calcleng method calculates a representative length of hillslope based on the weighted lengths of all flowpaths in a hillslope as identified through a DEM. The Chanleng method calculates the length of hillslopes adjacent to channels by matching the width of the hillslope to the length of adjacent channel. The Flowpath method works by applying the WEPP model to all possible flowpaths within a watershed as identified from a DEM. However, this method does not currently have a channel routing component, which limits its use to predicting spatially variable erosion on hillslopes within the watershed or from watersheds whose channels are not in a depositional or erodible mode. These methods were evaluated with six research watersheds from across the U.S., one from Treynor, Iowa, two from Watkinsville, Georgia, and three from Holly Springs, Mississippi. The effects of using different-sized DEM resolutions on simulations and the ability to accurately predict sediment yield and runoff from different event sizes were studied. Statistical analyses for all methods, resolutions, and event sizes were performed by comparing predicted vs. measured runoff and sediment yield from the watershed outlets on an event by event basis. Comparisons to manual applications by expert users and comparisons of

  11. A global vegetation corrected SRTM DEM for use in hazard modelling

    NASA Astrophysics Data System (ADS)

    Bates, P. D.; O'Loughlin, F.; Neal, J. C.; Durand, M. T.; Alsdorf, D. E.; Paiva, R. C. D.

    2015-12-01

    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 hazard 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 hazard 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. Our new 'Bare-Earth' SRTM DEM combines multiple remote sensing datasets, including ICESat GLA14 ground elevations, the vegetation continuous field dataset as a proxy for penetration depth of SRTM and a global vegetation height map, to remove the vegetation artefacts present in the original SRTM DEM. 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

  12. DEM extraction and its accuracy analysis with ground-based SAR interferometry

    NASA Astrophysics Data System (ADS)

    Dong, J.; Yue, J. P.; Li, L. H.

    2014-03-01

    Two altimetry models extracting DEM (Digital Elevation Model) with the GBSAR (Ground-Based Synthetic Aperture Radar) technology are studied and their accuracies are analyzed in detail. The approximate and improved altimetry models of GBSAR were derived from the spaceborne radar altimetry based on the principles of the GBSAR technology. The error caused by the parallel ray approximation in the approximate model was analyzed quantitatively, and the results show that the errors cannot be ignored for the ground-based radar system. For the improved altimetry model, the elevation error expression can be acquired by simulating and analyzing the error propagation coefficients of baseline length, wavelength, differential phase and range distance in the mathematical model. By analyzing the elevation error with the baseline and range distance, the results show that the improved altimetry model is suitable for high-precision DEM and the accuracy can be improved by adjusting baseline and shortening slant distance.

  13. 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.

    2017-04-01

    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.

  14. Análisis DEM 3D de arcos en regiones activas solares

    NASA Astrophysics Data System (ADS)

    Nuevo, F. A.; Mandrini, C. H.; Vásquez, A. M.; López Fuentes, M.

    2016-08-01

    The solar corona is highly organized by the magnetic field. Because of their temperature and density, magnetic loops are directly observable in active regions (ARs) in the extreme ultraviolet (EUV) and soft X-ray images. The observational determination of the three-dimensional (3D) distribution of basic physical parameters (electronic density and temperature, and magnetic field) is a fundamental constraint of coronal heating models. In this work we develop a technique of differential emission measure (DEM) analysis and we apply it an EUV loop identified in the images of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The DEM is determined after background subtraction and the electronic density and temperature in the loop are estimated from its moments. The 3D structure of the magnetic field in the loop and its intensity are modeled using linear force free field extrapolations based on AR magnetograms. In this work we show preliminary results of this technique.

  15. 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.

  16. 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

    2009-09-01

    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.

  17. 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.

  18. 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.

  19. A time series of TanDEM-X digital elevation models to monitor a glacier surge

    NASA Astrophysics Data System (ADS)

    Wendt, Anja; Mayer, Christoph; Lambrecht, Astrid; Floricioiu, Dana

    2016-04-01

    Bivachny Glacier, a tributary of the more than 70 km long Fedchenko Glacier in the Pamir Mountains, Central Asia, is a surge-type glacier with three known surges during the 20th century. In 2011, the most recent surge started which, in contrast to the previous ones, evolved down the whole glacier and reached the confluence with Fedchenko Glacier. Spatial and temporal glacier volume changes can be derived from high-resolution digital elevation models (DEMs) based on bistatic InSAR data from the TanDEM-X mission. There are nine DEMs available between 2011 and 2015 covering the entire surge period in time steps from few months up to one year. During the surge, the glacier surface elevation increased by up to 130 m in the lower part of the glacier; and change rates of up to 0.6 m per day were observed. The surface height dataset was complemented with glacier surface velocity information from TerraSAR-X/ TanDEM-X data as well as optical Landsat imagery. While the glacier was practically stagnant in 2000 after the end of the previous surge in the 1990s, the velocity increase started in 2011 in the upper reaches of the ablation area and successively moved downwards and intensified, reaching up to 4.0 m per day. The combination of surface elevation changes and glacier velocities, both of high temporal and spatial resolution, provides the unique opportunity to describe and analyse the evolution of the surge in unprecedented detail. Especially the relation between the mobilization front and the local mass transport provides insight into the surge dynamics.

  20. 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.

  1. Development of DEM formalism to modeling the dynamic response of brittle solids

    NASA Astrophysics Data System (ADS)

    Grigoriev, Aleksandr S.; Shilko, Eugeny V.; Psakhie, Sergey G.

    2016-11-01

    The paper presents a numerical model of the response for brittle materials to dynamic mechanical loading and implementation of the model within the discrete element method (DEM) by the example of the movable cellular automaton method (MCA). Verification of the model was carried out using the numerical modeling of the uniaxial compression tests of concrete and sandstone samples at various strain rates. It is shown that the developed model is correct and adequately describes the behavior of brittle materials under dynamic loading.

  2. A 'Drift' algorithm for integrating vector polyline and DEM based on the spherical DQG

    NASA Astrophysics Data System (ADS)

    Wang, Jiaojiao; Wang, Lei; Cao, Wenmin; Zhao, Xuesheng

    2014-03-01

    The efficient integration method of vector and DEM data on a global scale is one of the important issues in the community of Digital Earth. Among the existing methods, geometry-based approach maintains the characteristics of vector data necessary for inquiry and analysis. However, the complexity of geometry-based approach, which needs lots of interpolation calculation, limits its applications greatly in the multi-source spatial data integration on a global scale. To overcome this serious deficiency, a novel 'drift' algorithm is developed based on the spherical Degenerate Quadtree Grid (DQG) on which the global DEMs data is represented. The main principle of this algorithm is that the vector node in a DQG cell can be moved to the cell corner-point without changing the visualization effects if the cell is smaller or equal to a pixel of screen. A detailed algorithm and the multi-scale operation steps are also presented. By the 'drift' algorithm, the vector polylines and DEM grids are integrated seamlessly, avoiding lots of interpolation calculating. Based on the approach described above, we have developed a computer program in platform OpenGL 3D API with VC++ language. In this experiment, USGS GTOPO30 DEM data and 1:1,000,000 DCW roads data sets in China area are selected. Tests have shown that time consumption of the 'drift' algorithm is only about 25% of that of the traditional ones, moreover, the mean error of drift operation on vector nodes can be controlled within about half a DQG cell. In the end, the conclusions and future works are also given.

  3. Auf der Suche nach dem Codierungs-Gral für genetische Algorithmen

    NASA Astrophysics Data System (ADS)

    Weicker, Karsten

    Die umstrittene Frage nach dem "wichtigsten" Operator im genetischen Algorithmus - Mutation oder Crossover - hängt eng zusammen mit der Frage nach der richtigen binären Codierung. Gray- und standardbinärer Code bringen unterschiedliche Vor- und Nachteile in einen genetischen Algorithmus ein. Diese Arbeit beschäftigt sich mit der Suche nach einer Codierung, welche die Vorteile beider Codes vereinbart, und berichtet von einem Teilerfolg für mit 4 Bits encodierten Zahlen.

  4. Aster Global dem Version 3, and New Aster Water Body Dataset

    NASA Astrophysics Data System (ADS)

    Abrams, M.

    2016-06-01

    In 2016, the US/Japan ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) project released Version 3 of the Global DEM (GDEM). This 30 m DEM covers the earth's surface from 82N to 82S, and improves on two earlier versions by correcting some artefacts and filling in areas of missing DEMs by the acquisition of additional data. The GDEM was produced by stereocorrelation of 2 million ASTER scenes and operation on a pixel-by-pixel basis: cloud screening; stacking data from overlapping scenes; removing outlier values, and averaging elevation values. As previously, the GDEM is packaged in ~ 23,000 1 x 1 degree tiles. Each tile has a DEM file, and a NUM file reporting the number of scenes used for each pixel, and identifying the source for fill-in data (where persistent clouds prevented computation of an elevation value). An additional data set was concurrently produced and released: the ASTER Water Body Dataset (AWBD). This is a 30 m raster product, which encodes every pixel as either lake, river, or ocean; thus providing a global inland and shore-line water body mask. Water was identified through spectral analysis algorithms and manual editing. This product was evaluated against the Shuttle Water Body Dataset (SWBD), and the Landsat-based Global Inland Water (GIW) product. The SWBD only covers the earth between about 60 degrees north and south, so it is not a global product. The GIW only delineates inland water bodies, and does not deal with ocean coastlines. All products are at 30 m postings.

  5. 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.

  6. Tropical forest heterogeneity from TanDEM-X InSAR and lidar observations in Indonesia

    NASA Astrophysics Data System (ADS)

    De Grandi, Elsa Carla; Mitchard, Edward

    2016-10-01

    Fires exacerbated during El Niño Southern Oscillation are a serious threat in Indonesia leading to the destruction and degradation of tropical forests and emissions of CO2 in the atmosphere. Forest structural changes which occurred due to the 1997-1998 El Niño Southern Oscillation in the Sungai Wain Protection Forest (East Kalimantan, Indonesia), a previously intact forest reserve have led to the development of a range of landcover from secondary forest to areas dominated by grassland. These structural differences can be appreciated over large areas by remote sensing instruments such as TanDEM-X and LiDAR that provide information that are sensitive to vegetation vertical and horizontal structure. One-point statistics of TanDEM-X coherence (mean and CV) and LiDAR CHM (mean, CV) and derived metrics such as vegetation volume and canopy cover were tested for the discrimination between 4 landcover classes. Jeffries-Matusita (JM) separability was high between forest classes (primary or secondary forest) and non-forest (grassland) while, primary and secondary forest were not separable. The study tests the potential and the importance of potential of TanDEM-X coherence and LiDAR observations to characterize structural heterogeneity based on one-point statistics in tropical forest but requires improved characterization using two-point statistical measures.

  7. 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.

  8. 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.

  9. Effects of Scale on DEM Derived Drainage Networks For a High Arctic Wetland Complex

    NASA Astrophysics Data System (ADS)

    Brown, L. C.; Young, K. L.

    2004-05-01

    The ability to automatically generate drainage patterns is a useful tool in hydrologic studies, especially in remote areas where limited data is available. However drainage patterns derived from digital elevation data can be significantly affected by the scale of the data from which they are generated. This study investigates the effects of scaling on drainage patterns extracted from elevation data for a low gradient wetland area on Somerset Island, Nunavut, in the Canadian High Arctic. A series of Digital Elevation Models (DEM's) were created from digitized topographic information at varying resolutions (2.5 m, 5 m. 10 m, 50 m, 100 m, 200 m). Automated drainage network extractions were performed for each resolution grid, using ESRI ArcInfo software. A series of flow networks were created for each resolution DEM using varying minimum stream lengths in order to examine the effects of this variable on flow pattern and direction. The modelled drainage at each resolution was then compared to the `actual' drainage mapped from aerial photography (air photos and low level oblique photographs) and topographic maps to examine differences as a result of scaling. Preliminary results suggest that reproducing correct flow direction was not possible with the coarser resolution DEMs (10 m and up), while the finer resolutions (2.5 m, 5 m) resulted in drainage networks most similar to the mapped drainage.

  10. 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.

  11. Fusion of Laser Altimetry Data with Dems Derived from Stereo Imaging Systems

    NASA Astrophysics Data System (ADS)

    Schenk, T.; Csatho, B. M.; Duncan, K.

    2016-06-01

    During the last two decades surface elevation data have been gathered over the Greenland Ice Sheet (GrIS) from a variety of different sensors including spaceborne and airborne laser altimetry, such as NASA's Ice Cloud and land Elevation Satellite (ICESat), Airborne Topographic Mapper (ATM) and Laser Vegetation Imaging Sensor (LVIS), as well as from stereo satellite imaging systems, most notably from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Worldview. The spatio-temporal resolution, the accuracy, and the spatial coverage of all these data differ widely. For example, laser altimetry systems are much more accurate than DEMs derived by correlation from imaging systems. On the other hand, DEMs usually have a superior spatial resolution and extended spatial coverage. We present in this paper an overview of the SERAC (Surface Elevation Reconstruction And Change detection) system, designed to cope with the data complexity and the computation of elevation change histories. SERAC simultaneously determines the ice sheet surface shape and the time-series of elevation changes for surface patches whose size depends on the ruggedness of the surface and the point distribution of the sensors involved. By incorporating different sensors, SERAC is a true fusion system that generates the best plausible result (time series of elevation changes) a result that is better than the sum of its individual parts. We follow this up with an example of the Helmheim gacier, involving ICESat, ATM and LVIS laser altimetry data, together with ASTER DEMs.

  12. A DEM-based partition adjustment for the interpolation of annual cumulative temperature in China

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Li, Fei; Fu, Haiyue; Tian, Ying; Hu, Zizhi

    2007-06-01

    The spatial interpolation of meteorological elements has more important application value. The interpolation methods of air temperature data have been wildly applied in the large scale region. It has been paid more attentions that taking altitude as a variable was introduced into the interpolation models so as to improve the interpolation precision of air temperature data. In a large area, it is difficult to find the relationship between annual cumulative temperature and altitude according to the distribution of meteorological stations. Compared whit it dividing the study area, introducing interpolation models modified by DEM in the smaller region, we can availably improve the spatial interpolation precision of the annual cumulative temperature. The result shows that: Applied in the partition study area, inverse distance squared method modified by DEM can reduce complexity of spatial data analysis in the process of annual cumulative temperature interpolation. Partition interpolation methods take into account some factors that affect the interpolation results, such as the spatial distribution imbalance of the meteorological stations, altitude and region difference. The methods are fit for the interpolation analysis of the large-scale region. Compared with the tradition interpolation methods such as Kriging, Inverse distance interpolation method, etc., inverse distance squared method modified by DEM has higher interpolation precision of annual cumulative temperature in China.

  13. LiDAR DEM for Slope regulations of land development in Taiwan

    NASA Astrophysics Data System (ADS)

    Liu, J.-K.; Yang, M.-S.; Wu, M.-C.; Hsu, W.-C.

    2012-04-01

    Slope gradient is a major parameter for regulating the development of slope-lands in Taiwan. According to official guidelines, only two methods can be adopted, namely the rectangular parcel method and the parcel contouring method. Both of them are manual methods using conventional analogue maps produced by photogrammetric method. As the trend of technology is in favor of adopting digital elevation models for automated production of slope maps and complete coverage of the territory of Taiwan with DEM in 40m, 5m and 1m grids have been mostly completed, it is needed to assess the difference of DEM approaches in comparison to the official approaches which is recognized as the only legal procedure until now. Thus, a 1/1000 contour map in the sloping land of suburban area of New Taipei City is selected for this study. Manual approaches are carried out using the contour lines with 2m intervals. DEM grids of 1m, 5m, and 10m are generated by LiDAR survey. It is shown that the slope maps generated by Eight Neighbors Unweighted method are comparable or even better than the conventional approaches. As the conventional approach is prone to error propagations and uncertainties, the new digital approach should be implemented and enforced in the due process of law.

  14. Suitability of COSMO-SkyMed constellation for radargrammetric DEM generation

    NASA Astrophysics Data System (ADS)

    Conte, Domenico; Bovenga, Fabio; Refice, Alberto; Nitti, Davide O.; Nutricato, Raffaele; Chiaradia, Maria T.

    2014-10-01

    The COSMO-SkyMed (CSK) constellation acquires data from its four SAR X-band satellites in several imaging modes, providing in particular different view angles. The present work investigates the potential of CSK constellation for ground elevation measurement through SAR radargrammetry. We selected an area around Parkfield (California), where several CSK acquisitions are available. We used for radargrammetric processing 2 CSK spotlight image pairs acquired at 1 day of separation, in Same Side Viewing configuration, with baselines of 350 km. Furthermore, a dataset of 33 spotlight images were selected to derive height measurements through both persistent scatterers interferometry(PSI) and interferometric processing of 5 1-day separated pairs included in the dataset. We first predict how the errors in the geometrical parameters and the correlation level between the images impact on the height accuracy. Then, two DEMs were derived by processing the radargrammetric CSK pairs. According to the outcomes of the feasibility analysis, processing parameters were chosen in order to guarantee nominal values of height accuracy within the HRTI Level 3 specifications. The products have a final resolution of 3 m. In order to assess the accuracy of these radargrammetric DEMs, we used the height values provided by the PSI, and an interferometric DEM derived from the CSK tandem-like pairs.

  15. 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...

  16. Defining optimal DEM resolutions and point densities for modelling hydrologically sensitive areas in agricultural catchments dominated by microtopography

    NASA Astrophysics Data System (ADS)

    Thomas, I. A.; Jordan, P.; Shine, O.; Fenton, O.; Mellander, P.-E.; Dunlop, P.; Murphy, P. N. C.

    2017-02-01

    Defining critical source areas (CSAs) of diffuse pollution in agricultural catchments depends upon the accurate delineation of hydrologically sensitive areas (HSAs) at highest risk of generating surface runoff pathways. In topographically complex landscapes, this delineation is constrained by digital elevation model (DEM) resolution and the influence of microtopographic features. To address this, optimal DEM resolutions and point densities for spatially modelling HSAs were investigated, for onward use in delineating CSAs. The surface runoff framework was modelled using the Topographic Wetness Index (TWI) and maps were derived from 0.25 m LiDAR DEMs (40 bare-earth points m-2), resampled 1 m and 2 m LiDAR DEMs, and a radar generated 5 m DEM. Furthermore, the resampled 1 m and 2 m LiDAR DEMs were regenerated with reduced bare-earth point densities (5, 2, 1, 0.5, 0.25 and 0.125 points m-2) to analyse effects on elevation accuracy and important microtopographic features. Results were compared to surface runoff field observations in two 10 km2 agricultural catchments for evaluation. Analysis showed that the accuracy of modelled HSAs using different thresholds (5%, 10% and 15% of the catchment area with the highest TWI values) was much higher using LiDAR data compared to the 5 m DEM (70-100% and 10-84%, respectively). This was attributed to the DEM capturing microtopographic features such as hedgerow banks, roads, tramlines and open agricultural drains, which acted as topographic barriers or channels that diverted runoff away from the hillslope scale flow direction. Furthermore, the identification of 'breakthrough' and 'delivery' points along runoff pathways where runoff and mobilised pollutants could be potentially transported between fields or delivered to the drainage channel network was much higher using LiDAR data compared to the 5 m DEM (75-100% and 0-100%, respectively). Optimal DEM resolutions of 1-2 m were identified for modelling HSAs, which balanced the need

  17. Dem Extraction from WORLDVIEW-3 Stereo-Images and Accuracy Evaluation

    NASA Astrophysics Data System (ADS)

    Hu, F.; Gao, X. M.; Li, G. Y.; Li, M.

    2016-06-01

    This paper validates the potentials of Worldview-3 satellite images in large scale topographic mapping, by choosing Worldview-3 along-track stereo-images of Yi Mountain area in Shandong province China for DEM extraction and accuracy evaluation. Firstly, eighteen accurate and evenly-distributed GPS points are collected in field and used as GCPs/check points, the image points of which are accurately measured, and also tie points are extracted from image matching; then, the RFM-based block adjustment to compensate the systematic error in image orientation is carried out and the geo-positioning accuracy is calculated and analysed; next, for the two stereo-pairs of the block, DSMs are separately constructed and mosaicked as an entirety, and also the corresponding DEM is subsequently generated; finally, compared with the selected check points from high-precision airborne LiDAR point cloud covering the same test area, the accuracy of the generated DEM with 2-meter grid spacing is evaluated by the maximum (max.), minimum (min.), mean and standard deviation (std.) values of elevation biases. It is demonstrated that, for Worldview-3 stereo-images used in our research, the planimetric accuracy without GCPs is about 2.16 m (mean error) and 0.55 (std. error), which is superior to the nominal value, while the vertical accuracy is about -1.61 m (mean error) and 0.49 m (std. error); with a small amount of GCPs located in the center and four corners of the test area, the systematic error can be well compensated. The std. value of elevation biases between the generated DEM and the 7256 LiDAR check points are about 0.62 m. If considering the potential uncertainties in the image point measurement, stereo matching and also elevation editing, the accuracy of generating DEM from Worldview-3 stereo-images should be more desirable. Judging from the results, Worldview-3 has the potential for 1:5000 or even larger scale mapping application.

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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

  5. Simulation of a tablet coating process at different scales using DEM.

    PubMed

    Boehling, P; Toschkoff, G; Just, S; Knop, K; Kleinebudde, P; Funke, A; Rehbaum, H; Rajniak, P; Khinast, J G

    2016-10-10

    Spray coating of tablets is an important unit operation in the pharmaceutical industry and is mainly used for modified release, enteric protection, better appearance and brand recognition. It can also be used to apply an additional active pharmaceutical ingredient to the tablet core. Scale-up of such a process is an important step in commercialization. However, scale-up is not trivial and frequently, at manufacturing scales the required coating quality cannot be reached. Thus, we propose a method where laboratory experiments are carried out, yet scale-up is done via computational methods, i.e., by extrapolating results to larger scales. In the recent years, the Discrete Element Method (DEM) has widely been used to simulate tablet behavior in a laboratory scale drum coater. Due the increasing computational power and more sophisticated DEM algorithms, it has become possible to simulate millions of particles on regular PCs and model industrial scale tablet coating devices. In this work, simulations were performed on the laboratory, pilot and industrial scales and DEM was used to study how different scale-up rules influence the bed behavior on larger scales. The material parameters of the tablets were measured in the laboratory and a glued sphere approach was applied to model the tablet shape. The results include a vast amount of qualitative and quantitative data at the different scales. In conclusion, the evolution of the inter-tablet coating variation for the different scales and process parameters is presented. The results suggest that keeping the Froude number constant during the scale up process leads to faster processes as the cycle time is shorter and the spray residence time is more uniform when compared to keeping the circumferential velocity constant.

  6. Analysis and Validation of Grid dem Generation Based on Gaussian Markov Random Field

    NASA Astrophysics Data System (ADS)

    Aguilar, F. J.; Aguilar, M. A.; Blanco, J. L.; Nemmaoui, A.; García Lorca, A. M.

    2016-06-01

    Digital Elevation Models (DEMs) are considered as one of the most relevant geospatial data to carry out land-cover and land-use classification. This work deals with the application of a mathematical framework based on a Gaussian Markov Random Field (GMRF) to interpolate grid DEMs from scattered elevation data. The performance of the GMRF interpolation model was tested on a set of LiDAR data (0.87 points/m2) provided by the Spanish Government (PNOA Programme) over a complex working area mainly covered by greenhouses in Almería, Spain. The original LiDAR data was decimated by randomly removing different fractions of the original points (from 10% to up to 99% of points removed). In every case, the remaining points (scattered observed points) were used to obtain a 1 m grid spacing GMRF-interpolated Digital Surface Model (DSM) whose accuracy was assessed by means of the set of previously extracted checkpoints. The GMRF accuracy results were compared with those provided by the widely known Triangulation with Linear Interpolation (TLI). Finally, the GMRF method was applied to a real-world case consisting of filling the LiDAR-derived DSM gaps after manually filtering out non-ground points to obtain a Digital Terrain Model (DTM). Regarding accuracy, both GMRF and TLI produced visually pleasing and similar results in terms of vertical accuracy. As an added bonus, the GMRF mathematical framework makes possible to both retrieve the estimated uncertainty for every interpolated elevation point (the DEM uncertainty) and include break lines or terrain discontinuities between adjacent cells to produce higher quality DTMs.

  7. 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.

  8. A detailed observation of a LMC supernova remnant DEM L241 with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Bamba, A.; Ueno, M.; Nakajima, H.; Mori, K.; Koyama, K.

    2006-05-01

    We report on an XMM-Newton observation of the supernova remnant (SNR) DEM L241 in the Large Magellanic Cloud. In the soft band image, the emission shows an elongated structure, like a killifish, with a central compact source. The compact source is point-like, and named XMMU J053559.3-673509. The source spectrum is reproduced well by a power-law model with a photon index of Γ = 1.57 (1.51-1.62); and the intrinsic luminosity is 2.2 × 1035~erg~s-1 in the 0.5-10.0 keV band, with an assumed distance of 50 kpc. The source has neither significant coherent pulsations in 2.0 × 10-3-8.0 Hz nor time variabilities. Its luminosity and spectrum suggest that the source might be a pulsar wind nebula (PWN) in DEM L241. The spectral feature classifies this source as rather bright and hard PWN, which is similar to those in Kes 75 and B0540-693. The elongated diffuse structure can be divided into a "Head" and "Tail", and both have soft and line-rich spectra. Their spectra are reproduced well by a plane-parallel shock plasma (vpshock) model with a temperature of 0.3-0.4 keV, over-abundance in O and Ne, and a relative under-abundance in Fe. Such an abundance pattern and the morphology imply both that the emission is from the ejecta of the SNR and that the progenitor of DEM L241 is a very massive star, more than 20 M_⊙. This result is also supported by the existence of the central point source and an OB star association, LH 88. The total thermal energy and plasma mass are ~4 × 1050 erg and ~200~M_⊙, respectively.

  9. Identification of Quaternary Faults in Southwest Western Australia Using DEM-based Hill Shading

    NASA Astrophysics Data System (ADS)

    Clark, D.; Collins, C. D.

    2004-12-01

    In Australia, the extreme infrequency of large earthquake events means that the historic record of seismicity is poorly suited to the task of assessing seismic hazard. Paleoseismological investigations provide the only viable avenue to obtain constraints on the recurrence intervals of large and damaging earthquakes. However, the prehistoric record is compromised by difficulties related to finding direct evidence for large earthquakes (e.g. fault scarps), which may be subtle or relatively short-lived in the landscape. In recent times, high resolution digital elevation models (DEMs) have emerged as an important tool for defining and mapping of areas of probable elevated earthquake hazard. An examination of selected Shuttle Radar Tomography Mission (SRTM) 3 second DEM tiles and a 10 m resolution Department of Land Administration DEM has resulted in the identification of seven previously unrecognised fault scarps of probably Quaternary age in the southwest of Western Australia (SWWA). This doubles the number of Quaternary scarps known from SWWA, and is an important advance in defining areas prone to large earthquakes. The new features range in length from ~15 km to over 45 km, and from ~1.5 m to 7.5 m in height. As might be expected given the prevailing E-W regional compressive stress direction, the scarps are dominantly north-trending. However, most scarps are also arranged within a broad ESE-trending belt. This belt aligns with oceanic transform faults to the west of Australia relating to the break up with India. Of the fourteen scarps only two have been the subject of detailed palaeoseismic investigation to determine recurrence for large events. Ongoing research seeks to characterise seismicity on these scarps and further explore their large-scale relationship to each other, and to the architecture of the Australian plate. This work has the potential to greatly enhance our understanding of the drivers behind seismicity in intraplate Australia, and hence improve

  10. ArcticDEM; A Publically Available, High Resolution Elevation Model of the Arctic

    NASA Astrophysics Data System (ADS)

    Morin, Paul; Porter, Claire; Cloutier, Michael; Howat, Ian; Noh, Myoung-Jong; Willis, Michael; Bates, Brian; Willamson, Cathleen; Peterman, Kennith

    2016-04-01

    A Digital Elevation Model (DEM) of the Arctic is needed for a large number of reasons, including: measuring and understanding rapid, ongoing changes to the Arctic landscape resulting from climate change and human use and mitigation and adaptation planning for Arctic communities. The topography of the Arctic is more poorly mapped than most other regions of Earth due to logistical costs and the limits of satellite missions with low-latitude inclinations. A convergence of civilian, high-quality sub-meter stereo imagery; petascale computing and open source photogrammetry software has made it possible to produce a complete, very high resolution (2 to 8-meter posting), elevation model of the Arctic. A partnership between the US National Geospatial-intelligence Agency and a team led by the US National Science Foundation funded Polar Geospatial Center is using stereo imagery from DigitalGlobe's Worldview-1, 2 and 3 satellites and the Ohio State University's Surface Extraction with TIN-based Search-space Minimization (SETSM) software running on the University of Illinois's Blue Water supercomputer to address this challenge. The final product will be a seemless, 2-m posting digital surface model mosaic of the entire Arctic above 60 North including all of Alaska, Greenland and Kamchatka. We will also make available the more than 300,000 individual time-stamped DSM strip pairs that were used to assemble the mosaic. The Arctic DEM will have a vertical precision of better than 0.5m and can be used to examine changes in land surfaces such as those caused by permafrost degradation or the evolution of arctic rivers and floodplains. The data set can also be used to highlight changing geomorphology due to Earth surface mass transport processes occurring in active volcanic and glacial environments. When complete the ArcticDEM will catapult the Arctic from the worst to among the best mapped regions on Earth.

  11. 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

  12. Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM): A Year 2000 Global Baseline for Measuring Topographic Change

    NASA Astrophysics Data System (ADS)

    Crippen, R. E.

    2002-12-01

    The SRTM DEM is the first near-global, high-resolution elevation model. The data were acquired in February 2000 aboard the Space Shuttle Endeavour and cover the Earth's land masses between 60N and 56S latitudes at about 30 meters spatial resolution. The data are a virtual global snapshot in that they were acquired in about 10 days by a single sensor. Absolute vertical accuracy was targeted at 16 meters. However, spatially broad temporal changes in topography have been detected and measured down to about one-meter precision by comparing the SRTM DEM to the USGS National Elevation Dataset (NED). NED has similar spatial properties, but was independently derived, commonly years (or decades) earlier. Such changes already noted include those related to volcanic processes, alluvial fan deposition, subsidence related to oil extraction, and direct anthropogenic changes such as landfills and major road cuts and fills. Large tectonic changes in topography are likewise potentially evident in such comparisons. New and forthcoming satellites include capabilities to produce elevation models that can be used to detect and measure ongoing and future topographic change when compared to the SRTM DEM. For example, the ASTER instrument on the Terra satellite (launched in 1999) produces targeted DEMs, and SPOT-5 (launched in 2002) is expected to produce a global DEM over a five-year period. Both of these DEM sources (and the NED and others) use optical wavelength sensors which may "observe a different surface" than the SRTM radar, particularly in heavily vegetated areas, and this must be considered in making the comparisons. However, having a "before" data set is often the roadblock in measuring change, and SRTM has now provided the first detailed "before" DEM for most of Earth's land surface.

