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Sample records for accuracy digital elevation

  1. Accuracy and reliability of the Hungarian digital elevation model (DEM)

    NASA Astrophysics Data System (ADS)

    Detrekoi, Akos; Melykuti, Gabor; Szabo, Gyorgy

    1994-08-01

    In the period 1991-92 a 50 X 50 meter grid digital elevation model (DEM) was created in Hungary. The design and the quality control of DEM are discussed in this paper. The paper has three parts: (1) the data acquisition methods for DEM by scanning and photogrammetry are discussed, (2) a general overview about the accuracy and reliability of DEMs is given, and (3) the algorithm for the checking of data and some general conclusions about the control activity of the Hungarian DEM are reviewed.

  2. Analysis of accuracy of digital elevation models created from captured data by digital photogrammetry method

    NASA Astrophysics Data System (ADS)

    Hudec, P.

    2011-12-01

    A digital elevation model (DEM) is an important part of many geoinformatic applications. For the creation of DEM, spatial data collected by geodetic measurements in the field, photogrammetric processing of aerial survey photographs, laser scanning and secondary sources (analogue maps) are used. It is very important from a user's point of view to know the vertical accuracy of a DEM. The article describes the verification of the vertical accuracy of a DEM for the region of Medzibodrožie, which was created using digital photogrammetry for the purposes of water resources management and modeling and resolving flood cases based on geodetic measurements in the field.

  3. Assessment of Required Accuracy of Digital Elevation Data for Hydrologic Modeling

    NASA Technical Reports Server (NTRS)

    Kenward, T.; Lettenmaier, D. P.

    1997-01-01

    The effect of vertical accuracy of Digital Elevation Models (DEMs) on hydrologic models is evaluated by comparing three DEMs and resulting hydrologic model predictions applied to a 7.2 sq km USDA - ARS watershed at Mahantango Creek, PA. The high resolution (5 m) DEM was resempled to a 30 m resolution using method that constrained the spatial structure of the elevations to be comparable with the USGS and SIR-C DEMs. This resulting 30 m DEM was used as the reference product for subsequent comparisons. Spatial fields of directly derived quantities, such as elevation differences, slope, and contributing area, were compared to the reference product, as were hydrologic model output fields derived using each of the three DEMs at the common 30 m spatial resolution.

  4. Accuracy assessment of photogrammetric digital elevation models generated for the Schultz Fire burn area

    NASA Astrophysics Data System (ADS)

    Muise, Danna K.

    This paper evaluates the accuracy of two digital photogrammetric software programs (ERDAS Imagine LPS and PCI Geomatica OrthoEngine) with respect to high-resolution terrain modeling in a complex topographic setting affected by fire and flooding. The site investigated is the 2010 Schultz Fire burn area, situated on the eastern edge of the San Francisco Peaks approximately 10 km northeast of Flagstaff, Arizona. Here, the fire coupled with monsoon rains typical of northern Arizona drastically altered the terrain of the steep mountainous slopes and residential areas below the burn area. To quantify these changes, high resolution (1 m and 3 m) digital elevation models (DEMs) were generated of the burn area using color stereoscopic aerial photographs taken at a scale of approximately 1:12000. Using a combination of pre-marked and post-marked ground control points (GCPs), I first used ERDAS Imagine LPS to generate a 3 m DEM covering 8365 ha of the affected area. This data was then compared to a reference DEM (USGS 10 m) to evaluate the accuracy of the resultant DEM. Findings were then divided into blunders (errors) and bias (slight differences) and further analyzed to determine if different factors (elevation, slope, aspect and burn severity) affected the accuracy of the DEM. Results indicated that both blunders and bias increased with an increase in slope, elevation and burn severity. It was also found that southern facing slopes contained the highest amount of bias while northern facing slopes contained the highest proportion of blunders. Further investigations compared a 1 m DEM generated using ERDAS Imagine LPS with a 1 m DEM generated using PCI Geomatica OrthoEngine for a specific region of the burn area. This area was limited to the overlap of two images due to OrthoEngine requiring at least three GCPs to be located in the overlap of the imagery. Results indicated that although LPS produced a less accurate DEM, it was much more flexible than OrthoEngine. It was also

  5. Statistical Evaluation of Fitting Accuracy of Global and Local Digital Elevation Models in Iran

    NASA Astrophysics Data System (ADS)

    Alidoost, F.; Samadzadegan, F.

    2013-09-01

    Digital Elevation Models (DEMs) are one of the most important data for various applications such as hydrological studies, topography mapping and ortho image generation. There are well-known DEMs of the whole world that represent the terrain's surface at variable resolution and they are also freely available for 99% of the globe. However, it is necessary to assess the quality of the global DEMs for the regional scale applications.These models are evaluated by differencing with other reference DEMs or ground control points (GCPs) in order to estimate the quality and accuracy parameters over different land cover types. In this paper, a comparison of ASTER GDEM ver2, SRTM DEM with more than 800 reference GCPs and also with a local elevation model over the area of Iran is presented. This study investigates DEM's characteristics such as systematic error (bias), vertical accuracy and outliers for DEMs using both the usual (Mean error, Root Mean Square Error, Standard Deviation) and the robust (Median, Normalized Median Absolute Deviation, Sample Quantiles) descriptors. Also, the visual assessment tools are used to illustrate the quality of DEMs, such as normalized histograms and Q-Q plots. The results of the study confirmed that there is a negative elevation bias of approximately 5 meters of GDEM ver2. The measured RMSE and NMAD for elevation differences of GDEM-GCPs are 7.1 m and 3.2 m, respectively, while these values for SRTM and GCPs are 9.0 m and 4.4 m. On the other hand, in comparison with the local DEM, GDEM ver2 exhibits the RMSE of about 6.7 m, a little higher than the RMSE of SRTM (5.1 m).The results of height difference classification and other statistical analysis of GDEM ver2-local DEM and SRTM-local DEM reveal that SRTM is slightly more accurate than GDEM ver2. Accordingly, SRTM has no noticeable bias and shift from Local DEM and they have more consistency to each other, while GDEM ver2 has always a negative bias.

  6. Application of the Shuttle Laser Altimeter in an Accuracy Assessment of Global 1-Kilometer Digital Elevation Data

    NASA Technical Reports Server (NTRS)

    Harding, David J.; Carabajal, Claudia C.; Luthcke, Scott B.; Gesch, Dean B.

    1998-01-01

    Shuttle Laser Altimeter (SLA) data have been used to evaluate the accuracy of GTOPO30, the first comprehensive, 1 km resolution, global topographic data set. GTOPO30 was developed by the USGS Eros Data Center (EDC), in part, to address NASA's needs for a global topographic model in support of remote sensing instruments aboard the Earth Observing System AM-1 spacecraft. SLA flew as a part of the STS-72 mission in January, 1996 observing the latitude band from +/- 28.5 deg, and on STS-85 in August, 1997 extending the observations to +/- 57 deg. Combining the SLA ranging data with shuttle position and pointing knowledge yields surface elevation data of very high vertical accuracy in an Earth-centered, absolute reference frame (2.8 m rms difference for SLA-01 with respect to ocean reference surface). Use of the well-determined mean sea surface reference for calibration allows propagation of high accuracy altimetry onto the continents. 436,635 SLA-01 land elevations were compared to the GTOPO30 grid after conversion to a mean sea level vertical datum using the Earth Geoid Model 96, jointly developed by Goddard and NIMA. The comparison reveals systematic elevation biases in southern Asia, Africa, Australia, and south America on the order 10's to 100 meters in the GTOPO30 compilation on spatial scales of 100's to 1000's of kilometers. These biases are likely due to vertical datum errors in the topographic source materials used to compile GTOPO30, which primarily consist of Defense Mapping Agency (DMA) digital elevation and topographic map products. These biases imply that elevation corrections applied to land gravity measurements using these DMA source materials will be biased, leading to errors in geoid models incorporating these land gravity data.

  7. Accuracy assessment of airborne photogrammetrically derived high-resolution digital elevation models in a high mountain environment

    NASA Astrophysics Data System (ADS)

    Müller, Johann; Gärtner-Roer, Isabelle; Thee, Patrick; Ginzler, Christian

    2014-12-01

    High-resolution digital elevation models (DEMs) generated by airborne remote sensing are frequently used to analyze landform structures (monotemporal) and geomorphological processes (multitemporal) in remote areas or areas of extreme terrain. In order to assess and quantify such structures and processes it is necessary to know the absolute accuracy of the available DEMs. This study assesses the absolute vertical accuracy of DEMs generated by the High Resolution Stereo Camera-Airborne (HRSC-A), the Leica Airborne Digital Sensors 40/80 (ADS40 and ADS80) and the analogue camera system RC30. The study area is located in the Turtmann valley, Valais, Switzerland, a glacially and periglacially formed hanging valley stretching from 2400 m to 3300 m a.s.l. The photogrammetrically derived DEMs are evaluated against geodetic field measurements and an airborne laser scan (ALS). Traditional and robust global and local accuracy measurements are used to describe the vertical quality of the DEMs, which show a non Gaussian distribution of errors. The results show that all four sensor systems produce DEMs with similar accuracy despite their different setups and generations. The ADS40 and ADS80 (both with a ground sampling distance of 0.50 m) generate the most accurate DEMs in complex high mountain areas with a RMSE of 0.8 m and NMAD of 0.6 m They also show the highest accuracy relating to flying height (0.14‰). The pushbroom scanning system HRSC-A produces a RMSE of 1.03 m and a NMAD of 0.83 m (0.21‰ accuracy of the flying height and 10 times the ground sampling distance). The analogue camera system RC30 produces DEMs with a vertical accuracy of 1.30 m RMSE and 0.83 m NMAD (0.17‰ accuracy of the flying height and two times the ground sampling distance). It is also shown that the performance of the DEMs strongly depends on the inclination of the terrain. The RMSE of areas up to an inclination <40° is better than 1 m. In more inclined areas the error and outlier occurrence

  8. Accuracy of interpolation techniques for the derivation of digital elevation models in relation to landform types and data density

    NASA Astrophysics Data System (ADS)

    Chaplot, Vincent; Darboux, Frédéric; Bourennane, Hocine; Leguédois, Sophie; Silvera, Norbert; Phachomphon, Konngkeo

    2006-07-01

    One of the most important scientific challenges of digital elevation modeling is the development of numerical representations of large areas with a high resolution. Although there have been many studies on the accuracy of interpolation techniques for the generation of digital elevation models (DEMs) in relation to landform types and data quantity or density, there is still a need to evaluate the performance of these techniques on natural landscapes of differing morphologies and over a large range of scales. To perform such an evaluation, we investigated a total of six sites, three in the mountainous region of northern Laos and three in the more gentle landscape of western France, with various surface areas from micro-plots, hillslopes, and catchments. The techniques used for the interpolation of point height data with density values from 4 to 10 9 points/km 2 include: inverse distance weighting (IDW), ordinary kriging (OK), universal kriging (UK), multiquadratic radial basis function (MRBF), and regularized spline with tension (RST). The study sites exhibited coefficients of variation (CV) of altitude between 12% and 78%, and isotropic to anisotropic spatial structures with strengths from weak (with a nugget/sill ratio of 0.8) to strong (0.01). Irrespective of the spatial scales or the variability and spatial structure of altitude, few differences existed between the interpolation methods if the sampling density was high, although MRBF performed slightly better. However, at lower sampling densities, kriging yielded the best estimations for landscapes with strong spatial structure, low CV and low anisotropy, while RST yielded the best estimations for landscapes with low CV and weak spatial structure. Under conditions of high CV, strong spatial structure and strong anisotropy, IDW performed slightly better than the other method. The prediction errors in height estimation are discussed in relation to the possible interactions with spatial scale, landform types, and

  9. Digital Elevation Models

    USGS Publications Warehouse

    U.S. Geological Survey

    1993-01-01

    The Earth Science Information Center (ESIC) distributes digital cartographic/geographic data files produced by the U.S. Geological Survey (USGS) as part of the National Mapping Program. Digital cartographic data files may be grouped into four basic types. The first of these, called a Digital Line Graph (DLG), is the line map information in digital form. These data files include information on base data categories, such as transportation, hypsography, hydrography, and boundaries. The second type, called a Digital Elevation Model (DEM), consists of a sampled array of elevations for a number of ground positions at regularly spaced intervals. The third type is Land Use and Land Cover digital data which provides information on nine major classes of land use such as urban, agricultural, or forest as well as associated map data such as political units and Federal land ownership. The fourth type, the Geographic Names Information System, provides primary information for all known places, features, and areas in the United States identified by a proper name.

  10. Fingerprinting digital elevation maps

    NASA Astrophysics Data System (ADS)

    Gou, Hongmei; Wu, Min

    2006-02-01

    Digital elevation maps (DEMs) provide a digital representation of 3-D terrain information. In civilian applications, high-precision DEMs carry a high commercial value owing to the large amount of effort in acquiring them; and in military applications, DEMs are often used to represent critical geospatial information in sensitive operations. These call for new technologies to prevent unauthorized distribution and to trace traitors in the event of information leak related to DEMs. In this paper, we propose a new digital fingerprinting technique to protect DEM data from illegal re-distribution. The proposed method enables reliable detection of fingerprints from both 3-D DEM data set and its 2-D rendering, whichever format that is available to a detector. Our method starts with extracting from a DEM a set of critical contours either corresponding to important topographic features of the terrain or having application-dependent importance. Fingerprints are then embedded into these critical contours by employing parametric curve modeling and spread spectrum embedding. Finally, a fingerprinted DEM is constructed to incorporate the marked 2-D contours. Through experimental results, we demonstrate the robustness of the proposed method against a number of challenging attacks applied to either DEMs or their contour representations.

  11. 1-Meter Digital Elevation Model specification

    USGS Publications Warehouse

    Arundel, Samantha T.; Archuleta, Christy-Ann M.; Phillips, Lori A.; Roche, Brittany L.; Constance, Eric W.

    2015-01-01

    In January 2015, the U.S. Geological Survey National Geospatial Technical Operations Center began producing the 1-Meter Digital Elevation Model data product. This new product was developed to provide high resolution bare-earth digital elevation models from light detection and ranging (lidar) elevation data and other elevation data collected over the conterminous United States (lower 48 States), Hawaii, and potentially Alaska and the U.S. territories. The 1-Meter Digital Elevation Model consists of hydroflattened, topographic bare-earth raster digital elevation models, with a 1-meter x 1-meter cell size, and is available in 10,000-meter x 10,000-meter square blocks with a 6-meter overlap. This report details the specifications required for the production of the 1-Meter Digital Elevation Model.

  12. The importance of the vertical accuracy of digital elevation models in gauging inundation by sea level rise along the Valdelagrana beach and marshes (Bay of Cádiz, SW Spain)

    NASA Astrophysics Data System (ADS)

    Fraile-Jurado, Pablo; Ojeda-Zújar, José

    2013-04-01

    The identification of potential coastal inundation caused by future sea level rise requires not only time series records from tide gauges, but also high-quality digital elevation models (DEMs). This study assesses the importance of DEM vertical accuracy in predicting inundation by sea level rise along the Valdelagrana beach and marshes of the Bay of Cádiz (SW Spain). A present-day (2000) and a projected (2100) high tide have been spatialized over a traditional (aerial photogrammetry) regional DEM of Andalusia with a horizontal spatial resolution of 10 m and a vertical accuracy of 0.68 m RMSE (root mean square error), and a LIDAR-derived DEM of the Valdelagrana study site with the same spatial resolution but a vertical accuracy of 0.205 m RMSE. The simulations are based on a bathtub model, which accounts for the effect of vertical barriers. The results reveal that the presence of infrastructures such as roads and salterns is the key to delimit the extent of water penetration during high tides in an otherwise homogeneously flat area comprising the beach and marshes of Valdelagrana. Moreover, in comparison with the highly accurate LIDAR DEM, the inundation areas derived from the lower-resolution DEM are overestimated by 72 % and 26 % for the present-day and future scenarios respectively. These findings demonstrate that DEM vertical accuracy is a critical variable in meaningfully gauging the impacts of sea level rise.