  13. 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

  14. Tropical-Forest Biomass Dynamics from X-Band, TanDEM-X DATA

    NASA Astrophysics Data System (ADS)

    Treuhaft, R. N.; Neumann, M.; Keller, M. M.; Goncalves, F. G.; Santos, J. R.

    2015-12-01

    The measurement of the change in above ground biomass (AGB) is key for understanding the carbon sink/source nature of tropical forests. Interferometric X-band radar from the only orbiting interferometer, TanDEM-X, shows sensitivity to standing biomass up to at least 300 Mg/ha. This sensitivity may be due in part to the propagation of the shorter X-band wavelength (0.031 m) through holes in the canopy. This talk focuses on estimating the change in AGB over time. Interferometric baselines from TanDEM-X have been obtained in Tapajós National Forest in the Brazilian Amazon over a 4-year period, from 2011 to 2015. Lidar measurements were also acquired during this period. Field measurements of height, height-to-base-of-crown, species, diameter, and position were acquired in 2010, 2013, and 2015. We show interferometric phase height changes, and suggest how these phase height changes are related to biomass change. First we show height changes between baselines separated by one month, over which we expect no change in AGB, to evaluate precision. We find an RMS of <2 m for ~85 stands in the phase height over one month, corresponding to about a 10% measurement of change, which suggests we can detect about a 17 Mg/ha change in AGB at Tapajos. In contrast, interferometric height changes over the period 2011 to 2014 have larger RMS scatters of > 3 m, due to actual change. Most stands show changes in interferometric phase height consistent with regrowth (~10 Mg/ha/yr), and several stands show abrupt, large changes in phase height (>10 m) due to logging and natural disturbance. At the end of 2015, we will acquire more TanDEM-X data over Tapajos, including an area subjected to selective logging. We are doing "before" (March 2015) and "after" (October 2015) fieldwork to be able to understand the signature of change due to selective logging in TanDEM-X interferometric data.

  15. Der Kalte Krieg in der Peripherie Griechische Physiker und Atomenergie nach dem Zweiten Weltkrieg

    NASA Astrophysics Data System (ADS)

    Vlahakis, George N.

    Die vorliegende Arbeit analysiert Ansichten griechischer Physiker zur Atomenergie und deren mögliche Anwendung nach dem Zweiten Weltkrieg, insbesondere während des Kalten Kriegs. Einerseits werden Ansichten von Physik- Professoren griechischer Universitäten präsentiert - beispielsweise von Dimitrios Hondros, der Student von Arnold Sommerfeld und Mitarbeiter von Peter Debye in München war, und andererseits wird die Politik der griechischen Regierung für die Etablierung eines Forschungsinstitutes diskutiert, das der Entwicklung der Atomenergie dienen sollte; ebenfalls wird eine öffentliche Meinungsumfrage zu diesen Thema, die in den Tageszeitungen der damaligen Zeit präsentiert wurde, diskutiert.

  16. 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}.

  17. The electric dipole moments in the ground states of gold oxide, AuO, and gold sulfide, AuS

    NASA Astrophysics Data System (ADS)

    Zhang, Ruohan; Yu, Yuanqin; Steimle, Timothy C.; Cheng, Lan

    2017-02-01

    The B2Σ- - X2Π3/2(0,0) bands of a cold molecular beam sample of gold monoxide, AuO, and gold monosulfide, AuS, have been recorded at high resolution both field free and in the presence of a static electric field. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ→ e l, of 2.94±0.06 D and 2.22±0.05 D for the X2Π3/2(v = 0) states of AuO and AuS, respectively. A molecular orbital correlation diagram is used to rationalize the trend in ground state μ→ e l values for AuX (X = F, Cl, O, and S) molecules. The experimentally determined μ→ e l are compared to those computed at the coupled-cluster singles and doubles (CCSD) level augmented with a perturbative inclusion of triple excitations (CCSD(T)) level of theory.

  18. 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

  19. Comparison of elevation derived from insar data with dem from topography map in Son Dong, Bac Giang, Viet Nam

    NASA Astrophysics Data System (ADS)

    Nguyen, Duy

    2012-07-01

    Digital Elevation Models (DEMs) are used in many applications in the context of earth sciences such as in topographic mapping, environmental modeling, rainfall-runoff studies, landslide hazard zonation, seismic source modeling, etc. During the last years multitude of scientific applications of Synthetic Aperture Radar Interferometry (InSAR) techniques have evolved. It has been shown that InSAR is an established technique of generating high quality DEMs from space borne and airborne data, and that it has advantages over other methods for the generation of large area DEM. However, the processing of InSAR data is still a challenging task. This paper describes InSAR operational steps and processing chain for DEM generation from Single Look Complex (SLC) SAR data and compare a satellite SAR estimate of surface elevation with a digital elevation model (DEM) from Topography map. The operational steps are performed in three major stages: Data Search, Data Processing, and product Validation. The Data processing stage is further divided into five steps of Data Pre-Processing, Co-registration, Interferogram generation, Phase unwrapping, and Geocoding. The Data processing steps have been tested with ERS 1/2 data using Delft Object-oriented Interferometric (DORIS) InSAR processing software. Results of the outcome of the application of the described processing steps to real data set are presented.

  20. Development of high-resolution coastal DEMs: Seamlessly integrating bathymetric and topographic data to support coastal inundation modeling

    NASA Astrophysics Data System (ADS)

    Eakins, B. W.; Taylor, L. A.; Warnken, R. R.; Carignan, K. S.; Sharman, G. F.

    2006-12-01

    The National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), is cooperating with the NOAA Pacific Marine Environmental Laboratory (PMEL), Center for Tsunami Research to develop high-resolution digital elevation models (DEMs) of combined bathymetry and topography. The coastal DEMs will be used as input for the Method of Splitting Tsunami (MOST) model developed by PMEL to simulate tsunami generation, propagation and inundation. The DEMs will also be useful in studies of coastal inundation caused by hurricane storm surge and rainfall flooding, resulting in valuable information for local planners involved in disaster preparedness. We present our methodology for creating the high-resolution coastal DEMs, typically at 1/3 arc-second (10 meters) cell size, from diverse digital datasets collected by numerous methods, in different terrestrial environments, and at various scales and resolutions; one important step is establishing the relationships between various tidal and geodetic vertical datums, which may vary over a gridding region. We also discuss problems encountered and lessons learned, using the Myrtle Beach, South Carolina DEM as an example.

  1. 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.

  2. 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.

  3. DEM-based Modeling at the Hillslope Scale: Recent Results and Future Process Research Needs

    NASA Astrophysics Data System (ADS)

    McDonnell, J.; Coles, A.; Gabrielli, C. P.; Appels, W. M.; Ameli, A.

    2015-12-01

    Hillslope scale patterns of overland flow, infiltration, subsurface stormflow and groundwater recharge are all topographically mediated. However, the mechanisms by which macro-, meso- and micro-topographies control filling and spilling of lateral flow, and vertical infiltration, are still poorly understood. Here we present high-resolution DEMs derived from ground-based LiDAR, airborne LiDAR, and GPR (ground penetrating rebar!) with model analysis to examine the topographic controls on water flow at three distinct hillslopes. We explore surface topographic effects on rainfall- and snowmelt-infiltration and overland flow on the Canadian Prairies; the surface and subsurface topographic controls on lateral subsurface stormflow generation and groundwater recharge at a steep, wet temperate rainforest in New Zealand; and subsurface topographic controls on patterns of groundwater recharge at a forested hillslope on the Georgia Piedmont in the United States. We demonstrate how these studies reveal future research needs for improving DEM-based watershed delineation and modeling along with some surprising similarities between topographic controls on soil surface infiltration and overland flow and twin subsurface processes at the soil-bedrock interface.

  4. 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.

  5. 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.

  6. 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.

  7. Potentials of TanDEM-X Interferometric Data for Global Forest/Non-Forest Classification

    NASA Astrophysics Data System (ADS)

    Martone, Michele; Rizzoli, Paola; Brautigam, Benjamin; Krieger, Gerhard

    2016-08-01

    This paper presents a method to generate forest/non- forest maps from TanDEM-X interferometric SAR data. Among the several contributions which may affect the quality of interferometric products, the coherence loss caused by volume scattering represents the contribution which is predominantly affected by the presence of vegetation, and is therefore here exploited as main indicator for forest classification. Due to the strong dependency of the considered InSAR quantity on the geometric acquisition configuration, namely the incidence angle and the interferometric baseline, a multi-fuzzy clustering classification approach is used. Some examples are provided which show the potential of the proposed method. Further, additional features such as urban settlements, water, and critical areas affected by geometrical distortions (e.g. shadow and layover) need to be extracted, and possible approaches are presented as well. Very promising results are shown, which demonstrate the potentials of TanDEM-X bistatic data not only for forest identification, but, more in general, for the generation of a global land classification map as a next step.

  8. Hydrological modeling using high resolution dem to level control on highways

    NASA Astrophysics Data System (ADS)

    Akbulut, Zeynep; Cömert, Çetin

    2016-04-01

    Floods are natural disasters that must be managed, controlled and taken precautions before it happens considering the damage they inflicted to environment and human lives. As to highways, the main vein of urban life flow, must be taken into consideration as a different entity that affected by excessive rainfalls and floods. Due to inadequate drainage that allow rainfall to form water ponds on highways cause vehicles to lose control and that lead vehicles to have traffic accidents. To reduce the traffic accidents caused by ponding waters on highways we need to know area of inundation and water depths. In this context we used FLO-2D Basic Model (2009) to hydrological modeling of Black Sea Coastal Highway with meteorological and hydrological data using a Digital Elevation Model (DEM). In this study, ponding areas on highways determined by simulating the rainfall with a high resolution DEM that can represent the actual road surface correctly. With this information, General Directorate of Highways (GDH) in Turkey can adjust the cross-sectional and longitudinal slope or build better and bigger drainage structures where water accumulated to prevent ponding. With the results obtained from Hydrological Model, GDH can rapidly control highways conformity to regulations before highways come into service. Also these ponding areas acquired by reveals where to prioritize in flood risk managements. Key Words: Area of Inundation, Digital Elevation Model, FLO-2D, Hydrological Modeling, Highway, Rainfall-Runoff Simulation, Water Depth.

  9. 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.

  10. 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.

  11. A knowledge-based, two-step procedure for extracting channel networks from noisy dem data

    NASA Astrophysics Data System (ADS)

    Smith, Terence R.; Zhan, Cixiang; Gao, Peng

    We present a new procedure for extracting channel networks from noisy DEM data. The procedure is a knowledge-based, two-step procedure employing both local and nonlocal information. In particular, we employ a model of an ideal drainage network as a source of constraints that must be satisfied by the output of the procedure. We embed these constraints as part of the network extraction procedure. In a first step, the procedure employs the facet model of Haralick to extract valley information from digital images. The constraints employed at this stage relate to conditions indicating reliable valley pixels. In a second step, the procedure applies knowledge of drainage networks to integrate reliable valley points discovered into a network of single-pixel width lines. This network satisfies the constraints imposed by viewing a drainage network as a binary tree in which the channel segments have a one-pixel width. The procedure performs well on DEM data in the example investigated. The overall worst-case performance of the procedure is O( N) log N), but the most computationally intensive step in the procedure is parallelized easily. Hence the procedure is a good candidate for automation.

  12. 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.

  13. TanDEM-X Across-Track Interferometry over Dry Snow Covered Terrain

    NASA Astrophysics Data System (ADS)

    Panagiotopoulou, Dimitra; Brown, Ian A.

    2016-08-01

    We analyse bistatic HH-polarised TanDEM-X interferometric synthetic aperture radar (InSAR) data acquired over winter, dry snow conditions in a sub- Arctic site in Norway. Exploiting the principles of across-track interferometry, the elevation of the scattering phase centre estimated by the phase difference between the two SAR acquisitions. Interference patterns were assessed both qualitatively and quantitatively. Clearings and forest stands, were analysed. Interferometric phase uncertainty and spatio-temporal consistency were analysed by means of scattering phase centre elevation accuracy and coherence degree, γ with respect to hydro-meteorological conditions. Clearings displayed absolute height errors of < 1 m. The sole approximation was to consider volume decorrelation effects as main source of elevation ambiguities and coherence decay. Principal Component Analysis was conducted to identify the combined influence of variables describing the radar response and scattering centre. However, the derived DEMs attained high vertical accuracy, the sub-meter height errors might relate to snowcover effects. Coherence was strongly influenced by snowpack parameters suggesting TDM coherence inversion may enable snow cover monitoring.

  14. A Method for Improving SRTM DEMs in High-Relief Terrain

    NASA Astrophysics Data System (ADS)

    Falorni, G.; Istanbulluoglu, E.; Bras, R. L.

    2003-12-01

    The Shuttle Radar Topography Mission (SRTM) had the objective of mapping the Earth's surface between 56 o S and 60 o N to produce the first near-global high resolution digital elevation model (DEM). The dataset, with a horizontal resolution of 1 arc second ( ˜ 30 m), has now been released for the conterminous U.S. Recent investigations aimed at assessing the vertical accuracy of the dataset have revealed that elevation accuracy is well within dataset specifications in areas of low- to modest-relief but that errors generally increase in high-relief terrains. Statistical analyses performed with the objective of characterizing the error structure in two study sites within the U.S. have highlighted the existence of correlations between elevation residuals and slope gradient, slope bearing and elevation. In particular, the analyses show that the largest errors occur on steep slopes and that slope bearing has a marked influence on the sign of the elevation residuals. Based on these findings we are currently investigating a method for correcting relevant vertical errors in SRTM-derived DEMs according to their topographic location. We propose to use a combination of indices derived from the statistical analyses to predict the occurrence, magnitude and sign of the vertical errors.

  15. Studying at the Universities of the Armed Forces: Comparative Results from the 1999 Student Questionnaire (Studieren an den UniBw: Vergleichende Ergebnisse aus der Studentenbefragung 1999)

    DTIC Science & Technology

    2002-12-01

    distanziert kollegial UniBw Miinchen: Auf den ersten Blick scheint das allgemeine Kommunikationsgeschehen in M • nchen im Prinzip dem an der Hamburger UniBw...Hochschulforschung m )chten wir an dieser Stelle danken fMr das Oberlassen des Frageinstrumen- tariums, das dem ZHQ zur Nutzung fu-r die eigene...gerweise war schon im Grandungskonzept der UniBw diesem Moment einer m ~glichst nahen, en- gen und transparenten Kommunikation besondere Beachtung

  16. Site-directed mutagenesis around the CuA site of a polyphenol oxidase from Coreopsis grandiflora (cgAUS1).

    PubMed

    Kaintz, Cornelia; Mayer, Rupert L; Jirsa, Franz; Halbwirth, Heidi; Rompel, Annette

    2015-03-24

    Aurone synthase from Coreopsis grandiflora (cgAUS1), catalyzing conversion of butein to sulfuretin in a type-3 copper center, is a rare example of a polyphenol oxidase involved in anabolism. Site-directed mutagenesis around the CuA site of AUS1 was performed, and recombinant enzymes were analyzed by mass spectrometry. Replacement of the coordinating CuA histidines with alanine resulted in the presence of a single copper and loss of diphenolase activity. The thioether bridge-building cysteine and a phenylalanine over the CuA site, exchanged to alanine, have no influence on copper content but appear to play an important role in substrate binding.

  17. 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

  18. Multi-Temporal Investigation of Greenland Ice Sheet Snow Facies Using TanDEM-X Mission Data

    NASA Astrophysics Data System (ADS)

    Rizzoli, Paola; Martone, Michele; Brautigam, Benjamin; Rott, Helmut; Moreira, Alberto

    2016-08-01

    This paper presents the first results of the developed approach for classifying Greenland ice sheet snow facies, based on the use of interferometric TanDEM-X SAR data. Large-scale mosaics of radar backscatter and volume decorrelation, derived from the interferometric coherence, are used as input data set for applying a classification algorithm based on the c-means fuzzy clustering. The unique data set provided by TanDEM-X is particularly suitable for this analysis due to the single-pass bistatic acquisition mode which does not suffer from temporal decorrelation. The obtained results have been verified with external snow melt data. Moreover, independent multi-temporal TanDEM-X backscatter data and interferometric time series have been analyzed as well.

  19. Delta-K Wideband SAR Interferometry for DEM Generation and Persistent Scatterers Using TeraSAR-X

    NASA Astrophysics Data System (ADS)

    Brcic, Ramon; Eineder, Michael; Bamler, Richard; Steinbrecher, Ulrich; Schulze, Daniel; Metzig, Robert; Papathanassiou, Konstantinos; Nagler, Thomas; Mueller, Florian; Suess, Martin

    2010-03-01

    Wideband SAR systems such as TerraSAR-X allow estimation of the absolute interferometric phase without resorting to error prone phase unwrapping. This is achieved through the delta-k technique that exploits frequency diversity within the range bandwidth to simulate a SAR system with a much longer carrier wavelength. This benefits all interferometric applications including DEM generation and land surface motion determination. Here we present the results of an ESA study (21318/07/NL/HE) into using delta-k absolute phase estimation for DEM generation and PSI (Persistent Scatterer Interferometry). Using TerraSAR- X data, examples from a delta-k DEM generation system are shown which avoid the errors induced by conventional phase unwrapping. For PSI, the possibilities of absolute phase estimation for a single PS are explored in theory and examples where wideband estimation is compared to conventional PSI processing for a stack of acquisitions over Paris.

  20. 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).

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Key, Kerry

    2016-10-01

    This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) data from onshore and offshore surveys. MARE2DEM parametrizes the inverse model using a grid of arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease of construction. Unstructured grids provide significantly more geometric flexibility and parameter efficiency than the structured rectangular grids commonly used by most other inversion codes. Transmitter and receiver components located on topographic slopes can be tilted parallel to the boundary so that the simulated electromagnetic fields accurately reproduce the real survey geometry. The forward solution is implemented with a goal-oriented adaptive finite-element method that automatically generates and refines unstructured triangular element grids that conform to the inversion parameter grid, ensuring accurate responses as the model conductivity changes. This dual-grid approach is significantly more efficient than the conventional use of a single grid for both the forward and inverse meshes since the more detailed finite-element meshes required for accurate responses do not increase the memory requirements of the inverse problem. Forward solutions are computed in parallel with a highly efficient scaling by partitioning the data into smaller independent modeling tasks consisting of subsets of the input frequencies, transmitters and receivers. Non-linear inversion is carried out with a new Occam inversion approach that requires fewer forward calls. Dense matrix operations are optimized for memory and parallel scalability using the ScaLAPACK parallel library. Free parameters can be bounded using a new non-linear transformation that leaves the transformed parameters nearly the same as the original parameters within the bounds, thereby reducing non-linear smoothing effects. Data

  6. Implementation of large-scale landscape evolution modelling to real high-resolution DEM

    NASA Astrophysics Data System (ADS)

    Schroeder, S.; Babeyko, A. Y.

    2012-12-01

    We have developed a surface evolution model to be naturally integrated with 3D thermomechanical codes like SLIM-3D to study coupled tectonic-climate interaction. The resolution of the surface evolution model is independent of that of the underlying continuum box. The surface model follows the concept of the cellular automaton implemented on a regular Eulerian mesh. It incorporates an effective filling algorithm that guarantees flow direction in each cell, D8 search for flow directions, computation of discharges and bedrock incision. Additionally, the model implements hillslope erosion in the form of non-linear, slope-dependent diffusion. The model was designed to be employed not only to synthetic topographies but also to real Digital Elevation Models (DEM). In present work we report our experience with model implication to the 30-meter resolution ASTER GDEM of the Pamir orogen, in particular, to the segment of the Panj river. We start with calibration of the model parameters (fluvial incision and hillslope diffusion coefficients) using direct measurements of Panj incision rates and volumes of suspended sediment transport. Since the incision algorithm is independent on hillslope processes, we first adjust the incision parameters. Power-law exponents of the incision equation were evaluated from the profile curvature of the main Pamir rivers. After that, incision coefficient was adjusted to fit the observed incision rate of 5 mm/y. Once the model results are consistent with the measured data, the calibration of hillslope processes follows. For given critical slope, diffusivity could be fitted to match the observed sediment discharge. Applying of surface evolution model to real DEM reveals specific problems which do not appear when working with synthetic landscapes. One of them is the noise of the satellite-measured topography. In particular, due to the non-vertical observation perspective, satellite may not be able to detect the bottom of the river channel, especially

  7. Sediment micromechanics in sheet flows induced by asymmetric waves: A CFD-DEM study

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Xiao, Heng

    2016-11-01

    Understanding the sediment transport in oscillatory flows is essential to the investigation of the overall sediment budget for coastal regions. This overall budget is crucial for the prediction of the morphological change of the coastline in engineering applications. Since the sediment transport in oscillatory flows is dense particle-laden flow, appropriate modeling the particle interaction is critical. Although traditional two-fluid approaches have been applied to the study of sediment transport in oscillatory flows, the approaches do not capture the interaction of the particles. The study of the motion of individual sediment particles and their micromechanics (e.g., packing and contact force) in oscillatory flows is still lacking. In this work, a parallel CFD-DEM solver SediFoam that can model the inter-particle collision is applied to study the granular micromechanics of sediment particles in oscillatory flows. The results obtained from the CFD-DEM solver are validated by using the experimental data of coarse and medium sands. The comparison with experimental results suggests that the flow velocity, the sediment flux and the net sediment transport rate predicted by SediFoam are satisfactory. Moreover, the micromechanic quantities of the sediment bed are presented in detail, including the Voronoi concentration, the coordination number, and the particle interaction force. It is demonstrated that the variation of these micromechanic quantities at different phases in the oscillatory cycle is significant, which is due to different responses of the sediment bed. To investigate the structural properties of the sediment bed, the correlation of the Voronoi volume fraction and coordination number is compared to the results from the fluidized bed simulations. The consistency in the comparison indicates the structural micromechanics of sediment transport and fluidized bed are similar despite the differences in flow patterns. From the prediction of the CFD-DEM model, we

  8. 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

  9. High-resolution Pleiades DEMs and improved mapping methods for the E-Corinth marine terraces

    NASA Astrophysics Data System (ADS)

    de Gelder, Giovanni; Fernández-Blanco, David; Delorme, Arthur; Jara-Muñoz, Julius; Melnick, Daniel; Lacassin, Robin; Armijo, Rolando

    2016-04-01

    The newest generation of satellite imagery provides exciting new possibilities for highly detailed mapping, with ground resolution of sub-metric pixels and absolute accuracy within a few meters. This opens new venues for the analysis of geologic and geomorphic landscape features, especially since photogrammetric methods allow the extraction of detailed topographic information from these satellite images. We used tri-stereo imagery from the Pleiades platform of the CNES in combination with Euclidium software for image orientation, and Micmac software for dense matching, to develop state-of-the-art, 2m-resolution digital elevation models (DEMs) for eight areas in Greece. Here, we present our mapping results for an area in the eastern Gulf of Corinth, which contains one of the most extensive and well-preserved flights of marine terraces world-wide. The spatial extent of the terraces has been determined by an iterative combination of an automated surface classification model for terrain slope and roughness, and qualitative assessment of satellite imagery, DEM hillshade maps, slope maps, as well as detailed topographic analyses of profiles and contours. We determined marine terrace shoreline angles by means of swath profiles that run perpendicularly to the paleo-seacliffs, using the graphical interface TerraceM. Our analysis provided us with a minimum and maximum estimate of the paleoshoreline location on ~750 swath profiles, by using the present-day cliff slope as an approximation for its paleo-cliff counterpart. After correlating the marine terraces laterally we obtained 16 different terrace-levels, recording Quaternary sea-level highstands of both major interglacial and several interstadial periods. Our high-resolution Pleiades-DEMs and improved method for paleoshoreline determination allowed us to produce a marine terrace map of unprecedented detail, containing more terrace sub-levels than hitherto. Our mapping demonstrates that we are no longer limited by the

  10. Design of Au/SPIO composite nanoparticle for facile and biocompatible surface functionalization via Au-S bond

    NASA Astrophysics Data System (ADS)

    Seino, Satoshi; Shibata, Yujin; Yamanaka, Masayuki; Nakagawa, Takashi; Mukai, Yohei; Nakagawa, Shinsaku; Yamamoto, Takao A.

    2013-01-01

    Immobilization of Au nanoparticles on super-paramagnetic iron-oxide (SPIO) enables facile and biocompatible surface functionalization via Au-S bond. Au/SPIO composite nanoparticle is easily modified by thiol-modified polyethylene glycol (PEG-SH), and they are successfully applied on MR tumor imaging. However, its large hydrodynamic size ( 150 nm) still causes the accumulation to liver in vivo. In this study, we controlled the hydrodynamic size of Au/SPIO by testing different raw SPIOs and stabilizing polymers. As the best candidate, Au/Molday-ION which was synthesized from Molday-ION and polyvinyl alcohol comprised the hydrodynamic size of 56 nm. Moreover, PEGylated Au/Molday-ION showed excellent dispersibility in blood serum, with the hydrodynamic size of 65 nm. This surface functionalization strategy is effective for the constructions of magnetic nanocarriers for in vivo applications.

  11. Fluid coupling in DEM simulation using Darcy's law: Formulation, and verification

    NASA Astrophysics Data System (ADS)

    Goodarzi, M.; Kwok, C. Y.; Tham, L. G.; Chen, F.

    2013-06-01

    The fluid coupled-DEM has recently become a popular topic in the field of granular material simulation. In most simulations, the averaged Navier-Stokes equations are implemented to consider the fluid flow through particles. In this paper, a simple algorithm based on Darcy's law was discussed to avoid expensive computational effort of solving of the Navier-Stokes equations. The results of this approach were compared quantitatively with the well-known analytical solution of 1D seepage through a soil column as a fully coupled problem in geotechnical engineering. The comparison between the developed pore pressure and induced displacement with analytical values revealed that this algorithm is capable of simulating fluid-particle interaction accurately within the laminar regime.

  12. 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.

  13. 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

  14. Modeling Particle Rolling Behavior by the Modified Eccentric Circle Model of DEM

    NASA Astrophysics Data System (ADS)

    Chang, Yi-Long; Chen, Tsung-Hsien; Weng, Meng-Chia

    2012-09-01

    This study proposes a modified eccentric circle model to simulate the rolling resistance of circle particles through the distinct element method (DEM) simulation. The proposed model contains two major concepts: eccentric circle and local rotational damping. The mass center of a circular particle is first adjusted slightly for eccentricity to provide rotational stiffness. Local rotational damping is adopted to dissipate energy in the rotational direction. These associated material parameters can be obtained easily from the rolling behavior of one rod. This study verifies the proposed model with the repose angle tests of chalk rod assemblies, and the simulated results were satisfactory. Simulations using other existing models were also conducted for comparison, showing that the proposed model achieved better results. A landslide model test was further simulated, and this simulation agreed with both the failure pattern and the sliding process. In conclusion, particle rolling simulation using the proposed model appears to approach the actual particle trajectory, making it useful for various applications.

  15. Simulation of Hydraulic and Natural Fracture Interaction Using a Coupled DFN-DEM Model

    SciTech Connect

    J. Zhou; H. Huang; M. Deo

    2016-03-01

    The presence of natural fractures will usually result in a complex fracture network due to the interactions between hydraulic and natural fracture. The reactivation of natural fractures can generally provide additional flow paths from formation to wellbore which play a crucial role in improving the hydrocarbon recovery in these ultra-low permeability reservoir. Thus, accurate description of the geometry of discrete fractures and bedding is highly desired for accurate flow and production predictions. Compared to conventional continuum models that implicitly represent the discrete feature, Discrete Fracture Network (DFN) models could realistically model the connectivity of discontinuities at both reservoir scale and well scale. In this work, a new hybrid numerical model that couples Discrete Fracture Network (DFN) and Dual-Lattice Discrete Element Method (DL-DEM) is proposed to investigate the interaction between hydraulic fracture and natural fractures. Based on the proposed model, the effects of natural fracture orientation, density and injection properties on hydraulic-natural fractures interaction are investigated.

  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

  17. Using TanDEM data for forest height estimation and change detection

    NASA Astrophysics Data System (ADS)

    Thiele, Antje; Dubois, Clémence; Boldt, Markus; Hinz, Stefan

    2016-10-01

    Mapping of forest coverage and forest changes became an increasing issue due to deforestation and forest degradation. Moreover, the estimation of related indicators such as carbon reduction, biomass and wood capacity is of large interest for industry and politics. As forest height is an important contributing parameter for these indicators, the region-wide estimation of forest heights is an essential step. This article investigates the accuracy potential of forest height estimation that can be reached by the current configuration of the two SAR satellites TerraSAR-X and TanDEM-X. Depending on the chosen acquisition mode and flight geometry, products of different quality can be achieved. Eight InSAR data sets showing different characteristics in geometric resolution, length of baseline, and mapping time, are processed and analyzed. To enable a thorough evaluation of the estimated heights, first-pulse LIDAR point clouds and aerial ortho-images are used as reference data.

  18. 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.

  19. 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.

  20. 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

  1. Open-source MFIX-DEM software for gas-solids flows: Part I verification studies

    SciTech Connect

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

    2012-01-01

    With rapid advancements in computer hardware, it is now possible to perform large simulations of granular flows using the Discrete Element Method (DEM). As a result, solids are increasingly treated in a discrete Lagrangian fashion in the gas solids flow community. In this paper, the open-source MFIX-DEM software is described that 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. This method is referred to as the continuum discrete method (CDM) to clearly make a distinction between the ambiguity of using a Lagrangian or Eulerian reference for either continuum or discrete formulations. This freely available CDM code for gas solids flows can accelerate the research in computational gas solids flows and establish a baseline that can lead to better closures for the continuum modeling (or traditionally referred to as two fluid model) of gas solids flows. In this paper, a series of verification cases is employed which tests the different aspects of the code in a systematic fashion by exploring specific physics in gas solids flows before exercising the fully coupled solution on simple canonical problems. It is critical to have an extensively verified code as the physics is complex with highly-nonlinear coupling, and it is difficult to ascertain the accuracy of the results without rigorous verification. These series of verification tests set the stage not only for rigorous validation studies (performed in part II of this paper) but also serve as a procedure for testing any new developments that couple continuum and discrete formulations for gas solids flows.

  2. Open-source MFIX-DEM software for gas-solids flows: Part 1 - Verification studies

    SciTech Connect

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

    2012-04-01

    With rapid advancements in computer hardware, it is now possible to perform large simulations of granular flows using the Discrete Element Method (DEM). As a result, solids are increasingly treated in a discrete Lagrangian fashion in the gas–solids flow community. In this paper, the open-source MFIX-DEM software is described that 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. This method is referred to as the continuum discrete method (CDM) to clearly make a distinction between the ambiguity of using a Lagrangian or Eulerian reference for either continuum or discrete formulations. This freely available CDM code for gas–solids flows can accelerate the research in computational gas–solids flows and establish a baseline that can lead to better closures for the continuum modeling (or traditionally referred to as two fluid model) of gas–solids flows. In this paper, a series of verification cases is employed which tests the different aspects of the code in a systematic fashion by exploring specific physics in gas–solids flows before exercising the fully coupled solution on simple canonical problems. It is critical to have an extensively verified code as the physics is complex with highly-nonlinear coupling, and it is difficult to ascertain the accuracy of the results without rigorous verification. These series of verification tests set the stage not only for rigorous validation studies (performed in part II of this paper) but also serve as a procedure for testing any new developments that couple continuum and discrete formulations for gas–solids flows.

  3. Open Source MFIX-DEM Software for Gas-Solids Flows: Part 1 - Verification Studies

    SciTech Connect

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

    2012-04-01

    With rapid advancements in computer hardware, it is now possible to perform large simulations of granular flows using the Discrete Element Method (DEM). As a result, solids are increasingly treated in a discrete Lagrangian fashion in the gas–solids flow community. In this paper, the open-source MFIX-DEM software is described that 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. This method is referred to as the continuum discrete method (CDM) to clearly make a distinction between the ambiguity of using a Lagrangian or Eulerian reference for either continuum or discrete formulations. This freely available CDM code for gas–solids flows can accelerate the research in computational gas–solids flows and establish a baseline that can lead to better closures for the continuum modeling (or traditionally referred to as two fluid model) of gas–solids flows. In this paper, a series of verification cases is employed which tests the different aspects of the code in a systematic fashion by exploring specific physics in gas–solids flows before exercising the fully coupled solution on simple canonical problems. It is critical to have an extensively verified code as the physics is complex with highly-nonlinear coupling, and it is difficult to ascertain the accuracy of the results without rigorous verification. These series of verification tests set the stage not only for rigorous validation studies (performed in part II of this paper) but also serve as a procedure for testing any new developments that couple continuum and discrete formulations for gas–solids flows.

  4. 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.

  5. 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.

  6. Interannual surface evolution of an Antarctic blue-ice moraine using multi-temporal DEMs

    NASA Astrophysics Data System (ADS)

    Westoby, Matthew J.; Dunning, Stuart A.; Woodward, John; Hein, Andrew S.; Marrero, Shasta M.; Winter, Kate; Sugden, David E.

    2016-06-01

    Multi-temporal and fine-resolution topographic data products are 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 with multi-view stereo (SfM-MVS) photogrammetry to a set of aerial photographs acquired 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) and surface lowering of a similar magnitude in some inter-moraine depressions and close to the current ice margin, although we are unable to validate the latter. 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.

  7. 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.

  8. Exploring the Potential of TanDEM-X Data in Rice Monitoring

    NASA Astrophysics Data System (ADS)

    Erten, E.

    2015-12-01

    In this work, phenological parameters such as growth stage, calendar estimation, crop density and yield estimation for rice fields are estimated employing TanDEM-X data. Currently, crop monitoring is country-dependent. Most countries have databases based on cadastral information and annual farmer inputs. Inaccuracies are coming from wrong or missing farmer declarations and/or coarsely updated cadastral boundary definitions. This leads to inefficient regulation of the market, frauds as well as to ecological risks. An accurate crop calendar is also missing, since farmers provide estimations in advance and there is no efficient way to know the growth status over large plantations. SAR data is of particular interest for these purposes. The proposed method includes two step approach including field detection and phenological state estimation. In the context of precise farming it is substantial to define field borders which are usually changing every cultivation period. Linking the SAR inherit properties to transplanting practice such as irrigation, the spatial database of rice-planted agricultural crops can be updated. Boundaries of agricultural fields will be defined in the database, and assignments of crops and sowing dates will be continuously updated by our monitoring system considering that sowing practice variously changes depending on the field owner decision. To define and segment rice crops, the system will make use of the fact that rice fields are characterized as flooded parcels separated by path networks composed by soil or rare grass. This natural segmentation is well detectable by inspecting low amplitude and coherence values of bistatic acquisitions. Once the field borders are defined, the phenology estimation of crops monitored at any time is the key point of monitoring. In this aspect the wavelength and the polarization option of TanDEM-X are enough to characterize the small phenological changes. The combination of bistatic interferometry and Radiative

  9. DEM analysis for AIA/SDO EUV channels using a probabilistic approach to the spectral inverse problem

    NASA Astrophysics Data System (ADS)

    Goryaev, Farid; Parenti, Susanna; Hochedez, Jean-François; Urnov, Alexander

    The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics Observatory (SDO) mis-sion is designed to observe the Sun from the photosphere to the flaring corona. These data have to improve our understanding of processes in the solar atmosphere. The differential emis-sion measure (DEM) analysis is one of the main methods to derive information about coronal optically thin plasma characteristics from EUV and SXR emission. In this work we analyze AIA/SDO EUV channels to estimate their ability to reconstruct DEM(T) distributions. We use an iterative method (called Bayesian iterative method, BIM) within the framework of a probabilistic approach to the spectral inverse problem for determining the thermal structures of the emitting plasma sources (Goryaev et al., submitted to AA). The BIM is an iterative procedure based on Bayes' theorem and used for the reconstruction of DEM profiles. Using the BIM algorithm we performed various numerical tests and model simulations demonstrating abilities of our inversion approach for DEM analysis with AIA/SDO EUV channels.

  10. High-quality seamless DEM generation blending SRTM-1, ASTER GDEM v2 and ICESat/GLAS observations

    NASA Astrophysics Data System (ADS)

    Yue, Linwei; Shen, Huanfeng; Zhang, Liangpei; Zheng, Xianwei; Zhang, Fan; Yuan, Qiangqiang

    2017-01-01

    The absence of a high-quality seamless global digital elevation model (DEM) dataset has been a challenge for the Earth-related research fields. Recently, the 1-arc-second Shuttle Radar Topography Mission (SRTM-1) data have been released globally, covering over 80% of the Earth's land surface (60°N-56°S). However, voids and anomalies still exist in some tiles, which has prevented the SRTM-1 dataset from being directly used without further processing. In this paper, we propose a method to generate a seamless DEM dataset blending SRTM-1, ASTER GDEM v2, and ICESat laser altimetry data. The ASTER GDEM v2 data are used as the elevation source for the SRTM void filling. To get a reliable filling source, ICESat GLAS points are incorporated to enhance the accuracy of the ASTER data within the void regions, using an artificial neural network (ANN) model. After correction, the voids in the SRTM-1 data are filled with the corrected ASTER GDEM values. The triangular irregular network based delta surface fill (DSF) method is then employed to eliminate the vertical bias between them. Finally, an adaptive outlier filter is applied to all the data tiles. The final result is a seamless global DEM dataset. ICESat points collected from 2003 to 2009 were used to validate the effectiveness of the proposed method, and to assess the vertical accuracy of the global DEM products in China. Furthermore, channel networks in the Yangtze River Basin were also extracted for the data assessment.

  11. Atmosphere sounding by GPS radio occultation: First results from TanDEM-X and comparison with TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Zus, Florian; Grunwaldt, Ludwig; Heise, Stefan; Michalak, Grzegorz; Schmidt, Torsten; Wickert, Jens

    2014-01-01

    On 21 June 2010 the TerraSAR-X satellite was joined by the TanDEM-X satellite. A Global Positioning System (GPS) radio occultation (RO) experiment using the twin satellites has been carried out to estimate the precision of GPS atmospheric soundings. For the Day Of Year (DOY) 330-336, 2011, we analyze phase and amplitude data recorded by GPS receivers separated by a few hundred meters in a low earth orbit and derive collocated atmospheric refractivity profiles. In the altitude range 10-20 km the standard deviation between TerraSAR-X and TanDEM-X refractivity does not exceed 0.15%. The standard deviation is rapidly increasing for lower and higher altitudes; close to the surface and at an altitude of 30 km the standard deviation reaches 0.8% and 0.5%, respectively. Systematic deviations between TerraSAR-X and TanDEM-X refractivity in the considered altitude range (0-30 km) are negligible. The results confirm the anticipated high precision of the GPS RO technique. However, the difference in the retrieved refractivity in the lower troposphere for different Open Loop (OL) signal tracking parameters, altered onboard TanDEM-X for DOY 49-55, 2012, calls for an in depth analysis. At the moment we can not exclude that a potential bias in the OL Doppler model introduces a bias in our retrieved refractivity at altitudes <8 km.

  12. Adaptive smoothing of valleys in DEMs using TIN interpolation from ridgeline elevations: An application to morphotectonic aspect analysis

    NASA Astrophysics Data System (ADS)

    Jordan, Gyozo

    2007-05-01

    This paper presents a smoothing method that eliminates valleys of various Strahler-order drainage lines from a digital elevation model (DEM), thus enabling the recovery of local and regional trends in a terrain. A novel method for automated extraction of high-density channel network is developed to identify ridgelines defined as the watershed boundaries of channel segments. A DEM using TIN interpolation is calculated based on elevations of digitally extracted ridgelines. This removes first-order watersheds from the DEM. Higher levels of DEM smoothing can be achieved by the application of the method to ridgelines of higher-order channels. The advantage of the proposed smoothing method over traditional smoothing methods of moving kernel, trend and spectral methods is that it does not require pre-definition of smoothing parameters, such as kernel or trend parameters, and thus it follows topography in an adaptive way. Another advantage is that smoothing is controlled by the physical-hydrological properties of the terrain, as opposed to mathematical filters. Level of smoothing depends on ridgeline geometry and density, and the applied user-defined channel order. The method requires digital extraction of a high-density channel and ridgeline network. The advantage of the smoothing method over traditional methods is demonstrated through a case study of the Kali Basin test site in Hungary. The smoothing method is used in this study for aspect generalisation for morphotectonic investigations in a small watershed.

  13. 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...

  14. 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).

  15. 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...

  16. Contemporary ice-elevation changes on central Chilean glaciers using SRTM1 and high-resolution DEMs

    NASA Astrophysics Data System (ADS)

    Vivero, Sebastian; MacDonell, Shelley

    2016-04-01

    Glaciers located in central Chile have undergone significant retreat in recent decades. Whilst studies have evaluated area loss of several glaciers, there are no detailed studies of volume losses. This lack of information restricts not only estimations of current and future contributions to sea level rise, but also has limited the evaluation of freshwater resource availability in the region. Recently, the Chilean Water Directorate has supported the collection of field and remotely sensed data in the region which has enabled glacier changes to be evaluated in greater detail. This study aims to compare high-resolution laser scanning DEMs acquired by the Chilean Water Directorate in April 2015 with the recently released SRTM 1 arc-second DEM (˜30 m) acquired in February 2000 to calculate geodetic mass balance changes for three glaciers in a catchment in central Chile over a 15-year period. Detailed analysis of the SRTM and laser scanning DEMs, together with the glacier outlines enable the quantification of elevation and volume changes. Glacier outlines from February 2000 were obtained using the multispectral analysis of a Landsat TM image, whereas outlines from April 2015 were digitised from high resolution glacier orthophotomosaics. Additionally, we accounted for radar penetration into snow and/or ice by evaluating elevation differences between SRTM C-and X-bands, as well as mis-registration between SRTM DEM and the high-resolution DEMs. Over the period all glaciers show similar ice wastage in the order of 0.03 km3 for the debris-covered and non-covered glaciers. However, whilst on the non-covered glaciers mass loss is largely related to elevation and the addition of surface sediment, on the debris-covered glacier, losses are related to the development of thermokarst features. By analysing the DEM in conjunction with Landsat images, we have detected changes in the sediment cover of the non-covered glaciers, which is likely to change the behaviour of the surface mass

  17. 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.

  18. Anti-aliasing filters for deriving high-accuracy DEMs from TLS data: A case study from Freeport, Texas

    NASA Astrophysics Data System (ADS)

    Xiong, Lin.; Wang, Guoquan; Wessel, Paul

    2017-03-01

    Terrestrial laser scanning (TLS), also known as ground-based Light Detection and Ranging (LiDAR), has been frequently applied to build bare-earth digital elevation models (DEMs) for high-accuracy geomorphology studies. The point clouds acquired from TLS often achieve a spatial resolution at fingerprint (e.g., 3 cm×3 cm) to handprint (e.g., 10 cm×10 cm) level. A downsampling process has to be applied to decimate the massive point clouds and obtain manageable DEMs. It is well known that downsampling can result in aliasing that causes different signal components to become indistinguishable when the signal is reconstructed from the datasets with a lower sampling rate. Conventional DEMs are mainly the results of upsampling of sparse elevation measurements from land surveying, satellite remote sensing, and aerial photography. As a consequence, the effects of aliasing caused by downsampling have not been fully investigated in the open literature of DEMs. This study aims to investigate the spatial aliasing problem of regridding dense TLS data. The TLS data collected from the beach and dune area near Freeport, Texas in the summer of 2015 are used for this study. The core idea of the anti-aliasing procedure is to apply a low-pass spatial filter prior to conducting downsampling. This article describes the successful use of a fourth-order Butterworth low-pass spatial filter employed in the Generic Mapping Tools (GMT) software package as an anti-aliasing filter. The filter can be applied as an isotropic filter with a single cutoff wavelength or as an anisotropic filter with two different cutoff wavelengths in the X and Y directions. The cutoff wavelength for the isotropic filter is recommended to be three times the grid size of the target DEM.

  19. 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

  20. 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

  1. 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.

  2. The Multi-Instrument, Comprehensive Differential Emission Measure (DEM) of the Solar Corona During Flares and Quiescent Periods

    NASA Astrophysics Data System (ADS)

    Caspi, Amir; McTiernan, James; Warren, Harry; Woods, Thomas N.

    2014-06-01

    Thermal plasma in the solar corona, while often modeled as isothermal for ease of analysis, is in fact decidedly multi-thermal, ranging from ~1-2 MK in the quiescent corona to ~30-50 MK in intensely flaring loops. It has proven difficult to obtain a well-constrained differential emission measure (DEM) from a single instrument, as the wavelength ranges of individual instruments, even those with broadband coverage, provide sensitivity to only a limited range of plasma temperatures. Recently, we developed a new technique using combined extreme ultraviolet (EUV) and soft and hard X-ray (SXR, HXR) data from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), respectively, to obtain a self-consistent DEM that is strongly constrained across the full range of coronal plasma temperatures (<2 to >50 MK). An accurate, precise determination of the plasma temperature distribution enables not only studies of plasma heating and thermal plasma evolution, but can also provide strong constraints on the non-thermal accelerated electron population, including the low-energy cutoff which is typically determined only as a loose upper limit.We present EVE+RHESSI DEM results from selected intense (X-class) flares from solar cycle 24, including determining the non-thermal low-energy cutoff and examining how this evolves with the temperature distribution. We also apply this technique to combine EUV data from EVE with SXR data from the GOES X-ray Sensor (XRS) and the X123, a new SXR spectrometer flown on two recent SDO/EVE calibration sounding rockets, to examine the DEM during quiescent (non-flaring) times with varying activity levels; the X-ray data provide crucial constraints on the high-temperate extent of the DEM and any potential non-thermal emission. We compare these results with those from a parallel technique to derive DEMs from imaging data from the Atmospheric Imaging Assembly (AIA

  3. 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.

  4. Classification of topography using DEM data and its correlation with the geology of Greece

    NASA Astrophysics Data System (ADS)

    Zargli, Eleni; Liodakis, Stelios; Kyriakidis, Phaedon; Savvaidis, Alexandros

    2013-08-01

    Continuous topography from Digital Elevation Model (DEM) data is frequently segmented into terrain classes based on local morphological characteristics of terrain elevation, e.g., local slope gradient and convexity. The resulting classes are often used as proxies for the average shear wave velocity up to 30 m, and the determination of ground types as required by the Eurocode (EC8) for computing elastic design spectra. In this work, we investigate the links between terrain related variables, particularly slope gradient, extracted for the area of Greece from the Shuttle Radar Topography Mission (SRTM) 30 arc second global topographic data available from the United States Geological Survey (USGS), with: (a) the global terrain classification product of Iwahashi and Pike (2007) in which 16 terrain types are identified for the same spatial resolution, and (b) information on geological units extracted at the same resolution from the geological map of Greece at a scale of 1/500000 as published from the Institute of Geology and Mineral Exploration (IGME). An interpretation of these links is presented within the context of understanding the reliability of using geology, slope and terrain classes for site characterizations of earthquake risk in a high seismicity area like Greece. Our results indicate that slope is a somewhat biased proxy for solid rocks, whereas in Alluvial deposits the distance to and type of the nearest geological formation appears to provide qualitative information on the size of the sedimentary deposit.

  5. DNS-DEM of Suspended Sediment Particles in an Open Channel Flow

    NASA Astrophysics Data System (ADS)

    Pakseresht, Pedram; Apte, Sourabh; Finn, Justin

    2016-11-01

    DNS with point-particle based discrete element model (DEM) is used to study particle-turbulence interactions in an open channel flow at Reτ of 710, corresponding to the experimental observations of Righetti & Romano. Large particles of diameter 200 microns (10 in wall units) with volume loading on the order of 10-3 are simulated using four-way coupling with closure models for drag, added mass, lift, pressure, and inter-particle collision forces. The point-particle model is able to accurately capture the effect of particles on the fluid flow in the outer layer. However, the particle is significantly larger than the wall-normal grid in the near-wall region, but slightly smaller than the axial and longitudinal grid resolutions. The point-particle model fails to capture the interactions in the near-wall region. In order to improve the near-wall predictions, particles are represented by Lagrangian material points which are used to perform interpolations from the grid to the Lagrangian points and to distribute the two-way coupling force to the Eulerian grid. Predictions using this approach is compared with the experimental data to evaluate its effectiveness. NSF project #1133363, Sediment-Bed-Turbulence Coupling in Oscillatory Flows.

  6. New DEMs may stimulate significant advancements in remote sensing of soil moisture

    NASA Astrophysics Data System (ADS)

    Nolan, Matt; Fatland, Dennis R.

    From Napoleon's defeat at Waterloo to increasing corn yields in Kansas to greenhouse gas flux in the Arctic, the importance of soil moisture is endemic to world affairs and merits the considerable attention it receives from the scientific community. This importance can hardly be overstated, though it often goes unstated.Soil moisture is one of the key variables in a variety of broad areas critical to the conduct of societies' economic and political affairs and their well-being; these include the health of agricultural crops, global climate dynamics, military trafficability planning, and hazards such as flooding and forest fires. Unfortunately the in situ measurement of the spatial distribution of soil moisture on a watershed-scale is practically impossible. And despite decades of international effort, a satellite remote sensing technique that can reliably measure soil moisture with a spatial resolution of meters has not yet been identified or implemented. Due to the lack of suitable measurement techniques and, until recently digital elevation models (DEMs), our ability to understand and predict soil moisture dynamics through modeling has largely remained crippled from birth [Grayson and Bloschl, 200l].

  7. DEM simulations of shear flow of spherical particles mixed with long granular rods

    NASA Astrophysics Data System (ADS)

    Baran, Oleh

    2015-11-01

    Using Discrete Element Method (DEM) I investigate the effect of adding rigid rod-shape particles to the granular flow of spherical particles inside ring shear tester. The simulated geometry includes an annulus, bounded by two concentric cylindrical walls rested on a stationary bottom disk and covered with a top lid. Both the top lid and the bottom have protruding vanes oriented radially and uniformly spaced around the annulus, to prevent slipping of the bulk solid, see image at this link. The top lid rotates with a controlled angular speed and applies a constant normal load to the tested material. I analyze the results for shear stress on the top lid as a function of time for the mixture of spheres and rods and compare these results with ones obtained for the same amount of spherical particles without rods. I also present the analysis of the orientation of granular rods in a shear flow and discuss the results in terms of new time-scale related to the mobility of rods.

  8. DEM simulation of particle mixing for optimizing the overcoating drum in HTR fuel fabrication

    NASA Astrophysics Data System (ADS)

    Liu, Malin; Lu, Zhengming; Liu, Bing; Shao, Youlin

    2013-06-01

    The rotating drum was used for overcoating coated fuel particles in HTR fuel fabrication process. All the coated particles should be adhered to equal amount of graphite powder, which means that the particle should be mixed quickly in both radial and axial directions. This paper investigated the particle flow dynamics and mixing behavior in different regimes using the discrete element method (DEM). By varying the rotation speed, different flow regimes such as slumping, rolling, cascading, cataracting, centrifuging were produced. The mixing entropy based on radial and axial grid was introduced to describe the radial and axial mixing behaviors. From simulation results, it was found that the radial mixing can be achieved in the cascading regime more quickly than the slumping, rolling and centrifuging regimes, but the traditional rotating drum without internal components can not achieve the requirements of axial mixing and should be improved. Three different structures of internal components are proposed and simulated. The new V-shaped deflectors were found to achieve a quick axial mixing behavior and uniform axial distribution in the rotating drum based on simulation results. At last, the superiority was validated by experimental results, and the new V-shaped deflectors were used in the industrial production of the overcoating coated fuel particles in HTR fuel fabrication process.

  9. 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.

  10. The value of a UAV-acquired DEM for flood inundation mapping and modeling

    NASA Astrophysics Data System (ADS)

    Schumann, Guy J.-P.; Muhlhausen, Joseph; Andreadis, Konstantinos

    2016-04-01

    Remotely Piloted Systems also known as Unmanned Aerial Vehicle have rapidly developed as tools for remote sensing and mapping and publications referring to RPS remote sensing applications is increasing each year. In particular Structure from Motion (SfM), a relatively new photogrammetry approach has been documented for various applications. Some papers have focused on the accuracy of the output generated by SfM by validating relative and absolute accuracy using ground control points, others have looked at various applications. Yet we argue that a major aspect of SfM has been overlooked, its ability to generate highly accurate point cloud models without the use of ground control points. We demonstrate this by comparing with a LIDAR DEM, a dataset which has been transformative in flood inundation research and applications. Our results demonstrate that a point cloud collected using a RPS and a 16M pixel Bayer sensor camera using a rolling shutter can achieve a RMSE of 39 cm compared to LIDAR. We conclude that a SfM model is not only highly accurate but could complement LIDAR for floodplain mapping and modelling, especially in cases where smaller coverage is sufficient and LiDAR acquisition via airplane may be too costly or impractical.

  11. The TerraSAR-X/TanDEM-X Formation Acquisition-from Planning to Realization

    NASA Astrophysics Data System (ADS)

    Kahle, Ralph; Schlepp, Benjamin; Meissner, Florian; Kirschner, Michael; Kiehling, Reinhard

    2012-09-01

    On June 21, 2010 the TanDEM-X satellite (TDX) was injected into orbit at 15,700 km distance from its twin satellite TerraSAR-X (TSX), which has been in orbit since 2007. Already one month later TDX acquired a formation with TSX in order to build up the first single-pass radar interferometer in space. Within three years of close formation flying with flexible baselines ranging from 150 m to a few kilometers the twin satellites will collect interferometric radar measurements for the generation of a global digital elevation model with unprecedented accuracy. This paper elaborates on the TDX pre-launch analysis performed in the fields of collision assessment during orbit injection and target formation acquisition. To avoid a critical close approach shortly after TDX separation, the risk of collision between the already flying TSX satellite and the newly injected elements (DNEPR upper-stage, gas dynamic shield, and TDX satellite) had to be carefully analyzed. Further, the paper discusses a fuel-saving formation acquisition strategy, for which the maneuver budget is analyzed as a function of launch day and launch injection accuracy. Finally, flight results are presented to illustrate the successful formation acquisition realized in July 2010 and the formation reconfiguration process from the 20 km wide formation into the 300-400 m close formation performed in October 2010. This reconfiguration marked the start of the bi-static TDX/TSX instrument operation.

  12. Phenological tracking og agricultural feilds investigated by using dual polarimetry tanDEM-X images

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Remote sensing plays a key role in monitoring and assessing environmental changes. Because of its special imaging characteristics such as high-resolution, capabilities to obtain data in all weather conditions and sensitivity to geometrical and dielectric properties of the features, Synthetic Aperture Radar (SAR) technology has become a powerful technique to detect small scale changes related to earth surface.SAR images contain the information of both phase and intensity in different modes like single, dual and full polarimetric states which are important in order to extract information about various targets. In this study we investigate phenological changes in an agricultural region using high-resolution X-band SAR data. The case study is located in Doroud region of Lorestan province, west of Iran. The purpose is to investigate the ability of copolar and interferometric coherence extracted from TanDEM-X dual polarimetry (HH/VV) in bistatic StripMap mode for tracking the phenological changes of crops during growing season. The data include 11 images acquired between 12.06.2012 and 02.11.2012 and 6 images acquired between 30.05.2013 and 04.08.2013 in the CoSSC format. Results show that copolar coherence is almost able to follow phenological changes but interferometric coherence has a near constant behaviour with fluctuations mainly related to baseline variations.

  13. Estimation of river based transportable volcanic material distribution using satellite DEM and precipitation data

    NASA Astrophysics Data System (ADS)

    Wisoyo, A.; Putra, S. S.

    2017-01-01

    The transportable volcanic materials of Mt. Marapi, which are deposited around the caldera, as a result from last eruption in November 2015, must be estimated as a first step to handle the lahar/ debris flow disaster. In this research, the method used to determine the amount of river-based transportable volcanic material distribution was offered. The LIDAR Satellite DEM and TRMM data from Global Precipitation Climatology Project (GPCP) have been used to estimate the deposited volcanic materials. Based on the GPCP data analysis, it was found that the rainfall pattern distribute into two area, which are 0.52 mm/ hr on west side and 0.61 mm/ hr on east side relative to the mountain summit. The deposited materials from Mt. Marapi 14 November 2015 eruption (volcanic boulders and lava) were located in the upstream of six prioritized watershed. The transportable volcanic material will predominantly flows to the South and North West direction. The potentially transported boulder and lava are around 80.33 % of the total erupted material that are deposited in the river upstream. Batang Kadurang Watershed has the highest transportable material of 1,905.18 m3. The results of study can be used as a rapid disaster countermeasure for lahar disaster mitigation.

  14. Markers of assimilation of problematic experiences in dementia within the LivDem project.

    PubMed

    Cheston, Richard; Gatting, Lauren; Marshall, Ann; Spreadbury, John H; Coleman, Peter

    2015-09-01

    This study aimed to determine whether the Markers of Assimilation of Problematic Experiences in Dementia scale (MAPED) can be used to identify whether the way in which participants talk about dementia changed during the group. All eight sessions of a LivDem group, which were attended by participants were recorded and transcribed. An initial analysis identified 160 extracts, which were then rated using the MAPED system. Inter-rater reliability was 61% and following a resolution meeting, 35 extracts were discarded, leaving 125 extracts with an agreed marker code. All of the participants were identified as producing a speech marker relating to dementia, and these varied between 0 (warding off) to 6 (problem solution). Examples of these markers are provided. The proportion of emergence markers (indicating the initial stages of assimilation) compared to later markers changed significantly between the first four sessions and the final sessions. This difference was still significant even when the markers produced by the most verbal participant, Graham, were excluded. The use of process measures within psychotherapy complements more conventional outcome measures and has both theoretical and clinical implications.

  15. Hydrological characterization of volcanic island by DEM generation using ASAR (ENVISAT): Galapagos

    NASA Astrophysics Data System (ADS)

    D'Ozouville, N.; Violette, S.; Benveniste, J.; Wegmuller, U.; Deffontaines, B.; de Marsily, G.

    2007-12-01

    Low topographic oceanic islands often suffer from scarcity of freshwater resources and are poorly characterized due to their complex internal structure and challenging access. Remote sensing has proved to be an effective tool to generate valuable data for hydrological analysis. However, these are usually tested over areas with existing validation databases and not always where the need is greatest. Here we address the need for topographical data for hydrological understanding of Santa Cruz Island (Galapagos Archipelago) where no high resolution, no high accuracy topographical data exists. 97 percent of Galapagos territory consists of inaccessible National Park land which makes the use of indirect methods indispensable. We used new ASAR data (ENVISAT) for Digital Elevation Model generation, in order to extract drainage network, watersheds, and flow characteristics from a morpho-structural analysis. Results show the high potential of this data for both interferometric and radargrammetric generation methods. If interferometry suffered from low coherence over highly vegetated areas, it showed high precision over the rest of the island. Radargrammetry gave consistent results over the entire island, and detail was enhanced by integrating the SRTM as an external DEM. Validation of the extracted river networks and watersheds was carried out using ground-based field observations, comparison to drainage network extracted from aerial photographs and to high resolution (1 m) satellite imagery. For the first time watershed characteristics and flow paths are made available for an island of the Galapagos archipelago. Drainage networks and underground percolation are strongly influenced by fractures.

  16. 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.

  17. Lithospheric reworking at the Proterozoic-Phanerozoic transition of Australia imaged using AusLAMP Magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Robertson, Kate; Heinson, Graham; Thiel, Stephan

    2016-10-01

    Seventy-four stations from the long-period Australia-wide AusLAMP (Australian Lithospheric Architecture Magnetotelluric Project) dataset were used to image the electrical resistivity beneath the Neoproterozoic Ikara-Flinders Ranges and adjacent Palaeo-Mesoproterozoic Curnamona Province. Results from 3D inversions using ModEM software show a relatively resistive Ikara-Flinders Ranges, with two parallel arcuate conductors at 20 to 80 km depth in the Nackara Arc. There is a good correlation of diamondiferous kimberlites occurring over conductors, which we interpret as evidence for these conductors to be residing on large lithospheric structures that have been conduits for partial melt and volatile movement in the Jurassic. The Curnamona Province is remarkably conductive for a region that is thought to have a cratonic core, with Delamerian reworking only at its edges. The conductor covers most of the province at depths of 10-40 km, and its presence at lower crustal depths suggests that conductive sediments can not entirely explain it. Fluids associated with subduction may have pervasively modified the crust in the past, resulting in an enrichment of carbon, enhancing the conductivity. Additionally, we conclude that the notion of a single continuous arcuate Flinders Conductivity Anomaly is unlikely and that the anomalous response observed is instead a result of the combined response of three separate anomalies; the Curnamona Province Conductor and the two Nackara Arc Conductors.