  13. Accuracy of Digital vs. Conventional Implant Impressions

    PubMed Central

    Lee, Sang J.; Betensky, Rebecca A.; Gianneschi, Grace E.; Gallucci, German O.

    2015-01-01

    The accuracy of digital impressions greatly influences the clinical viability in implant restorations. The aim of this study is to compare the accuracy of gypsum models acquired from the conventional implant impression to digitally milled models created from direct digitalization by three-dimensional analysis. Thirty gypsum and 30 digitally milled models impressed directly from a reference model were prepared. The models were scanned by a laboratory scanner and 30 STL datasets from each group were imported to an inspection software. The datasets were aligned to the reference dataset by a repeated best fit algorithm and 10 specified contact locations of interest were measured in mean volumetric deviations. The areas were pooled by cusps, fossae, interproximal contacts, horizontal and vertical axes of implant position and angulation. The pooled areas were statistically analysed by comparing each group to the reference model to investigate the mean volumetric deviations accounting for accuracy and standard deviations for precision. Milled models from digital impressions had comparable accuracy to gypsum models from conventional impressions. However, differences in fossae and vertical displacement of the implant position from the gypsum and digitally milled models compared to the reference model, exhibited statistical significance (p<0.001, p=0.020 respectively). PMID:24720423

  14. Accuracy evaluation of an ASTER-Derived Global Digital Elevation Model (GDEM) Version 1 and Version 2 for two sites in western Africa

    USGS Publications Warehouse

    Chirico, Peter G.; Malpeli, Katherine C.; Trimble, Sarah M.

    2012-01-01

    This study compares the ASTER Global DEM version 1 (GDEMv1) and version 2 (GDEMv2) for two study sites with distinct terrain and land cover characteristics in western Africa. The effects of land cover, slope, relief, and stack number are evaluated through both absolute and relative DEM statistical comparisons. While GDEMv2 at times performed better than GDEMv1, this improvement was not consistent, revealing the complex nature and interaction of terrain and land cover characteristics, which influences the accuracy of GDEM tiles on local and regional scales.

  15. Failure prediction in automatically generated digital elevation models

    NASA Astrophysics Data System (ADS)

    Gooch, M. J.; Chandler, J. H.

    2001-10-01

    Developments in digital photogrammetry have provided the ability to generate digital elevation models (DEMs) automatically and are increasingly used by geoscientists. Using overlapping imagery, dense grids of digital elevations can be collected at high speeds (150 points per second) with a high level of accuracy. The trend towards using PC-based hardware, the widespread use of geographical information systems, and the forthcoming availability of high-resolution satellite imagery over the Internet at ever lower costs mean that the use of automated digital photogrammetry for elevation modelling is likely to become more widespread. Automation can reduce the need for an in-depth knowledge of the subject thus rendering the technology an option for more users. One criticism of the trend towards the automated "black box" approach is the lack of quality control procedures within the software, particularly with reference to identifying areas of the DEM with low accuracy. The traditional method of accuracy assessment is through the use of check point data (data collected by an independent method which has a higher level of accuracy against which the DEM can be compared). Check point data are, however, rarely available and it is typically recommended that the user manually check and edit the data using stereo viewing methods, a potentially lengthy process which can negate the obvious speed advantages brought about by automation. A data processing model has been developed that is capable of identifying areas where elevations are unreliable and to which the user should pay attention when editing and checking the data. The software model developed will be explained and described in detail in the paper. Results from tests on different scales of imagery, different types of imagery and other software packages will also be presented to demonstrate the efficacy and significantly the generality of the technique with other digital photogrammetric software systems.

  16. The Rational Polynomial Coefficients Modification Using Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Alidoost, F.; Azizi, A.; Arefi, H.

    2015-12-01

    The high-resolution satellite imageries (HRSI) are as primary dataset for different applications such as DEM generation, 3D city mapping, change detection, monitoring, and deformation detection. The geo-location information of HRSI are stored in metadata called Rational Polynomial Coefficients (RPCs). There are many methods to improve and modify the RPCs in order to have a precise mapping. In this paper, an automatic approach is presented for the RPC modification using global Digital Elevation Models. The main steps of this approach are: relative digital elevation model generation, shift parameters calculation, sparse point cloud generation and shift correction, and rational polynomial fitting. Using some ground control points, the accuracy of the proposed method is evaluated based on statistical descriptors in which the results show that the geo-location accuracy of HRSI can be improved without using Ground Control Points (GCPs).

  17. US GeoData Digital Elevation Models

    USGS Publications Warehouse

    U.S. Geological Survey

    2000-01-01

    Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The U.S. Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.

  18. US GeoData digital elevation models

    USGS Publications Warehouse

    U.S. Geological Survey

    1997-01-01

    Digital elevation model (DEM) data consist of a sampled array of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. the U.S> Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.

  19. [True color accuracy in digital forensic photography].

    PubMed

    Ramsthaler, Frank; Birngruber, Christoph G; Kröll, Ann-Katrin; Kettner, Mattias; Verhoff, Marcel A

    2016-01-01

    Forensic photographs not only need to be unaltered and authentic and capture context-relevant images, along with certain minimum requirements for image sharpness and information density, but color accuracy also plays an important role, for instance, in the assessment of injuries or taphonomic stages, or in the identification and evaluation of traces from photos. The perception of color not only varies subjectively from person to person, but as a discrete property of an image, color in digital photos is also to a considerable extent influenced by technical factors such as lighting, acquisition settings, camera, and output medium (print, monitor). For these reasons, consistent color accuracy has so far been limited in digital photography. Because images usually contain a wealth of color information, especially for complex or composite colors or shades of color, and the wavelength-dependent sensitivity to factors such as light and shadow may vary between cameras, the usefulness of issuing general recommendations for camera capture settings is limited. Our results indicate that true image colors can best and most realistically be captured with the SpyderCheckr technical calibration tool for digital cameras tested in this study. Apart from aspects such as the simplicity and quickness of the calibration procedure, a further advantage of the tool is that the results are independent of the camera used and can also be used for the color management of output devices such as monitors and printers. The SpyderCheckr color-code patches allow true colors to be captured more realistically than with a manual white balance tool or an automatic flash. We therefore recommend that the use of a color management tool should be considered for the acquisition of all images that demand high true color accuracy (in particular in the setting of injury documentation). PMID:27386623

  20. Digital Elevation Models of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Cook, A. C.; Robinson, M. S.

    1999-01-01

    Several digital elevation models (DEMs) have been produced at a scale of 1km/pixel and covering approximately one-fifth of the lunar surface. These were produced mostly by semiautomatically matching the stereo available between Clementine UV/VIS images, although some localized DEMs have been produced by applying this technique to Apollo Metric stereo pairs, or by digitizing an existing Apollo Metric contour map. The DEMS that result from Clementine UV/VIS images, although Of Poorer height accuracy (1300-600 in for a single matched point) than the Clementine laser altimeter point measurements (<+/-100 m), do provide considerably higher spatial resolution (e.g., every kilometer vs. every tens of kilometers) and allow topography in the polar regions to be determined. Nadir-pointing Clementine UV-VIS stereo pairs are automatically stereo matched using a patch-based matcher and fed through A stereo intersection camera model to yield a digital terrain model (DTM) of longitude, latitude, and height points. The DTM for each stereo pair is then replotted and interpolated to form map-projected DEM tiles. The DEM files can then be fitted to absolute height laser altimeter points, or iteratively to each other, to form a DEM mosaic. Uncertainties in UV-VIS camera pointing and the need to accumulate a sufficiently good topographic S/N ratio necessitates the use of 1 km pixels for the UV-VIS derived DEMs. For Apollo Metric stereo, an internal camera geometry correction and a full photogrammetric block adjustment must be performed using ground- control points to derive a DEM. The image scale of Apollo Metric, as well as the stereo angle, allow for a DEM with 100 m pixels and a height accuracy of +/- 25m. Apollo Metric imagery had previously been used to derive contour maps for much of the lunar equatorial regions; however, to recover this information in digital form these maps must be digitized. Most of the mare areas mapped contain noticeable topographic noise. This results from

  1. Digital Elevation Model Mosaic of Mercury

    NASA Technical Reports Server (NTRS)

    Cook, A. C.; Watters, T. R.; Robinson, M. S.

    2001-01-01

    At CEPS (Center for Earth and Planetary Studies) work has been underway since 2000 to semi-automatically stereo match all Mariner 10 stereo pairs. The resulting matched image coordinates are converted into longitude, latitude, and height points and then combined to form a map projected Digital Elevation Model (DEM) mosaic of the planet's surface. Stereo images from Mariner 10 cover one quarter of the planet's surface, mostly in the southern hemisphere. Additional information is contained in the original extended abstract.

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

  4. Digital Elevation Models of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Cook, A. C.; Robinson, M. S.

    1999-01-01

    Several digital elevation models (DEMs) have been produced at a scale of 1km/pixel and covering approximately one-fifth of the lunar surface. These were produced mostly by semiautomatically matching the stereo available between Clementine UV/VIS images, although some localized DEMs have been produced by applying this technique to Apollo Metric stereo pairs, or by digitizing an existing Apollo Metric contour map. The DEMS that result from Clementine UV/VIS images, although Of Poorer height accuracy (1300-600 in for a single matched point) than the Clementine laser altimeter point measurements (<+/-100 m), do provide considerably higher spatial resolution (e.g., every kilometer vs. every tens of kilometers) and allow topography in the polar regions to be determined. Nadir-pointing Clementine UV-VIS stereo pairs are automatically stereo matched using a patch-based matcher and fed through A stereo intersection camera model to yield a digital terrain model (DTM) of longitude, latitude, and height points. The DTM for each stereo pair is then replotted and interpolated to form map-projected DEM tiles. The DEM files can then be fitted to absolute height laser altimeter points, or iteratively to each other, to form a DEM mosaic. Uncertainties in UV-VIS camera pointing and the need to accumulate a sufficiently good topographic S/N ratio necessitates the use of 1 km pixels for the UV-VIS derived DEMs. For Apollo Metric stereo, an internal camera geometry correction and a full photogrammetric block adjustment must be performed using ground- control points to derive a DEM. The image scale of Apollo Metric, as well as the stereo angle, allow for a DEM with 100 m pixels and a height accuracy of +/- 25m. Apollo Metric imagery had previously been used to derive contour maps for much of the lunar equatorial regions; however, to recover this information in digital form these maps must be digitized. Most of the mare areas mapped contain noticeable topographic noise. This results from

  5. Stochastic Downscaling of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Rasera, Luiz Gustavo; Mariethoz, Gregoire; Lane, Stuart N.

    2016-04-01

    High-resolution digital elevation models (HR-DEMs) are extremely important for the understanding of small-scale geomorphic processes in Alpine environments. In the last decade, remote sensing techniques have experienced a major technological evolution, enabling fast and precise acquisition of HR-DEMs. However, sensors designed to measure elevation data still feature different spatial resolution and coverage capabilities. Terrestrial altimetry allows the acquisition of HR-DEMs with centimeter to millimeter-level precision, but only within small spatial extents and often with dead ground problems. Conversely, satellite radiometric sensors are able to gather elevation measurements over large areas but with limited spatial resolution. In the present study, we propose an algorithm to downscale low-resolution satellite-based DEMs using topographic patterns extracted from HR-DEMs derived for example from ground-based and airborne altimetry. The method consists of a multiple-point geostatistical simulation technique able to generate high-resolution elevation data from low-resolution digital elevation models (LR-DEMs). Initially, two collocated DEMs with different spatial resolutions serve as an input to construct a database of topographic patterns, which is also used to infer the statistical relationships between the two scales. High-resolution elevation patterns are then retrieved from the database to downscale a LR-DEM through a stochastic simulation process. The output of the simulations are multiple equally probable DEMs with higher spatial resolution that also depict the large-scale geomorphic structures present in the original LR-DEM. As these multiple models reflect the uncertainty related to the downscaling, they can be employed to quantify the uncertainty of phenomena that are dependent on fine topography, such as catchment hydrological processes. The proposed methodology is illustrated for a case study in the Swiss Alps. A swissALTI3D HR-DEM (with 5 m resolution

  6. Geometric correction and digital elevation extraction using multiple MTI datasets

    USGS Publications Warehouse

    Mercier, Jeffrey A.; Schowengerdt, Robert A.; Storey, James C.; Smith, Jody L.

    2007-01-01

    Digital Elevation Models (DEMs) are traditionally acquired from a stereo pair of aerial photographs sequentially captured by an airborne metric camera. Standard DEM extraction techniques can be naturally extended to satellite imagery, but the particular characteristics of satellite imaging can cause difficulties. The spacecraft ephemeris with respect to the ground site during image collects is the most important factor in the elevation extraction process. When the angle of separation between the stereo images is small, the extraction process typically produces measurements with low accuracy, while a large angle of separation can cause an excessive number of erroneous points in the DEM from occlusion of ground areas. The use of three or more images registered to the same ground area can potentially reduce these problems and improve the accuracy of the extracted DEM. The pointing capability of some sensors, such as the Multispectral Thermal Imager (MTI), allows for multiple collects of the same area from different perspectives. This functionality of MTI makes it a good candidate for the implementation of a DEM extraction algorithm using multiple images for improved accuracy. Evaluation of this capability and development of algorithms to geometrically model the MTI sensor and extract DEMs from multi-look MTI imagery are described in this paper. An RMS elevation error of 6.3-meters is achieved using 11 ground test points, while the MTI band has a 5-meter ground sample distance.

  7. Digital elevation extraction from multiple MTI data sets.

    SciTech Connect

    Mercier, Jeffrey Alan; Schowengerdt, Robert A.; Smith, Jody Lynn; Storey, James C.

    2003-06-01

    The Digital Elevation Model (DEM) extraction process traditionally uses a stereo pair of aerial photographs that are sequentially captured using an airborne metric camera. Standard DEM extraction techniques have been naturally extended to utilize satellite imagery. However, the particular characteristics of satellite imaging can cause difficulties in the DEM extraction process. The ephemeris of the spacecraft during the collects, with respect to the ground test site, is the most important factor in the elevation extraction process. When the angle of separation between the stereo images is small, the extraction process typically produces measurements with low accuracy. A large angle of separation can cause an excessive number of erroneous points in the output DEM. There is also a possibility of having occluded areas in the images when drastic topographic variation is present, making it impossible to calculate elevation in the blind spots. The use of three or more images registered to the same ground area can potentially reduce these problems and improve the accuracy of the extracted DEM. The pointing capability of the Multispectral Thermal Imager (MTI) allows for multiple collects of the same area to be taken from different perspectives. This functionality of MTI makes it a good candidate for the implementation of DEM extraction using multiple images for improved accuracy. This paper describes a project to evaluate this capability and the algorithms used to extract DEMs from multi-look MTI imagery.

  8. Geometric correction and digital elevation extraction using multiple MTI datasets.

    SciTech Connect

    Mercier, Jeffrey Alan; Schowengerdt, Robert A.; Smith, Jody Lynn; Storey, James C.

    2004-08-01

    Digital Elevation Models (DEMs) are traditionally acquired from a stereo pair of aerial photographs sequentially captured by an airborne metric camera. Standard DEM extraction techniques can be naturally extended to satellite imagery, but the particular characteristics of satellite imaging can cause difficulties. The spacecraft ephemeris with respect to the ground site during image collects is the most important factor in the elevation extraction process. When the angle of separation between the stereo images is small, the extraction process typically produces measurements with low accuracy, while a large angle of separation can cause an excessive number of erroneous points in the DEM from occlusion of ground areas. The use of three or more images registered to the same ground area can potentially reduce these problems and improve the accuracy of the extracted DEM. The pointing capability of some sensors, such as the Multispectral Thermal Imager (MTI), allows for multiple collects of the same area from different perspectives. This functionality of MTI makes it a good candidate for the implementation of a DEM extraction algorithm using multiple images for improved accuracy. Evaluation of this capability and development of algorithms to geometrically model the MTI sensor and extract DEMs from multi-look MTI imagery are described in this paper. An RMS elevation error of 6.3-meters is achieved using 11 ground test points, while the MTI band has a 5-meter ground sample distance.