  18. 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

  19. 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.

  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. Observations of glacier mass changes and their system inherent drivers over Western Himalaya (Himachal Pradesh, India) during 2000-2013 using TanDEM-X and SRTM-C DEMs

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2016-04-01

    The glaciers in Himachal Pradesh (HP), India (Western Himalaya) are a part of widely spread Hindu Kush-Karakoram-Himalaya mountain ranges. The glacier mass changes depend on system inherent (size, topography, aspect etc.) and climatic factors (precipitation, temperature etc.). The glaciers in this region are mostly debris-covered with supraglacial ponds. They are mostly land-terminating but few of them terminate at the lakes. The two different precipitation regimes namely, Indian summer monsoon and mid-latitude winter westerlies, influence the glaciers in the region. The continuous observations of such glacier changes using field experiments are often limited and repeat pass satellite data potentially fills this gap. Previous studies notified that the bench mark glacier, called Chhota Shigri Glacier, experienced a transition from mass gain (or equilibrium) to loss around 1999. This study aims to estimate the mass change of glaciers in HP at two different time scales. During 2000-2012, we subtract TanDEM-X DEMs of Feb, 2012 from the SRTM C/X band DEM of Feb, 2000. The published ice thickness change of Chhota Shigri Glacier from field observations is compared with ice thickness change derived from DEM differencing. This potentially estimates the bias in thickness change due to different radar frequencies (C band for SRTM, X band for TanDEM-X). For 2012-2013, we use repeat pass TanDEM-X DEMs which don't require any further bias correction. We perform hypsometry analysis (25 m elevation bin) of thickness change of ~800 km2 of ice covered area during these times scales. The analysis shows a transition of thickness change -2.0 myr-1 (4000-4200 m elevation) to -2.7 myr-1 at higher elevations (4200-4800) and further transits upstream. This clearly shows that the presence of thick debris at the glacier tongue act as insulator and reduce the downwasting. The downwasting increases as the surface consists of thin debris and exposed more to radiation. The downwasting linearly

  2. New morphometric properties for channel network classification using the graph theory and DEM

    NASA Astrophysics Data System (ADS)

    Moussa, R.; Colin, F.; Rabotin, M.; A; Crabit

    2012-04-01

    The channel network controls the spatial pattern of hydrological processes within a catchment. Hence the identification of key hydrological features characterising the channel network can contribute to a rational classification of catchments. This presentation aims to investigate morphometric properties of the channel network derived from DEM using the graph theory, and estimate whether these properties can be used as similarity indices for the classification of channel networks. The graph theory was used in order to represent the contributing drainage area which has properties of a scale free network, and was subsequently characterised by highly connected nodes called hubs. The method involves ranking the hubs of a channel network according to the contributing drainage area and the distance to the outlet. The hubs' characteristics can be considered as morphometric descriptors of the channel network and are used to compare and classify channel network. Applications were conducted on 788 French catchments with the same area (between 100 and 105 km2) and on 18 catchments having an area between 43 and 116450 km2. First, we present some newly found invariance properties of headwater subcatchments and show that some invariant morphometric properties characterize only natural channel networks verifying Optimal Channel Networks (OCN) properties, but are not verified for non-OCN (Moussa et al., 2011, Water Resources Research, 47, W08518). A new empirical model based on self-affine properties was developed in order to calculate the number N and the total headwater area H as a function of the cutoff area S used to extract the channel network from DEM. Results show that H(S) / S0 (S0 being the catchment area) is independent from S and seems constant (0.29 +/- 0.03) for various shapes and sizes of channel networks, and consequently can be considered as invariant general descriptor of natural channel networks. On the contrary, this is not the case when the approach is applied

  3. Two types of the regular stratovolcano shape: a DEM-based morphometrical analysis

    NASA Astrophysics Data System (ADS)

    Karátson, Dávid; Favalli, Massimiliano; Tarquini, Simone; Fornaciai, Alessandro; Wörner, Gerhard

    2010-05-01

    We studied the shape of the most regular-shaped stratovolcanoes of the world to mathematically define the form of the ideal stratovolcano. Based on the Shuttle Radar Topographic Mission (SRTM) DEM data, we selected the 20 most circular and symmetrical volcanoes, which incidentally all belong to subduction-related arcs surrounding the Pacific. The selection of volcanoes benefits from the introduction of a new definition of circularity, which is more robust than previous definitions, being independent of the erosional dissection of the cone. Our study on the shape of stratovolcanoes was based on the analysis of the radial elevation profiles of each volcano. The lower half section of the volcanoes is always well fitted by a logarithmic curve, while the upper half section is not, and falls into two groups: it is fitted either by a line ("C-type", conical upper part) or by a parabolic arc ("P-type", parabolic/concave upper part). Chemical composition of the two groups' eruptive products indicates higher SiO2 and/or higher H2O content for C-type volcanoes, which could imply a higher incidence of mildly explosive (e.g. strombolian) eruptions. We propose that this higher explosivity is responsible for forming the constant uppermost slopes by the deposition of ballistic tephra and its subsequent stabilisation at a constant angle. In contrast, P-type volcanoes are characterized by a smaller SiO2 and H2O content, which can be responsible for a higher incidence of effusive events and/or a lower incidence of upper flank-forming (i.e. mild) explosive eruptions. Therefore, the concave upper flanks of these volcanoes may be shaped prevailingly by lava flows. Based on this hypothesis, we propose that the advanced morphometric analysis of the elevation profile of stratovolcanoes can provide insights into their dominant eruptive style.

  4. Integration of SRTM DEM and Hydraulic Analysis for Flood Response Planning.

    NASA Astrophysics Data System (ADS)

    Pervez, M.; Asante, K. O.; Smith, J. L.; Verdin, J. P.; Rowland, J.

    2006-12-01

    The ability to delineate potential flood inundation areas is one of the most important requirements for flood response planning. Historical hydrologic records and high-resolution topographic data are essential to model flood inundation and to map areas at risk of inundation. For Afghanistan, historical hydrologic data enable the analysis of flood frequency, but the accurate delineation of flood inundation zones is limited by the lack of high- resolution elevation data. This study has developed a method for coupling hydraulic analysis and Geographic Information System (GIS) technology to delineate flood risk maps of the Helmand and Kabul drainage basins in Afghanistan. Land surface elevation data from the Shuttle Radar Topography Mission (SRTM) were used to create an area-elevation profile with respect to the rivers that flow into these two basins. Using the profile, we computed cross-sectional area and wetted perimeter for each 1-m increment in elevation. Manning's equation was applied to compute river discharge for each 1-m increment in water level using cross-sectional area, wetted perimeter and slope of the respective river reach. Results for the gauged river reaches were compared with 25, 50, and 100-year return period floods based on a flood frequency from the historical stream flow data, and associated depths of water were estimated for each return period flood. Peak flows at gauge stations were extrapolated to ungauged river reaches based on upstream drainage area. The estimated depths of water for each river reach were used as thresholds to identify areas subject to flood inundation, using the SRTM Digital Elevation Model (DEM) with respect to the rivers. The resulting flood inundation polygons were combined in a GIS with roads, infrastructure, settlements, and higher resolution satellite imagery to identify potential hazards due to flooding, and provide detailed information for flood response planning.

  5. Global DEM Errors Underpredict Coastal Vulnerability to Sea Level Rise and Flooding

    NASA Astrophysics Data System (ADS)

    Kulp, Scott; Strauss, Benjamin

    2016-04-01

    Elevation data based on NASA's Shuttle Radar Topography Mission (SRTM) have been widely used to evaluate threats from global sea level rise, storm surge, and coastal floods. However, SRTM data are known to include large vertical errors in densely urban or densely vegetated areas. The errors may propagate to derived land and population exposure assessments. We compare assessments based on SRTM data against references employing high-accuracy bare-earth elevation data generated from lidar data available for coastal areas of the United States. We find that both 1-arcsecond and 3-arcsecond horizontal resolution SRTM data systemically underestimate exposure across all assessed spatial scales and up to at least 10m above the high tide line. At 3m, 1-arcsecond SRTM underestimates U.S. population exposure by more than 60%, and under-predicts population exposure in 90% of coastal states, 87% of counties, and 83% of municipalities. These fractions increase with elevation, but error medians and variability fall to lower levels, with national exposure underestimated by just 24% at 10m. Results using 3-arcsecond SRTM are extremely similar. Coastal analyses based on SRTM data thus appear to greatly underestimate sea level and flood threats, especially at lower elevations. However, SRTM-based estimates may usefully be regarded as providing lower bounds to actual threats. We additionally assess the performance of NOAA's Global Land One-km Base Elevation Project (GLOBE), another publicly-available global DEM, but do not reach any definitive conclusion because of the spatial heterogeneity in its quality.

  6. 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.

  7. Analysis of Influence of Terrain Relief Roughness on dem Accuracy Generated from LIDAR in the Czech Republic Territory

    NASA Astrophysics Data System (ADS)

    Hubacek, M.; Kovarik, V.; Kratochvil, V.

    2016-06-01

    Digital elevation models are today a common part of geographic information systems and derived applications. The way of their creation is varied. It depends on the extent of area, required accuracy, delivery time, financial resources and technologies available. The first model covering the whole territory of the Czech Republic was created already in the early 1980's. Currently, the 5th DEM generation is being finished. Data collection for this model was realized using the airborne laser scanning which allowed creating the DEM of a new generation having the precision up to a decimetre. Model of such a precision expands the possibilities of employing the DEM and it also offers new opportunities for the use of elevation data especially in a domain of modelling the phenomena dependent on highly accurate data. The examples are precise modelling of hydrological phenomena, studying micro-relief objects, modelling the vehicle movement, detecting and describing historical changes of a landscape, designing constructions etc. Due to a nature of the technology used for collecting data and generating DEM, it is assumed that the resulting model achieves lower accuracy in areas covered by vegetation and in built-up areas. Therefore the verification of model accuracy was carried out in five selected areas in Moravia. The network of check points was established using a total station in each area. To determine the reference heights of check points, the known geodetic points whose heights were defined using levelling were used. Up to several thousands of points were surveyed in each area. Individual points were selected according to a different configuration of relief, different surface types, and different vegetation coverage. The sets of deviations were obtained by comparing the DEM 5G heights with reference heights which was followed by verification of tested elevation model. Results of the analysis showed that the model reaches generally higher precision than the declared one in

  8. Application of Bistatic TanDEM-X Interferometry to Measure Lava Flow Volume and Lava Extrusion Rates During the 2012-13 Tolbachik, Kamchatka Fissure Eruption

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Aerial imaging methods are a well approved source for mapping lava flows during eruptions and can serve as a base to assess the eruption dynamics and to determine the affected area. However, clouds and smoke often hinder optical systems like the Earth Observation Advanced Land Imager (EO-1-ALI, operated by NASA) to map lava flows properly, which hence affects its reliability. Furthermore, the amount of lava that is extruded during an eruption cannot be determined from optical images - however, it can significantly contribute to assess the accompanying hazard and risk. One way to monitor active lava flows is to quantify the topographic changes over time while using up-to-date high-resolution digital elevation models (DEMs). Whereas photogrammetric methods still fail when clouds and fume obstruct the sight, innovative radar satellite missions have the potential to generate high-resolution DEMs at any time. The innovative bistatic TanDEM-X (TerraSAR-X Add-on for Digital Elevation Measurements) satellite mission enables for the first time generating high-resolution DEMs from synthetic aperture radar satellite data repeatedly with reasonable costs and high resolution. The satellite mission consists of the two nearly identical satellites TerraSAR-X and TanDEM-X that build a large synthetic aperture radar interferometer with adaptable across- and along-track baselines aiming to generate topographic information globally. In the present study, we apply the TanDEM-X data to study the lava flows that were emplaced during the 2012-13 Tolbachik, Kamchatka fissure eruption. The eruption was composed of very fluid lava flows that effused along a northeast-southwest trending fissure. We used about fifteen bistatic data pairs to generate DEMs prior to, during, and after the eruption. The differencing of the DEMs enables mapping the lava flow field at different times. This allows measuring the extruded volume and to derive the changes in lava extrusion over time.

  9. The influence of accuracy, grid size, and interpolation method on the hydrological analysis of LiDAR derived dems: Seneca Nation of Indians, Irving NY

    NASA Astrophysics Data System (ADS)

    Clarkson, Brian W.

    Light Detection and Ranging (LiDAR) derived Digital Elevation Models (DEMs) provide accurate, high resolution digital surfaces for precise topographic analysis. The following study investigates the accuracy of LiDAR derived DEMs by calculating the Root Mean Square Error (RMSE) of multiple interpolation methods with grid cells ranging from 0.5 to 10-meters. A raster cell with smaller dimensions will drastically increase the amount of detail represented in the DEM by increasing the number of elevation values across the study area. Increased horizontal resolutions have raised the accuracy of the interpolated surfaces and the contours generated from the digitized landscapes. As the raster grid cells decrease in size, the level of detail of hydrological processes will significantly improve compared to coarser resolutions including the publicly available National Elevation Datasets (NEDs). Utilizing a LiDAR derived DEM with the lowest RMSE as the 'ground truth', watershed boundaries were delineated for a sub-basin of the Clear Creek Watershed within the territory of the Seneca Nation of Indians located in Southern Erie County, NY. An investigation of the watershed area and boundary location revealed considerable differences comparing the results of applying different interpretation methods on DEM datasets of different horizontal resolutions. Stream networks coupled with watersheds were used to calculate peak flow values for the 10-meter NEDs and LiDAR derived DEMs.

  10. 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

  11. 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

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

    NASA Technical Reports Server (NTRS)

    Valenti, Elizabeth; Fitzpatrick, Patrick

    2006-01-01

    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.

  13. With high resolution DEM to enhanced maps of Dominant Runoff Processes (DRP)

    NASA Astrophysics Data System (ADS)

    Margreth, Michael; Naef, Felix

    2010-05-01

    The reaction of a river on intense rainfall depends on the distribution of the dominant runoff processes (DRP) Hortonian Overland Flow (HOF), Saturated Overland Flow (SOF), Sub-surface Flow (SSF) or Deep Percolation (DP) within its catchment area. A decision scheme to determine the DRP was implemented in a GIS, using high resolution data of soils, geology, land use and topography. With the scheme, a DRP map was derived for the Kanton of Zurich with an area of 1730 km2, which lies in the Swiss Plateau and covers a wide range of topography, geology and flood producing precipitation regimes. Detailed soil maps are essential for the derivation of high resolution dominant runoff processes maps because they contain information about the soil infiltration and the storage capacity. In the Kanton of Zurich, only a small part of the forested areas is covered by detailed soil maps. Information like soil depth and soil water regime had to be derived from the forest vegetation map (1:5'000). In this map, species of plants, grouped to forest communities, are delineated, depending on their preferred site conditions. Besides geology, topography and climate, also soil water regime and soil depth influence the occurence of plant species. However, a comparison between the soil water regime, indicated by detailed soil maps and the forest vegetation map shows that not all forest communities are selective for the soil water regime and soil depth. Thus, only some forest communities can be used, to derive the DRP. For the other forest communities, an automatic method had to be developed to derive soil water regime and soil depth, based on a high resolution geological map and a laser scanned DEM. With the high resolution topographic information, small creeks, drainage ditches and erosion ditches could be identified. These areas indicate where a fast runoff reaction during heavy rainfalls can be expected. Creeks and drainage ditches suggest that soils do not drain properly and are saturated

  14. 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

  15. AusEinetter, 1999.

    ERIC Educational Resources Information Center

    AusEinetter, 1999

    1999-01-01

    This document contains issues eight and nine of the 1999 Australian Early Intervention Network for Mental Health in Young People newsletters for health professionals. The newsletters disseminate information about the national and local initiatives for intervention and prevention of mental health problems in young children and youth. The issues…

  16. AusEinetter, 1998.

    ERIC Educational Resources Information Center

    AusEinetter, 1998

    1998-01-01

    This publication contains the 1998 issues of the Australian Early Intervention Network for Mental Health in Young People newsletters for health professionals. The newsletters disseminate information about the national and local initiatives for intervention and prevention of mental health problems in young children and youth. Each issue also offers…

  17. 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.

  18. 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

  19. Parallelizing flow-accumulation calculations on graphics processing units—From iterative DEM preprocessing algorithm to recursive multiple-flow-direction algorithm

    NASA Astrophysics Data System (ADS)

    Qin, Cheng-Zhi; Zhan, Lijun

    2012-06-01

    As one of the important tasks in digital terrain analysis, the calculation of flow accumulations from gridded digital elevation models (DEMs) usually involves two steps in a real application: (1) using an iterative DEM preprocessing algorithm to remove the depressions and flat areas commonly contained in real DEMs, and (2) using a recursive flow-direction algorithm to calculate the flow accumulation for every cell in the DEM. Because both algorithms are computationally intensive, quick calculation of the flow accumulations from a DEM (especially for a large area) presents a practical challenge to personal computer (PC) users. In recent years, rapid increases in hardware capacity of the graphics processing units (GPUs) provided in modern PCs have made it possible to meet this challenge in a PC environment. Parallel computing on GPUs using a compute-unified-device-architecture (CUDA) programming model has been explored to speed up the execution of the single-flow-direction algorithm (SFD). However, the parallel implementation on a GPU of the multiple-flow-direction (MFD) algorithm, which generally performs better than the SFD algorithm, has not been reported. Moreover, GPU-based parallelization of the DEM preprocessing step in the flow-accumulation calculations has not been addressed. This paper proposes a parallel approach to calculate flow accumulations (including both iterative DEM preprocessing and a recursive MFD algorithm) on a CUDA-compatible GPU. For the parallelization of an MFD algorithm (MFD-md), two different parallelization strategies using a GPU are explored. The first parallelization strategy, which has been used in the existing parallel SFD algorithm on GPU, has the problem of computing redundancy. Therefore, we designed a parallelization strategy based on graph theory. The application results show that the proposed parallel approach to calculate flow accumulations on a GPU performs much faster than either sequential algorithms or other parallel GPU

  20. Can DEM time series produced by UAV be used to quantify diffuse erosion in an agricultural watershed?

    NASA Astrophysics Data System (ADS)

    Pineux, N.; Lisein, J.; Swerts, G.; Bielders, C. L.; Lejeune, P.; Colinet, G.; Degré, A.

    2017-03-01

    Erosion and deposition modelling should rely on field data. Currently these data are seldom available at large spatial scales and/or at high spatial resolution. In addition, conventional erosion monitoring approaches are labour intensive and costly. This calls for the development of new approaches for field erosion data acquisition. As a result of rapid technological developments and low cost, unmanned aerial vehicles (UAV) have recently become an attractive means of generating high resolution digital elevation models (DEMs). The use of UAV to observe and quantify gully erosion is now widely established. However, in some agro-pedological contexts, soil erosion results from multiple processes, including sheet and rill erosion, tillage erosion and erosion due to harvest of root crops. These diffuse erosion processes often represent a particular challenge because of the limited elevation changes they induce. In this study, we propose to assess the reliability and development perspectives of UAV to locate and quantify erosion and deposition in a context of an agricultural watershed with silt loam soils and a smooth relief. Erosion and deposition rates derived from high resolution DEM time series are compared to field measurements. The UAV technique demonstrates a high level of flexibility and can be used, for instance, after a major erosive event. It delivers a very high resolution DEM (pixel size: 6 cm) which allows us to compute high resolution runoff pathways. This could enable us to precisely locate runoff management practices such as fascines. Furthermore, the DEMs can be used diachronically to extract elevation differences before and after a strongly erosive rainfall and be validated by field measurements. While the analysis for this study was carried out over 2 years, we observed a tendency along the slope from erosion to deposition. Erosion and deposition patterns detected at the watershed scale are also promising. Nevertheless, further development in the

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Modeling the motion and orientation of various pharmaceutical tablet shapes in a film coating pan using DEM.

    PubMed

    Ketterhagen, William R

    2011-05-16

    Film coating uniformity is an important quality attribute of pharmaceutical tablets. Large variability in coating thickness can limit process efficiency or cause significant variation in the amount or delivery rate of the active pharmaceutical ingredient to the patient. In this work, the discrete element method (DEM) is used to computationally model the motion and orientation of several novel pharmaceutical tablet shapes in a film coating pan in order to predict coating uniformity. The model predictions are first confirmed with experimental data obtained from an equivalent film coating pan using a machine vision system. The model is then applied to predict coating uniformity for various tablet shapes, pan speeds, and pan loadings. The relative effects of these parameters on both inter- and intra-tablet film coating uniformity are assessed. The DEM results show intra-tablet coating uniformity is strongly influenced by tablet shape, and the extent of this can be predicted by a measure of the tablet shape. The tablet shape is shown to have little effect on the mixing of tablets, and thus, the inter-tablet coating uniformity. The pan rotation speed and pan loading are shown to have a small effect on intra-tablet coating uniformity but a more significant impact on inter-tablet uniformity. These results demonstrate the usefulness of modeling in guiding drug product development decisions such as selection of tablet shape and process operating conditions.

  7. Evaluation of the performance of the cross-flow air classifier in manufactured sand processing via CFD-DEM simulations

    NASA Astrophysics Data System (ADS)

    Petit, H. A.; Irassar, E. F.; Barbosa, M. R.

    2017-03-01

    Manufactured sands are particulate materials obtained as by product of rock crushing. Particle sizes in the sand can be as high as 6 mm and as low as a few microns. The concrete industry has been increasingly using these sands as fine aggregates to replace natural sands. The main shortcoming is the excess of particles smaller than <0.075 mm (Dust). This problem has been traditionally solved by a washing process. Air classification is being studied to replace the washing process and avoid the use of water. The complex classification process can only been understood with the aid of CFD-DEM simulations. This paper evaluates the applicability of a cross-flow air classifier to reduce the amount of dust in manufactured sands. Computational fluid dynamics (CFD) and discrete element modelling (DEM) were used for the assessment. Results show that the correct classification set up improves the size distribution of the raw materials. The cross-flow air classification is found to be influenced by the particle size distribution and the turbulence inside the chamber. The classifier can be re-designed to work at low inlet velocities to produce manufactured sand for the concrete industry.

  8. An Investigation of Transgressive Deposits in Late Pleistocene Lake Bonneville using GPR and UAV-produced DEMs.

    NASA Astrophysics Data System (ADS)

    Schide, K.; Jewell, P. W.; Oviatt, C. G.; Jol, H. M.

    2015-12-01

    Lake Bonneville was the largest of the Pleistocene pluvial lakes that once filled the Great Basin of the interior western United States. Its two most prominent shorelines, Bonneville and Provo, are well documented but many of the lake's intermediate shoreline features have yet to be studied. These transgressive barriers and embankments mark short-term changes in the regional water budget and thus represent a proxy for local climate change. The internal and external structures of these features are analyzed using the following methods: ground penetrating radar, 5 meter auto-correlated DEMs, 1-meter DEMs generated from LiDAR, high-accuracy handheld GPS, and 3D imagery collected with an unmanned aerial vehicle. These methods in mapping, surveying, and imaging provide a quantitative analysis of regional sediment availability, transportation, and deposition as well as changes in wave and wind energy. These controls help define climate thresholds and rates of landscape evolution in the Great Basin during the Pleistocene that are then evaluated in the context of global climate change.

  9. Correction of the SRTMGL1 Space-Borne Dem and Flooding Dynamics On The Lower Amazon Floodplain

    NASA Astrophysics Data System (ADS)

    Satgé, F.; Pinel, S. S.; Bonnet, M. P.; Moreira, D. M.; Santos da Silva, J.; Calmant, S.; Seyler, F.

    2015-12-01

    Modeling floods events across large floodplains is challenging because flows respond to dynamic hydraulic controls from several water sources, complex geomorphology, and vegetation. In the Amazon basin, the recently liberated SRTM Global 1 arc-second (SRTMGL1) remains the best topographic information in view of hydrodynamic modeling purposes. Its accuracy is however hindered by errors partly due to vegetation leading to erroneous simulations. Previous efforts to remove the vegetation signal do not account for its spatial variability or relied on upon single assumed percentage of penetration of the SRTM signal. In this study, we propose to a systematic approach, over an Amazonian floodplain (Fig. 1), to remove the vegetation signal, which consider its heterogeneity combining estimates of vegetation height and land cover map. We improve this approach by interpolating first results with drainage network, field and altimetry data to obtain a hydrological conditioned DEM. Averaged interferometric and vegetation bias over the forest zone were found to be -2.0 m and 7.4 m, respectively (Fig. 2). Comparing original DEM and corrected one, vertical validation against Ground Control Points shows a RMSE diminution of 64%. Floodplain inundation was simulated using the 3D model IPH-ECO model. Flood extent accuracy, controlled against ALOS-PALSAR and JERS-1 images, stresses improvements at low and high waters (Fig. 3). This study also highlights that a ground truth drainage network as unique input during the interpolation permits reaching reasonable in terms of flood extent and hydrological characteristics.

  10. 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.

  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. Glacial Surface Topography and its Changes in the Western Qilian Mountains Derived from TanDEM-X Bi-Static InSAR

    NASA Astrophysics Data System (ADS)

    Sun, Yafei; Jiang, Liming; Liu, Lin; Wang, Hansheng; Hsu, Houtse; Shen, Qiang

    2016-08-01

    The high-resolution and high-precision glacier surface topography is one of the most important fundamental data for the research of glacial dynamic process of mountain glaciers. It is noteworthy that the TanDEM- X mission, launched in 2010 by the German Aerospace Center (DLR), opens a new era in single-pass satellite SAR remote sensing [1]. The TanDEM-X (TDX) mission employs a bi-static interferometric configuration of the two identical satellites TerraSAR-X (TSX) and TDX flying in a closely controlled formation, the primary objective of which is to generate a global, high-accurate, and homogeneous DEM following the high standard accuracy HRTI-3 [1].In this study, we aim to quantitatively evaluate the potential of the TDX bi-static SAR data for measuring glacier surface topography and elevation changes over mountain regions.

  13. 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.

  14. The mass balance record and surge behavior of Drangajökull Ice Cap (Iceland) from 1946 to 2011 deduced from aerial photographs and LiDAR DEM

    NASA Astrophysics Data System (ADS)

    Muñoz-Cobo Belart, Joaquín; Magnússon, Eyjólfur; Pálsson, Finnur

    2014-05-01

    High resolution and accuracy (e.g. based on LiDAR survey) Digital Elevation Models (DEMs) of glaciers and their close vicinity have significantly improved the methods for calculation of geodetic mass balance and study of changes in glacier dynamics. However additional data is needed to extend such studies back in time. Here we present a geodetically derived mass balance record for Drangajökull ice cap (NW-Iceland) since 1946 to present. The mass balance is calculated from a series of DEMs derived by photogrammetric processing of aerial photographs (years: 1946, 1975, 1985, 1994) and a LiDAR DEM (2011). All Ground Control Points (GCPs) used to constrain the orientation of the aerial photographs, used in the photogrammetric processing, are picked from the LiDAR derived DEM, thus eliminating the time consuming and expensive in situ survey of GCPs. The LiDAR DEM also helps to assess the accuracy of the photogrammetrically derived DEMs, by analyzing the residuals in elevation in ice-free areas. For the DEMs of 1975, 1985 and 1994 the Root Mean Square Error (RMSE) of the residuals is less than 2 m, whereas the accuracy of the DEM of 1946 is worse, with RMSE of 5.5 m, caused by the deteriorated images. The geodetic mass balance yields a negative specific mass balance of ~-0.5 m w.e.a-¹ for the period 1946-1975, followed by periods of positive mass balance: ~0.2 m w.e.a-¹ for the period 1975-1985 and ~0.3 m w.e.a-¹ for the period 1985-1994. Negative specific mass balance of ~-0.6 m w.e.a-¹ is derived for the period 1994-2011. High mass redistribution is observed during 1985-1994 and 1994-2011 on the three main outlets of the ice cap, related to surges. The derived orthophotographs allow tracking of stable features at individual locations on the northern part of Drangajökull, indicating an average velocity of 5-10 m a-¹ for the period 1946-1985 and speeding up in the last two periods due to a surge.

  15. Seasonal and interannual evolution of Jakobshavn Isbrae, Greenland from a 2008-2015 high-res DEM and velocity time series

    NASA Astrophysics Data System (ADS)

    Shean, D. E.; Joughin, I.; Smith, B.; Floricioiu, D.

    2015-12-01

    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 a comprehensive analysis of high-resolution elevation (~2-5 m/px) and velocity (~100 m/px) time series with dense temporal coverage (daily-monthly). The Jakobshavn DEM time series consists of >70 WorldView-1/2/3 stereo DEMs and >11 TanDEM-X DEMs spanning 2008-2015. Complementary point elevation data from Operation IceBridge (ATM, LVIS), pre-IceBridge ATM flights, and ICESat-1 GLAS extend the surface elevation record to 1999 and provide essential absolute control data, enabling sub-meter horizontal/vertical accuracy for gridded DEMs. Velocity data are primarily derived from TerraSAR-X/TanDEM-X image pairs with 11-day interval from 2009-2015. These elevation and velocity data capture outlet glacier evolution with unprecedented detail during the post-ICESat era. The lower trunk of Jakobshavn displays significant seasonal velocity variations, with recent rates of ~8 km/yr during winter and >17 km/yr during summer. DEM data show corresponding seasonal elevation changes of -30 to -45 m in summer and +15 to +20 m in winter, with decreasing magnitude upstream. Seasonal discharge varies from ~30-35 Gt/yr in winter to ~45-55 Gt/yr in summer, and we integrate these measurements for improved long-term mass-balance estimates. Recent interannual trends show increased discharge, velocity, and thinning (-15 to -20 m/yr), which is consistent with long-term altimetry records. The DEM time series also reveal new details about calving front and mélange evolution during the seasonal cycle. Similar time series are available for Kangerdlugssuaq and Helheim Glaciers. These observations are improving our understanding of outlet glacier dynamics, while complementing ongoing efforts to constrain estimates

  16. 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

  17. 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

  18. 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

  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

  20. Morphotectonic control of the Białka drainage basin (Central Carpathians): Insights from DEM and morphometric analysis.

    NASA Astrophysics Data System (ADS)

    Wołosiewicz, Bartosz

    2016-06-01

    The Białka river valley is directly related to a deep NNW-SSE oriented fault zone. According to the results of previous morphometric analyses, the Białka drainage basin is one of the most tectonically active zones in the Central Carpathians. It is also located within an area of high seismic activity. In this study Digital Elevation Model (DEM) based, morphometric analyses were used to investigate the morphotectonic conditions of the watershed. The results reveal the relationships between the main tectonic feature and the landforms within the research area. The lineaments, as obtained from the classified aspect map, seem to coincide with the orientation of the main structures as well as the trends revealed by the theoretical Riedel-Skempton shear model. Base-level and isolong maps support the conclusion that the Białka and Biały Dunajec fault zones exert a strong influence on the morphology of the adjacent area.

  1. Adsorption and hydrogenation of simple alkenes at Pt-group metal electrodes studied by DEMS: influence of the crystal orientation

    NASA Astrophysics Data System (ADS)

    Müller, Ulrich; Schmiemann, Udo; Dülberg, Andreas; Baltruschat, Helmut

    1995-07-01

    The adsorption of ethene and cyclohexene on mono-and polycrystalline Pt and on polycrystalline Pd electrodes was studied using differential electrochemical mass spectrometry (DEMS). Both molecules are partially hydrated to an oxygen containing species upon adsorption on Pt. In the case of ethene, this species dissociated to methane and adsorbed CO at negative potentials. Another part of the adsorbed ethene can be cathodically desorbed as ethane and butane. The ratio of the various species formed strongly depends on crystal orientation and adsorption potential. Contrary to heterogenous gas phase hydrogenation (and also contrary to some earlier reports on electrochemical hydrogenation), the rate of the Faradaic hydrogenation reaction is also strongly dependent on the crystallographic orientation, being faster on Pt(110) or roughened surfaces. During hydrogenation, H/D exchange occurs to an appreciable degree, suggesting the participation of adsorbed intermediates.

  2. Geospatial approach in mapping soil erodibility using CartoDEM - A case study in hilly watershed of Lower Himalayan Range

    NASA Astrophysics Data System (ADS)

    Kumar, Suresh; Gupta, Surya

    2016-10-01

    Soil erodibility is one of the most important factors used in spatial soil erosion risk assessment. Soil information derived from soil map is used to generate soil erodibility factor map. Soil maps are not available at appropriate scale. In general, soil maps at small scale are used in deriving soil erodibility map that largely generalized spatial variability and it largely ignores the spatial variability since soil map units are discrete polygons. The present study was attempted to generate soil erodibilty map using terrain indices derived from DTM and surface soil sample data. Soil variability in the hilly landscape is largely controlled by topography represented by DTM. The CartoDEM (30 m) was used to derive terrain indices such as terrain wetness index (TWI), stream power index (SPI), sediment transport index (STI) and slope parameters. A total of 95 surface soil samples were collected to compute soil erodibility factor ( K) values. The K values ranged from 0.23 to 0.81 t ha-1R-1 in the watershed. Correlation analysis among K-factor and terrain parameters showed highest correlation of soil erodibilty with TWI ( r 2= 0.561) followed by slope ( r 2= 0.33). A multiple linear regression model was developed to derive soil erodibilty using terrain parameters. A set of 20 soil sample points were used to assess the accuracy of the model. The coefficient of determination ( r 2) and RMSE were computed to be 0.76 and 0.07 t ha-1R-1 respectively. The proposed methodology is quite useful in generating soil erodibilty factor map using digital elevation model (DEM) for any hilly terrain areas. The equation/model need to be established for the particular hilly terrain under the study. The developed model was used to generate spatial soil erodibility factor ( K) map of the watershed in the lower Himalayan range.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. The 10 m-resolution TINITALY DEM as a trans-disciplinary basis for the analysis of the Italian territory: Current trends and new perspectives

    NASA Astrophysics Data System (ADS)

    Tarquini, Simone; Nannipieri, Luca

    2017-03-01

    The increasing availability of high resolution digital elevation models (DEMs) is changing our viewpoint towards Earth surface landforms. Nevertheless, large-coverage, intermediate-resolution DEMs are still largely used, and can be the ideal choice in several applications based on the processing of spatially-integrated information. In 2012 the Istituto Nazionale di Geofisica e Vulcanologia opened a website for the free download of the "TINTALY" Digital Elevation Model (DEM), which covers the whole Italian territory. Since then, about 700 users from 28 different countries have been accredited for data download, and a report of 4 years of data dissemination and use is presented. The analysis of the intended use reveals that the 10 m-resolution, seamless TINITALY DEM is of use for an extremely assorted research community. Accredited users are working in virtually any branch of the Earth Sciences (e.g. Volcanology, Seismology, and Geomorphology), in spatially integrated humanities (e.g. History and Archaeology), and in other thematic areas such as in applied Physics and Zoology. Many users are also working in local administrations (e.g. Regions and Municipalities) for civil protection or land use planning purposes. In summary, the documented activity shows that the dissemination of seamless, large coverage elevation datasets can fertilize the technological progress of the whole society providing a significant benefit to stakeholders.

  8. 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.

  9. 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

  10. TanDEM-X IDEM precision and accuracy assessment based on a large assembly of differential GNSS measurements in Kruger National Park, South Africa

    NASA Astrophysics Data System (ADS)

    Baade, J.; Schmullius, C.

    2016-09-01

    High resolution 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 unprecedented geometric resolution, precision and accuracy. First TanDEM Intermediate Digital Elevation Models (i.e. IDEM) with a geometric resolution from 0.4 to 3 arcsec have been made available for scientific purposes in November 2014. This includes four 1° × 1° tiles covering the Kruger National Park in South Africa. Here, we document the results of a local scale IDEM height accuracy validation exercise utilizing over 10,000 RTK-GNSS-based ground survey points from fourteen sites characterized by mainly pristine Savanna vegetation. The vertical precision of the ground checkpoints is 0.02 m (1σ). Selected precursor data sets (SRTMGL1, SRTM41, ASTER-GDEM2) are included in the analysis to facilitate the comparison. Although IDEM represents an intermediate product on the way to the new global TanDEM-X DEM, expected to be released in late 2016, it allows first insight into the properties of the forthcoming product. Remarkably, the TanDEM-X tiles include a number of auxiliary files providing detailed information pertinent to a user-based quality assessment. We present examples for the utilization of this information in the framework of a local scale study including the identification of height readings contaminated by water. Furthermore, this study provides evidence for the high precision and accuracy of IDEM height readings and the sensitivity to canopy cover. For open terrain, the 0.4 arcsec resolution edition (IDEM04) yields an average bias of 0.20 ± 0.05 m (95% confidence interval, Cl95), a RMSE = 1.03 m and an absolute vertical height error (LE90) of 1.5 [1.4, 1.7] m (Cl95). The corresponding values for the lower resolution IDEM editions are about the same and provide evidence for the high quality of the IDEM products

  11. Allgemeine Sprachfaehigkeit und Fremdsprachenerwerb. Zur Struktur von Leistungsdimensionen und linguistischer Kompetenz des Fremdsprachenlerners (General Language Ability and Foreign Language Acquisition. On the Structure of Performance Dimensions and the Linguistic Competence of the Foreign Language Learner). Diskussions beitraege aus dem Institute fuer Bildungsforschung, No. 1.

    ERIC Educational Resources Information Center

    Sang, Fritz; Vollmer, Helmut J.

    This study investigates the theoretical plausibility and empirical validity of the assumption that all performance in a foreign language can be traced back to a single factor, the general language ability factor. The theoretical background of this hypothesis is reviewed in detail. The concept of a unitary linguistic competence, interpreted as an…

  12. Estimating Digital Terrain Model in forest areas from TanDEM-X and Stereo-photogrammetric technique by means of Random Volume over Ground model

    NASA Astrophysics Data System (ADS)

    Lee, S. K.; Fatoyinbo, T. E.; Lagomasino, D.; Osmanoglu, B.; Feliciano, E. A.

    2015-12-01

    The Digital Terrain Model (DTM) in forest areas is invaluable information for various environmental, hydrological and ecological studies, for example, watershed delineation, vegetation canopy height, water dynamic modeling, forest biomass and carbon estimations. There are few solutions to extract bare-earth Digital Elevation Model information. Airborne lidar systems are widely and successfully used for estimating bare-earth DEMs with centimeter-order accuracy and high spatial resolution. However, expensive cost of operation and small image coverage prevent the use of airborne lidar sensors for large- or global-scale. Although IceSAT/GLAS (Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System) lidar data sets have been available for global DTM estimate with relatively lower cost, the large footprint size of 70 m and the interval of 172 m are insufficient for various applications. In this study we propose to extract higher resolution bare-earth DEM over vegetated areas from the combination of interferometric complex coherence from single-pass TanDEM-X (TDX) data at HH polarization and Digital Surface Model (DSM) derived from high-resolution WorldView (WV) images by means of random volume over ground (RVoG) model. The RVoG model is a widely and successfully used model for polarimetric SAR interferometry (Pol-InSAR) forest canopy height inversion. The bare-earth DEM is obtained by complex volume decorrelation in the RVoG model with the DSM estimated by stereo-photogrammetric technique. Forest canopy height can be estimated by subtracting the estimated bare-earth model from the DSM. Finally, the DTM from airborne lidar system was used to validate the bare-earth DEM and forest canopy height estimates.

  13. Topographic changes due to the 2008 Mw 7.9 Wenchuan earthquake as revealed by the differential DEM method

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    Landscape evolution in active orogenic regions is inevitably affected by the repeated strong earthquakes triggered by the corresponding active faults. However, the lack of adequate methods for the documentation and monitoring of mountain-building processes has resulted in a shortage of quantitative estimates of orogenic and eroded volumes. A strong earthquake and its associated co-seismic landslides represent a sudden pulse in landscape evolution in tectonically active areas. The 2008 Mw 7.9 Wenchuan earthquake dramatically modified the topography of the Longmen Shan region. Based on topographic data before the earthquake and stereo pairs of post-earthquake remote sensing imagery, we derived pre- and post-earthquake DEMs (digital elevation models) of the three regions along the Longmen Shan Thrust Belt. By comparing the geomorphic features before and after the earthquake, we find that the Wenchuan earthquake smoothed the steep relief and caused a co-seismic uplift of the Longmen Shan region. The medium-relief regions increased; however, the high-relief regions decreased, indicating that the local relief is controlled by repeated strong earthquakes. The changed slope aspect indicates that the formation and modification of the east- and west-facing slopes are controlled by tectonic events in the Longmen Shan region, which might be associated with the regional stress field. However, the unchanged aspects of other slopes might be controlled by long-term erosion rather than tectonic events. The topographic changes, landslide volume and co-seismic uplift indicate that the greatest seismically induced denudation occurred in association with a thrust faulting mechanism and low-angle fault geometry. Our findings reveal that the local relief has been shaped by the localized, seismically induced high rate of denudation within the plateau margins, and that the formation of local relief is also related to tectonic events, especially the events that have occurred on low

  14. Identifying hydrologically sensitive areas using LiDAR DEMs to mitigate critical source areas of diffuse pollution: development and application

    NASA Astrophysics Data System (ADS)

    Thomas, Ian; Jordan, Phil; Mellander, Per-Erik; Fenton, Owen; Shine, Oliver; hUallacháin, Daire Ó.; Creamer, Rachel; McDonald, Noeleen; Dunlop, Paul; Murphy, Paul

    2016-04-01

    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 such as phosphorus (P). A new GIS-based HSA Index is presented that identifies HSAs at the sub-field scale. It uses a soil topographic index (STI) and accounts for the hydrological disconnection of overland flow via topographic impediment from flow sinks such as hedgerows and depressions. High resolution (0.25-2 m) LiDAR Digital Elevation Models (DEMs) are utilised to capture these microtopographic controls on flow pathways and hydrological connectivity. The HSA Index was applied to four agricultural catchments (~7.5-12 km2) with contrasting topography and soil types. Catchment HSA sizes were estimated using high resolution rainfall-quickflow measurements during saturated winter storm events in 2009-2014, and mapped using the HSA Index. HSA sizes ranged from 1.6-3.4% of the catchment area during median storm events and 2.9-8.5% during upper quartile events depending on whether well or poorly drained soils dominated, which validated HSA Index value distributions. Total flow sink volume capacities ranged from 8,298-59,584 m3 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 'delivery points' along surface runoff pathways where transported pollutants such as P are delivered to the open drainage network. Using these as proposed locations for targeting mitigation measures such as riparian buffer strips (RBS) reduced costs compared to blanket implementation within an example agri-environment scheme by 66% and 91% over 1 and 5 years respectively, which included LiDAR DEM acquisition costs. Considering that HSAs are often the dominant P CSA factor in agricultural catchments and can override

  15. Fine Resolution Tree Height Estimation from Lidar Data and Its Application in SRTM DEM Correction across Forests of Sierra Nevada, California, USA

    NASA Astrophysics Data System (ADS)

    Su, Y.; Guo, Q.; Ma, Q.; Li, W.

    2015-12-01

    Sierra Nevada (SN) is a mountain range located in the northeastern California, USA, covering an area of 63,100 km2. As one of the most diverse temperate conifer forests on the Earth, forests of SN serve a series of ecosystem functions and are valuable natural heritages for the region and even the country. The still existed gap of accurate fine-resolution tree height estimation has lagged ecological, hydrological and forestry studies within the region. Moreover, the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), as one of the most frequently used land surface elevation product in the region, has been proved systematically higher than actual land surface in vegetated mountain areas due to the absorption and reflection effects of canopy on the SRTM radar signal. An accurate fine resolution tree height product across the region is urgently needed for developing models to correct SRTM DEM. In this study, we firstly developed a method to estimate SN tree height distribution (defined by Lorey's height) through the combination of airborne lidar data, spaceborne lidar data, optical imagery, climate surfaces, and field measurements. Over 5 470 km2airborne lidar data and 1 000 plot measurements were collected across the SN to address this mission. Our method involved three main steps: 1) estimate tree heights within airborne lidar footprints using step-wise regression; 2) link the airborne lidar derived tree height to spaceborne lidar data and compute tree heights at spaceborne lidar footprints; 3) extrapolate tree height estimation from spaceborne lidar footprints to the whole region using Random Forest. The obtained SN tree height product showed good correspondence with independent field plot measurements. The coefficient of determination is higher than 0.65, and the root-mean-square error is around 5 m. With the obtained tree height product, we further explored the possibility of correcting SRTM DEM. The results showed that the obtained tree height

  16. Electrochemical behavior of sodium azide at Pt and Au electrodes in sodium sulfate electrolyte: A DEMS study

    SciTech Connect

    Dalmia, A.; Wasmus, S.; Savinell, R.F.; Liu, C.C.

    1995-11-01

    Azides are widely used in chemical technology for a large variety of applications, such as detonators (Pb(N{sub 3}){sub 2}), getters in electric discharge tubes, anticorrosive agents, or additives for the production of foam rubber. The electro-oxidation and -reduction of sodium azide at porous painted platinum and gold electrodes was studied using the multipurpose electrochemical mass spectrometry (MPEMS) which was operated in the differential electrochemical mass spectrometry (DEMS) mode. The platinum electrode was found to be active for electro-oxidation as well as for electroreduction. Above 0.3 V vs. Hg/Hg{sub 2}SO{sub 4}, azide is oxidized to give N{sub 2}, NO, NO{sub 2}, and N{sub 2}O. Reduction of azide takes place below {minus}0.9 V forming N{sub 2}, N{sub 2}H{sub 4}, and possibly NH{sub 3}. In contrast to platinum, gold showed only activity for the electro-oxidation of azide leading to the formation of N{sub 2}, NO, NO{sub 2}, and N{sub 2}O above 0.5 V. Evidence for a reaction without evolution of volatile products was also found taking place above 0.1 V. A reaction mechanism is discussed emphasizing the role of adsorbed hydrogen and oxygen.

  17. Body Mass Index in Different Dementia Disorders: Results from the Swedish Dementia Quality Registry (SveDem)

    PubMed Central

    Faxén-Irving, Gerd; Fereshtehnejad, Seyed-Mohammad; Falahati, Farshad; Cedergren, Lars; Göranzon, Helen; Wallman, Kristine; García-Ptacek, Sara; Eriksdotter, Maria; Religa, Dorota

    2014-01-01

    Background Most patients with dementia lose body weight over the course of the disease and have a lower body mass index (BMI) than subjects with normal cognition. Aims To examine body mass index and how it correlates with cognitive status, age and gender in patients with different dementia disorders. Materials and Methods Data from newly diagnosed dementia patients in the Swedish Dementia Quality Registry (SveDem) and recorded information about age, gender, cognitive status and BMI was analyzed using independent samples t tests and one-way analysis of variance. Results A total of 12,015 patients, 7,121 females and 4,894 males were included in the study. The average BMI was 24. More than a quarter of the patients had a BMI of <22. Females were significantly older (p < 0.001) and males had a significantly higher BMI (p < 0.001) at the time of diagnosis. BMI differed significantly by gender in various dementia disorders and correlated significantly with cognitive status and age. Conclusion At the time of diagnosis, patients with various dementia disorders had a BMI within the normal range. However, a significant number had a BMI in a lower, suboptimal range for older persons stressing the need for nutritional assessment as part of the dementia work up. Further analyses with longitudinal follow-up are needed to investigate BMI changes over time. PMID:24847345

  18. 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.

  19. The role of method of production and resolution of the DEM on slope-units delineation for landslide susceptibility assessment - Ubaye Valley, French Alps case study

    NASA Astrophysics Data System (ADS)

    Schlögel, Romy; Marchesini, Ivan; Alvioli, Massimiliano; Reichenbach, Paola; Rossi, Mauro; Malet, Jean-Philippe

    2016-04-01

    Landslide susceptibility assessment forms the basis of any hazard mapping, which is one of the essential parts of quantitative risk mapping. For the same study area, different susceptibility maps can be achieved depending on the type of susceptibility mapping methods, mapping unit, and scale. In the Ubaye Valley (South French Alps), we investigate the effect of resolution and method of production of the DEM to delineate slope units for landslide susceptibility mapping method. Slope units delineation has been processed using multiple combinations of circular variance and minimum area size values, which are the input parameters for a new software for terrain partitioning. We rely on this method taking into account homogeneity of aspect direction inside each unit and inhomogeneity between different units. We computed slope units delineation for 5, 10 and 25 meters resolution DEM, and investigate statistical distributions of morphometric variables within the different polygons. Then, for each different slope units partitioning, we calibrated a landslide susceptibility model, considering landslide bodies and scarps as a dependent variable (binary response). This work aims to analyse the role of DEM resolution on slope-units delineation for landslide susceptibility assessment. Area Under the Curve of the Receiver Operating Characteristic is investigated for the susceptibility model calculations. In addition, we analysed further the performance of the Logistic Regression Model by looking at the percentage of significant variable in the statistical analyses. Results show that smaller slope units have a better chance of containing a smaller number of thematic and morphometric variables, allowing for an easier classification. Reliability of the models according to the DEM resolution considered as well as scarp area and landslides bodies presence/absence as dependent variable are discussed.

  20. 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.

  1. Shape-from-shading using Landsat 8 and airborne laser altimetry over ice sheets: toward new regional DEMs of Greenland and Antarctica

    NASA Astrophysics Data System (ADS)

    Moussavi, M. S.; Scambos, T.; Haran, T. M.; Klinger, M. J.; Abdalati, W.

    2015-12-01

    We investigate the capability of Landsat 8's Operational Land Imager (OLI) instrument to quantify subtle ice sheet topography of Greenland and Antarctica. We use photoclinometry, or 'shape-from-shading', a method of deriving surface topography from local variations in image brightness due to varying surface slope. Photoclinomeetry is applicable over ice sheet areas with highly uniform albedo such as regions covered by recent snowfall. OLI imagery is available from both ascending and descending passes near the summer solstice period for both ice sheets. This provides two views of the surface features from two distinct solar azimuth illumination directions. Airborne laser altimetry data from the Airborne Topographic Mapper (ATM) instrument (flying on the Operation Ice Bridge program) are used to quantitatively convert the image brightness variations of surface undulations to surface slope. To validate the new DEM products, we use additional laser altimetry profiles collected over independent sites from Ice Bridge and ICESat, and high-resolution WorldView-2 DEMs. The photoclinometry-derived DEM products will be useful for studying surface elevation changes, enhancing bedrock elevation maps through inversion of surface topography, and inferring local variations in snow accumulation rates.

  2. The contributions of solar ultraviolet radiation exposure and other determinants to serum 25-hydroxyvitamin D concentrations in Australian adults: the AusD Study.

    PubMed

    Kimlin, Michael G; Lucas, Robyn M; Harrison, Simone L; van der Mei, Ingrid; Armstrong, Bruce K; Whiteman, David C; Kricker, Anne; Nowak, Madeleine; Brodie, Alison M; Sun, Jiandong

    2014-04-01

    The Quantitative Assessment of Solar UV [ultraviolet] Exposure for Vitamin D Synthesis in Australian Adults (AusD) Study aimed to better define the relationship between sun exposure and serum 25-hydroxyvitamin D (25(OH)D) concentration. Cross-sectional data were collected between May 2009 and December 2010 from 1,002 participants aged 18-75 years in 4 Australian sites spanning 24° of latitude. Participants completed the following: 1) questionnaires on sun exposure, dietary vitamin D intake, and vitamin D supplementation; 2) 10 days of personal ultraviolet radiation dosimetry; 3) a sun exposure and physical activity diary; and 4) clinical measurements and blood collection for 25(OH)D determination. Our multiple regression model described 40% of the variance in 25(OH)D concentration; modifiable behavioral factors contributed 52% of the explained variance, and environmental and demographic or constitutional variables contributed 38% and 10%, respectively. The amount of skin exposed was the single strongest contributor to the explained variance (27%), followed by location (20%), season (17%), personal ultraviolet radiation exposure (8%), vitamin D supplementation (7%), body mass index (weight (kg)/height (m)(2)) (4%), and physical activity (4%). Modifiable behavioral factors strongly influence serum 25(OH)D concentrations in Australian adults. In addition, latitude was a strong determinant of the relative contribution of different behavioral factors.

  3. Dr.Phil. et Med. Hermann Von Schrötter: Skizzen eines feldarztes aus Montenegro- observations of a military physician on his visit to Montenegro.

    PubMed

    Vujovic, Veselin

    2008-01-01

    This essay gives a review of a book by an Austrian physician Hermann von Schrötter Skizzen Eines Feldartes aus Montenegro (Observations of a Military Physician from Montenegro), Berlin - Wien 1913 on the occasion of its translation to Montenegrin and reprint in Cetinje, Montenegro in 2007. The book takes us back to the time of the preparations and attack on Scutari, which took place in 1912 and 1913. The Montenegrin army achieved their military goal, but with numerous casualties, whose exact number has never been determined. The author, Hermann von Schrötter, confirmed this in his observations in the book. When the Montenegrin Red Cross asked for help, the organizations of the following countries responded: Austria, Czechoslovakia, England, France, The Netherlands, Italy, Germany, Russia, Switzerland, and Sweden. Apart from them, physicians were sent by the Slavonic Voluntary Society from St. Petersburg, the Boards of the Red Cross from Dubrovnik and Split, the National Board from Zadar; seven physicians came from the Bay of Boka and three physicians with three nurses came from Bosnia. I wish to stress that in those times the Red Cross offered aid, as it does today, to all the people in need, regardless of their political beliefs. The relations between Montenegro and Austria were poor back then, yet the Mission of the Austrian Red Cross generously gave assistance and relief to the Montenegrin people!

  4. Post-Closure Inspection Report for Corrective Action Unit 333: U-3auS Disposal Site Annual Report, Nevada Test Site, Nevada

    SciTech Connect

    K. K. Knapp

    2003-09-01

    The U-3auS Disposal Site Corrective Action Unit (CAU) 333 is a closed construction landfill located in Area 3 of the Nevada Test Site. The closure of this site was approved by the Nevada Division of Environmental Protection (NDEP) in a letter to the U.S. Department of Energy, National Nuclear Security Administration Nevada Operations Office (NNSA/NV) dated June 27, 2001. Post-closure monitoring requirements are described in a letter from NNSA/NV to NDEP dated October 9, 2001, and were approved by the NDEP in a letter from NDEP to NNSA/NV dated November 5, 2001. Post-closure care consists of the following: Semiannual inspections of the unit using an inspection checklist; Photographic documentation of site conditions; Field note documentation; Performing minor site maintenance as necessary; and Preparation and submittal of an annual report. The annual report consists of copies of the inspection checklist, repair records (if any), photographs, and recommendations and conclusions. The Post-Closure Inspection Checklists are provided in Attachment A, a copy of the field notes is found in Attachment B, and copies of the inspection photographs are provided in Attachment C. Field note documentation is not formally required for this CAU, however in order to be consistent with other reports, it has been added to this report.

  5. 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

  6. Improved analysis of the marine terraces and rivers of E-Corinth based on high-resolution Pleiades DEMs

    NASA Astrophysics Data System (ADS)

    de Gelder, Giovanni; Fernández-Blanco, David; Jara-Muñoz, Julius; Melnick, Daniel; Lacassin, Robin; Armijo, Rolando

    2016-04-01

    The Corinth rift, one of the fastest extending regions in the world, is a key area to understand the large-scale mechanics of an evolving rift system. It comprises a complicated en-echelon pattern of normal faults that shape a large, mostly asymmetric E-W-trending graben driven by large north-dipping faults located along the southern shore of the rift. The footwall of one of these faults in eastern Gulf of Corinth, the Xylokastro Fault, has been uplifted by ~2000m during Pleistocene times, which is evidenced by presently-onshore marine sediments, a drainage reversal of several major river systems and an extensive and remarkably well-preserved flight of marine terraces. The greatly improved resolution and accuracy of present-day satellite imagery facilitates extraction of detailed topographic information. This in turn provides an encouraging possibility to refine tectono-geomorphic constraints extracted from the flight of marine terraces and the drainage networks. We used tri-stereo satellite images from the Pleiades platform of the CNES to develop a 2m-resolution digital elevation model (DEM) for an area of ~200 km2 around the best-preserved terrace sequence between the towns of Xylokastro and Corinth. We produced a terrace map of unprecedented detail, with more terrace sub-levels than previously mapped, and improved the method of shoreline angle determination using the graphical interface TerraceM. With swath profiles perpendicular to the paleo-seacliffs we determined ~750 estimates of the paleoshoreline. The resulting 16 terrace levels display both a long wavelength trend related to flexural uplift within the footwall of Xylokastro fault, and smaller-scale height variations in relation to secondary faults and/or natural variations in coastal morphology. To strengthen the age correlation of the terraces, we applied 2D numerical models of terrace formation to reproduce our observed geometry. This also allows us to test uplift rate variations in both space and time

  7. Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation

    NASA Technical Reports Server (NTRS)

    Ardaens, J. S.; D'Amico, S.; Kazeminejad, B.; Montenbruck, O.; Gill, E.

    2007-01-01

    TerraSAR-X (TSX) and TanDEM-X (TDX) are two advanced synthetic aperture radar (SAR) satellites flying in formation. SAR interferometry allows a high resolution imaging of the Earth by processing SAR images obtained from two slightly different orbits. TSX operates as a repeat-pass interferometer in the first phase of its lifetime and will be supplemented after two years by TDX in order to produce digital elevation models (DEM) with unprecedented accuracy. Such a flying formation makes indeed possible a simultaneous interferometric data acquisition characterized by highly flexible baselines with range of variations between a few hundreds meters and several kilometers [1]. TSX has been successfully launched on the 15th of June, 2007. TDX is expected to be launched on the 31st of May, 2009. A safe and robust maintenance of the formation is based on the concept of relative eccentricity/inclination (e/i) vector separation whose efficiency has already been demonstrated during the Gravity Recovery and Climate Experiment (GRACE) [2]. Here, the satellite relative motion is parameterized by mean of relative orbit elements and the key idea is to align the relative eccentricity and inclination vectors to minimize the hazard of a collision. Previous studies have already shown the pertinence of this concept and have described the way of controlling the formation using an impulsive deterministic control law [3]. Despite the completely different relative orbit control requirements, the same approach can be applied to the TSX/TDX formation. The task of TDX is to maintain the close formation configuration by actively controlling its relative motion with respect to TSX, the leader of the formation. TDX must replicate the absolute orbit keeping maneuvers executed by TSX and also compensate the natural deviation of the relative e/i vectors. In fact the relative orbital elements of the formation tend to drift because of the secular non-keplerian perturbations acting on both satellites

  8. On the Derivation of Pan-European River Networks and Catchment Boundaries from a 250m DEM

    NASA Astrophysics Data System (ADS)

    Colombo, R.; Vogt, J. V.; Soille, P.; Paracchini, M. L.; de Jager, A. L.

    2003-04-01

    Mapping and characterisation of catchments and river courses for the European continent is of relevant interest to support the environmental monitoring activities of the European Environmental Agency (EEA) and for the implementation of the Water Framework Directive (WFD). At continental or global scale the river networks and associated catchments are generally derived from a set of standard DEM processing techniques, including pit filling, stream burning, and the calculation of flow direction and flow accumulation grids. The continental final river networks are generally detected by imposing a constant critical contributing area threshold, independently of widely varying landscape conditions. If the same critical area for all environments is assumed, the resulting drainage density does not reflect the real degree of dissection and the produced river map may be unrealistic. To overcome this limitation, we propose a classification of the landscape and we present a new approach to derive river networks and catchments over extended heterogeneous areas from medium resolution digital elevation data (250 m grid cell size) and environmental characteristics,. We show that the implementation of a European landscape characterisation, coupled with the analysis of the local slope versus contributing area represents a viable way for mapping the spatial variability of the river networks. Such landscape classification has been realised using a parametric model that keeps into account a set of five variables [annual rainfall (P), local relief (R), vegetation cover (V), soil transmissivity (T), and bedrock erodibility (E)] that quantify the environmental factors governing drainage density. The critical contributing area was derived for each landscape drainage density class by analysing the log-log plot of local slope contributing area relationships derived from the digital elevation data. The scaling break corresponding to the main valley networks was defined as the last inflection

  9. Malignancy is associated with microcalcification and higher AP/T ratio in ultrasonography, but not with Hashimoto's thyroiditis in histopathology in patients with thyroid nodules evaluated as Bethesda Category III (AUS/FLUS) in cytology.