  9. Improving merge methods for grid-based digital elevation models

    NASA Astrophysics Data System (ADS)

    Leitão, J. P.; Prodanović, D.; Maksimović, Č.

    2016-03-01

    Digital Elevation Models (DEMs) are used to represent the terrain in applications such as, for example, overland flow modelling or viewshed analysis. DEMs generated from digitising contour lines or obtained by LiDAR or satellite data are now widely available. However, in some cases, the area of study is covered by more than one of the available elevation data sets. In these cases the relevant DEMs may need to be merged. The merged DEM must retain the most accurate elevation information available while generating consistent slopes and aspects. In this paper we present a thorough analysis of three conventional grid-based DEM merging methods that are available in commercial GIS software. These methods are evaluated for their applicability in merging DEMs and, based on evaluation results, a method for improving the merging of grid-based DEMs is proposed. DEMs generated by the proposed method, called MBlend, showed significant improvements when compared to DEMs produced by the three conventional methods in terms of elevation, slope and aspect accuracy, ensuring also smooth elevation transitions between the original DEMs. The results produced by the improved method are highly relevant different applications in terrain analysis, e.g., visibility, or spotting irregularities in landforms and for modelling terrain phenomena, such as overland flow.

  10. Sparse Representation and Multiscale Methods - Application to Digital Elevation Models

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    In general, a Digital Elevation Model (DEM) is produced either digitizing existing maps and elevation values are interpolated from the contours, or elevation information is collected from stereo imagery on digital photogrammetric workstations. Both methods produce a DEM to the required specification, but each method contains a variety of possible production scenarios, and each method results in DEM cells with totally different character. Common artifacts found in DEM are missing-values at different location which can influence the output of the application that uses this particular DEM. In this work we introduce a numerically-stable multiscale scheme to evaluate the missing-value DEM's quantity of interest (elevation, slope, etc.). This method is very efficient for the case when dealing with large high resolution DEMs that cover large area, resulting in O(106-1010) data points. Our scheme relies on graph-based algorithms and low-rank approximations of the entire adjacency matrix of the DEM's graph. When dealing with large data sets such as DEMs, the Laplacian or kernel matrix resulted from the interaction of the data points is stupendously big. One needs to identify a subspace that capture most of the action of the kernel matrix. By the application of a randomized projection on the graph affinity matrix, a well-conditioned basis is identified for it numerical range. This basis is later used in out-of-sample extension at missing-value location. In many cases, this method beats its classical competitors in terms of accuracy, speed, and robustness.

  11. A global digital elevation model - GTOP030

    USGS Publications Warehouse

    1999-01-01

    GTOP030, the U.S. Geological Survey's (USGS) digital elevation model (DEM) of the Earth, provides the flrst global coverage of moderate resolution elevation data.  The original GTOP30 data set, which was developed over a 3-year period through a collaborative effort led by the USGS, was completed in 1996 at the USGS EROS Data Center in Sioux Falls, South Dakota.  The collaboration involved contributions of staffing, funding, or source data from cooperators including the National Aeronautics and Space Administration (NASA), the United Nations Environment Programme Global Resource Information Database (UNEP/GRID), the U.S. Agency for International Development (USAID), the Instituto Nacional de Estadistica Geografia e Informatica (INEGI) of Mexico, the Geographical Survey Institute (GSI) of Japan, Manaaki Whenua Landcare Research of New Zealand, and the Scientific Committee on Antarctic Research (SCAR). In 1999, work was begun on an update to the GTOP030 data set. Additional data sources are being incorporated into GTOP030 with an enhanced and improved data set planned for release in 2000.

  12. Ice Cloud and Land Elevation Satellite (ICESat) Altimetry and Digital Elevation Models in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Carabajal, C. C.; Boy, J.

    2012-12-01

    A global set of Ground Control Points (GCPs) from altimetry measurements from the Ice, Cloud and land Elevation Satellite (ICESat) has been produced with the support of the NASA's Earth Surface and Interior Program. The highest quality altimetry measurements that can be used for ground control have been selected by applying rigorous editing criteria. This database represents a key means to establishing a much-needed global topography reference frame to aid solid Earth application studies, particularly useful at high latitudes, where other topographic control is scarce. ICESat GCPs were used to characterize and quantify spatially varying elevation biases in Digital Elevation Models (DEMs) in the polar regions, assessing the horizontal and vertical accuracy of valuable topographic datasets produced by sensors like ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) missions, and datasets like GMTED2010 (Global Multi-resolution Terrain Elevation Data), developed by the USGS (United States Geological Survey) and NGA (National Geospatial-Intelligence Agency), a large improvement over the global GTOPO30 dataset. We have analyzed error statistics globally and per continent, in conjunction with MODIS (Moderate Resolution Imaging Spectro-Radiometer) and MERIS (Medium Resolution Imaging Spectrometer) land cover products, relief, topography and other DEM and altimetry specific parameters, and will present the results of these evaluations.

  13. Accuracy and performance analysis of digital levels

    NASA Astrophysics Data System (ADS)

    Skeivalas, Jonas; Giniotis, V.

    2005-02-01

    Optical-electronic leveling devices using a staff with bar codes are discussed. The reading of the staff is taken along its longitudinal axis; the distance to the staff and its vertical position are determined by the readings of a translational transducer connected to the optical system during its focusing on the bars of the staff. The height is determined according to coded signals of the image of the bars transferred into an array of photoelectric cells in the instrument and processed by a microprocessor to the height values. Three main types of image processing are used in various types of digital levels: a correlation method, a geometric method, and a phase method. The correlation functions of measuring and reference codes in the electronic level are calculated in this paper, showing possible errors of height determination. The information obtained during the measurement shows the relationship between the information entropy received from different values of readings from the staff. A new digital level design is proposed, simplifying the design of the instrument and the staff as well. The principal correlation and error determination equations are given, and diagrams of the new design are included.

  14. Online, On Demand Access to Coastal Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Long, J.; Bristol, S.; Long, D.; Thompson, S.

    2014-12-01

    Process-based numerical models for coastal waves, water levels, and sediment transport are initialized with digital elevation models (DEM) constructed by interpolating and merging bathymetric and topographic elevation data. These gridded surfaces must seamlessly span the land-water interface and may cover large regions where the individual raw data sources are collected at widely different spatial and temporal resolutions. In addition, the datasets are collected from different instrument platforms with varying accuracy and may or may not overlap in coverage. The lack of available tools and difficulties in constructing these DEMs lead scientists to 1) rely on previously merged, outdated, or over-smoothed DEMs; 2) discard more recent data that covers only a portion of the DEM domain; and 3) use inconsistent methodologies to generate DEMs. The objective of this work is to address the immediate need of integrating land and water-based elevation data sources and streamline the generation of a seamless data surface that spans the terrestrial-marine boundary. To achieve this, the U.S. Geological Survey (USGS) is developing a web processing service to format and initialize geoprocessing tasks designed to create coastal DEMs. The web processing service is maintained within the USGS ScienceBase data management system and has an associated user interface. Through the map-based interface, users define a geographic region that identifies the bounds of the desired DEM and a time period of interest. This initiates a query for elevation datasets within federal science agency data repositories. A geoprocessing service is then triggered to interpolate, merge, and smooth the data sources creating a DEM based on user-defined configuration parameters. Uncertainty and error estimates for the DEM are also returned by the geoprocessing service. Upon completion, the information management platform provides access to the final gridded data derivative and saves the configuration parameters

  15. ACE2 Global Digital Elevation Model : User Analysis

    NASA Astrophysics Data System (ADS)

    Smith, R. G.; Berry, P. A. M.; Benveniste, J.

    2013-12-01

    Altimeter Corrected Elevations 2 (ACE2), first released in October 2009, is the Global Digital Elevation Model (GDEM) created by fusing the high accuracy of over 100 million altimeter retracked height estimates, derived primarily from the ERS-1 Geodetic Mission, with the high frequency content available within the near-global Shuttle Radar Topography Mission. This novel ACE2 GDEM is freely available at 3”, 9”, 30” and 5' and has been distributed via the web to over 680 subscribers. This paper presents the results of a detailed analysis of geographical distribution of subscribed users, along with fields of study and potential uses. Investigations have also been performed to determine the most popular spatial resolutions and the impact these have on the scope of data downloaded. The analysis has shown that, even though the majority of users have come from Europe and America, a significant number of website hits have been received from South America, Africa and Asia. Registered users also vary widely, from research institutions and major companies down to individual hobbyists looking at data for single projects.

  16. Evaluation Digital Elevation Model Generated by Synthetic Aperture Radar Data

    NASA Astrophysics Data System (ADS)

    Makineci, H. B.; Karabörk, H.

    2016-06-01

    Digital elevation model, showing the physical and topographical situation of the earth, is defined a tree-dimensional digital model obtained from the elevation of the surface by using of selected an appropriate interpolation method. DEMs are used in many areas such as management of natural resources, engineering and infrastructure projects, disaster and risk analysis, archaeology, security, aviation, forestry, energy, topographic mapping, landslide and flood analysis, Geographic Information Systems (GIS). Digital elevation models, which are the fundamental components of cartography, is calculated by many methods. Digital elevation models can be obtained terrestrial methods or data obtained by digitization of maps by processing the digital platform in general. Today, Digital elevation model data is generated by the processing of stereo optical satellite images, radar images (radargrammetry, interferometry) and lidar data using remote sensing and photogrammetric techniques with the help of improving technology. One of the fundamental components of remote sensing radar technology is very advanced nowadays. In response to this progress it began to be used more frequently in various fields. Determining the shape of topography and creating digital elevation model comes the beginning topics of these areas. It is aimed in this work , the differences of evaluation of quality between Sentinel-1A SAR image ,which is sent by European Space Agency ESA and Interferometry Wide Swath imaging mode and C band type , and DTED-2 (Digital Terrain Elevation Data) and application between them. The application includes RMS static method for detecting precision of data. Results show us to variance of points make a high decrease from mountain area to plane area.

  17. Preparation of the Digital Elevation Model for Orthophoto CR Production

    NASA Astrophysics Data System (ADS)

    Švec, Z.; Pavelka, K.

    2016-06-01

    The Orthophoto CR is produced in co-operation with the Land Survey Office and the Military Geographical and Hydrometeorological Office. The product serves to ensure a defence of the state, integrated crisis management, civilian tasks in support of the state administration and the local self-government of the Czech Republic as well. It covers the whole area of the Republic and for ensuring its up-to-datedness is reproduced in the biennial period. As the project is countrywide, it keeps the project within the same parameters in urban and rural areas as well. Due to economic reasons it cańt be produced as a true ortophoto because it requires large side and forward overlaps of the aerial photographs and a preparation of the digital surface model instead of the digital terrain model. Use of DTM without some objects of DSM for orthogonalization purposes cause undesirable image deformations in the Orthophoto. There are a few data sets available for forming a suitable elevation model. The principal source should represent DTMs made from data acquired by the airborne laser scanning of the entire area of the Czech Republic that was carried out in the years 2009-2013, the DMR4G in the grid form and the DMR5G in TIN form respectively. It can be replenished by some vector objects (bridges, dams, etc.) taken from the geographic base data of the Czech Republic or obtained by new stereo plotting. It has to be taken into account that the option of applying DSM made from image correlation is also available. The article focuses on the possibilities of DTM supplement for ortogonalization. It looks back to the recent transition from grid to hybrid elevation models, problems that occurred, its solution and getting some practical remarks. Afterwards it assesses the current state and deals with the options for updating the model. Some accuracy analysis are included.

  18. Digital elevation modeling via curvature interpolation for lidar data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Digital elevation model (DEM) is a three-dimensional (3D) representation of a terrain's surface - for a planet (including Earth), moon, or asteroid - created from point cloud data which measure terrain elevation. Its modeling requires surface reconstruction for the scattered data, which is an ill-p...

  19. Quantification of terrestrial laser scanner (TLS) elevation accuracy in oil palm plantation for IFSAR improvement

    NASA Astrophysics Data System (ADS)

    Muhadi, N. A.; Abdullah, A. F.; Kassim, M. S. M.

    2016-06-01

    In order to ensure the oil palm productivity is high, plantation site should be chosen wisely. Slope is one of the essential factors that need to be taken into consideration when doing a site selection. High quality of plantation area map with elevation information is needed for decision-making especially when dealing with hilly and steep area. Therefore, accurate digital elevation models (DEMs) are required. This research aims to increase the accuracy of Interferometric Synthetic Aperture Radar (IFSAR) by integrating Terrestrial Laser Scanner (TLS) to generate DEMs. However, the focus of this paper is to evaluate the z-value accuracy of TLS data and Real-Time Kinematic GPS (RTK-GPS) as a reference. Besides, this paper studied the importance of filtering process in developing an accurate DEMs. From this study, it has been concluded that the differences of z-values between TLS and IFSAR were small if the points were located on route and when TLS data has been filtered. This paper also concludes that laser scanner (TLS) should be set up on the route to reduce elevation error.

  20. Validation of diagnostic accuracy using digital slides in routine histopathology

    PubMed Central

    2012-01-01

    Background Robust hardware and software tools have been developed in digital microscopy during the past years for pathologists. Reports have been advocated the reliability of digital slides in routine diagnostics. We have designed a retrospective, comparative study to evaluate the scanning properties and digital slide based diagnostic accuracy. Methods 8 pathologists reevaluated 306 randomly selected cases from our archives. The slides were scanned with a 20× Plan-Apochromat objective, using a 3-chip Hitachi camera, resulting 0.465 μm/pixel resolution. Slide management was supported with dedicated Data Base and Viewer software tools. Pathologists used their office PCs for evaluation and reached the digital slides via intranet connection. The diagnostic coherency and uncertainty related to digital slides and scanning quality were analyzed. Results Good to excellent image quality of slides was recorded in 96%. In half of the critical 61 digital slides, poor image quality was related to section folds or floatings. In 88.2% of the studied cases the digital diagnoses were in full agreement with the consensus. Out of the overall 36 incoherent cases, 7 (2.3%) were graded relevant without any recorded uncertainty by the pathologist. Excluding the non-field specific cases from each pathologist's record this ratio was 1.76% of all cases. Conclusions Our results revealed that: 1) digital slide based histopathological diagnoses can be highly coherent with those using optical microscopy; 2) the competency of pathologists is a factor more important than the quality of digital slide; 3) poor digital slide quality do not endanger patient safety as these errors are recognizable by the pathologist and further actions for correction could be taken. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1913324336747310. PMID:22463804

  1. Carving and adaptive drainage enforcement of grid digital elevation models

    NASA Astrophysics Data System (ADS)

    Soille, Pierre; Vogt, Jürgen; Colombo, Roberto

    2003-12-01

    An effective and widely used method for removing spurious pits in digital elevation models consists of filling them until they overflow. However, this method sometimes creates large flat regions which in turn pose a problem for the determination of accurate flow directions. In this study, we propose to suppress each pit by creating a descending path from it to the nearest point having a lower elevation value. This is achieved by carving, i.e., lowering, the terrain elevations along the detected path. Carving paths are identified through a flooding simulation starting from the river outlets. The proposed approach allows for adaptive drainage enforcement whereby river networks coming from other data sources are imposed to the digital elevation model only in places where the automatic river network extraction deviates substantially from the known networks. An improvement to methods for routing flow over flat regions is also introduced. Detailed results are presented over test areas of the Danube basin.