    PubMed

    Topaloglu, Oya; Baser, Husniye; Cuhaci, Fatma Neslihan; Sungu, Nuran; Yalcin, Abdussamed; Ersoy, Reyhan; Cakir, Bekir

    2016-10-01

    The predictors of malignancy are important for the decision of appropriate management in nodules with atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS). Our aim was to determine the ultrasonographical, clinical, and biochemical predictors of malignancy in these patients. A total of 427 patients with cytologically Bethesda Category III (AUS/FLUS) thyroid nodules were included in this retrospective study. We divided the nodules into two subgroups according to the histopathology as benign and malignant, and compared the preoperative ultrasonographical, clinical, and biochemical findings. In overall, 427 patients with 449 AUS/FLUS nodules who had undergone surgery, the rate of malignancy was 23.4 % (105/449). When evaluated separately, the rate of malignancy was 25.8 % in nodules with AUS (82/318) and 17.6 % in nodules with FLUS (23/131) (p = 0.061). The vast majority of malignant specimens in histopathology consisted of papillary thyroid carcinoma (PTC) (n = 91, 86.7 %). Preoperative ultrasonographic features of 105 malignant nodules in histopathology were compared with the 344 benign nodules in histopathology. Anteroposterior/Transverse (AP/T) ratio was significantly higher in malignant group compared to benign group (p = 0.013). In multiple logistic analysis, we found that higher AP/T ratio and microcalcification were independently associated with malignancy (p < 0.05). The malignancy-associated cut-off value of AP/T ratio at maximum sensitivity and specificity was ≥0.81. We did not find any correlation between malignancy and Hashimoto's thyroiditis in histopathology in multivariate analysis (p > 0.05). In Bethesda Category III nodules with higher AP/T ratio and microcalcification, surgery might be considered as a first therapeutic option instead of repeat fine-needle aspiration biopsy or observation.

  10. 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.

  11. The Multi-Instrument (EVE-RHESSI) DEM for Solar Flares, and Implications for Non-thermal Emission

    NASA Astrophysics Data System (ADS)

    McTiernan, J. M.; Caspi, A.; Warren, H. P.

    2013-12-01

    Observations of hard X-ray bremmstrahlung from solar flares directly probe the non-thermal electron population. For low energies, however, the spectra are typically dominated by thermal emission and the low energy extent of the non-thermal spectrum can be only loosely quantified. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) and X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). For a sample of solar flares, we model the emission using a Differential Emission Measure (DEM) for the thermal emission seen with both instruments and a power law fit for the non-thermal emission observed by RHESSI. Spectra for both instruments are fit simultaneously in a self-consistent manner. This improvement over the traditional isothermal approximation for thermal flare emission is intended 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 for medium to large solar flares. It is expected that a low energy cutoff of the non-thermal electron spectrum is in this energy range, but is obscured by thermal emission. For each flare in the sample we establish limits for the low energy cutoff of the non-thermal spectrum. These limits, in turn, can be used to establish limits on the energy of non-thermal electrons accelerated during the flare. This research is supported by NASA contract NAS5-98033 and NASA Heliophysics Guest Investigator Grant NNX12AH48G.

  12. Lava emplacements at Shiveluch volcano (Kamchatka) from June 2011 to September 2014 observed by TanDEM-X SAR-Interferometry

    NASA Astrophysics Data System (ADS)

    Heck, Alexandra; Kubanek, Julia; Westerhaus, Malte; Gottschämmer, Ellen; Heck, Bernhard; Wenzel, Friedemann

    2016-04-01

    As part of the Ring of Fire, Shiveluch volcano is one of the largest and most active volcanoes on Kamchatka Peninsula. During the Holocene, only the southern part of the Shiveluch massive was active. Since the last Plinian eruption in 1964, the activity of Shiveluch is characterized by periods of dome growth and explosive eruptions. The recent active phase began in 1999 and continues until today. Due to the special conditions at active volcanoes, such as smoke development, danger of explosions or lava flows, as well as poor weather conditions and inaccessible area, it is difficult to observe the interaction between dome growth, dome destruction, and explosive eruptions in regular intervals. Consequently, a reconstruction of the eruption processes is hardly possible, though important for a better understanding of the eruption mechanism as well as for hazard forecast and risk assessment. A new approach is provided by the bistatic radar data acquired by the TanDEM-X satellite mission. This mission is composed of two nearly identical satellites, TerraSAR-X and TanDEM-X, flying in a close helix formation. On one hand, the radar signals penetrate clouds and partially vegetation and snow considering the average wavelength of about 3.1 cm. On the other hand, in comparison with conventional InSAR methods, the bistatic radar mode has the advantage that there are no difficulties due to temporal decorrelation. By interferometric evaluation of the simultaneously recorded SAR images, it is possible to calculate high-resolution digital elevation models (DEMs) of Shiveluch volcano and its surroundings. Furthermore, the short recurrence interval of 11 days allows to generate time series of DEMs, with which finally volumetric changes of the dome and of lava flows can be determined, as well as lava effusion rates. Here, this method is used at Shiveluch volcano based on data acquired between June 2011 and September 2014. Although Shiveluch has a fissured topography with steep slopes

  13. Seasonal changes of surface velocity and elevation of Columbia Glacier, Alaska using time-series TerraSAR-X/TanDEM-X data

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2015-04-01

    Alaskan glaciers are a major contributor to global sea-level rise from glaciers and ice caps outside the polar ice sheets. Columbia Glacier is a large tidewater glacier located on the coast of south-central Alaska. The glacier has retreated ˜ 21 km and 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. In this study, we used time series of high-resolution TerraSAR-X/TanDEM-X stripmap satellite imagery during 2011-2014 to investigate the temporal development of glacier surface velocities, elevation and mass changes. The active SLC images of the bistatic TanDEM-X acquisitions, acquired over 11 or 22 days repeat intervals, are utilized to derive surface velocity fields using SAR intensity offset tracking. We observed a very strong seasonal variability in the surface velocities. Maximum values at the ice front reach up to 14.43 m/day in May and reduced to 2 m/day in October in the year 2012. However, at a distance of 17.5 km from the ice front, almost no seasonal variability can be observed. A significant influence in the distance to the terminus and elevation was detected. We attributed this temporal and spatial variability of surface velocity to changes in the basal hydrology and lubrification of the glacier bed. Similar fluctuations are observed in consecutive years. In a second step, we exploited TanDEM-X data by interferometrically generating time series of digital elevation models (DEMs) . For quantitative volume change estimates, we used DEMs of almost similar months of the observational years in order to minimize errors resulting from variable X-band radar penetration. The main branch gained a volume of 12.77± 2.89km^3in 2011-12, but lost -18.94± 3.21km^3in 2012-13 . A slight gain was observed with 1.05± .88km^3in 2013-14. However, the west branch gained volume only in 2011-12 and lost in the consecutive years. Moreover, the west branch retreated by ˜ 3km and lost its

  14. Recent Elevation Changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, Alaska, from ICESat Altimetry, Star-3i Airborne, and SRTM Spaceborne DEMs

    NASA Astrophysics Data System (ADS)

    Muskett, R. R.; Sauber, J. M.; Lingle, C. S.; Rabus, B. T.; Tangborn, W. V.; Echelmeyer, K. A.

    2005-12-01

    Three- to 5-year surface elevation changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, in the eastern Chugach and St. Elias Mtns of south-central Alaska, are estimated using ICESat-derived data and digital elevation models (DEMs) derived from interferometric synthetic aperture radar (InSAR) data. The surface elevations of these glaciers are influenced by climatic warming superimposed on surge dynamics (in the case of Bagley Ice Valley) and tidewater glacier dynamics (in the cases of Guyot and Yahtse Glaciers) in this coastal high-precipitation regime. Bagley Ice Valley / Bering Glacier last surged in 1993-95. Guyot and Yahtse Glaciers, as well as the nearby Tyndell Glacier, have experienced massive tidewater retreat during the past century, as well as during recent decades. The ICESat-derived elevation data we employ were acquired in early autumn in both 2003 and 2004. The NASA/NIMA Shuttle Radar Topography Mission (SRTM) DEM that we employ was derived from X-band InSAR data acquired during this 11-22 Feb. 2000 mission and processed by the German Aerospace Center. This DEM was corrected for estimated systematic error, and a mass balance model was employed to account for seasonal snow accumulation. The Star-3i airborne, X-band, InSAR-derived DEM that we employ was acquired 4-13 Sept. 2000 by Intermap Technologies, Inc., and was also processed by them. The ICESat-derived profiles crossing Bagley Ice Valley, differenced with Star-3i DEM elevations, indicate preliminary mean along-profile elevation increases of 5.6 ± 3.4 m at 1315 m altitude, 7.4 ± 2.7 m at 1448 m altitude, 4.7 ± 1.9 m at 1557 m altitude, 1.3 ± 1.4 m at 1774 m altitude, and 2.5 ± 1.5 m at 1781 m altitude. This is qualitatively consistent with the rising surface on Bagley Ice Valley observed by Muskett et al. [2003]. The ICESat-derived profiles crossing Yahtse Glacier, differenced with the SRTM DEM elevations, indicate preliminary mean elevation changes (negative implies decrease) of -0.9 ± 3

  15. Predict Dem Bones!

    ERIC Educational Resources Information Center

    Gray, John S.

    1994-01-01

    A detailed analysis and computer-based solution to a puzzle addressing the arrangement of dominoes on a grid is presented. The problem is one used in a college-level data structures or algorithms course. The solution uses backtracking to generate all possible answers. Details of the use of backtracking and techniques for mapping abstract problems…

  16. 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...

  17. 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.

  18. Diagnosis of Dementia in the Specialist Setting: A Comparison Between the Swedish Dementia Registry (SveDem) and the Registry of Dementias of Girona (ReDeGi)

    PubMed Central

    Garre-Olmo, Josep; Garcia-Ptacek, Sara; Calvó-Perxas, Laia; Turró-Garriga, Oriol; López-Pousa, Secundino; Eriksdotter, Maria

    2016-01-01

    The aim of this study was to compare the frequency of dementia diagnoses from two dementia registries in Europe. Patients registered between 2007 and 2013 in the Swedish Dementia Registry (SveDem; Sweden) and in the Registry of Dementias of Girona (ReDeGi; North-East of Spain) were selected. We compared sociodemographic data, Mini-Mental State Examination (MMSE) scores, dementia subtype, and medication consumption of 22,384 cases from SveDem and 5,032 cases from ReDeGi. The average age (78.1 years SveDem versus 79.7 years ReDeGi) and the gender (female 58.2% SveDem versus 61.5% ReDeGi) did not greatly differ. MMSE score at diagnosis was higher for SveDem cases (22.1 versus 17.8). Alzheimer’s disease (AD) accounted for the main dementia subtype (36.6% SveDem versus 55.6% ReDeGi). The proportion of vascular dementia (VaD) and mixed dementia was higher in SveDem (18.8% versus 6.4% and 24.9 versus 13.4%), with an odds ratio (OR) and 95% confidence interval (CI) for SveDem relative to the ReDeGi of 3.41 (3.03–3.84) for VaD, and 2.15 (1.97–2.35) for mixed dementia. This was at the expense of a lower frequency of AD in SveDem (OR 0.41; 95% CI 0.39–0.44). Other dementia diagnoses such as frontotemporal dementia or dementia with Lewy bodies did not significantly differ between registries (2.3% versus 2.9%; 1.9 versus 3.1%). Large differences in medication consumption at the time of dementia diagnosis were detected (4.7 treatments SveDem versus 6.8 ReDeGi). Northern and southern European dementia cohorts differ in demographic characteristics, MMSE score at diagnosis, and drug treatment profile. PMID:27392854

  19. Capturing poromechanical coupling effects of the reactive fracturing process in porous rock via a DEM-network model

    NASA Astrophysics Data System (ADS)

    Ulven, Ole Ivar; Sun, WaiChing

    2016-04-01

    Fluid transport in a porous medium has important implications for understanding natural geological processes. At a sufficiently large scale, a fluid-saturated porous medium can be regarded as a two-phase continuum, with the fluid constituent flowing in the Darcian regime. Nevertheless, a fluid mediated chemical reaction can in some cases change the permeability of the rock locally: Mineral dissolution can cause increased permeability, whereas mineral precipitation can reduce the permeability. This might trigger a complicated hydro-chemo-mechanical coupling effect that causes channeling of fluids or clogging of the system. If the fluid is injected or produced at a sufficiently high rate, the pressure might increase enough to cause the onset and propagation of fractures. Fractures in return create preferential flow paths that enhance permeability, localize fluid flow and chemical reaction, prevent build-up of pore pressure and cause anisotropy of the hydro-mechanical responses of the effective medium. This leads to a complex coupled process of solid deformation, chemical reaction and fluid transport enhanced by the fracture formation. In this work, we develop a new coupled numerical model to study the complexities of feedback among fluid pressure evolution, fracture formation and permeability changes due to a chemical process in a 2D system. We combine a discrete element model (DEM) previously used to study a volume expanding process[1, 2] with a new fluid transport model based on poroelasticity[3] and a fluid-mediated chemical reaction that changes the permeability of the medium. This provides new insights into the hydro-chemo-mechanical process of a transforming porous medium. References [1] Ulven, O. I., Storheim, H., Austrheim, H., and Malthe-Sørenssen, A. "Fracture Initiation During Volume Increasing Reactions in Rocks and Applications for CO2 Sequestration", Earth Planet. Sc. Lett. 389C, 2014a, pp. 132 - 142, doi:10.1016/j.epsl.2013.12.039. [2] Ulven, O. I

  20. 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

  1. 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

  2. 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

  3. 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

    2016-09-01

    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

  4. InSAR techniques for reliable deformation estimation in volcanic areas and a first glance of Tandem-DEM accuracy - test site El Hierro Island

    NASA Astrophysics Data System (ADS)

    Cong, X.; Eineder, M.; Fritz, T.

    2013-12-01

    The accuracy and availability of deformation measurements using InSAR techniques is limited due to decorrelation effects, atmospheric disturbances and the SAR side-looking geometry (layover and shadowing). In this talk, we present our recent research and achievements on advanced InSAR techniques in order to retrieve reliable deformation signals from active volcanoes using high resolution TerraSAR-X (TSX) images. Another highlight of this talk is the evaluation of an experimental TanDEM-X (TDX) RawDEM with a resolution of approximately 6 m in order to compensate the topographic phase. A volcanic test site which is currently highly active -El Hierro- has been selected to demonstrate the developed techniques: 1) PSI processing in volcanic areas using high resolution TSX images; 2) Mitigation of atmospheric delay distortions; 3) Fusion of multi-geometrical PSI clouds. In order to measure the deformation from 2011 to 2013 at El Hierro [1], two stacks of stripmap TSX Mission data have been acquired, one in ascending orbit and one in descending. Each stack has more than 25 scenes. More than 1.5 million PSs have been detected (SCR>3.0 dB). The stratified atmospheric delay for each acquisition has been integrated for the PSI reference network and, afterwards, interpolated and compensated for all PSs. A linear deformation model has been assumed for PSI processing. For the descending orbit stack, a relative deformation from -21.7 to 131.8 mm/y from Sep. 2011 to Jan. 2013 with respect to a reference point located on the northeast coast has been measured. On the one hand, the spatial variation of the deformation has a good agreement with the seismicity distribution [1]. On the other hand, the deformation magnitude agrees with in-situ GPS measurements [2]. In ascending orbit, the linear deformation rate varies from -22.8 to 90.9 mm/y. This different range of value is due to a scene acquired on Feb. 2010, which has been included in order to obtain the pre-seismic deformation

  5. The Multi-Instrument (EVE-RHESSI) DEM for Solar Flares, and Implications for Residual Non-Thermal Soft X-Ray Emission

    NASA Astrophysics Data System (ADS)

    McTiernan, James M.; Caspi, Amir; Warren, Harry

    2015-04-01

    In the soft X-ray energy range, solar flare spectra are typically dominated by thermal emission. 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). The improvement over the isothermal approximation is intended 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 for medium to large solar flares.Previous work (Caspi et.al. 2014ApJ...788L..31C) has concentrated on obtaining DEM models that fit both instruments' observations well. Now we are interested in any 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. Thermal emission is again modeled using a DEM that is parametrized as multiple gaussians in temperature; the 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. The results for non-thermal parameters then are compared with those found using RHESSI data alone, with isothermal and double-thermal models.

  6. 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.

  7. Near-real time orbit determination for the GPS, CHAMP, GRACE, TerraSAR-X, and TanDEM-X satellites

    NASA Astrophysics Data System (ADS)

    Michalak, Grzegorz; Koenig, Rolf

    The GFZ German Research Centre for Geosciences developed a near-real time (NRT) orbit gen-eration system for GPS and Low Earth Orbiting (LEO) satellites to support radio occultation data processing for the CHAMP, GRACE, Terra-SAR-X and the upcoming TanDEM-X mis-sions and fast baseline determination for the TanDEM-X mission. Precise NRT orbits are being generated for the CHAMP and GRACE-A satellites since August 2006 and for TerraSAR-X since August 2007. For each LEO, the system consists of three independent chains delivering NRT orbits with different latencies and accuracies. The first chain generates in a preceding step NRT GPS orbits and clock biases and based thereon LEO orbits with delays of 30 minutes counted from the last measurement point to the time the orbit product is available. The orbit accuracies can be assessed via Satellite Laser Ranging (SLR) to 7 cm. The second chain is based on predicted GPS orbits from the International GNSS Service (IGS) but endowed with in-house estimated clock biases. This chain generates orbits with the same latency of 30 minutes but with better accuracies of 5 cm SLR RMS. The third chain, the least accurate but the fastest, is based on predicted IGS GPS orbits and clocks and delivers LEO orbits with latencies of 13 minutes and accuracies of 10 cm SLR RMS. The system design is such that it can easily be extended to cope with new satellites like TanDEM-X requiring precise and fast available orbits.

  8. High-resolution DEMs in the study of rainfall- and earthquake-induced landslides: Use of a variable window size method in digital terrain analysis

    NASA Astrophysics Data System (ADS)

    Iwahashi, Junko; Kamiya, Izumi; Yamagishi, Hiromitsu

    2012-06-01

    We undertake digital terrain analyses of rainfall- and earthquake-induced landslides in Japan, using high-resolution orthoimagery and Light Detection and Ranging (LiDAR) DEMs. Our aims are twofold: to demonstrate an effective method for dealing with high-resolution DEMs, which are often too detailed for landslide assessments, and to evaluate the topographic differences between rainfall- and earthquake-induced landslides. The study areas include the Izumozaki (1961 and 2004 heavy rainfalls), Niihama (2004 heavy rainfalls), Houfu (2009 heavy rainfalls), and Hanokidachi/Kurikoma-dam regions (the 2008 M 7.2 Iwate-Miyagi Nairiku earthquake). The study areas include 7,106 landslides in these five regions. We use two topographic attributes (the slope gradient and the Laplacian) calculated from DEMs in varying window sizes. The hit rates for statistical prediction of landslide cells through discriminant analyses are calculated using the two topographic attributes as explanatory variables, and the landslide inventory data as the dependent variable. In cases of surface failure, the hit rates are found to diminish when the window size of the topographic attributes is too large or too small, indicating that an optimal scale factor is key in assessing shallow landslides. The representative window sizes are approximately 30 m for shallow landslides; the optimal window size may be directly related to the average size of landslides in each region. We also find a stark contrast between rainfall- and earthquake-induced landslides. Rainfall-induced landslides are always most common at a slope gradient of 30°, but the frequency of earthquake-induced landslides increases exponentially with slope gradient. We find that the Laplacian, i.e., the attributes of surface convexity and concavity, and the slope gradient are both important factors for rainfall-induced landslides, whereas earthquake-induced landslides are influenced mainly by slope steepness.

  9. Development of an unresolved CFD-DEM model for the flow of viscous suspensions and its application to solid-liquid mixing

    NASA Astrophysics Data System (ADS)

    Blais, Bruno; Lassaigne, Manon; Goniva, Christoph; Fradette, Louis; Bertrand, François

    2016-08-01

    Although viscous solid-liquid mixing plays a key role in the industry, the vast majority of the literature on the mixing of suspensions is centered around the turbulent regime of operation. However, the laminar and transitional regimes face considerable challenges. In particular, it is important to know the minimum impeller speed (Njs) that guarantees the suspension of all particles. In addition, local information on the flow patterns is necessary to evaluate the quality of mixing and identify the presence of dead zones. Multiphase computational fluid dynamics (CFD) is a powerful tool that can be used to gain insight into local and macroscopic properties of mixing processes. Among the variety of numerical models available in the literature, which are reviewed in this work, unresolved CFD-DEM, which combines CFD for the fluid phase with the discrete element method (DEM) for the solid particles, is an interesting approach due to its accurate prediction of the granular dynamics and its capability to simulate large amounts of particles. In this work, the unresolved CFD-DEM method is extended to viscous solid-liquid flows. Different solid-liquid momentum coupling strategies, along with their stability criteria, are investigated and their accuracies are compared. Furthermore, it is shown that an additional sub-grid viscosity model is necessary to ensure the correct rheology of the suspensions. The proposed model is used to study solid-liquid mixing in a stirred tank equipped with a pitched blade turbine. It is validated qualitatively by comparing the particle distribution against experimental observations, and quantitatively by compairing the fraction of suspended solids with results obtained via the pressure gauge technique.

  10. 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

  11. 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

  12. 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.

  13. Morphometric evaluation of the Afşin-Elbistan lignite basin using kernel density estimation and Getis-Ord's statistics of DEM derived indices, SE Turkey

    NASA Astrophysics Data System (ADS)

    Sarp, Gulcan; Duzgun, Sebnem

    2015-11-01

    A morphometric analysis of river network, basins and relief using geomorphic indices and geostatistical analyses of Digital Elevation Model (DEM) are useful tools for discussing the morphometric evolution of the basin area. In this study, three different indices including valley floor width to height ratio (Vf), stream gradient (SL), and stream sinuosity were applied to Afşin-Elbistan lignite basin to test the imprints of tectonic activity. Perturbations of these indices are usually indicative of differences in the resistance of outcropping lithological units to erosion and active faulting. To map the clusters of high and low indices values, the Kernel density estimation (K) and the Getis-Ord Gi∗ statistics were applied to the DEM-derived indices. The K method and Gi∗ statistic highlighting hot spots and cold spots of the SL index, the stream sinuosity and the Vf index values helped to identify the relative tectonic activity of the basin area. The results indicated that the estimation by the K and Gi∗ including three conceptualization of spatial relationships (CSR) for hot spots (percent volume contours 50 and 95 categorized as high and low respectively) yielded almost similar results in regions of high tectonic activity and low tectonic activity. According to the K and Getis-Ord Gi∗ statistics, the northern, northwestern and southern parts of the basin indicates a high tectonic activity. On the other hand, low elevation plain in the central part of the basin area shows a relatively low tectonic activity.

  14. 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

  15. 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

  16. PERSPECTIVES AND FEASIBILITY OF DERIVING MASS BALANCE OF MID LATITUDE MOUNTAIN GLACIERS FROM DIRECT GLACIOLOGIOCAL MEASUREMENTS, REPEATED OPTICAL IMAGERY AND DEMS

    NASA Astrophysics Data System (ADS)

    Fischer, A.

    2009-12-01

    The melt of mountain glaciers provides the second major contribution to today’s sea level rise. Direct measurements are restricted to a small percentage of glaciers and the distribution of these measurements is biased towards developed regions. Therefore, the important task of calculating the actual and future contribution of mountain glaciers to sea level rise must be based on remote sensing and modelling. In the last years, technical progress increased the possibilities for repeated imaging of the glacier surface texture and elevation. The extent of snow, firn and ice cover is imaged ground based, from aircraft or satellite in optical or microwave spectral bands resulting in albedo information that in case of a suitable temporal distribution is used to model mass balance. Repeatedly acquired DEMs of the glacier surface allow the calculation of the mass balance based on volume changes and assumptions on the density of the surface layers. The accuracy of both methods depends on the temporal and spatial resolution of the data acquisition. In this study, the mass balance data of one specific glacier calculated from direct measurements, optical images and volume change measurements are compared. Various temporal and spatial resolution of the optical and geodetic input data allow the simulation of sensor characteristics and their impact on the accuracy of the result. The test glacier Hintereisferner (Austria) is a typical mid-latitude valley glacier with a mean annual mass balance of about -0.7 m w.e.. Typically, the duration of the ablation season is 4 to 5 months. For the test period 2004-2009, the surface texture is registered daily with a web cam, which allows the determination of mass balance based on information of the depletion of snow cover. This procedure is carried out for various time steps to simulate the results of optical satellite data with repeat passes ranging from 3 to 60 days. The directly measured mass balance is retrieved from about 50 stakes and

  17. 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.

  18. Tectonic architecture through Landsat-7 ETM+/SRTM DEM-derived lineaments and relationship to the hydrogeologic setting in Siwa region, NW Egypt

    NASA Astrophysics Data System (ADS)

    Masoud, Alaa; Koike, Katsuaki

    2006-08-01

    Fracture zones on the Earth's surface are important elements in the understanding of plate motion forces, the dynamics of the subsurface fluid flow, and earthquake distributions. However, good exposures of these features are always lacking in arid regions, characterized by flat topography and where sand dunes extensively cover the terrain. During field surveys these conditions, in many cases, hinder the proper characterization of such features. Therefore, an approach that identifies the regional fractures as lineaments on remotely-sensed images or shaded digital terrain models, with its large scale synoptic coverage, could be promising. In the present work, a segment tracing algorithm (STA), for lineament detection from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) imagery, and the data from the Shuttle Radar Topographic Mission (SRTM) 30 m digital elevation model (DEM), has been applied in the Siwa region, located in the northwest of the Western Desert of Egypt. The objectives are to analyze the spatial variation in orientation of the detected linear features and its relation to the hydrogeologic setting in the area and the underlying geology, and to evaluate the performance of the algorithm applied to the ETM+ and the DEM data. Detailed structural analysis and better understanding of the tectonic evolution of the area could provide useful tools for hydrologists for reliable groundwater management and development planning. The results obtained have been evaluated by the structural analysis of the area and field observations. Four major vertical fracture zones were detected corresponding to two conjugate sets of strike-slip faults that governed the surface, and subsurface environments of the lakes in the region, and these correlate well with the regional tectonics.

  19. Effect of polarization orientation angle shift on X-band TDM SAR COSSC product of TerraSAR-X and TanDEM-X

    NASA Astrophysics Data System (ADS)

    Gupta, Asmita; Kumar, Shashi; Pandey, Uttara

    2016-05-01

    Polarization orientation angle (POA) shift in the backscattered SAR wave induced, due to irregularity of the target surface. Polarimetric signatures of the backscatter SAR wave gets affected by the POA shift, causes error in the decomposition modelling as shift in POA makes coherency matrix asymmetric. POA shift compensation is very necessary to avoid misinterpretation of decomposition modelling results. POA shift effect has been observed using coherency matrix and decomposition model results. This study is conducted over Dudhwa National Park in the state of Uttar Pradesh, using high resolution, TDM SAR COSSC Product of TerraSAR-X and TanDEM-X in Bistatic mode. Present study mainly focused on the comparative analysis of resultant scattering component of decomposition model before and after POA shift compensation. Shift in POA is investigated using circular polarization technique. Yamaguchi four component decomposition model is used to express total backscatter information in terms of volume, double bounce, surface and helix scattering. Volume scattering is overestimated however double bounce and surface scattering is under estimated in decomposition model due to POA shift present in the backscatter SAR wave. Different scattering mechanisms resulted after POA compensation were analyzed using 100 random points taken from forest structure. The results obtained by TerraSAR-X and TanDEM-X shows an overall increase in double bounce scattering and decrease in volume scattering component after POA shift compensation. It is observed that there is negligible effect of POA shift on surface scattering. POA shift compensation necessarily required to improve the accuracy of decomposition models used in the forest parameter retrieval applications.

  20. Elevation change estimates of the Barnes Ice Cap from combined CryoSat-2 altimetry measurements and high resolution stereo-photogrammetric DEM

    NASA Astrophysics Data System (ADS)

    de la Peña, S.; Howat, I. M.; Noh, M. J.; Shum, C. K.

    2015-12-01

    Mass losses from glaciers and small ice caps in the Canadian Arctic have accelerated dramatically in the last decade due to warming. The Barnes Ice Cap, a remnant of the Laurentide Ice Sheet, contains the oldest ice in the Canadian Arctic, and has been particularly sensitive to changes in atmospheric temperature. Although relatively flat at the top, the ice cap is located along the Arctic Cordillera, dominated by alpine mountains with sharp peaks and ridges which limited the accuracy of measurements from past satellite radar altimeter missions. The interferometric capabilities of the CryoSat-2 radar altimeter has improved our capacity to measure volume changes over steep topography, but still face potential limitations over irregular terrain and glaciated areas with high surface roughness, which in the Arctic has increased as a consequence of intensified surface melt. Over rough topography, such as the one characterized by crevassed fields, surface roughness is high relative to the altimeter footprint, and estimating the incidence angle of the altimeter signal is not always possible. Here, a high-resolution stereo-photogrammetric DEM generated from stereo-mode Worldview satellite imagery is used to estimate surface slope of the glaciated terrain and derive the across-track incidence angle of the CryoSat-2 radar echo. The unprecedented accuracy of the DEM allows it to then be used as a reference to increase spatial density of elevation change measurements. Elevation change estimates for the period of 2011-2015 show a thinning of 1.46 ± 0.21 yr-1 on average, more than twice the thinning rates estimated a decade ago. The methodology increase spatial coverage of repeated altimetry measurements, and may improve elevation retrieval from altimetry signals in glaciated areas subject to summer surface melt.

  1. A visual basic program for ridge axis picking on DEM data using the profile-recognition and polygon-breaking algorithm

    NASA Astrophysics Data System (ADS)

    Chang, Yet-Chung; Sinha, Gaurav

    2007-02-01

    For many scientists working with digital topographic data, extracting lineaments or linear features is an important step in structuring and analyzing raw data. A ridge axis, which represents the top a mountain ridge, is one of the most important topographic features used in a wide variety of applications. Algorithms and software for automating the extraction of ridges or ridge axes from DEMs are, however, still not easily available or not widely acceptable. In this paper, we present a user-friendly Visual Basic program that automates the extraction of the ridge axis system from DEM data, based on the profile-recognition and polygon-breaking algorithm (PPA). An important feature of PPA is that it takes a global approach, as opposed to the local neighborhood operators used in many other algorithms. Each segment detected by PPA considers not only relations with contiguous neighboring grid points, but also strives to preserve the continuity of the global trend. This is an attempt to simulate human operators, who always factor in the overall trend of the lineament before delineating its local parts. PPA starts by connecting all points in a neighborhood that can possibly lie on the ridge axis, thus forming a belt of polygons in the first step. Next, a polygon breaking process eliminates unwanted segments according to the assumption that a ridge segment cannot be the side of any closed polygon, and that the result should be a purely dendritic line pattern. Finally, a branch-reduction process is executed to eliminate all parallel false ridges that remained due to the conservative approach taken in the first step. Results indicate that PPA is reasonably successful in picking out ridges that would have been identified manually by experts. In addition to providing a detailed user interface for executing PPA, several modifications were made to significantly improve the computational efficiency of PPA, as compared to the original version published in 1998. The source codes are

  2. 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.

  3. 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.

  4. 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

  5. A methodology to generate high-resolution digital elevation model (DEM) and surface water profile for a physical model using close range photogrammetric (CRP) technique

    NASA Astrophysics Data System (ADS)

    Méndez Incera, F. J.; Erikson, L. H.; Ruggiero, P.; Barnard, P.; Camus, P.; Rueda Zamora, A. C.

    2014-12-01

    Comprehensive understanding of the river flow dynamics with varying topography in a real field is very intricate and difficult. Conventional experimental methods based on manual data collection are time consuming and prone to many errors. Recently, remotely sensed satellite imageries are at the best to provide necessary information for large area provided the high resolution but which are very expensive and untimely, consequently, attaining accurate river bathymetry from relatively course resolution and untimely imageries are inaccurate and impractical. Despite of that, these data are often being used to calibrate the river flow models, though these models require highly accurate morpho-dynamic data in order to predict the flow field precisely. Under this circumstance, these data could be supplemented through experimental observations in a physical model with modern techniques. This paper proposes a methodology to generate highly accurate river bathymetry and water surface (WS) profile for a physical model of river network system using CRP technique. For the task accomplishment, a number of DSLR Nikon D5300 cameras (mounted at 3.5 m above the river bed) were used to capture the images of the physical model and the flooding scenarios during the experiments. During experiment, non-specular materials were introduced at the inlet and images were taken simultaneously from different orientations and altitudes with significant overlap of 80%. Ground control points were surveyed using two ultrasonic sensors with ±0.5 mm vertical accuracy. The captured images are, then processed in PhotoScan software to generate the DEM and WS profile. The generated data were then passed through statistical analysis to identify errors. Accuracy of WS profile was limited by extent and density of non-specular powder and stereo-matching discrepancies. Furthermore, several factors of camera including orientation, illumination and altitude of camera. The CRP technique for a large scale physical

  6. A methodology to generate high-resolution digital elevation model (DEM) and surface water profile for a physical model using close range photogrammetric (CRP) technique

    NASA Astrophysics Data System (ADS)

    Mali, V. K.; Kuiry, S. N.

    2015-12-01

    Comprehensive understanding of the river flow dynamics with varying topography in a real field is very intricate and difficult. Conventional experimental methods based on manual data collection are time consuming and prone to many errors. Recently, remotely sensed satellite imageries are at the best to provide necessary information for large area provided the high resolution but which are very expensive and untimely, consequently, attaining accurate river bathymetry from relatively course resolution and untimely imageries are inaccurate and impractical. Despite of that, these data are often being used to calibrate the river flow models, though these models require highly accurate morpho-dynamic data in order to predict the flow field precisely. Under this circumstance, these data could be supplemented through experimental observations in a physical model with modern techniques. This paper proposes a methodology to generate highly accurate river bathymetry and water surface (WS) profile for a physical model of river network system using CRP technique. For the task accomplishment, a number of DSLR Nikon D5300 cameras (mounted at 3.5 m above the river bed) were used to capture the images of the physical model and the flooding scenarios during the experiments. During experiment, non-specular materials were introduced at the inlet and images were taken simultaneously from different orientations and altitudes with significant overlap of 80%. Ground control points were surveyed using two ultrasonic sensors with ±0.5 mm vertical accuracy. The captured images are, then processed in PhotoScan software to generate the DEM and WS profile. The generated data were then passed through statistical analysis to identify errors. Accuracy of WS profile was limited by extent and density of non-specular powder and stereo-matching discrepancies. Furthermore, several factors of camera including orientation, illumination and altitude of camera. The CRP technique for a large scale physical

  7. 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.

  8. 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).

  9. 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.

  10. Ethanol electrooxidation on a carbon-supported Pt catalyst at elevated temperature and pressure: A high-temperature/high-pressure DEMS study

    NASA Astrophysics Data System (ADS)

    Sun, S.; Halseid, M. Chojak; Heinen, M.; Jusys, Z.; Behm, R. J.

    The electrooxidation of ethanol on a Pt/Vulcan catalyst was investigated in model studies by on-line differential electrochemical mass spectrometry (DEMS) over a wide range of reaction temperatures (23-100 °C). Potentiodynamic and potentiostatic measurements of the Faradaic current and the CO 2 formation rate, performed at 3 bar overpressure under well-defined transport and diffusion conditions reveal significant effects of temperature, potential and ethanol concentration on the total reaction activity and on the selectivity for the pathway toward complete oxidation to CO 2. The latter pathway increasingly prevails at higher temperature, lower concentration and lower potentials (∼90% current efficiency for CO 2 formation at 100 °C, 0.01 M, 0.48 V), while at higher ethanol concentrations (0.1 M), higher potentials or lower temperatures the current efficiency for CO 2 formation drops, reaching values of a few percent at room temperature. These trends result in a significantly higher apparent activation barrier for complete oxidation to CO 2 (68 ± 2 kJ mol -1 at 0.48 V, 0.1 M) compared to that of the overall ethanol oxidation reaction determined from the Faradaic current (42 ± 2 kJ mol -1 at 0.48 V, 0.1 M). The mechanistic implications of these results and the importance of relevant reaction and mass transport conditions in model studies for reaction predictions in fuel cell applications are discussed.

  11. Anti-nuclear liberals and the bomb: A comparative history of Kampf dem Atomtod and the Committee for a Sane Nuclear Policy, 1957-1963

    SciTech Connect

    Thiede, B.

    1992-01-01

    The premises of Kampf dem Atomtod (KdA) and Citizens for a Sane Nuclear Policy (SANE) were based on nineteenth century traditions of liberal peace advocacy. Both groups gained substantial public support for their goals to prevent the nuclear armament of the Bundeswehr and to stop nuclear testing. Both organizations won well-educated middle-class and mostly white supporter. The dissertation examines the role of women: whether housewife or doctor, women stressed their special concerns as mothers. Both KdA and SANE had troubled relations with the labor movement. Their leaders hoped to gain government leaders' respect by winning a respectable, non-Communist constituency and claiming their goals were reasonable ones. Government officials attacked KdA and SANE as dupes of Moscow. Many supporters left the organizations because of their strict anti-Communism. Local groups accused their leaders of lacking initative. KdA and SANE's leaders wasted time and energy rehashing issues and postponing decisions. After a period of providing initiatives and ideas local committees disintegrated. Both organizations considered education their paramount goal but their arguments primarily reached the converted, who often preferred more political action. KdA and SANE's leaders instead chose to support respectable projects based on humanitarian ideals. Since these projects offered little in the way of concrete action agendas, supporters defected to more active organizations or slipped into apathy. Neither organization achieved its national goals. Both governments generally denied them access to the policymaking process, ignored them as irrelavant, or attacked them as Communist sympathizers. While SANE and KdA were heard by those concerned by nuclear policy, and while members of SANE's National Board did help muster support for the Partial Test Ban Treaty, both organizations failed to make liberal peace values productive in the nuclear decisionmaking process.

  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

  13. 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

  14. 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

  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.

  16. Astronomie mit dem Personal Computer.

    NASA Astrophysics Data System (ADS)

    Montenbruck, O.; Pfleger, T.

    Dritte, völlig neubearbeitete Auflage, Programmiersprache C++ (2. Auflage 1994, Abstr. 61.003.023). Die CD-ROM enthält neben den Quelltexten auch die ausführbaren Programme für Windows 95/98/NT und Linux. Contents: 1. Einführung. 2. Koordinatensysteme. 3. Auf- und Untergangsrechnung. 4. Kometenbahnen. 5. Störungsrechnung. 6. Planetenbahnen. 7. Physische Planetenephemeriden. 8. Die Mondbahn. 9. Sonnenfinsternisse. 10. Sternbedeckungen. 11. Bahnbestimmung. 12. Astrometrie.

  17. Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs)

    NASA Astrophysics Data System (ADS)

    Bechet, Jacques; Duc, Julien; Loye, Alexandre; Jaboyedoff, Michel; Mathys, Nicolle; Malet, Jean-Philippe; Klotz, Sébastien; Le Bouteiller, Caroline; Rudaz, Benjamin; Travelletti, Julien

    2016-10-01

    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 erosion and weathering processes. For 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope processes on the scale of elementary gullies. Since 2007, surface changes have been monitored by comparing high-resolution digital elevation models (HRDEMs) 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 digital elevation model (DEM) on the centimetre scale. The topographic changes over a time span of 2 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes show and confirm that during winter, loose regolith is created by mechanical weathering, and it is eroded and accumulates in the rills and gullies. Because of limited rainfall intensity in spring, part of the material is transported in the main gullies, which are assumed to be a transport-limited erosion system. In the late spring and summer the rainfall intensities increase, allowing the regolith, weathered and accumulated in the gullies and rills during the earlier seasons, to be washed out. Later in the year the catchment acts as a sediment-limited system because no more loose regolith is available. One interesting result is the fact that in the gullies the erosion-deposition processes are more active around the slope angle value of 35°, which probably indicates a behaviour close to dry granular material. It is also observed that there exist thresholds for the rainfall events that are able to

  18. 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

  19. Insights on the 2010 Lava Flows of Piton de la Fournaise Using Cosmo-SkyMed and TanDEM-X Data: Lava Displacement Rates, Thicknesses, and Volume Estimates

    NASA Astrophysics Data System (ADS)

    Bato, M. G.; Froger, J. L.; Harris, A. J. L.; Villeneuve, N.

    2014-12-01

    Characterization of lava flow after its emplacement provides volume and constraints for lava flow emplacement simulations that help assess pending volcanic hazards. Additionally, it gives us better insights in understanding the dynamics of the underlying magmatic plumbing system and the possible mechanism of the eruption. In this work, we developed a technique using monostatic Cosmo-SkyMed and bistatic TanDEM-X data to calculate the volume, measure the thickness, and the horizontal and vertical displacements immediately after the emplacement of the October 2010 lava flow at Piton de la Fournaise. Results show that the thickest part of the October 2010 lava flow is about 13 to 16 m and the DRE volume is estimated to fall within the range of 1.71 to 3.00 x 106 m3 (±1σ), depending on which InSAR database was used. We also observe that the October 2010 lava flow is subsiding at a maximum rate of 14 cm yr-1. Apart from the vertical displacement, joint sliding and centripetal displacement were also identified with a maximum rate of 4.0 cm yr-1. We cross-validated our InSAR results with the mixed-pixel technique of Harris [1997] in terms of the estimated volumes. Our analysis shows that the volume derived using a few TanDEM-X interferograms fitted well within the range of volume given by the mixed-pixel technique as compared to the huge monostatic Cosmo-SkyMed database. In addition to the October 2010 lava flow, we also characterized the thin lava flow deposit of the December 2010 eruption, however using only bistatic TanDEM-X data. In this case of thin lava deposits, we expect that TanDEM-X are best to use in deriving the thickness and estimating the volume as these type of data are more sensitive to topographic change. Reference: Harris AJL, Blake S, Rothery DA, Stevens NF., 1997. A chronology of the 1991 to 1993 Mount Etna eruption using advanced very high resolution radiometer data: implications for real-time thermal volcano monitoring. Geophys. Res. Lett. 102:7985-8003.

  20. An algorithm for generalizing topography to grids while preserving subscale morphologic characteristics—creating a glacier bed DEM for Jakobshavn trough as low-resolution input for dynamic ice-sheet models

    NASA Astrophysics Data System (ADS)

    Herzfeld, Ute C.; Wallin, Bruce F.; Leuschen, Carlton J.; Plummer, Joel

    2011-11-01

    The objective of this paper is to derive an algorithm for preserving important subscale morphologic characteristics at grids of lower-resolution, in particular for linear features such as canyons and ridge lines. The development of such an algorithm is necessitated by applications that require reduced spatial resolution, as is common in cartographic generalization, GIS applications, and geophysical modeling. Since any algorithm that results in weighted averages, including optimum interpolation and ordinary kriging, cannot reproduce correct depths, a new algorithm is designed based on principles of mathematical morphology. The algorithm described here is applied to derive a subglacial bed of the Greenland Ice Sheet that includes the trough of Jakobshavn Isbræ as a continuous canyon at correct depth in a low-resolution (5-km) digital elevation model (DEM). Data from recent airborne radar measurements of the elevation of the subglacial bed as part of the CReSIS project are utilized. The morphologic algorithm is designed with geophysical ice-sheet modeling in mind, in the following context. Currently occurring changes in the Earth's climate and the cryosphere cause changes in sea level, and the societal relevance of these natural processes motivates estimation of maximal sea-level rise in the medium-term future. The fast-moving outlet glaciers are more sensitive to climatic change than other parts of the Greenland ice sheet. Jakobshavn Isbrae, the fastest-moving ice stream in Greenland, follows a subglacial geologic trough. Since the existence of the trough causes the acceleration of the slow-moving inland ice in the Jakobshavn region and the formation of the ice stream, correct representation of the trough in a DEM is essential to model changes in the dynamics of the ice sheet and resultant sea-level predictions, even if current ice-sheet models can typically be run only at 5-km resolution. The DEM resultant from this study helps to bridge the conceptual gap between

  1. The use of DEM analysis for structural characterization of landslide-prone areas in crystalline rock slopes using GIS-based techniques. The case of the Matter Valley, Switzerland

    NASA Astrophysics Data System (ADS)

    Yugsi Molina, F. X.; Loew, S.; Button, E.

    2009-04-01

    Mountainous regions influenced by glacial processes are often prone to slope instabilities. One reason for this relationship is their characteristic morphology (high relief and steep slopes) and the surface processes associated with glacial advance and retreat. In the Matter Valley, Switzerland these factors interact with brittle-ductile faults and joint sets and induce rock slope failures at multiple scales, including the 3x107 m3 Randa and the 1x105 m3 Medji events. The general lithological and tectonic disposition in the study area is quite homogeneous, while the local fracture systems and their characteristics vary spatially. These features provide the opportunity to evaluate potential relationships between the local fracture systems and the potential failure modes they develop with the observed slope morphology and its state of stability. In order to investigate this hypothesis the fracture pattern of the area was analyzed using a new combination of data collected from the field and data extracted from an aerial-based LIDAR high resolution DEM (SWISSTOPO, 2m pixel resolution). This is possible for the area because the fracture pattern has been observed to have a strong influence in the morphology of the slopes. To identify slope faces controlled by structures a 3D shaded relief map of the area was produced. A 3D shaded relief map is a color-coded image based on HSV color composition showing changes in color according with the changes on slope orientation (dip and dip direction). A careful selection of the planes used for the analysis was carried out taking in consideration that not all values in the 3D shaded relief image represent fracture orientations; this is due to multiple factors such as cell size of the DEM, presence of land cover (soil), and presence of overhanging blocks. Selection of cells was done using 3D visualizations (an orthophoto mosaic created with aerial photographs acquired in 2005 was used as the top-most layer) and photographs of the

  2. 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

  3. Lidarsensorik

    NASA Astrophysics Data System (ADS)

    Geduld, Georg

    LIDAR: Light Detection And Ranging ist ein optisches Messverfahren zur Ortung und Messung der Entfernung von Objekten im Raum. Prinzipiell ähnelt das System dem Radar-Verfahren, wobei allerdings anstelle von Mikrowellen beim LIDAR Ultraviolett-, Infrarot- oder Strahlen aus dem Bereich des sichtbaren Lichts (daher LIDAR) verwendet werden (vgl. Bild 13-1).

  4. Shape-selected nanocrystals for in situ spectro-electrochemistry studies on structurally well defined surfaces under controlled electrolyte transport: A combined in situ ATR-FTIR/online DEMS investigation of CO electrooxidation on Pt

    PubMed Central

    Jusys, Zenonas; Behm, R Jürgen

    2014-01-01

    Summary The suitability and potential of shape selected nanocrystals for in situ spectro-electrochemical and in particular spectro-electrocatalytic studies on structurally well defined electrodes under enforced and controlled electrolyte mass transport will be demonstrated, using Pt nanocrystals prepared by colloidal synthesis procedures and a flow cell set-up allowing simultaneous measurements of the Faradaic current, FTIR spectroscopy of adsorbed reaction intermediates and side products in an attenuated total reflection configuration (ATR-FTIRS) and differential electrochemical mass spectrometry (DEMS) measurements of volatile reaction products. Batches of shape-selected Pt nanocrystals with different shapes and hence different surface structures were prepared and structurally characterized by transmission electron microscopy (TEM) and electrochemical methods. The potential for in situ spectro-electrocatalytic studies is illustrated for COad oxidation on Pt nanocrystal surfaces, where we could separate contributions from two processes occurring simultaneously, oxidative COad removal and re-adsorption of (bi)sulfate anions, and reveal a distinct structure sensitivity in these processes and also in the structural implications of (bi)sulfate re-adsorption on the CO adlayer. PMID:24991511

  5. 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.

  6. Fractal Image Informatics: from SEM to DEM

    NASA Astrophysics Data System (ADS)

    Oleschko, K.; Parrot, J.-F.; Korvin, G.; Esteves, M.; Vauclin, M.; Torres-Argüelles, V.; Salado, C. Gaona; Cherkasov, S.

    2008-05-01

    In this paper, we introduce a new branch of Fractal Geometry: Fractal Image Informatics, devoted to the systematic and standardized fractal analysis of images of natural systems. The methods of this discipline are based on the properties of multiscale images of selfaffine fractal surfaces. As proved in the paper, the image inherits the scaling and lacunarity of the surface and of its reflectance distribution [Korvin, 2005]. We claim that the fractal analysis of these images must be done without any smoothing, thresholding or binarization. Two new tools of Fractal Image Informatics, firmagram analysis (FA) and generalized lacunarity (GL), are presented and discussed in details. These techniques are applicable to any kind of image or to any observed positive-valued physical field, and can be used to correlate between images. It will be shown, by a modified Grassberger-Hentschel-Procaccia approach [Phys. Lett. 97A, 227 (1983); Physica 8D, 435 (1983)] that GL obeys the same scaling law as the Allain-Cloitre lacunarity [Phys. Rev. A 44, 3552 (1991)] but is free of the problems associated with gliding boxes. Several applications are shown from Soil Physics, Surface Science, and other fields.

  7. 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%.

  8. 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)

  9. 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

    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.

  10. Ein Kredit für Weihnachtsbaumkugeln

    NASA Astrophysics Data System (ADS)

    Tutsch, Sina

    Eine Mathematikerin aus dem DFG-Forschungszentrum Matheon arbeitet an Methoden zur dreidimensionalen Visualisierung. Sie hat die Geschäftsidee, Weihnachtsbaumkugeln mit bewegten Hologrammen herzustellen, die sich individuell gestalten lassen, und plant eine Existenzgründung. Aus einem öffentlichen Förderprogramm erhält sie ein günstiges Darlehen in Höhe von 50 000 Euro. Für die Startphase ihres Unternehmens benötigt sie jedoch den vierfachen Betrag.

  11. Amor und der Abstand zur Sonne. Geschichten aus meinem Kosmos

    NASA Astrophysics Data System (ADS)

    Kippenhahn, Rudolf

    2001-10-01

    R. Kippenhahn hat in vielen Büchern die Astronomie populär gemacht. Ihn interessieren dabei immer auch die kuriosen Aspekte seiner Wissenschaft. Von ihnen erzählt er in den kleinen Geschichten dieses Buches.

  12. Energetische Verwertung von Biomasse

    NASA Astrophysics Data System (ADS)

    Zahoransky, Richard; Allelein, Hans-Josef; Bollin, Elmar; Oehler, Helmut; Schelling, Udo

    Etwa 0,1% der Solarenergie wandeln sich durch Photosynthese aus dem Kohlendioxid der Luft in Biomasse um. Die Biomassen sind als Festbrennstoff nutzbar oder zu gasförmigen Brennstoffen weiterverarbeitbar. Zwei Arten von Biomassen sind zu unterscheiden: Anfallende Biomasse

  13. Normung (Standardisierung)

    NASA Astrophysics Data System (ADS)

    Kostmann, Dirk

    Normung ist aus dem täglichen Leben nicht wegzudenken. In allen Bereichen des Lebens begegnet man Normen, die Aktivitäten reichen von Festlegungen für Kindersitze im Auto über Implantate zum Gelenkersatz bis zu Schraubengrößen oder Verfahren zur Optimierung von Unternehmen.

  14. Computerunterstütztes Modellieren mit Musiknetzen

    NASA Astrophysics Data System (ADS)

    Levens, Ulla

    In der folgenden Ausführung geht es um eine Anwendung von Petri-Netzen im Bereich Musik. Ausgehend von der Implementierung einer speziellen Anwendung, dem Programmsystem ScoreSynth, wird das zugrundeliegende Konzept erläutert und anschließend an einem kleinen Beispiel veranschaulicht. Dieser Beitrag ist ein Auszug aus [Lev95b].

  15. Linear and Angolar Moment of a general spherical TEM and DEM beam radio wave detection with a quadratic order system processor in state of art technology implementation: a three axis sensors array quadratic order correlator for the 21cm radiation radio detection coming from Early Universe

    NASA Astrophysics Data System (ADS)

    Romano, Francesco; Trifiletti, Alessandro; Cimmino, Rosario F.

    2016-07-01

    The paper focuses on an innovative spherical wave beam quadratic order processor, HSCS-1. It is an IP, Coulob Gauge based, to directly mesure, ∀t and in any single P ∀P (along the propagation axis too) the quadratic order Poynting Vector, with both the complex Linear Momentum (LiM) and Angolar Momentum (AnM) contributions, as well as the mutual quadratic order coherence function of any total or pseudo monochromatic observed beam wave. The focoused spherical quadratic order method, directly mesure the spherical complex OAM (time and propagation axsis invariant) which is composed by the observed beam wave modes. Such solenoidal energy modes, becomes relevant to mesure far distance (as exemple: distance greater than billions of light years away) sources radiations. Furthermore, HSCS-1 contemporary and directly measure the mutual (spatial as well as temporal) complex coherence of any general complex divergent or not strictly TEM (as example: TEM+DEM) observed radiations. Tipically TEM+DEM radiations are characterized by N=LPM+1 complex wave beam modes. N is the number of considered EM fields modes, as great as requested; N and L are integer, which values are internal to a closed interval [0; ∞] P and M are integer, which values are internal to a closed interval [1; ∞] n=0,1,…,N is the mode or beam channel index; with l=0, 1,…,L; p= 1,…, P; and m = 1,…,M; n=l=0 is the fundamental mode index). Here are considered only the wave beam modes which satisfy the related Helmoltz monochromatic wave equation soluctions. As well known in Physics, only adopting a quadratic order energy processor it is possible ∀t to contemporary and directely mesure in P, ∀P(θ Φ z) and ∀(P-P0), both the proper P0 position and quantity of motion (proper space time variations), or by a Fourier Transformation to contemporary and directely mesure proper phase and frequency spectrum variations, of the observed general radiation source.

  16. Gewebe

    NASA Astrophysics Data System (ADS)

    Shah-Derler, Brigitte; Wintermantel, Erich; Ha, Suk-Woo

    Als Gewebe wird ein durch spezifische Leistungen gekennzeichneter Verband gleichartig differenzierter Zellen bezeichnet. Gewebe entstehen aus jungen, noch nicht differenzierten Zellen, die sich ihrer künftigen Funktion entsprechend umwandeln. Gewebe aus differenzierten Zellen wird als Dauergewebe bezeichnet. Verschiedene Gewebe haben allerdings eine mehr oder weniger starke Potenz, sich neu aufzubauen. Beim Menschen unterscheidet man diesbezüglich zwischen labilem Gewebe, bei dem die Bildung und der Aufbau der Zellen rasch erfolgt, stabilem Gewebe, bei dem der Zellumsatz sehr langsam geschieht und permanentem Gewebe, bei dem absterbende Zellen nicht mehr ersetzt werden können (Tabelle 8.1). Es gibt vier Grundtypen von Geweben: Epithelgewebe, Binde- und Stützgewebe, Muskelgewebe und Nervengewebe. Im Körper treten in der Regel verschiedene Gewebe funktionell zusammen (z. B. Muskeln und Sehnen des Bindegewebes).

  17. Blut

    NASA Astrophysics Data System (ADS)

    Shah-Derler, Brigitte; Wintermantel, Erich; Ha, Suk-Woo

    Das Blut zirkuliert in einem System von Blutgefässen und erfüllt dabei wesentliche Transportaufgaben im Organismus. Hauptfunktionen des Blutes sind die Stoffversorgung und -entsorgung der Zellen (Sauerstoff, CO2, Nährstoffe, Stoffwechselprodukte, etc.), der Transport von Hormonen und die Regulation der Körpertemperatur. Das Blut besteht zu 40-45% aus zellulären Bestandteilen und zu 55-60% aus dem Blutplasma (Abb. 7.1). Die Gesamtmenge beträgt beim erwachsenen Menschen etwa 5 bis 6 Liter, was 7-8% des Körpergewichtes entspricht. Aufgrund seiner zahlreichen Aufgaben wird das Blut als "fliessendes Organ“ bezeichnet. Das Blutplasma besteht zu rund 90 Vol.% aus Wasser und zu 10 Vol.% aus Elektrolyten, gelösten Gasen, Proteinen (Albumine, Globuline) und Stoffwechselprodukten. Die annähernd gleichbleibende Zusammensetzung dieser Blutbestandteile gewährleistet u. a. einen relativ konstanten osmotischen Druck und pH-Wert.

  18. Heteronukleare Spinentkopplung unter dem Einfluß thermischer Bewegungen

    NASA Astrophysics Data System (ADS)

    Ernst, H.; Fenzke, D.; Pfeifer, H.

    Unter der Annahme magnetischer Dipol-IS-Wechselwirkung wird eine Theorie der heteronuklearen Spinentkopplung für kurze Korrelationszeiten entwickelt. Diese enthält als Spezialfälle die kernmagnetischen Relaxationsraten im rotierenden und im festen Koordinatensystem sowie die Kreuzpolarisation zwischen den Spins I und S. In Übereinstimmung mit dieser Theorie tritt für die protonenentkoppelte C-13 Resonanz von Butanol, das in einem NaY-Zeolith adsorbiert ist, ein Maximum der Linienbreite als Funktion der Temperatur zwischen - 150°C und + 90°C auf.Translated AbstractHeteronuclear Spin Decoupling in the Presence of Thermal MotionAssuming magnetic dipolar I-S interaction, a general short -correlation time theory is presented which includes as special cases also well-known formulas for relaxation rates in the rotating and laboratory frame and for the cross polarization between I and S spins. In accordance with this theory for the proton-decoupled C-13 resonance of butanol adsorbed in a NaY zeolite, a maximum of the linewidth is observed as a function of temperature between - 150°C and + 90°C.

  19. DEM Based Modeling: Grid or TIN? The Answer Depends

    NASA Astrophysics Data System (ADS)

    Ogden, F. L.; Moreno, H. A.

    2015-12-01

    The availability of petascale supercomputing power has enabled process-based hydrological simulations on large watersheds and two-way coupling with mesoscale atmospheric models. Of course with increasing watershed scale come corresponding increases in watershed complexity, including wide ranging water management infrastructure and objectives, and ever increasing demands for forcing data. Simulations of large watersheds using grid-based models apply a fixed resolution over the entire watershed. In large watersheds, this means an enormous number of grids, or coarsening of the grid resolution to reduce memory requirements. One alternative to grid-based methods is the triangular irregular network (TIN) approach. TINs provide the flexibility of variable resolution, which allows optimization of computational resources by providing high resolution where necessary and low resolution elsewhere. TINs also increase required effort in model setup, parameter estimation, and coupling with forcing data which are often gridded. This presentation discusses the costs and benefits of the use of TINs compared to grid-based methods, in the context of large watershed simulations within the traditional gridded WRF-HYDRO framework and the new TIN-based ADHydro high performance computing watershed simulator.

  20. Visualization of small scale structures on high resolution DEMs

    NASA Astrophysics Data System (ADS)

    Kokalj, Žiga; Zakšek, Klemen; Pehani, Peter; Čotar, Klemen; Oštir, Krištof

    2015-04-01

    Knowledge on the terrain morphology is very important for observation of numerous processes and events and digital elevation models are therefore one of the most important datasets in geographic analyses. Furthermore, recognition of natural and anthropogenic microrelief structures, which can be observed on detailed terrain models derived from aerial laser scanning (lidar) or structure-from-motion photogrammetry, is of paramount importance in many applications. In this paper we thus examine and evaluate methods of raster lidar data visualization for the determination (recognition) of microrelief features and present a series of strategies to assist selecting the preferred visualization of choice for structures of various shapes and sizes, set in varied landscapes. Often the answer is not definite and more frequently a combination of techniques has to be used to map a very diverse landscape. Researchers can only very recently benefit from free software for calculation of advanced visualization techniques. These tools are often difficult to understand, have numerous options that confuse the user, or require and produce non-standard data formats, because they were written for specific purposes. We therefore designed the Relief Visualization Toolbox (RVT) as a free, easy-to-use, standalone application to create visualisations from high-resolution digital elevation data. It is tailored for the very beginners in relief interpretation, but it can also be used by more advanced users in data processing and geographic information systems. It offers a range of techniques, such as simple hillshading and its derivatives, slope gradient, trend removal, positive and negative openness, sky-view factor, and anisotropic sky-view factor. All included methods have been proven to be effective for detection of small scale features and the default settings are optimised to accomplish this task. However, the usability of the tool goes beyond computation for visualization purposes, as sky-view factor, for example, is an essential variable in many fields, e.g. in meteorology. RVT produces two types of results: 1) the original files have a full range of values and are intended for further analyses in geographic information systems, 2) the simplified versions are histogram stretched for visualization purposes and saved as 8-bit GeoTIFF files. This means that they can be explored in non-GIS software, e.g. with simple picture viewers, which is essential when a larger community of non-specialists needs to be considered, e.g. in public collaborative projects. The tool recognizes all frequently used single band raster formats and supports elevation raster file data conversion.

  1. 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)

  2. 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.