  2. Calculation and Error Analysis of a Digital Elevation Model of Hofsjokull, Iceland from SAR Interferometry

    NASA Technical Reports Server (NTRS)

    Barton, Jonathan S.; Hall, Dorothy K.; Sigurosson, Oddur; Williams, Richard S., Jr.; Smith, Laurence C.; Garvin, James B.

    1999-01-01

    Two ascending European Space Agency (ESA) Earth Resources Satellites (ERS)-1/-2 tandem-mode, synthetic aperture radar (SAR) pairs are used to calculate the surface elevation of Hofsjokull, an ice cap in central Iceland. The motion component of the interferometric phase is calculated using the 30 arc-second resolution USGS GTOPO30 global digital elevation product and one of the ERS tandem pairs. The topography is then derived by subtracting the motion component from the other tandem pair. In order to assess the accuracy of the resultant digital elevation model (DEM), a geodetic airborne laser-altimetry swath is compared with the elevations derived from the interferometry. The DEM is also compared with elevations derived from a digitized topographic map of the ice cap from the University of Iceland Science Institute. Results show that low temporal correlation is a significant problem for the application of interferometry to small, low-elevation ice caps, even over a one-day repeat interval, and especially at the higher elevations. Results also show that an uncompensated error in the phase, ramping from northwest to southeast, present after tying the DEM to ground-control points, has resulted in a systematic error across the DEM.

  3. A quality control system for digital elevation data

    NASA Astrophysics Data System (ADS)

    Knudsen, Thomas; Kokkendorf, Simon; Flatman, Andrew; Nielsen, Thorbjørn; Rosenkranz, Brigitte; Keller, Kristian

    2015-04-01

    In connection with the introduction of a new version of the Danish national coverage Digital Elevation Model (DK-DEM), the Danish Geodata Agency has developed a comprehensive quality control (QC) and metadata production (MP) system for LiDAR point cloud data. The architecture of the system reflects its origin in a national mapping organization where raw data deliveries are typically outsourced to external suppliers. It also reflects a design decision of aiming at, whenever conceivable, doing full spatial coverage tests, rather than scattered sample checks. Hence, the QC procedure is split in two phases: A reception phase and an acceptance phase. The primary aim of the reception phase is to do a quick assessment of things that can typically go wrong, and which are relatively simple to check: Data coverage, data density, strip adjustment. If a data delivery passes the reception phase, the QC continues with the acceptance phase, which checks five different aspects of the point cloud data: Vertical accuracy Vertical precision Horizontal accuracy Horizontal precision Point classification correctness The vertical descriptors are comparatively simple to measure: The vertical accuracy is checked by direct comparison with previously surveyed patches. The vertical precision is derived from the observed variance on well defined flat surface patches. These patches are automatically derived from the road centerlines registered in FOT, the official Danish map data base. The horizontal descriptors are less straightforward to measure, since potential reference material for direct comparison is typically expected to be less accurate than the LiDAR data. The solution selected is to compare photogrammetrically derived roof centerlines from FOT with LiDAR derived roof centerlines. These are constructed by taking the 3D Hough transform of a point cloud patch defined by the photogrammetrical roof polygon. The LiDAR derived roof centerline is then the intersection line of the two primary

  4. Accuracy of digital surface models generated from UAV images

    NASA Astrophysics Data System (ADS)

    Eltner, Anette; Zenker, Albrecht

    2014-05-01

    The interest in unmanned aerial vehicles (UAV) as a common survey and monitoring technology in geosciences is growing. Progress in digital photogrammetry and computer vision enables fast and precise creation of digital surface models (DSM). Measuring soil erosion with DSM derived from overlapping images is one potential application of UAV data. Therefor, the calculation of DSM with high resolution and accuracy is necessary. However, due to the chaotic characteristic of natural surfaces measuring the accuracy of a UAV-DSM is a difficult task. A first comparison of a field plot captured by UAV and terrestrial laser scanning (TLS) allows for qualitative conclusions, but probable errors within the TLS-DSM (e.g. due to low incidence angles) impede comprised quantitative accuracy information. Thus, a millimetre accurate reference field with the size of 35 m² is designed and measured with a total station. DSM of the test area are generated with different cameras - single-lens reflex camera, compact system camera and compact camera - to account for different camera geometries and their performance at automatic image matching and orientation. Furthermore, different software is tested which on the one hand uses structure from motion and on the other hand a combination of methods from photogrammetry and computer vision. Results show accuracies within few millimetres for a simulated flying height of four metres.

  5. Online Mars Digital Elevation Model Derived from Profiles

    NASA Astrophysics Data System (ADS)

    Delacourt, C.; Gros, N.; Allemand, P.; Baratoux, D.

    The topography of Mars is a key parameter for understanding the geological evolution of the planet. Since 1997, the Mars Orbital Laser Altimeter (MOLA), launched in the frame of Mars Global Surveyor, has acquired more than 600 million topographic measurements. However, despite the high vertical accuracy of those profiles, the main limitation of this technique appears when topographic maps are required. To create a Digital Elevation Model (DEM) or a topographic map, an interpolation on individual MOLA measurements on regular grids is required. Calculating the global full-resolution Martian DEM requires very intensive computation and large disk capacities. Only a few teams throughout the world have computed a full resolution DEM from MOLA data. Even if a scientist is interested in a small area of Mars, numerous profiles have to be processed and extracted from 44 CD-ROMs. To facilitate the exploitation of the high potential of MOLA data, we propose an Internet application that allows any user to extract the individual MOLA measurements from all profiles over a given area and to process local DEMs of the surface of Mars with adjustable parameters of computation. This facility, developed in Interactive Data Language by Research Systems, Inc., allows users to select the zone of interest and the resolution of the output DEM. After online processing, various products in standard formats can be downloaded on the user's computer, including DEMs, individual MOLA points, list and map of the MOLA ground tracks used for the DEM generation, and a quality map. This map is computed by evaluating the distance between each point of the DEM and the closest measurements of the altimeter. Furthermore, IDL tools are supplied to facilitate data integration and use.

  6. The ASTER Global Digital Elevation Model (GDEM) -for societal benefit -

    NASA Astrophysics Data System (ADS)

    Hato, M.; Tsu, H.; Tachikawa, T.; Abrams, M.; Bailey, B.

    2009-12-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) was developed jointly by the Ministry of Economy, Trade and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) under the agreement of contribution to GEOSS and a public release was started on June 29th. ASTER GDEM can be downloaded to users from the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan and NASA’s Land Processes Distributed Active Archive Center (LP DAAC) free of charge. The ASTER instrument was built by METI and launched onboard NASA’s Terra spacecraft in December 1999. It has an along-track stereoscopic capability using its near infrared spectral band (NIR) and its nadir-viewing and backward-viewing telescopes to acquire stereo image data with a base-to-height ratio of 0.6. The ASTER GDEM was produced by applying newly-developed automated algorithm to more than 1.2 million NIR data Produced DEMs of all scene data was stacked after cloud masking and finally partitioned into 1° x 1°unit (called ‘tile’) data for convenience of distribution and handling by users. Before start of public distribution, ERSDAC and USGS/NASA together with many volunteers did validation and characterization by using a preliminary product of the ASTER GDEM. As a result of validation, METI and NASA evaluated that Version 1 of the ASTER GDEM has enough quality to be used as “experimental” or “research grade” data and consequently decided to release it. The ASTER GDEM covering almost all land area of from 83N to 83S on the earth represents as an important contribution to the global earth observation community. We will show our effort of development of ASTER GDEM and its accuracy and character.

  7. Interferometric synthetic aperture radar and the Data Collection System Digital Terrain Elevation Demonstration

    NASA Astrophysics Data System (ADS)

    Heidelbach, Robert; Bolus, R.; Chadwick, J.

    1994-08-01

    Digital Terrain Elevations (DTE) that can be rapidly generated, and that have better fidelity and accuracy than Digital Terrain Elevation Data (DTED) Levels 1 or 2, would be extremely beneficial to Department of Defense (DOD) military operations, civil works programs, and various commercial applications. As a result, the Advanced Research Projects Agency (ARPA), along with the U.S. Army Topographic Engineering Center (TEC), are developing an Interferometric Synthetic Aperture Radar (IFSAR) elevation mapping capability. This system, the Interferometric Synthetic Aperture Radar for Digital Radar Elevations (IFSARE), is capable of collecting and providing data in all weather (reasonable), in day or night scenarios, and where obscurants are present. The IFSARE, which is currently undergoing Integration and Test, will allow for rapid on-line automatic processing of the collected digital radar data into DTE and high quality imagery. The prime contractor is the Environmental Research Institute of Michigan (ERIM). This paper addresses the proof of concept for civil works applications by analyzing a data set taken by the Wright Labs/ERIM Data Collection System (DCS). The objective was to demonstrate the capability of an IFSAR system to provide high fidelity, fine resolution DTE that can be employed in hydraulic models of the Mississippi River watershed. The demonstration was sponsored by ARPA and TEC.

  8. ICESat Lidar and Global Digital Elevation Models: Application to DESDynI

    NASA Technical Reports Server (NTRS)

    Carabajal, Claudia C.; Harding, David J.; Suchdeo, Vijay P.

    2010-01-01

    Geodetic control is extremely important in the production and quality control of topographic data sets, enabling elevation results to be referenced to an absolute vertical datum. Global topographic data with improved geodetic accuracy achieved using global Ground Control Point (GCP) databases enable more accurate characterization of land topography and its change related to solid Earth processes, natural hazards and climate change. The multiple-beam lidar instrument that will be part of the NASA Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) mission will provide a comprehensive, global data set that can be used for geodetic control purposes. Here we illustrate that potential using data acquired by NASA's Ice, Cloud and land Elevation Satellite (ICEsat) that has acquired single-beam, globally distributed laser altimeter profiles (+/-86deg) since February of 2003 [1, 2]. The profiles provide a consistently referenced elevation data set with unprecedented accuracy and quantified measurement errors that can be used to generate GCPs with sub-decimeter vertical accuracy and better than 10 m horizontal accuracy. Like the planned capability for DESDynI, ICESat records a waveform that is the elevation distribution of energy reflected within the laser footprint from vegetation, where present, and the ground where illuminated through gaps in any vegetation cover [3]. The waveform enables assessment of Digital Elevation Models (DEMs) with respect to the highest, centroid, and lowest elevations observed by ICESat and in some cases with respect to the ground identified beneath vegetation cover. Using the ICESat altimetry data we are developing a comprehensive database of consistent, global, geodetic ground control that will enhance the quality of a variety of regional to global DEMs. Here we illustrate the accuracy assessment of the Shuttle Radar Topography Mission (SRTM) DEM produced for Australia, documenting spatially varying elevation biases of several meters

  9. 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.

  10. Accuracy of optical dental digitizers: an in vitro study.

    PubMed

    Vandeweghe, Stefan; Vervack, Valentin; Vanhove, Christian; Dierens, Melissa; Jimbo, Ryo; De Bruyn, Hugo

    2015-01-01

    The aim of this study was to evaluate the accuracy, in terms of trueness and precision, of optical dental scanners. An experimental acrylic resin cast was created and digitized using a microcomputed tomography (microCT) scanner, which served as the reference model. Five polyether impressions were made of the acrylic resin cast to create five stone casts. Each dental digitizer (Imetric, Lava ST, Smart Optics, KaVo Everest) made five scans of the acrylic resin cast and one scan of every stone cast. The scans were superimposed and compared using metrology software. Deviations were calculated between the datasets obtained from the dental digitizers and the microCT scanner (= trueness) and between datasets from the same dental digitizer (= precision). With exception of the Smart Optics scanner, there were no significant differences in trueness for the acrylic resin cast. For the stone casts, however, the Lava ST performed better than Imetric, which did better than the KaVo scanner. The Smart Optics scanner demonstrated the highest deviation. All digitizers demonstrated a significantly higher trueness for the acrylic resin cast compared to the plaster cast, except the Lava ST. The Lava ST was significantly more precise compared to the other scanners. Imetric and Smart Optics also demonstrated a higher level of precision compared to the KaVo scanner. All digitizers demonstrated some degree of error. Stone cast copies are less accurate because of difficulties with scanning the rougher surface or dimensional deformations caused during the production process. For complex, large-span reconstructions, a highly accurate scanner should be selected. PMID:25734714

  11. Orthographic terrain views using data derived from digital elevation models

    NASA Technical Reports Server (NTRS)

    Dubayah, R. O.; Dozier, J.

    1986-01-01

    A fast algorithm for producing three-dimensional orthographic terrain views uses digital elevation data and co-registered imagery. These views are created using projective geometry and are designed for display on high-resolution raster graphics devices. The algorithm's effectiveness is achieved by (1) the implementation of two efficient gray-level interpolation routines that offer the user a choice between speed and smoothness, and (2) a unique visible surface determination procedure based on horizon angles derived from the elevation data set.

  12. Extraction of terrain features from digital elevation models

    USGS Publications Warehouse

    Price, Curtis V.; Wolock, David M.; Ayers, Mark A.

    1989-01-01

    Digital elevation models (DEMs) are being used to determine variable inputs for hydrologic models in the Delaware River basin. Recently developed software for analysis of DEMs has been applied to watershed and streamline delineation. The results compare favorably with similar delineations taken from topographic maps. Additionally, output from this software has been used to extract other hydrologic information from the DEM, including flow direction, channel location, and an index describing the slope and shape of a watershed.

  13. Digital elevation model visibility including Earth's curvature and atmosphere refraction

    NASA Astrophysics Data System (ADS)

    Santossilva, Ewerton; Vieiradias, Luiz Alberto

    1990-03-01

    There are some instances in which the Earth's curvature and the atmospheric refraction, optical or electronic, are important factors when digital elevation models are used for visibility calculations. This work deals with this subject, suggesting a practical approach to solve this problem. Some examples, from real terrain data, are presented. The equipment used was an IBM-PC like computer with a SITIM graphic card.

  14. 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.

  15. Accuracy of digital videodensitometry in quantitating contrast medium concentration.

    PubMed

    Yang, X M; Manninen, H; Ji, H X; Vainio, P; Soimakallio, S

    1994-07-01

    To evaluate the accuracy of digital videodensitometric technique in directly quantitating concentration of contrast medium, iohexol 300 mg I/ml was injected into a 2-mm-diameter plastic tube, in which clean water was circulated at a 190 ml/min flow, for digital subtraction angiography. Altogether 27 injections were performed with 3, 4 and 5 ml volumes at 3-, 4- and 5-ml/s flows of the contrast medium. A time-density curve was achieved by selecting a "vessel" region of interest (ROI) and a background ROI. Then, a frame corresponding to the maximum opacification of the contrast medium could be calculated. Finally, the average density and the time to peak density of the contrast medium were obtained. The average density was statistically higher (p < 0.01) with 5 ml/s flow than with 4- and 3-ml/s flows. Times to peak density reduced as injection flows or volumes increased. The results support the conclusion that digital videodensitometric technique is an accurate method for quantitation of contrast medium concentration during angiography. The angiographic opacification may be improved by injecting the iodine contrast medium with higher flows or larger volumes. PMID:8011389

  16. High-Accuracy Elevation Data at Large Scales from Airborne Single-Pass SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Schumann, Guy; Moller, Delwyn; Mentgen, Felix

    2015-12-01

    Digital elevation models (DEMs) are essential data sets for disaster risk management and humanitarian relief services as well as many environmental process models. At present, on the hand, globally available DEMs only meet the basic requirements and for many services and modeling studies are not of high enough spatial resolution and lack accuracy in the vertical. On the other hand, LiDAR-DEMs are of very high spatial resolution and great vertical accuracy but acquisition operations can be very costly for spatial scales larger than a couple of hundred square km and also have severe limitations in wetland areas and under cloudy and rainy conditions. The ideal situation would thus be to have a DEM technology that allows larger spatial coverage than LiDAR but without compromising resolution and vertical accuracy and still performing under some adverse weather conditions and at a reasonable cost. In this paper, we present a novel single pass In-SAR technology for airborne vehicles that is cost-effective and can generate DEMs with a vertical error of around 0.3 m for an average spatial resolution of 3 m. To demonstrate this capability, we compare a sample single-pass In-SAR Ka-band DEM of the California Central Valley from the NASA/JPL airborne GLISTIN-A to a high-resolution LiDAR DEM. We also perform a simple sensitivity analysis to floodplain inundation. Based on the findings of our analysis, we argue that this type of technology can and should be used to replace large regions of globally available lower resolution DEMs, particularly in coastal, delta and floodplain areas where a high number of assets, habitats and lives are at risk from natural disasters. We conclude with a discussion on requirements, advantages and caveats in terms of instrument and data processing.

  17. A geomorphology based approach for digital elevation model fusion - case study in Danang City, Vietnam

    NASA Astrophysics Data System (ADS)

    Tran, T. A.; Raghavan, V.; Masumoto, S.; Vinayaraj, P.; Yonezawa, G.

    2014-04-01

    Global Digital Elevation Model (DEM) is considered as vital spatial information and finds wide use in several applications. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM (GDEM) and Shuttle Radar Topographic Mission (SRTM) DEM offer almost global coverage and provide elevation data for geospatial analysis. However, GDEM and SRTM still contain some height errors that affect the quality of elevation data significantly. This study aims to examine methods to improve the resolution as well as accuracy of available free DEMs by data fusion technique and evaluating the results with high quality reference DEM. The DEM fusion method is based on the accuracy assessment of each global DEM and geomorphological characteristics of the study area. Land cover units were also considered to correct the elevation of GDEM and SRTM with respect to the bare earth surface. Weighted averaging method was used to fuse the input DEMs based on landform classification map. According to the landform types, the different weights were used for GDEM and SRTM. Finally, a denoising algorithm (Sun et al., 2007) was applied to filter the output fused DEM. This fused DEM shows excellent correlation to the reference DEM having correlation coefficient R2 = 0.9986 and the accuracy was also improved from Root Mean Square Error (RMSE) 14.9 m in GDEM and 14.8 m in SRTM into 11.6 m in fused DEM.

  18. Impact of Digital Panoramic Radiograph Magnification on Vertical Measurement Accuracy

    PubMed Central

    El Hage, Marc; Bernard, Jean-Pierre; Combescure, Christophe; Vazquez, Lydia

    2015-01-01

    Objectives. The purpose of this panoramic radiography study was to assess the impact of image magnification on the accuracy of vertical measurements in the posterior mandible. Methods. Six dental implants, inserted in the posterior segments of a resin model, were used as reference objects. Two observers performed implant length measurements using a proprietary viewer with two preset image magnifications: the low (1.9 : 1) and the medium (3.4 : 1) image magnifications. They also measured the implant lengths in two Digital Imaging Communications in Medicine viewers set at low (1.9 : 1), medium (3.4 : 1), and high (10 : 1) image magnifications. Results. The error between the measured length and the real implant length was close to zero for all three viewers and image magnifications. The percentage of measurements equal to the real implant length was the highest (83.3%) for the high image magnification and below 30% for all viewers with the low image magnification. Conclusions. The high and medium image magnifications used in this study allowed accurate vertical measurements, with all three imaging programs, in the posterior segments of a mandibular model. This study suggests that a low image magnification should not be used for vertical measurements on digital panoramic radiographs when planning an implant in the posterior mandible. PMID:26557851

  19. Validation of Orthorectified Interferometric Radar Imagery and Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    Smith Charles M.

    2004-01-01

    This work was performed under NASA's Verification and Validation (V&V) Program as an independent check of data supplied by EarthWatch, Incorporated, through the Earth Science Enterprise Scientific Data Purchase (SDP) Program. This document serves as the basis of reporting results associated with validation of orthorectified interferometric interferometric radar imagery and digital elevation models (DEM). This validation covers all datasets provided under the first campaign (Central America & Virginia Beach) plus three earlier missions (Indonesia, Red River: and Denver) for a total of 13 missions.

  20. Registering Thematic Mapper imagery to digital elevation models

    NASA Technical Reports Server (NTRS)

    Frew, J.

    1984-01-01

    The problems encountered when attempting to register Landsat Thematic Mapper (TM) data to U.S. geological survey digital elevation models (DEMs) are examined. It is shown that TM and DEM data are not available in the same map projection, necessitating geometric transformation of one of the data type, that the TM data are not accurately located in their nominal projection, and that TM data have higher resolution than most DEM data, but oversampling the DEM data to TM resolution introduces systematic noise. Further work needed in this area is discussed.

  1. Applications of hydrologic information automatically extracted from digital elevation models

    USGS Publications Warehouse

    Jenson, S.K.

    1991-01-01

    Digital elevation models (DEMs) can be used to derive a wealth of information about the morphology of a land surface. Traditional raster analysis methods can be used to derive slope, aspect, and shaded relief information; recently-developed computer programs can be used to delineate depressions, overland flow paths, and watershed boundaries. These methods were used to delineate watershed boundaries for a geochemical stream sediment survey, to compare the results of extracting slope and flow paths from DEMs of varying resolutions, and to examine the geomorphology of a Martian DEM. -Author

  2. An evaluation of onshore digital elevation models for modelling tsunami inundation zones

    NASA Astrophysics Data System (ADS)

    Griffin, Jonathan; Latief, Hamzah; Kongko, Widjo; Harig, Sven; Horspool, Nick; Hanung, Raditya; Rojali, Aditia; Maher, Nicola; Fuchs, Annika; Hossen, Jakir; Upi, Supriyati; Edi, Dewanto; Rakowsky, Natalja; Cummins, Phil

    2015-06-01

    A sensitivity study is undertaken to assess the utility of different onshore digital elevation models (DEM) for simulating the extent of tsunami inundation using case studies from two locations in Indonesia. We compare airborne IFSAR, ASTER and SRTM against high resolution LiDAR and stereo-camera data in locations with different coastal morphologies. Tsunami inundation extents modelled with airborne IFSAR DEMs are comparable with those modelled with the higher resolution datasets and are also consistent with historical run-up data, where available. Large vertical errors and poor resolution of the coastline in the ASTER and SRTM elevation datasets cause the modelled inundation extent to be much less compared with the other datasets and observations. Therefore ASTER and SRTM should not be used to underpin tsunami inundation models. a model mesh resolution of 25 m was sufficient for estimating the inundated area when using elevation data with high vertical accuracy in the case studies presented here. Differences in modelled inundation between digital terrain models (DTM) and digital surface models (DSM) for LiDAR and IFSAR are greater than differences between the two data types. Models using DTM may overestimate inundation while those using DSM may underestimate inundation when a constant Manning’s roughness value is used. We recommend using DTM for modelling tsunami inundation extent with further work needed to resolve the scale at which surface roughness should be parameterised.

  3. Void-Filled SRTM Digital Elevation Model of Afghanistan

    USGS Publications Warehouse

    Chirico, Peter G.; Barrios, Boris

    2005-01-01

    EXPLANATION The purpose of this data set is to provide a single consistent elevation model to be used for national scale mapping, GIS, remote sensing applications, and natural resource assessments for Afghanistan's reconstruction. For 11 days in February of 2000, the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency ian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed Shuttle Radar Topography Mission (SRTM) DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Afghanistan DEM was gap-filling areas where the SRTM data contained a data void. These void areas are as a result of radar shadow, layover, standing water, and other effects of terrain as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:200,000 - scale Soviet General Staff Topographic Maps which date from the middle to late 1980's. Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and image processing techniques. The data contained in this publication includes SRTM DEM quadrangles projected and clipped in geographic coordinates for the entire country. An index of all available SRTM DEM quadrangles is displayed here: Index_Geo_DD.pdf. Also

  4. How processing digital elevation models can affect simulated water budgets

    USGS Publications Warehouse

    Kuniansky, E.L.; Lowery, M.A.; Campbell, B.G.

    2009-01-01

    For regional models, the shallow water table surface is often used as a source/sink boundary condition, as model grid scale precludes simulation of the water table aquifer. This approach is appropriate when the water table surface is relatively stationary. Since water table surface maps are not readily available, the elevation of the water table used in model cells is estimated via a two-step process. First, a regression equation is developed using existing land and water table elevations from wells in the area. This equation is then used to predict the water table surface for each model cell using land surface elevation available from digital elevation models (DEM). Two methods of processing DEM for estimating the land surface for each cell are commonly used (value nearest the cell centroid or mean value in the cell). This article demonstrates how these two methods of DEM processing can affect the simulated water budget. For the example presented, approximately 20% more total flow through the aquifer system is simulated if the centroid value rather than the mean value is used. This is due to the one-third greater average ground water gradients associated with the centroid value than the mean value. The results will vary depending on the particular model area topography and cell size. The use of the mean DEM value in each model cell will result in a more conservative water budget and is more appropriate because the model cell water table value should be representative of the entire cell area, not the centroid of the model cell.

  5. Preliminary development of digital elevation and relief models for ICESat-2 onboard processing

    NASA Astrophysics Data System (ADS)

    Leigh, H. W.; Magruder, L. A.; Carabajal, C. C.

    2012-12-01

    ATLAS (Advanced Topographic Laser Altimeter System) is a photon-counting laser ranging instrument that will fly onboard NASA's ICESat-2 mission to collect global altimetry data for the primary purpose of determining volumetric changes in the Polar Regions. While photon-counting systems provide the advantage of using small, low power lasers, they are typically much more susceptible to noise and require the use of sophisticated algorithms both onboard and in ground based processing to ensure capture of valid data and production of accurate data products. An onboard receiver algorithm is being developed for ATLAS to ensure that valid data is returned while adhering to the 577 Gb/day limit on data telemetry. The onboard receiver algorithm makes use of multiple onboard databases, two of which are the DEM (Digital Elevation Model) and the DRM (Digital Relief Map). The DEM provides start and stop times for software-induced range gating on the ATLAS detectors, and is a nested, three-tiered grid to account for a 6 km overall constraint on the allowable limit for ranging acquisition. The DRM contains the maximum values of relief seen across 140m- and 700m-long flight path segments, which are used in statistically determining the presence of a valid surface return and in deciding which bands to telemeter. Both onboard databases are to be primarily constructed from existing digital elevation models and must provide global coverage referenced to latitude and longitude. Production of the grids is complicated by the lack of global data products of sufficient resolution and accuracy such that preliminary analysis is required for DEM selection and usage in addition to the determination of how to intelligently merge differing data sets. This initial investigation is also focused on determining the impact of the selected DEM quality on the ICESat-2 onboard algorithms as well as the precipitated error induced on the DRM. These results are required in order to determine the expected

  6. Registratiom of TM data to digital elevation models

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

  7. The ASTER Global Digital Elevation Model version 2.0 - Early Validation Results

    NASA Astrophysics Data System (ADS)

    Meyer, D. J.; Tachikawa, T.; Abrams, M.; Tsu, H.; Hato, M.; Gesch, D. B.; Crippen, R. E.

    2011-12-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra spacecraft is capable of collecting in-track stereo using nadir- and aft looking near infrared cameras. Since 2001, these stereo pairs have been used to produce single-scene (60 x 60 km) digital elevation models having vertical (root-mean-squared-error) accuracies generally between 10 m and 25 m. On June 29, 2009, NASA and the Ministry of Economy, Trade and Industry (METI) of Japan released a Global Digital Elevation Model (GDEM) to users worldwide at no charge as a contribution to the Global Earth Observing System of Systems (GEOSS). This "version 1.0" ASTER GDEM (GDEM v1.0) was compiled from over 1.2 million scene-based DEMs covering land surface between 83°N and 83°S latitudes. This GDEM is a 1 arc-second elevation grid divided and distributed as 1°-by-1° tiles. ** A joint US-Japan validation team assessed the accuracy of the GDEM v1.0, augmented by a team of 20 cooperators selected through an Announcement of Opportunity (AO). In summary, the GDEM v1.0 was found to have an overall accuracy of around 20 meters at the 95% confidence interval. The team also noted several artifacts associated with poor coverage, cloud contamination, water masking issues and the stacking process used to produce the GDEM from individual scene-based DEMs. An independent horizontal resolution study estimated the effective spatial resolution of the GDEM v1.0 to be on the order of 120 meters. ** NASA & METI will release a second version of the ASTER GDEM (v2.0) in mid-October, 2011. The GDEM v2.0 has the same gridding and tile structure as v1.0, but benefits from the inclusion of 300,000 additional scenes to improve coverage, a smaller correlation kernel (5x5 versus 9x9 for v1.0) yielding higher spatial resolution, and improved water masking. This abstract presents early validation results available at the time of submission. Early results indicate: (1) the overall accuracy (both horizontal and

  8. Watershed boundaries and digital elevation model of Oklahoma derived from 1:100,000-scale digital topographic maps

    USGS Publications Warehouse

    Cederstrand, J.R.; Rea, A.H.

    1995-01-01

    This document provides a general description of the procedures used to develop the data sets included on this compact disc. This compact disc contains watershed boundaries for Oklahoma, a digital elevation model, and other data sets derived from the digital elevation model. The digital elevation model was produced using the ANUDEM software package, written by Michael Hutchinson and licensed from the Centre for Resource and Environmental Studies at The Australian National University. Elevation data (hypsography) and streams (hydrography) from digital versions of the U.S. Geological Survey 1:100,000-scale topographic maps were used by the ANUDEM package to produce a hydrologically conditioned digital elevation model with a 60-meter cell size. This digital elevation model is well suited for drainage-basin delineation using automated techniques. Additional data sets include flow-direction, flow-accumulation, and shaded-relief grids, all derived from the digital elevation model, and the hydrography data set used in producing the digital elevation model. The watershed boundaries derived from the digital elevation model have been edited to be consistent with contours and streams from the U.S. Geological Survey 1:100,000-scale topographic maps. The watershed data set includes boundaries for 11-digit Hydrologic Unit Codes (watersheds) within Oklahoma, and 8-digit Hydrologic Unit Codes (cataloging units) outside Oklahoma. Cataloging-unit boundaries based on 1:250,000-scale maps outside Oklahoma for the Arkansas, Red, and White River basins are included. The other data sets cover Oklahoma, and where available, portions of 1:100,000-scale quadrangles adjoining Oklahoma.

  9. Sensitivity Analysis of Uav-Photogrammetry for Creating Digital Elevation Models (dem)

    NASA Astrophysics Data System (ADS)

    Rock, G.; Ries, J. B.; Udelhoven, T.

    2011-09-01

    This study evaluates the potential that lies in the photogrammetric processing of aerial images captured by unmanned aerial vehicles. UAV-Systems have gained increasing attraction during the last years. Miniaturization of electronic components often results in a reduction of quality. Especially the accuracy of the GPS/IMU navigation unit and the camera are of the utmost importance for photogrammetric evaluation of aerial images. To determine the accuracy of digital elevation models (DEMs), an experimental setup was chosen similar to the situation of data acquisition during a field campaign. A quarry was chosen to perform the experiment, because of the presence of different geomorphologic units, such as vertical walls, piles of debris, vegetation and even areas. In the experimental test field, 1042 ground control points (GCPs) were placed, used as input data for the photogrammetric processing and as high accuracy reference data for evaluating the DEMs. Further, an airborne LiDAR dataset covering the whole quarry and additional 2000 reference points, measured by total station, were used as ground truth data. The aerial images were taken using a MAVinci Sirius I - UAV equipped with a Canon 300D as imaging system. The influence of the number of GCPs on the accuracy of the indirect sensor orientation and the absolute deviation's dependency on different parameters of the modelled DEMs was subject of the investigation. Nevertheless, the only significant factor concerning the DEMs accuracy that could be isolated was the flying height of the UAV.