  3. "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…

  4. A DEM contact model for history-dependent powder flows

    NASA Astrophysics Data System (ADS)

    Hashibon, Adham; Schubert, Raphael; Breinlinger, Thomas; Kraft, Torsten

    2016-11-01

    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.

  5. An Investigation of Flare Footpoint DEMs using AIA Diffraction Patterns

    NASA Astrophysics Data System (ADS)

    Raftery, Claire; Bain, Hazel; Schwartz, Richard; Torre, Gabriele; Krucker, Sam

    2015-04-01

    The heating of flare footpoints by accelerated electrons is a well-established component of the standard flare model. However, limitations of current instruments make it challenging to obtain high cadence, high resolution observations of the brightest footpoint regions, predominantly due to low cadence, or pixel saturation.In moderate and large flares observed by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly, CCD pixels in the footpoint regions are frequently saturated despite the automatic exposure control. Using the method of Schwartz et al. (2014), we reconstruct saturated footpoint kernels in the brightest flaring regions and investigate the evolving footpoint differential emission measure at the full 12 second AIA cadence. This is compared to the changing electron fluxes observed with the Reuven Ramaty Solar Spectroscopic Imager (RHESSI) to investigate the relationship between the non-thermal electron energy flux and the footpoint thermal response.(Schwartz, R. A., Torre, G., & Piana, M. (2014), Astrophysical Journal Letters, 793, LL23 )

  6. Interpolation of phenological phases on a digital elevation model (DEM)

    NASA Astrophysics Data System (ADS)

    Schöngaßner, Thomas C.; Scheifinger, Helfried

    2010-05-01

    The main objective of the VegDyn project (a cooperation between Joanneum Research, Institute of Digital Image Processing, LFZ Raumberg-Gumpenstein and ZAMG) consists in quantifying and modelling the relationship between individual growth stages of grassland on the one hand and atmospheric parameters, remotely sensed data and phenological observations on the other. The model simulates the beginning and the end of the vegetation period and the growth stages of grassland with temperature as input variable. Thus it will be possible to explore changes of the timing of the vegetation period and the growth stages of grassland in possible future climate scenarios, which are calculated by climate models. In the context of the VegDyn project we developed methods for the spatial interpolation of phenological phases on a digital elevation model with a 250 m grid resolution in the complex terrain of the Alps. The final result is a series of maps of long term mean entry dates and maps of entry dates of individual years, which can for instance be related with the Net Difference Vegetation Index (NDVI) parameter maps from satellite observations. Apart from the yearly input via the conventional observational network based on voluntary observers and the input via the web interface, the Austrian phenological data base is still being supplemented by data from the paper archive. The elevation of the station network ranges from 100 to 1700 m. The station density can reach up to 100 or more stations per phase and season during 1951 - 2009. From more than 280 observed phases including phases from wild (woody and herbaceous) and agricultural plants those have been selected, which are related to cultivated grassland and which can be detected by remote sensing. In order to be selected for spatial interpolation the phase must satisfy a number of criteria: a minimum number of stations and, in order to have a meaningful long term mean entry date, a minimum number of observations per station during 1951 - 2009. If this minimum number is set to 20 years, there remain averagely 129 stations per phase, which fulfil the criterion. An average observer notes about 51 phases. This results in a rather high year to year fluctuation of observing stations and observed phases. The applied interpolation methods are linear regression with the entry dates as dependent and the station coordinates as independent variables, height reduced inverse distance weighting, and height reduced mean. For the latter two methods the search radius and the number of selected nearest neighbouring stations for interpolation have been optimised via trial and error. Interpolation quality is being checked via spatial cross validation, where the average anomaly, explained spatial variance (correlation squared or RSQ) and the root mean squared error (RMSE) serve as quality criteria. The resulting set of maps contains the interpolated long term mean phenological entry date and the entry dates of a series of individual years (1990 - 2009) for each of the three methods. This enables a comparison of the three interpolation methods and an evaluation of the quality of the results.

  7. 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.

  8. CORONAL RESPONSE TO AN EUV WAVE FROM DEM ANALYSIS

    SciTech Connect

    Vanninathan, K.; Veronig, A. M.; Dissauer, K.; Hannah, I. G.; Kontar, E. P.

    2015-10-20

    Extreme-Ultraviolet (EUV) waves are globally propagating disturbances that have been observed since the era of the Solar and Heliospheric Observatory/Exteme-ultraviolet Imaging Telescope instrument. Although the kinematics of the wave front and secondary wave components have been widely studied, there is not much known about the generation and plasma properties of the wave. In this paper we discuss the effect of an EUV wave on the local plasma as it passes through the corona. We studied the EUV wave, generated during the 2011 February 15 X-class flare/coronal mass ejection event, using Differential Emission Measure diagnostics. We analyzed regions on the path of the EUV wave and investigated the local density and temperature changes. From our study we have quantitatively confirmed previous results that during wave passage the plasma visible in the Atmospheric Imaging Assembly (AIA) 171 Å channel is getting heated to higher temperatures corresponding to AIA 193 and 211 Å channels. We have calculated an increase of 6%–9% in density and 5%–6% in temperature during the passage of the EUV wave. We have compared the variation in temperature with the adiabatic relationship and have quantitatively demonstrated the phenomenon of heating due to adiabatic compression at the wave front. However, the cooling phase does not follow adiabatic relaxation but shows slow decay indicating slow energy release being triggered by the wave passage. We have also identified that heating is taking place at the front of the wave pulse rather than at the rear. Our results provide support for the case that the event under study here is a compressive fast-mode wave or a shock.

  9. Physikgeschichte Das Rätsel bleibt

    NASA Astrophysics Data System (ADS)

    Hoffmann, Dieter

    2002-05-01

    Die jüngst erfolgte Veröffentlichung von Dokumenten aus dem Privatarchiv der Familie Bohr [1] über den geheimnisumwitterten Besuch von Werner Heisenberg in Kopenhagen im September 1941 hat in den deutschen Medien große Resonanz gefunden [2]. Tatsächlich verraten uns die jetzt veröffentlichten Dokumente sehr viel mehr über die Zeit ihres Entstehens als über den Besuch selbst.

  10. 25 Jahre - Institut fuer Geodaesie, Teil 2: Forschungsarbeiten und Veroeffentlichungen (25 Years - Institute of Geodesy, Part 2: Research Areas and Publications)

    DTIC Science & Technology

    2000-01-01

    Festpunktfeld Ruanda - 1992 - SIRGAS ( Sistema de refer6ncia geocdntrico para Amdrica del Sur) - 1995 - Festpunktfeld Per6 - 1996 Die DOENAV-Kampagne...Forschungsschwerpunkte Mit dem Sistema di Referdncia Geoc6ntrico para a Amd~rica do Sul (SIRGAS) wurde 1995 in einer Gerneinschaftsaktion aller... digitaler Form gespei- chert werden. Aus demn dabei anfallenden redundanten Datensatz erhalt man im Wege einer Ausgleichung den H6henunterschied

  11. Experimental Validation of a Differential Variational Inequality-Based Approach for Handling Friction and Contact in Vehicle

    DTIC Science & Technology

    2015-11-20

    Friction and Contact in Vehicle/Granular-Terrain Interaction Daniel Melanza,b, Paramsothy Jayakumara, Dan Negrutb aU.S. Army Tank Automotive Research...Handling Friction and Contact in Vehicle 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Daniel Melanz; Paramsothy...and non-homogeneity. There are multiple formulations of DEM, classified based on how the contact and impact are handled when two bodies collide. This

  12. Materials Data on KP2AuS7 (SG:15) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-11

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  13. Zweiwegintegration durch zweisprachige Bildung? Ergebnisse aus der Staatlichen Europa-Schule Berlin

    NASA Astrophysics Data System (ADS)

    Meier, Gabriela

    2012-06-01

    While there is no simple recipe of how to respond to the multitude of languages present in many European schools, this article presents a promising alternative to monolingual education. The focus is on Staatliche Europa-Schule Berlin (SESB), a two-way immersion (TWI) model that unites children whose mother tongue is German with children whose mother tongue is another locally spoken language in one class and teaches them together in two languages. Thus in this model, offered by 17 primary schools and 13 secondary schools in Berlin, pupils learn in two languages from and with each other. Based on a largely quantitative, quasi-experimental study with 603 students, evidence is provided that there are a number of peace-linguistic benefits that can promote two-way social integration, besides fostering personal and societal multilingualism. This suggests that TWI education as practised in Berlin could serve as an educational model for other multilingual parts of Europe.

  14. Drei neue gamma-Doradus-Sterne aus der ASAS-3 Datenbank

    NASA Astrophysics Data System (ADS)

    Bernhard, Klaus; Huemmerich, Stefan

    2016-02-01

    By analysis of data from the ASAS-3 archive, the stars HD 18011, NSV 16873 and NSV 3272 were identified as multiperiodic gamma Doradus variables. Essential information on these variables is presented, along with unwhitened frequency spectra and statistically significant frequencies, as derived with Period 04.

  15. More Effective Aid Policy? AusAID and the Global Development Agenda

    ERIC Educational Resources Information Center

    Cassity, Elizabeth A.

    2008-01-01

    A first glance at almost any policy document generated by a bilateral or multilateral donor agency reveals a familiar rhetoric of participation, partnership, community, good governance, growth and strong democracy as key ingredients for a successful development program. While some critics of this rhetoric argue that this is merely a recasting of…

  16. Persönlichkeitsentwicklung als ziel der Bildung: Aus der Sicht eines Psychologen

    NASA Astrophysics Data System (ADS)

    Heinze, Burger

    1990-06-01

    Personality, which is a term almost always used in a positive sense, does not exist from the moment of birth, but it develops under the influence of heredity and environment. Adolescence, which is seen as a transition from childhood to adulthood, raises difficulties in many modern industrialized countries as a result of the often arduous search for individual identity. In this context identity is seen as an interaction between heredity and environment. While developing his own personality, the young person has to maintain an integral existence vis-à-vis himself, society and life. Psychology defines the personality as the sum of numerous psychological characteristics, through which differences between people are revealed. The development of these characteristics is to be seen in the environment, maturation and actions of the individual. It can be subdivided into causes, conditions and processes. Finally the article discusses various aspects of the general question of education. The author concludes that the development of the personality should be an aim of education, but that this aim is presently unattainable because of a lack of clarity in the concept of education.

  17. Materials Data on Ag4AuS2 (SG:10) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2016-04-22

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. National Stocktake of Early Intervention Programs--July 1998. AusEkit Number 1.

    ERIC Educational Resources Information Center

    Davis, Cathy; Martin, Graham; Kosky, Robert; O'Hanlon, Anne

    This project consists of three interrelated streams which aim to: (1) develop and maintain a national network of mental health service providers, and an easily accessible clearinghouse of relevant information, to facilitate the development of innovative early intervention services across Australia; (2) address challenges in reorienting service…

  19. Materials Data on K3AuSe13 (SG:13) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Auranofin disrupts selenium metabolism in Clostridium difficile by forming a stable Au-Se adduct.

    PubMed

    Jackson-Rosario, Sarah; Cowart, Darin; Myers, Andrew; Tarrien, Rebecca; Levine, Rodney L; Scott, Robert A; Self, William Thomas

    2009-05-01

    Clostridium difficile is a nosocomial pathogen whose incidence and importance are on the rise. Previous work in our laboratory characterized the central role of selenoenzyme-dependent Stickland reactions in C. difficile metabolism. In this work we have identified, using mass spectrometry, a stable complex formed upon reaction of auranofin (a gold-containing drug) with selenide in vitro. X-ray absorption spectroscopy supports the structure that we proposed on the basis of mass-spectrometric data. Auranofin potently inhibits the growth of C. difficile but does not similarly affect other clostridia that do not utilize selenoproteins to obtain energy. Moreover, auranofin inhibits the incorporation of radioisotope selenium ((75)Se) in selenoproteins in both Escherichia coli, the prokaryotic model for selenoprotein synthesis, and C. difficile without impacting total protein synthesis. Auranofin blocks the uptake of selenium and results in the accumulation of the auranofin-selenide adduct in the culture medium. Addition of selenium in the form of selenite or L-selenocysteine to the growth medium significantly reduces the inhibitory action of auranofin on the growth of C. difficile. On the basis of these results, we propose that formation of this complex and the subsequent deficiency in available selenium for selenoprotein synthesis is the mechanism by which auranofin inhibits C. difficile growth. This study demonstrates that targeting selenium metabolism provides a new avenue for antimicrobial development against C. difficile and other selenium-dependent pathogens.

  1. Keplers Weg der Erforschung der wahren Planetenbahn. Ergebnisse aus der Durchsicht der handschriftlichen Manuskripte.

    NASA Astrophysics Data System (ADS)

    Bialas, V.

    The handwriting manuscripts with Kepler's preliminary studies for his Astronomia Nova (some 700 pages) represent the most important source material. By reconstructing his mathematical-geometrical considerations of planetary astronomy, especially his hypothesis vicaria and the introduction of an oval orbit, here modern mathematical formulas are used. A smaller part of the manuscripts deals with Kepler's - so to speak - "speculative" physics as actual cause of the planetary motion. The whole handwriting material together with a detailed commentary will be published in the next volume of the Munich Kepler Edition in 1998.

  2. Umweltrelevanz von natürlichen polyzyklischen aromatischen Kohlenwasserstoffen aus Steinkohlen - eine Übersicht

    NASA Astrophysics Data System (ADS)

    Achten, C.; Hofmann, T.

    2010-03-01

    Releases of PAHs from hard (bituminous) coals into the environment have not been widely recognized. In hard coals, some hundreds of mg/kg of EPA-PAH and some thousands of mg/kg total PAH concentrations can occur and the concentrations vary significantly depending on hard coal maturity and origin. Highest PAH concentrations are present in the maturity range of the so-called “oil-window” (high volatile bituminous coal rank), however there is no general correlation. Only coals from the same origin can be compared. Naphthalene and phenanthrene as well as their alkylated derivatives are the dominant single polyaromatic compounds in hard coals. The PAH distribution patterns change with increasing rank from the low molecular weight, mostly alkylated compounds with linkage to the original organic material to the predominantly higher molecular weight parent compounds. The former are characteristic for coals of petrogenic origin and the latter for those of pyrogenic origin. Currently, PAHs from coals and from crude oil and its products cannot be distinguished by use of common simple diagnostic parameters. In countries holding large coal basins and associated mining activity, coal particles can comprise 10-15 % of the sediment or soil. Until today, little has been known about desorption and bioavailability of native PAH from coals. Literature studies so far show slow and very slow desorption and hardly any or no effects on organisms. This shows that there is a lack of systematic studies using heterogeneous coals from different countries. Bioavailability of PAH from coal particles in soils and sediments has an impact on risk assessment and should be included in sediment and soil standards.

  3. Do different medical curricula influence self-assessed clinical thinking of students?

    PubMed

    Gehlhar, Kirsten; Klimke-Jung, Kathrin; Stosch, Christoph; Fischer, Martin R

    2014-01-01

    Zielsetzung: Das klinische Denken ist eine zentrale Grundlage des ärztlichen Handelns und sollte durch das Studium in den humanmedizinischen Studiengängen gefördert werden. Welche Lehr- und Lernformen hierzu vor allem beitragen, ist bis heute allerdings noch nicht abschließend gezeigt. Zur Messung der wissensunabhängigen Komponente des klinischen Denkens wurde das Diagnostic Thinking Inventory (DTI) entwickelt. Die vorliegende Pilotstudie untersucht, ob dieses Instrument dazu geeignet ist, Unterschiede im klinischen Denken von Studierenden in unterschiedlichen Ausbildungsabschnitten dreier medizinischer Curricula aufzuzeigen. Methodik: Das Diagnostic Thinking Inventory (DTI) umfasst 41 Items in zwei Subskalen („Flexibilität des Denkens“ und „Strukturierung des Wissens“). Jedes Item enthält eine Aussage oder Feststellung über das klinische Denken in Form eines Stammes und darunter jeweils eine 6-Punkt-Skala an deren beiden Enden gegensätzliche Aussagen stehen. Zwischen diesen beiden Extremen sollen die Probanden ihr eigenes klinisches Denken einordnen. Die deutsche Übersetzung des DTI wurde von 247 freiwilligen Studierenden aus drei Fakultäten und verschiedenen klinischen Semestern ausgefüllt. In einem quasi experimentellen Design waren 219 Teilnehmer aus Regel- und Modellstudiengängen in Nordrheinwestfalen beteiligt, genauer aus dem 5., 6. und 8. Semester des Modellstudiengangs der Universität Witten/Herdecke (UW/H), aus dem Modell- (7. und 9. Semester) und Regelstudiengang (7. Semester) der Ruhr-Universität Bochum (RUB) und aus dem Modellstudiengang (9. Semester) der Universität zu Köln (UzK). Die gewonnenen Daten wurden quantitativ ausgewertet.Ergebnisse: Die Reliabilität des Gesamt-Fragebogens war gut (Cronbachs alpha zwischen 0,71 und 0,83); die Reliabilität der Subskalen lag zwischen 0,49 und 0,75. Die unterschiedlichen Gruppen wurden mittels Mann-Whitney Test miteinander verglichen. Dabei wurden signifikante Unterschiede sowohl

  4. Design und Analyse elektrisch kleiner Antennen für den Einsatz in UHF RFID Transpondern

    NASA Astrophysics Data System (ADS)

    Herschmann, R.; Camp, M.; Eul, H.

    2006-09-01

    RFID Systeme werden seit Anfang der neunziger Jahre mit stetig zunehmender Verbreitung im Bereich der automatischen Produktidentifikation, der Diebstahlsicherung (EAS, Electronic Article Surveillance) und für automatische Zutrittskontrollsysteme eingesetzt. Objekte werden hierzu mit einem Transponder ausgestattet, der aus einer Antenne und einem Chip auf einem Trägermaterial besteht. Von großem Interesse ist die Entwicklung und Optimierung von passiven Transpondern für den Einsatz in UHF RFID Systemen. Diese Transponder beziehen die Energie zum Betrieb des Chips aus dem elektromagnetischen Feld einer Schreib-Leseeinheit. Hierfür ist neben der Anpassung der Eingangsimpedanz der Antenne an die Chipimpedanz auch eine möglichst hohe Bandbreite der Antennen wünschenswert, um die Funktion des Transponders bei Schwankungen der Chipimpedanz und variablen Umgebungsparametern zu gewährleisten. Der aus Platzgründen notwendige Einsatz elektrisch kleiner Antennen bedingt eine möglichst optimale Ausnutzung der zur Verfügung stehenden Fläche auf dem Trägermaterial zur Aufnahme der Antenne. Die vorliegende Arbeit beschreibt ein Verfahren zur Analyse und Synthese neuartiger Antennendesigns auf der Basis parametrisierter meandrierter, spiralförmiger und logarithmisch periodischer Dipole.

  5. The Learning Objective Catalogue for Patient Safety in Undergraduate Medical Education--A Position Statement of the Committee for Patient Safety and Error Management of the German Association for Medical Education.

    PubMed

    Kiesewetter, Jan; Gutmann, Johanna; Drossard, Sabine; Gurrea Salas, David; Prodinger, Wolfgang; Mc Dermott, Fiona; Urban, Bert; Staender, Sven; Baschnegger, Heiko; Hoffmann, Gordon; Hübsch, Grit; Scholz, Christoph; Meier, Anke; Wegscheider, Mirko; Hoffmann, Nicolas; Ohlenbusch-Harke, Theda; Keil, Stephanie; Schirlo, Christian; Kühne-Eversmann, Lisa; Heitzmann, Nicole; Busemann, Alexandra; Koechel, Ansgar; Manser, Tanja; Welbergen, Lena; Kiesewetter, Isabel

    2016-01-01

    Hintergrund: Seit dem vom Institute of Medicine im Jahr 2000 veröffentlichten Bericht „To err is human“ rückten die Themen Patientensicherheit und Fehlermanagement zunehmend in den wissenschaftlichen und politischen Fokus. Obwohl sich dem Thema bereits international auf verschiedensten Ebenen angenähert wurde, fehlt bislang eine strukturierte und flächendeckende Ausbildung von Ärztinnen und Ärzten in diesem Bereich.Ziele: Mit dem im Folgenden beschriebenen Lernzielkatalog Patientensicherheit möchte der Ausschuss für Patientensicherheit und Fehlermanagement der Gesellschaft für medizinische Ausbildung (GMA) eine erste gemeinsame Grundlage für die Implementierung strukturierter Patientensicherheitscurricula zur Ausbildung der Medizinstudierenden an medizinischen Fakultäten im deutschsprachigen Raum schaffen.Methoden: Die Erarbeitung des Lernzielkataloges erfolgte unter Beteiligung von 13 medizinischen Fakultäten im Rahmen von zwei Ausschusstreffen, zwei mehrtägigen Workshops und mit Hilfe von Beurteilungen durch externe fachliche Expertinnen und Experten.Ergebnisse: Der vom Ausschuss für Patientensicherheit und Fehlermanagement der GMA entwickelte Lernzielkatalog Patientensicherheit für das Medizinstudium besteht aus den drei Kapiteln: Grundlagen, Erkennen von Ursachen als Basis für proaktives Handeln und Lösungsansätze. Die Lernziele innerhalb der Kapitel sind hierarchisch auf drei Ebenen organisiert. Insgesamt beinhaltet der Lernzielkatalog 38 Lernziele. Alle Lernziele wurden mit dem Nationalen Kompetenzbasierten Lernzielkatalog Medizin referenziert. Diskussion: Der vorliegende Lernzielkatalog ist ein Produkt der Zusammenarbeit von Vertretern aus immerhin 13 medizinischen Fakultäten. Er soll im deutschsprachigen Raum die Diskussion des Themas Patientensicherheit und Fehlermanagement im Fach Medizin und die Entwicklung entsprechender Ausbildungsstrukturen voranbringen. Zukünftig kann der Lernzielkatalog Patientensicherheit für das

  6. Biokompatible Polymere

    NASA Astrophysics Data System (ADS)

    Ha, Suk-Woo; Wintermantel, Erich; Maier, Gerhard

    Der klinische Einsatz von synthetischen Polymeren begann in den 60-er Jahren in Form von Einwegartikeln, wie beispielsweise Spritzen und Kathetern, vor allem aufgrund der Tatsache, dass Infektionen infolge nicht ausreichender Sterilität der wiederverwendbaren Artikel aus Glas und metallischen Werkstoffen durch den Einsatz von sterilen Einwegartikeln signifikant reduziert werden konnten [1]. Die Einführung der medizinischen Einwegartikel aus Polymeren erfolgte somit nicht nur aus ökonomischen, sondern auch aus hygienischen Gründen. Wegen der steigenden Anzahl synthetischer Polymere und dem zunehmenden Bedarf an ärztlicher Versorgung reicht die Anwendung von Polymeren in der Medizin von preisgünstigen Einwegartikeln, die nur kurzzeitig intrakorporal eingesetzt werden, bis hin zu Implantaten, welche über eine längere Zeit grossen Beanspruchungen im menschlichen Körper ausgesetzt sind. Die steigende Verbreitung von klinisch eingesetzten Polymeren ist auf ihre einfache und preisgünstige Verarbeitbarkeit in eine Vielzahl von Formen und Geometrien sowie auf ihr breites Eigenschaftsspektrum zurückzuführen. Polymere werden daher in fast allen medizinischen Bereichen eingesetzt.

  7. Osteognathostomata

    NASA Astrophysics Data System (ADS)

    Schultze, Hans-Peter

    Noch häufig, vor allem im englischen Sprachraum, wird für die fischartigen Wirbeltiere mit Knochenskelett, also die Actinopterygii und Sarcopterygii, der Begriff "Osteichthyes" (Knochenfische) verwendet. Da sich jedoch aus einem Subtaxon der Sarcopterygier die Tet rapoda entwickelten (S. 322), würde diese Gruppierung ein paraphyletisches Taxon darstellen. Hier wird daher dem Vorschlag W. Hennigs (1983) gefolgt und die Schwestergruppe der Chondrichthyes Osteognathostomata genannt: Sie enthält alle weiteren kiefertragenden Wirbeltiere mit Knochenskelett (Name!) (Abb. 201). Die Sarcopterygii umfassen demnach verschiedene fossile Gruppen, die rezenten Reliktgruppen der Dipnoi (Lungenfische) und Actinistia (Hohlstachler) sowie die Tetrapoda und ihre Stammgruppenvertreter. (Neuerdings wird in der Literatur aus denselben Gründen einer konsequent phylogenetischen Systematisierung wieder die Gruppierung Osteichthyes, aber unter Einschluss der Tetrapoda, verwendet!).

  8. Statistik in Naturwissenschaft und Technik

    NASA Astrophysics Data System (ADS)

    Wilrich, Peter-Theodor

    Mit dem Aufschwung von Naturwissenschaft und Technik zu Beginn des 19. Jahrhunderts entstand die mathematische Statistik, angeregt aus der Geodäsie (wie die Methode der kleinsten Quadrate) und der Anthropologie (wie die statistische Analyse mehrdimensionaler Beobachtungen und ihrer stochastischen Abhängigkeiten). Im Gegensatz zu den Wirtschafts- und Sozialwissenschaften, in denen Daten vorwiegend aus Beobachtungsstudien gewonnen werden, stehen in den Naturwissenschaften Experimente im Vordergrund. Daher gehört die statistische Versuchsplanung zu den insbesondere in Naturwissenschaft und Technik angewendeten statistischen Methoden, aber auch die Extremwertstatistik und Lebensdaueranalysen sowie die Methoden der räumlichen Statistik (insbesondere in der Umweltforschung). Im 20. Jahrhundert wurden Stichprobenpläne und Regelkarten (Kontrollkarten) zur Prozessregelung als Hilfsmittel der statistischen Qualitätssicherung entwickelt. Diese Methodenbündel, mit denen sich der Ausschuss Statistik in Naturwissenschaft und Technik immer wieder befasst, werden im Folgenden vorgestellt.

  9. Unfälle mit Kleintransportern

    NASA Astrophysics Data System (ADS)

    Tschirschwitz, Christian

    Auf einer außerörtlichen Bundesstraße geriet ein mit vier Personen besetzter Pkw Toyota Corolla aus letztlich nicht vollständig geklärten Gründen ins Schleudern. Nachdem sich das Fahrzeug beträchtlich entgegen dem Uhrzeigersinn ausgedreht hatte, prallte ein entgegenkommender Kleintransporter VW T4 frontal an die rechte Flanke des Toyota. Der Transporter wurde gedreht, ausgehoben und durch einen Pkw Ford Escort unterfahren. Alle Fahrzeuge kamen in Kollisionsortnähe zum Endstand. Die vier Toyota-Insassen wurden getötet. Aus den anderen Fahrzeugen wurden sechs Personen überwiegend schwer verletzt. Unbeteiligte Zeugen waren nicht vorhanden.

  10. Sitzungsberichte der Heidelberger Akademie der Wissenschaften¬Jahrgang 1990 Sitzungsber.Heidelberg 90¬"Gott hat die Natur einfältig gemacht, sie aber suchen viel Künste"

    NASA Astrophysics Data System (ADS)

    Zehe, Horst

    Der Aufsatz demonstriert anhand ausgiebig kommentierter zeitgenössischer Zeugnisse Goethes Reaktion auf die Arbeiten Fraunhofers, insbesondere auf die Entdeckung der dunklen Linien im Sonnenspektrum. Den Fehlurteilen Goethes werden dabei die Urteile zeitgenössischer Physiker wie Chladni und J.F.W. Herschel gegenübergestellt. Bislang noch ungedruckte Dokumente aus dem Weimarer Goethe- und Schiller-Archiv belegen, daß sich Goethe nicht nur literarisch mit Fraunhofer beschäftigte, sondern daß er auch dessen Versuche mit Hilfe des Jenaer Universitätsmechanikers Körner getreulich zu wiederholen suchte.

  11. Sitzungsberichte der Heidelberger Akademie der Wissenschaften> " Jahrgang 1990 Sitzungsber.Heidelberg 90 " "Gott hat die Natur einfältig gemacht, sie aber suchen viel Künste"

    NASA Astrophysics Data System (ADS)

    Zehe, Horst

    Der Aufsatz demonstriert anhand ausgiebig kommentierter zeitgenössischer Zeugnisse Goethes Reaktion auf die Arbeiten Fraunhofers, insbesondere auf die Entdeckung der dunklen Linien im Sonnenspektrum. Den Fehlurteilen Goethes werden dabei die Urteile zeitgenössischer Physiker wie Chladni und J.F.W. Herschel gegenübergestellt. Bislang noch ungedruckte Dokumente aus dem Weimarer Goethe- und Schiller-Archiv belegen, daß sich Goethe nicht nur literarisch mit Fraunhofer beschäftigte, sondern daß er auch dessen Versuche mit Hilfe des Jenaer Universitätsmechanikers Körner getreulich zu wiederholen suchte.

  12. PCR und Real-Time PCR

    NASA Astrophysics Data System (ADS)

    Konrad, Regina; Busch, Ulrich

    Die vielfältigen Anwendungsmöglichkeiten der Polymerasekettenreaktion (polymerase chain reaction, PCR) machen sie zu einer der wichtigsten und am häufigsten eingesetzten Methoden in der molekularbiologischen Forschung und Diagnostik. Für diese Technologie wurde der Erfinder der Methode, Kary Mullis, 1993 mit dem Nobelpreis ausgezeichnet. Die PCR erlaubt einen hochsensitiven und spezifischen in-vitro-Nachweis von Desoxyribonukleinsäuren (DNA), da im Zuge der Reaktion Sequenzabschnitte gezielt vermehrt werden. Innerhalb weniger Stunden können aus einem einzigen Zielmolekül 1012 identische Moleküle entstehen [1].

  13. Werkzeugverschleißdetektion beim Fräsen mittels Infrarotmesstechnik

    NASA Astrophysics Data System (ADS)

    Pittner, Walter

    Heute ist es praxisüblich, bei der spanenden Bearbeitung mittels definierter Schneide die Werkzeuge aus Gründen der Qualitätssicherung vorzeitig, im Allgemeinen nach Ermessen des Maschinenbedieners, zu wechseln. Dadurch entstehen zwangsläufig höhere Werkzeugkosten als notwendig, die dann an den Verbraucher weitergegeben werden. Wird jedoch ein rechtzeitiger Werkzeugwechsel verpasst, so entstehen insbesondere bei Hochleistungsbearbeitungsprozessen hohe Ausschussraten. Daher sollte die Entscheidung zum Werkzeugwechsel nicht mehr dem Maschinenbediener allein überlassen werden [1, 2].