  10. A geomorphology-based approach for digital elevation model fusion - case study in Danang city, Vietnam

    NASA Astrophysics Data System (ADS)

    Tran, T. A.; Raghavan, V.; Masumoto, S.; Vinayaraj, P.; Yonezawa, G.

    2014-07-01

    Global digital elevation models (DEM) are considered a source of vital spatial information and find wide use in several applications. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM (GDEM) and Shuttle Radar Topographic Mission (SRTM) DEM offer almost global coverage and provide elevation data for geospatial analysis. However, GDEM and SRTM still contain some height errors that affect the quality of elevation data significantly. This study aims to examine methods to improve the resolution as well as accuracy of available free DEMs by data fusion techniques and evaluating the results with a high-quality reference DEM. The DEM fusion method is based on the accuracy assessment of each global DEM and geomorphological characteristics of the study area. Land cover units were also considered to correct the elevation of GDEM and SRTM with respect to the bare-earth surface. The weighted averaging method was used to fuse the input DEMs based on a landform classification map. According to the landform types, the different weights were used for GDEM and SRTM. Finally, a denoising algorithm (Sun et al., 2007) was applied to filter the output-fused DEM. This fused DEM shows excellent correlation to the reference DEM, having a correlation coefficient R2 = 0.9986, and the accuracy was also improved from a root mean square error (RMSE) of 14.9 m in GDEM and 14.8 m in SRTM to 11.6 m in the fused DEM. The results of terrain-related parameters extracted from this fused DEM such as slope, curvature, terrain roughness index and normal vector of topographic surface are also very comparable to reference data.

  11. Practical target location and accuracy indicator in digital close range photogrammetry using consumer grade cameras

    NASA Astrophysics Data System (ADS)

    Moriya, Gentaro; Chikatsu, Hirofumi

    2011-07-01

    Recently, pixel numbers and functions of consumer grade digital camera are amazingly increasing by modern semiconductor and digital technology, and there are many low-priced consumer grade digital cameras which have more than 10 mega pixels on the market in Japan. In these circumstances, digital photogrammetry using consumer grade cameras is enormously expected in various application fields. There is a large body of literature on calibration of consumer grade digital cameras and circular target location. Target location with subpixel accuracy had been investigated as a star tracker issue, and many target location algorithms have been carried out. It is widely accepted that the least squares models with ellipse fitting is the most accurate algorithm. However, there are still problems for efficient digital close range photogrammetry. These problems are reconfirmation of the target location algorithms with subpixel accuracy for consumer grade digital cameras, relationship between number of edge points along target boundary and accuracy, and an indicator for estimating the accuracy of normal digital close range photogrammetry using consumer grade cameras. With this motive, an empirical testing of several algorithms for target location with subpixel accuracy and an indicator for estimating the accuracy are investigated in this paper using real data which were acquired indoors using 7 consumer grade digital cameras which have 7.2 mega pixels to 14.7 mega pixels.

  12. Initial Everglades Depth Estimation Network (EDEN) Digital Elevation Model Research and Development

    USGS Publications Warehouse

    Jones, John W.; Price, Susan D.

    2007-01-01

    Introduction The Everglades Depth Estimation Network (EDEN) offers a consistent and documented dataset that can be used to guide large-scale field operations, to integrate hydrologic and ecological responses, and to support biological and ecological assessments that measure ecosystem responses to the Comprehensive Everglades Restoration Plan (Telis, 2006). To produce historic and near-real time maps of water depths, the EDEN requires a system-wide digital elevation model (DEM) of the ground surface. Accurate Everglades wetland ground surface elevation data were non-existent before the U.S. Geological Survey (USGS) undertook the collection of highly accurate surface elevations at the regional scale. These form the foundation for EDEN DEM development. This development process is iterative as additional high accuracy elevation data (HAED) are collected, water surfacing algorithms improve, and additional ground-based ancillary data become available. Models are tested using withheld HAED and independently measured water depth data, and by using DEM data in EDEN adaptive management applications. Here the collection of HAED is briefly described before the approach to DEM development and the current EDEN DEM are detailed. Finally future research directions for continued model development, testing, and refinement are provided.

  13. Incremental terrain processing for large digital elevation models

    NASA Astrophysics Data System (ADS)

    Ye, Z.

    2012-12-01

    Incremental terrain processing for large digital elevation models Zichuan Ye, Dean Djokic, Lori Armstrong Esri, 380 New York Street, Redlands, CA 92373, USA (E-mail: zye@esri.com, ddjokic@esri.com , larmstrong@esri.com) Efficient analyses of large digital elevation models (DEM) require generation of additional DEM artifacts such as flow direction, flow accumulation and other DEM derivatives. When the DEMs to analyze have a large number of grid cells (usually > 1,000,000,000) the generation of these DEM derivatives is either impractical (it takes too long) or impossible (software is incapable of processing such a large number of cells). Different strategies and algorithms can be put in place to alleviate this situation. This paper describes an approach where the overall DEM is partitioned in smaller processing units that can be efficiently processed. The processed DEM derivatives for each partition can then be either mosaicked back into a single large entity or managed on partition level. For dendritic terrain morphologies, the way in which partitions are to be derived and the order in which they are to be processed depend on the river and catchment patterns. These patterns are not available until flow pattern of the whole region is created, which in turn cannot be established upfront due to the size issues. This paper describes a procedure that solves this problem: (1) Resample the original large DEM grid so that the total number of cells is reduced to a level for which the drainage pattern can be established. (2) Run standard terrain preprocessing operations on the resampled DEM to generate the river and catchment system. (3) Define the processing units and their processing order based on the river and catchment system created in step (2). (4) Based on the processing order, apply the analysis, i.e., flow accumulation operation to each of the processing units, at the full resolution DEM. (5) As each processing unit is processed based on the processing order defined

  14. Planialtimetric Accuracy Evaluation of Digital Surface Model (dsm) and Digital Terrain Model (dtm) Obtained from Aerial Survey with LIDAR

    NASA Astrophysics Data System (ADS)

    Cruz, C. B. M.; Barros, R. S.; Rabaco, L. M. L.

    2012-07-01

    characteristics may be evaluated to get an indication for other situations. As to the assessment of the altimetric accuracy, we are going to do more analysis with points obtained under the forest canopy in order to be able to assess the real accuracy of the DTM in areas with forest cover. Studies that focus the development of new methodologies for obtaining Digital Elevation Models (DEM) are very important, especially in large scales, seeking to generate data with cost-benefit's advantages. This way, topographic features can be obtained for wider areas of our country, meeting the needs of most studies and activities related to the representation of these kind of data.

  15. Advances in the data compression of digital elevation models

    NASA Astrophysics Data System (ADS)

    Kidner, David B.; Smith, Derek H.

    2003-10-01

    The maintenance and dissemination of spatial databases requires efficient strategies for handling the large volumes of data that are now publicly available. In particular, satellite and aerial imagery, radar, LiDAR, and digital elevation models (DEMs) are being utilised by a sizeable user-base, for predominantly environmental applications. The efficient dissemination of such datasets has become a key issue in the development of web-based and distributed computing environments. However, the physical size of these datasets is a major bottleneck in their storage and transmission. The problem is often exaggerated when the data is supplied in less efficient, proprietary or national data formats. This paper presents a methodology for the lossless compression of DEMs, based on the statistical correlation of terrain data in local neighbourhoods. Most data and image compression algorithms fail to capitalise fully on the inherent redundancy in spatial data. At the same time, users often prefer a uniform solution to all their data compression requirements, but these solutions may be far from optimal. The approach presented here can be thought of as a simple pre-processing of the elevation data before the use of traditional data compression software frequently applied to spatial data sets, such as GZIP. Identification and removal of the spatial redundancy in terrain data, with the use of optimal predictors for DEMs and optimal statistical encoders such as Arithmetic Coding, gives even higher compression ratios. Both GZIP and our earlier approach of combining a simple linear prediction algorithm with Huffman Coding are shown to be far from optimal in identifying and removing the spatial redundancy in DEMs. The new approaches presented here typically halve the file sizes of our earlier approach, and give a 40-62% improvement on GZIP-compressed DEMs.

  16. Quality Assessment for the First Part of the Tandem-X Global Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Brautigam, B.; Martone, M.; Rizzoli, P.; Gonzalez, C.; Wecklich, C.; Borla Tridon, D.; Bachmann, M.; Schulze, D.; Zink, M.

    2015-04-01

    TanDEM-X is an innovative synthetic aperture radar (SAR) mission with the main goal to generate a global and homogeneous digital elevation model (DEM) of the Earth's land masses. The final DEM product will reach a new dimension of detail with respect to resolution and quality. The absolute horizontal and vertical accuracy shall each be less than 10 m in a 90% confidence interval at a pixel spacing of 12 m. The relative vertical accuracy specification for the TanDEM-X mission foresees a 90% point-to-point error of 2 m (4 m) for areas with predominant terrain slopes smaller than 20% (greater than 20%) within a 1° longitude by 1° latitude cell. The global DEM is derived from interferometric SAR acquisitions performed by two radar satellites flying in close orbit formation. Interferometric performance parameters like the coherence between the two radar images have been monitored and evaluated throughout the mission. In a further step, over 500,000 single SAR scenes are interferometrically processed, calibrated, and mosaicked into a global DEM product which will be completely available in the second half of 2016. This paper presents an up-todate quality status of the single interferometric acquisitions as well as of 50% of the final DEM. The overall DEM quality of these first products promises accuracies well within the specification, especially in terms of absolute height accuracy.

  17. 3D Color Digital Elevation Map of AFM Sample

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This color image is a three dimensional (3D) view of a digital elevation map of a sample collected by NASA's Phoenix Mars Lander's Atomic Force Microscope (AFM).

    The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate, which is the background plane shown in red. This image has been processed to reflect the levelness of the substrate.

    A Martian particle only one micrometer, or one millionth of a meter, across is held in the upper left pit.

    The rounded particle shown at the highest magnification ever seen from another world is a particle of the dust that cloaks Mars. Such dust particles color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars' distinctive red soil.

    The particle was part of a sample informally called 'Sorceress' delivered to the AFM on the 38th Martian day, or sol, of the mission (July 2, 2008). The AFM is part of Phoenix's microscopic station called MECA, or the Microscopy, Electrochemistry, and Conductivity Analyzer.

    The AFM was developed by a Swiss-led consortium, with Imperial College London producing the silicon substrate that holds sampled particles.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  18. Fast Ray Tracing of Lunar Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    McClanahan, Timothy P.; Evans, L. G.; Starr, R. D.; Mitrofanov, I.

    2009-01-01

    Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment.

  19. Validation of the ASTER Global Digital Elevation Model Version 2 over the conterminous United States

    USGS Publications Warehouse

    Gesch, Dean B.; Oimoen, Michael J.; Zhang, Zheng; Meyer, David J.; Danielson, Jeffrey J.

    2012-01-01

    The ASTER Global Digital Elevation Model Version 2 (GDEM v2) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009. The absolute vertical accuracy of GDEM v2 was calculated by comparison with more than 18,000 independent reference geodetic ground control points from the National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v2 is 8.68 meters. This compares with the RMSE of 9.34 meters for GDEM v1. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v2 mean error of -0.20 meters is a significant improvement over the GDEM v1 mean error of -3.69 meters. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover to examine the effects of cover types on measured errors. The GDEM v2 mean errors by land cover class verify that the presence of aboveground features (tree canopies and built structures) cause a positive elevation bias, as would be expected for an imaging system like ASTER. In open ground classes (little or no vegetation with significant aboveground height), GDEM v2 exhibits a negative bias on the order of 1 meter. GDEM v2 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v2 has elevations that are higher in the canopy than SRTM.

  20. Analytical basis for determining slope lines in grid digital elevation models

    NASA Astrophysics Data System (ADS)

    Orlandini, Stefano; Moretti, Giovanni; Gavioli, Andrea

    2014-01-01

    An analytical basis for the determination of slope lines in grid digital elevation models is provided by using the D8-LTD method (eight slope directions, least transverse deviation). The D8-LTD method's capability to predict consistently exact slope lines as the grid cell size goes to zero is shown analytically by applying mathematical analysis methods. The use of cumulative, least transverse deviations is found to be the key factor allowing for globally unbiased approximations of slope lines. The D8-LTD method's properties are also demonstrated numerically by using digital elevation models of a synthetic sloping surface obtained from the Himmelblau function. It is shown that slope lines obtained from the D8-LTD method can approximate the exact slope lines as close as desired by selecting a grid cell size that is small enough. In contrast, the standard D8 method is found to produce significantly biased results even when small grid cells are used. The D8-LTD method outperforms the D8 method over a wide range of grid cell sizes (up to 20 m in this application), beyond which grid cell size becomes too large to validly represent the underlying sloping surface. It is therefore concluded that the D8-LTD method should be used in preference to the standard D8 method in order to obtain slope lines that are only limited in reliability by the detail of topographic data, and not by the accuracy of the slope direction method applied.

  1. Google Earth's derived digital elevation model: A comparative assessment with Aster and SRTM data

    NASA Astrophysics Data System (ADS)

    Rusli, N.; Majid, M. R.; Din, A. H. M.

    2014-02-01

    This paper presents a statistical analysis showing additional evidence that Digital Elevation Model (DEM) derived from Google Earth is commendable and has a good correlation with ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) and SRTM (Shuttle Radar Topography Mission) elevation data. The accuracy of DEM elevation points from Google Earth was compared against that of DEMs from ASTER and SRTM for flat, hilly and mountainous sections of a pre-selected rural watershed. For each section, a total of 5,000 DEM elevation points were extracted as samples from each type of DEM data. The DEM data from Google Earth and SRTM for flat and hilly sections are strongly correlated with the R2 of 0.791 and 0.891 respectively. Even stronger correlation is shown for the mountainous section where the R2 values between Google Earth's DEM and ASTER's and between Google Earth's DEM and SRTM's DEMs are respectively 0.917 and 0.865. Further accuracy testing was carried out by utilising the DEM dataset to delineate Muar River's watershed boundary using ArcSWAT2009, a hydrological modelling software. The result shows that the percentage differences of the watershed size delineated from Google Earth's DEM compared to those derived from Department of Irrigation and Drainage's data (using 20m-contour topographic map), ASTER and SRTM data are 9.6%, 10.6%, and 7.6% respectively. It is therefore justified to conclude that the DEM derived from Google Earth is relatively as acceptable as DEMs from other sources.

  2. Assessing the accuracy and repeatability of automated photogrammetrically generated digital surface models from unmanned aerial system imagery

    NASA Astrophysics Data System (ADS)

    Chavis, Christopher

    Using commercial digital cameras in conjunction with Unmanned Aerial Systems (UAS) to generate 3-D Digital Surface Models (DSMs) and orthomosaics is emerging as a cost-effective alternative to Light Detection and Ranging (LiDAR). Powerful software applications such as Pix4D and APS can automate the generation of DSM and orthomosaic products from a handful of inputs. However, the accuracy of these models is relatively untested. The objectives of this study were to generate multiple DSM and orthomosaic pairs of the same area using Pix4D and APS from flights of imagery collected with a lightweight UAS. The accuracy of each individual DSM was assessed in addition to the consistency of the method to model one location over a period of time. Finally, this study determined if the DSMs automatically generated using lightweight UAS and commercial digital cameras could be used for detecting changes in elevation and at what scale. Accuracy was determined by comparing DSMs to a series of reference points collected with survey grade GPS. Other GPS points were also used as control points to georeference the products within Pix4D and APS. The effectiveness of the products for change detection was assessed through image differencing and observance of artificially induced, known elevation changes. The vertical accuracy with the optimal data and model is ≈ 25 cm and the highest consistency over repeat flights is a standard deviation of ≈ 5 cm. Elevation change detection based on such UAS imagery and DSM models should be viable for detecting infrastructure change in urban or suburban environments with little dense canopy vegetation.

  3. Digital Elevation Model, 0.25 m, Barrow Environmental Observatory, Alaska, 2013

    DOE Data Explorer

    Cathy Wilson; Garrett Altmann

    2015-11-20

    This 0.25m horizontal resolution digital elevation model, DEM, was developed from Airborne Laser Altimetry flown by Aerometric Inc, now known as Quantum Spatial, Inc. on 12 July, 2013. One Mission was flown and the data jointly processed with LANL personnel to produce a 0.25m DEM covering a region approximately 2.8km wide and 12.4km long extending from the coast above North Salt Lagoon to south of Gas Well Road. This DEM encompasses a diverse range of hydrologic, geomorphic, geophysical and biological features typical of the Barrow Peninsula. Vertical accuracy at the 95% confidence interval was computed as 0.143m. The coordinate system, datum, and geoid for this DEM are UTM Zone 4N, NAD83 (2011), NAVD88 (GEOID09).

  4. Robust Mosaicking of Stereo Digital Elevation Models from the Ames Stereo Pipeline

    NASA Technical Reports Server (NTRS)

    Kim, Tae Min; Moratto, Zachary M.; Nefian, Ara Victor

    2010-01-01

    Robust estimation method is proposed to combine multiple observations and create consistent, accurate, dense Digital Elevation Models (DEMs) from lunar orbital imagery. The NASA Ames Intelligent Robotics Group (IRG) aims to produce higher-quality terrain reconstructions of the Moon from Apollo Metric Camera (AMC) data than is currently possible. In particular, IRG makes use of a stereo vision process, the Ames Stereo Pipeline (ASP), to automatically generate DEMs from consecutive AMC image pairs. However, the DEMs currently produced by the ASP often contain errors and inconsistencies due to image noise, shadows, etc. The proposed method addresses this problem by making use of multiple observations and by considering their goodness of fit to improve both the accuracy and robustness of the estimate. The stepwise regression method is applied to estimate the relaxed weight of each observation.

  5. Hydrological landscape analysis based on digital elevation data

    NASA Astrophysics Data System (ADS)

    Seibert, J.; McGlynn, B.; Grabs, T.; Jensco, K.

    2008-12-01

    Topography is a major factor controlling both hydrological and soil processes at the landscape scale. While this is well-accepted qualitatively, quantifying relationships between topography and spatial variations of hydrologically relevant variables at the landscape scale still remains a challenging research topic. In this presentation, we describe hydrological landscape analysis HLA) as a way to derive relevant topographic indicies to describe the spatial variations of hydrological variables at the landscape scale. We demonstrate our HLA approach with four high-resolution digital elevation models (DEMs) from Sweden, Switzerland and Montana (USA). To investigate scale effects HLA metrics, we compared DEMs of different resolutions. These LiDAR-derived DEMs of 3m, 10m, and 30m, resolution represent catchments of ~ 5 km2 ranging from low to high relief. A central feature of HLA is the flowpath-based analysis of topography and the separation of hillslopes, riparian areas, and the stream network. We included the following metrics: riparian area delineation, riparian buffer potential, separation of stream inflows into right and left bank components, travel time proxies based on flowpath distances and gradients to the channel, and as a hydrologic similarity to the hypsometric curve we suggest the distribution of elevations above the stream network (computed based on the location where a certain flow pathway enters the stream). Several of these indices depended clearly on DEM resolution, whereas this effect was minor for others. While the hypsometric curves all were S-shaped the 'hillslope-hypsometric curves' had the shape of a power function with exponents less than 1. In a similar way we separated flow pathway lengths and gradients between hillslopes and streams and compared a topographic travel time proxy, which was based on the integration of gradients along the flow pathways. Besides the comparison of HLA-metrics for different catchments and DEM resolutions we present

  6. Dune Morphometry in the Age of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Lancaster, N.

    2014-12-01

    Dune patterns can be characterized in many different ways. Relationships between dune height, width and spacing, and the spatial variation in these parameters have been widely employed to provide quantitative information that can be used to describe dune patterns and make comparisons between dunes in widely separated areas, as well as to identify different generations of dunes. Digital elevation models (e.g. ASTER GDEM) provide a rich resource of data for analyses of dune patterns at landscape scales in several ways, including: (1) more extensive analyses using traditional measures, such as relationships between dune height and spacing, and the spatial variation in these parameters; and (2) estimation of sediment thickness on a regional scale. Analyses of data for Arabian and Namibian sand seas and dune fields show that dune height and spacing relationships are much more variable than previously reported and call into question existing models. Regional patterns of sediment thickness reveal areas of erosion, bypass, and accumulation that can be related to transport pathways and wind regimes. The widespread occurrence of complex dune patterns as well as the magnitude of the newly available data sets however requires more sophisticated analyses than simple extraction of dune morphometric parameters using GIS approaches. Geostatistical analyses using spatial autocorrelation, Fourier, and Wavelet methods have been employed in analyses of sub-aqueous bedforms and show promise for dune systems. Automated or semi-automated identification of dune length, width, spacing, and trends using advanced image analysis techniques such as linear segment detection is a potentially transformative approach. The strengths and weaknesses of these methods to provide pertinent geomorphic information are currently being evaluated, but they have the potential to provide new insights into the nature of dune patterns.

  7. Uav Aerial Survey: Accuracy Estimation for Automatically Generated Dense Digital Surface Model and Orthothoto Plan

    NASA Astrophysics Data System (ADS)

    Altyntsev, M. A.; Arbuzov, S. A.; Popov, R. A.; Tsoi, G. V.; Gromov, M. O.

    2016-06-01

    A dense digital surface model is one of the products generated by using UAV aerial survey data. Today more and more specialized software are supplied with modules for generating such kind of models. The procedure for dense digital model generation can be completely or partly automated. Due to the lack of reliable criterion of accuracy estimation it is rather complicated to judge the generation validity of such models. One of such criterion can be mobile laser scanning data as a source for the detailed accuracy estimation of the dense digital surface model generation. These data may be also used to estimate the accuracy of digital orthophoto plans created by using UAV aerial survey data. The results of accuracy estimation for both kinds of products are presented in the paper.

  8. Self-mixing digital closed-loop vibrometer for high accuracy vibration measurements

    NASA Astrophysics Data System (ADS)

    Magnani, Alessandro; Melchionni, Dario; Pesatori, Alessandro; Norgia, Michele

    2016-04-01

    The novelty of Self-mixing interferometry is represented by the combination of high accuracy and contactless operation with compact, very-low-cost and user-friendly setup. This paper introduces state of the art techniques to monitor vibrations focusing on a novel digital feedback vibrometer. It exploits a control loop to delete interferometric signal distortion and improve measurement accuracy. A digital implementation is proposed to enhance system performances through a real-time elaboration.

  9. Global Digital Image Mosaics of Mars: Assessment of Geodetic Accuracy

    NASA Technical Reports Server (NTRS)

    Kirk, R.; Archinal, B. A.; Lee, E. M.; Davies, M. E.; Colvin, T. R.; Duxbury, T. C.

    2001-01-01

    A revised global image mosaic of Mars (MDIM 2.0) was recently completed by USGS. Comparison with high-resolution gridded Mars Orbiter Laser Altimeter (MOLA) digital image mosaics will allow us to quantify its geodetic errors; linking the next MDIM to the MOLA data will help eliminate those errors. Additional information is contained in the original extended abstract.

  10. Enhancing a RADARSAT/ICESat Digital Elevation Model of West Antarctica Using MODIS Imagery

    NASA Astrophysics Data System (ADS)

    Haran, T. M.; Scambos, T. A.

    2007-12-01

    An image enhancement approach is used to develop a new digital elevation map of West Antarctica, combining multiple MODIS images and both radar altimetry and ICESat laser altimetry Digital Elevation Model (DEM) data. The method combines the wide image coverage of MODIS, and its high radiometric sensitivity (which equates to high sunward slope sensitivity), with the high precision and accuracy of ICESat and combined ICESat and radar altimetry DEMs. We calibrate brightness-to-slope relationships for several MODIS images of the central West Antarctic using smoothed DEMs derived from both sources. Using the calibrations, we then created, first, a slope map of the ice sheet surface from the image data (regressing slope information from many images), and then integrated this absolute slope map to yield complete DEMs for the region. ICESat (as of September 2007) has acquired a series of eleven near-repeat tracks over the Antarctic during the period September 2003 to April 2007, covering the continent to 86 deg S. ICESat data are acquired as a series of spot elevations, averaging a ~60m diameter surface region every ~172m. However, ICESat track paths have spacings wide enough (2 km at 85 deg; 20 - 50 km at 75 deg) that some surface ice dynamical features (e.g. flowlines, undulations, ice rises) are missed by the track data used to construct the ICESat DEM. Radar altimetry can provide some of the missing data north of 81.5 deg, but only to a maximum resolution of about 5 km. A set of cloud-cleared MODIS band 1 data from both the Aqua and Terra platforms acquired during the 2003-2004 austral summer, used in generating the Mosaic of Antarctica, MOA, surface morphology image map, were used for the image enhancement. Past analyses of the slope-brightness relationship for MODIS have shown ice surface slope precisions of +/- 0.00015. ICESat spot elevations have nominal precisions of ~5 cm under ideal conditions, although thin-cloud effects and mislocation errors can magnify these

  11. Assessing the quality for hydrological applications of digital elevation models derived from contours

    NASA Astrophysics Data System (ADS)

    Wise, Stephen

    2000-07-01

    Digital elevation models (DEMs) are becoming increasingly important tools in hydrological research and in water resources management. The quality of DEMs, however, normally is reported simply as the root mean square error of elevation, a statistic that fails to capture the numerous sources of error in DEMs or to predict their effect on the result of using the DEM. This paper presents a review of other approaches to assessing DEM quality, and argues that a full assessment of DEM quality must focus on the accuracy and reliability of the final product of the DEM analysis. A number of DEMs for the Slapton Ley catchments in Devon derived from digitized contour data are compared in an initial assessment of their sustainability for use in hydrological work. Two are available for purchase from data suppliers, and five more were created using a variety of interpolation techniques in widely available geographical information system software. The different interpretation methods produce DEMs with different artefacts, although analyses of the distribution of elevation values, and visual techniques, suggested that none of these were of a particularly pronounced nature. The results of using the DEMs to derive drainage networks and catchment areas showed that at the broad scale there was a high level of agreement between the DEMs. There were, however, important differences of detail. For example, some DEMs predicted drainage lines that occasionally crossed the original contours. The results of calculating the TOPMODEL topographic index showed far more variation, because the index is calculated for each pixel in the area, rather than being an aggregate result derived from numerous pixels. The main conclusion was that care should always be taken to assess the quality of a DEM before attempting to use it, and that results should always be checked to ensure that they appear to be reasonable.

  12. Back to the Future: Have Remotely Sensed Digital Elevation Models Improved Hydrological Parameter Extraction?

    NASA Astrophysics Data System (ADS)

    Jarihani, B.

    2015-12-01

    Digital Elevation Models (DEMs) that accurately replicate both landscape form and processes are critical to support modeling of environmental processes. Pre-processing analysis of DEMs and extracting characteristics of the watershed (e.g., stream networks, catchment delineation, surface and subsurface flow paths) is essential for hydrological and geomorphic analysis and sediment transport. This study investigates the status of the current remotely-sensed DEMs in providing advanced morphometric information of drainage basins particularly in data sparse regions. Here we assess the accuracy of three available DEMs: (i) hydrologically corrected "H-DEM" of Geoscience Australia derived from the Shuttle Radar Topography Mission (SRTM) data; (ii) the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) version2 1-arc-second (~30 m) data; and (iii) the 9-arc-second national GEODATA DEM-9S ver3 from Geoscience Australia and the Australian National University. We used ESRI's geospatial data model, Arc Hydro and HEC-GeoHMS, designed for building hydrologic information systems to synthesize geospatial and temporal water resources data that support hydrologic modeling and analysis. A coastal catchment in northeast Australia was selected as the study site where very high resolution LiDAR data are available for parts of the area as reference data to assess the accuracy of other lower resolution datasets. This study provides morphometric information for drainage basins as part of the broad research on sediment flux from coastal basins to Great Barrier Reef, Australia. After applying geo-referencing and elevation corrections, stream and sub basins were delineated for each DEM. Then physical characteristics for streams (i.e., length, upstream and downstream elevation, and slope) and sub-basins (i.e., longest flow lengths, area, relief and slopes) were extracted and compared with reference datasets from LiDAR. Results showed that

  13. Digital Elevation Model from Non-Metric Camera in Uas Compared with LIDAR Technology

    NASA Astrophysics Data System (ADS)

    Dayamit, O. M.; Pedro, M. F.; Ernesto, R. R.; Fernando, B. L.

    2015-08-01

    Digital Elevation Model (DEM) data as a representation of surface topography is highly demanded for use in spatial analysis and modelling. Aimed to that issue many methods of acquisition data and process it are developed, from traditional surveying until modern technology like LIDAR. On the other hands, in a past four year the development of Unamend Aerial System (UAS) aimed to Geomatic bring us the possibility to acquire data about surface by non-metric digital camera on board in a short time with good quality for some analysis. Data collectors have attracted tremendous attention on UAS due to possibility of the determination of volume changes over time, monitoring of the breakwaters, hydrological modelling including flood simulation, drainage networks, among others whose support in DEM for proper analysis. The DEM quality is considered as a combination of DEM accuracy and DEM suitability so; this paper is aimed to analyse the quality of the DEM from non-metric digital camera on UAS compared with a DEM from LIDAR corresponding to same geographic space covering 4 km2 in Artemisa province, Cuba. This area is in a frame of urban planning whose need to know the topographic characteristics in order to analyse hydrology behaviour and decide the best place for make roads, building and so on. Base on LIDAR technology is still more accurate method, it offer us a pattern for test DEM from non-metric digital camera on UAS, whose are much more flexible and bring a solution for many applications whose needs DEM of detail.

  14. High Resolution Digital Elevation Models of Pristine Explosion Craters

    NASA Technical Reports Server (NTRS)

    Farr, T. G.; Krabill, W.; Garvin, J. B.

    2004-01-01

    In order to effectively capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained high resolution digital elevation models of several pristine explosion craters at the Nevada Test Site. We used the Airborne Terrain Mapper (ATM), operated by NASA's Wallops Flight Facility to obtain DEMs with 1 m spacing and 10 cm vertical errors of 4 main craters and many other craters and collapse pits. The main craters that were mapped are Sedan, Scooter, Schooner, and Danny Boy. The 370 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of a controlled detonation of a 100 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a simple crater. Sedan was formed in alluvium of mixed lithology and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also mapped by ATM. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m) craters were also important targets for ATM as they were excavated in hard basalt and therefore have much rougher ejecta. This will allow study of ejecta patterns in hard rock as well as engineering tests of crater and rock avoidance and rover trafficability. In addition to the high resolution DEMs, crater geometric characteristics, RMS roughness maps, and other higher-order derived data products will be generated using these data. These will provide constraints for models of landing hazards on Mars and for rover trafficability. Other planned studies will include ejecta size-frequency distribution at the resolution of the DEM and at finer resolution through air photography and field measurements

  15. Accuracy of intraoral and extraoral digital data acquisition for dental restorations

    PubMed Central

    Rudolph, Heike; Salmen, Harald; Moldan, Matthias; Kuhn, Katharina; Sichwardt, Viktor; Wöstmann, Bernd; Luthardt, Ralph Gunnar

    2016-01-01

    ABSTRACT The computer-aided design (CAD) and computer-aided manufacturing (CAM) process chain for dental restorations starts with taking an impression of the clinical situation. For this purpose, either extraoral digitization of gypsum models or intraoral digitization can be used. Despite the increasing use of dental digitizing systems, there are only few studies on their accuracy. Objective This study compared the accuracy of various intraoral and extraoral digitizing systems for dental CAD/CAM technology. Material and Methods An experimental setup for three-dimensional analysis based on 2 prepared ceramic master dies and their corresponding virtual CAD-models was used to assess the accuracy of 10 extraoral and 4 intraoral optical non-contact dental digitizing systems. Depending on the clinical procedure, 10 optical measurements of either 10 duplicate gypsum dies (extraoral digitizing) or directly of the ceramic master dies (intraoral digitizing) were made and compared with the corresponding CAD-models. Results The digitizing systems showed differences in accuracy. However, all topical systems were well within the benchmark of ±20 µm. These results apply to single tooth measurements. Conclusions Study results are limited, since only single teeth were used for comparison. The different preparations represent various angles and steep and parallel opposing tooth surfaces (incisors). For most digitizing systems, the latter are generally the most difficult to capture. Using CAD/CAM technologies, the preparation angles should not be too steep to reduce digitizing errors. Older systems might be limited to a certain height or taper of the prepared tooth, whereas newer systems (extraoral as well as intraoral digitization) do not have these limitations. PMID:27008261

  16. Accuracy of intraoral and extraoral digital data acquisition for dental restorations.

    PubMed

    Rudolph, Heike; Salmen, Harald; Moldan, Matthias; Kuhn, Katharina; Sichwardt, Viktor; Wöstmann, Bernd; Luthardt, Ralph Gunnar

    2016-02-01

    The computer-aided design (CAD) and computer-aided manufacturing (CAM) process chain for dental restorations starts with taking an impression of the clinical situation. For this purpose, either extraoral digitization of gypsum models or intraoral digitization can be used. Despite the increasing use of dental digitizing systems, there are only few studies on their accuracy. Objective This study compared the accuracy of various intraoral and extraoral digitizing systems for dental CAD/CAM technology. Material and Methods An experimental setup for three-dimensional analysis based on 2 prepared ceramic master dies and their corresponding virtual CAD-models was used to assess the accuracy of 10 extraoral and 4 intraoral optical non-contact dental digitizing systems. Depending on the clinical procedure, 10 optical measurements of either 10 duplicate gypsum dies (extraoral digitizing) or directly of the ceramic master dies (intraoral digitizing) were made and compared with the corresponding CAD-models. Results The digitizing systems showed differences in accuracy. However, all topical systems were well within the benchmark of ±20 µm. These results apply to single tooth measurements. Conclusions Study results are limited, since only single teeth were used for comparison. The different preparations represent various angles and steep and parallel opposing tooth surfaces (incisors). For most digitizing systems, the latter are generally the most difficult to capture. Using CAD/CAM technologies, the preparation angles should not be too steep to reduce digitizing errors. Older systems might be limited to a certain height or taper of the prepared tooth, whereas newer systems (extraoral as well as intraoral digitization) do not have these limitations. PMID:27008261

  17. Comparison of Surface Flow Features from Lidar-Derived Digital Elevation Models with Historical Elevation and Hydrography Data for Minnehaha County, South Dakota

    USGS Publications Warehouse

    Poppenga, Sandra K.; Worstell, Bruce B.; Stoker, Jason M.; Greenlee, Susan K.

    2009-01-01

    The U.S. Geological Survey (USGS) has taken the lead in the creation of a valuable remote sensing product by incorporating digital elevation models (DEMs) derived from Light Detection and Ranging (lidar) into the National Elevation Dataset (NED), the elevation layer of 'The National Map'. High-resolution lidar-derived DEMs provide the accuracy needed to systematically quantify and fully integrate surface flow including flow direction, flow accumulation, sinks, slope, and a dense drainage network. In 2008, 1-meter resolution lidar data were acquired in Minnehaha County, South Dakota. The acquisition was a collaborative effort between Minnehaha County, the city of Sioux Falls, and the USGS Earth Resources Observation and Science (EROS) Center. With the newly acquired lidar data, USGS scientists generated high-resolution DEMs and surface flow features. This report compares lidar-derived surface flow features in Minnehaha County to 30- and 10-meter elevation data previously incorporated in the NED and ancillary hydrography datasets. Surface flow features generated from lidar-derived DEMs are consistently integrated with elevation and are important in understanding surface-water movement to better detect surface-water runoff, flood inundation, and erosion. Many topographic and hydrologic applications will benefit from the increased availability of accurate, high-quality, and high-resolution surface-water data. The remotely sensed data provide topographic information and data integration capabilities needed for meeting current and future human and environmental needs.

  18. An algorithm for treating flat areas and depressions in digital elevation models using linear interpolation

    EPA Science Inventory

    Digital elevation model (DEM) data are essential to hydrological applications and have been widely used to calculate a variety of useful topographic characteristics, e.g., slope, flow direction, flow accumulation area, stream channel network, topographic index, and others. Excep...

  19. Quantifying Slopes with Digital Elevation Models of the Verdugo Hills, California: Effects of Resolution

    NASA Technical Reports Server (NTRS)

    Fielding, E. J.; Burbank, D. W.; Duncan, C. C.

    1996-01-01

    Quantification of surface slope angles is valuable in a wide variety of earth sciences. Slopes measured from digital elevation models (DEMs) or other topographic data sets depend strongly on the length scale or window size used in the slope calculations.

  20. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978-1987.

    PubMed

    Korsgaard, Niels J; Nuth, Christopher; Khan, Shfaqat A; Kjeldsen, Kristian K; Bjørk, Anders A; Schomacker, Anders; Kjær, Kurt H

    2016-01-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978-1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps. PMID:27164457

  1. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978–1987

    PubMed Central

    Korsgaard, Niels J.; Nuth, Christopher; Khan, Shfaqat A.; Kjeldsen, Kristian K.; Bjørk, Anders A.; Schomacker, Anders; Kjær, Kurt H.

    2016-01-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978–1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps. PMID:27164457

  2. A new lunar digital elevation model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera

    NASA Astrophysics Data System (ADS)

    Barker, M. K.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Haruyama, J.; Smith, D. E.

    2016-07-01

    We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512 pixels per degree (∼60 m at the equator) and a typical vertical accuracy ∼3 to 4 m. This DEM is constructed from ∼ 4.5 ×109 geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1° × 1°) from the SELENE Terrain Camera (TC) (∼1010 pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of <5 m compared to ∼ 50% prior to co-registration. We use the co-registered TC data to estimate and correct orbital and pointing geolocation errors from the LOLA altimetric profiles (typically amounting to <10 m horizontally and <1 m vertically). By combining both co-registered datasets, we obtain a near-global DEM with high geodetic accuracy, and without the need for surface interpolation. We evaluate the resulting LOLA + TC merged DEM (designated as "SLDEM2015") with particular attention to quantifying seams and crossover errors.

  3. Levee crest elevation profiles derived from airborne lidar-based high resolution digital elevation models in south Louisiana

    USGS Publications Warehouse

    Palaseanu-Lovejoy, Monica; Thatcher, Cindy A.; Barras, John A.

    2014-01-01

    This study explores the feasibility of using airborne lidar surveys to derive high-resolution digital elevation models (DEMs) and develop an automated procedure to extract levee longitudinal elevation profiles for both federal levees in Atchafalaya Basin and local levees in Lafourche Parish. Generally, the use of traditional manual surveying methods to map levees is a costly and time consuming process that typically produces cross-levee profiles every few hundred meters, at best. The purpose of our paper is to describe and test methods for extracting levee crest elevations in an efficient, comprehensive manner using high resolution lidar generated DEMs. In addition, the vertical uncertainty in the elevation data and its effect on the resultant estimate of levee crest heights is addressed in an assessment of whether the federal levees in our study meet the USACE minimum height design criteria.

  4. Digital Elevation Models of the Earth derived from space-based observations: Advances and potential for geomorphological studies

    NASA Astrophysics Data System (ADS)

    Mouratidis, Antonios

    2013-04-01

    Digital Elevation Models (DEMs) are an inherently interdisciplinary topic, both due to their production and validation methods, as well as their significance for numerous disciplines. The most utilized contemporary topographic datasets worldwide are those of global DEMs. Several space-based sources have been used for the production of (almost) global DEMs, namely satellite Synthetic Aperture Radar (SAR) Interferometry/InSAR, stereoscopy of multispectral satellite images and altimetry, producing several versions of autonomous or mixed products (i.e. SRTM, ACE, ASTER-GDEM). Complementary space-based observations, such as those of Global Navigation Satellite Systems (GNSS), are also used, mainly for validation purposes. The apparent positive impact of these elevation datasets so far has been consolidated by the plethora of related scientific, civil and military applications. Topography is a prominent element for almost all Earth sciences, but in Geomorphology it is even more fundamental. In geomorphological studies, elevation data and thus DEMs can be extensively used for the extraction of both qualitative and quantitative information, such as relief classification, determination of slope and slope orientation, delineation of drainage basins, extraction of drainage networks and much more. Global DEMs are constantly becoming finer, i.e. of higher spatial resolution and more "sensitive" to elevation changes, i.e. of higher vertical accuracy and these progresses are undoubtedly considered as a major breakthrough, each time a new improved global DEM is released. Nevertheless, for Geomorphology in particular, if not already there, we are close to the point in time, where the need for discrimination between DSM (Digital Surface Model) and DTM (Digital Terrain Model) is becoming critical; if the distinction between vegetation and man-made structures on one side (DSM), and actual terrain elevation on the other side (DTM) cannot be made, then, in many cases, any further

  5. Validation of the Aster Global Digital Elevation Model Version 3 Over the Conterminous United States

    NASA Astrophysics Data System (ADS)

    Gesch, D.; Oimoen, M.; Danielson, J.; Meyer, D.

    2016-06-01

    The ASTER Global Digital Elevation Model Version 3 (GDEM v3) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009 and GDEM Version 2 (v2) in 2011. The absolute vertical accuracy of GDEM v3 was calculated by comparison with more than 23,000 independent reference geodetic ground control points from the U.S. National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v3 is 8.52 meters. This compares with the RMSE of 8.68 meters for GDEM v2. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v3 mean error of -1.20 meters reflects an overall negative bias in GDEM v3. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover type to provide insight into how GDEM v3 performs in various land surface conditions. While the RMSE varies little across cover types (6.92 to 9.25 meters), the mean error (bias) does appear to be affected by land cover type, ranging from -2.99 to +4.16 meters across 14 land cover classes. These results indicate that in areas where built or natural aboveground features are present, GDEM v3 is measuring elevations above the ground level, a condition noted in assessments of previous GDEM versions (v1 and v2) and an expected condition given the type of stereo-optical image data collected by ASTER. GDEM v3 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v3 has elevations that are higher in the canopy than SRTM. The overall validation effort also included an evaluation of the GDEM v3 water mask. In general, the number of distinct water polygons in GDEM v3 is much lower than the number in a reference land cover dataset, but the total areas compare much more closely.

  6. Hydrology, secondary growth, and elevation accuracy in two preliminary Amazon Basin SRTM DEMs

    NASA Astrophysics Data System (ADS)

    Alsdorf, D.; Hess, L.; Sheng, Y.; Souza, C.; Pavelsky, T.; Melack, J.; Dunne, T.; Hendricks, G.; Ballantine, A.; Holmes, K.

    2003-04-01

    Two preliminary Shuttle Radar Topography Mission digital elevation models (SRTM DEMs) of Manaus (1S to 5S and 59W to 63W) and Rondonia (9S to 12S and 61W to 64W) were received from the "PI Processor" at NASA JPL. We compared the Manaus DEM (C-band) with a previously constructed Cabaliana floodplain classification based on Global RainForest Mapping (GRFM) JERS-1 SAR data (L-band) and determined that habitats of open water, bare ground, and flooded shrub contained the lowest elevations; macrophyte and non-flooded shrub habitats are marked by intermediate elevations; and the highest elevations are found within flooded and non-flooded forest. Although the water surface typically produces specular reflections, double-bounce travel paths result from dead, leafless trees found across the Balbina reservoir near Manaus. There (i.e., in Balbina) the water surface is marked by pixel-to-pixel height changes of generally 0 to 1 m and changes across a ˜100 km transect rarely exceed 3 m. Reported SRTM errors throughout the transect range from 1 to 2 m with some errors up to 5 m. The smooth Balbina surface contrasts with the wind-roughened Amazon River surface where SRTM height variations easily range from 1 to 10 m (reported errors often exceed 5 m). Deforestation and subsequent regrowth in the Rondonia DEM is remarkably clear. Our colleagues used a 20 year sequence of Landsat TM/MSS classified imagery to delineate areas in various stages of secondary growth and we find a general trend of increasing vegetation height with increasing age. Flow path networks derived from the Cabaliana floodplain DEM are in general agreement with networks previously extracted from the GRFM mosaics; however, watershed boundaries differ. We have also developed an algorithm for extracting channel widths, which is presently being applied to the DEM and classified imagery to determine morphological variations between reaches.

  7. Comparison of 7.5-minute and 1-degree digital elevation models

    NASA Technical Reports Server (NTRS)

    Isaacson, Dennis L.; Ripple, William J.

    1995-01-01

    We compared two digital elevation models (DEM's) for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

  8. Comparison of 7.5-minute and 1-degree digital elevation models

    NASA Technical Reports Server (NTRS)

    Isaacson, Dennis L.; Ripple, William J.

    1990-01-01

    Two digital elevation models are compared for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

  9. Accuracy of Intraoral Digital Impressions for Whole Upper Jaws, Including Full Dentitions and Palatal Soft Tissues

    PubMed Central

    Gan, Ning; Xiong, Yaoyang; Jiao, Ting

    2016-01-01

    Intraoral digital impressions have been stated to meet the clinical requirements for some teeth-supported restorations, though fewer evidences were proposed for larger scanning range. The aim of this study was to compare the accuracy (trueness and precision) of intraoral digital impressions for whole upper jaws, including the full dentitions and palatal soft tissues, as well as to determine the effect of different palatal vault height or arch width on accuracy of intraoral digital impressions. Thirty-two volunteers were divided into three groups according to the palatal vault height or arch width. Each volunteer received three scans with TRIOS intraoral scanner and one conventional impression of whole upper jaw. Three-dimensional (3D) images digitized from conventional gypsum casts by a laboratory scanner were chose as the reference models. All datasets were imported to a specific software program for 3D analysis by "best fit alignment" and "3D compare" process. Color-coded deviation maps showed qualitative visualization of the deviations. For the digital impressions for palatal soft tissues, trueness was (130.54±33.95)μm and precision was (55.26±11.21)μm. For the digital impressions for upper full dentitions, trueness was (80.01±17.78)μm and precision was (59.52±11.29)μm. Larger deviations were found between intraoral digital impressions and conventional impressions in the areas of palatal soft tissues than that in the areas of full dentitions (p<0.001). Precision of digital impressions for palatal soft tissues was slightly better than that for full dentitions (p = 0.049). There was no significant effect of palatal vault height on accuracy of digital impressions for palatal soft tissues (p>0.05), but arch width was found to have a significant effect on precision of intraoral digital impressions for full dentitions (p = 0.016). A linear correlation was found between arch width and precision of digital impressions for whole upper jaws (r = 0.326, p = 0

  10. Updating flood maps efficiently using existing hydraulic models, very-high-accuracy elevation data, and a geographic information system; a pilot study on the Nisqually River, Washington

    USGS Publications Warehouse

    Jones, Joseph L.; Haluska, Tana L.; Kresch, David L.

    2001-01-01

    A method of updating flood inundation maps at a fraction of the expense of using traditional methods was piloted in Washington State as part of the U.S. Geological Survey Urban Geologic and Hydrologic Hazards Initiative. Large savings in expense may be achieved by building upon previous Flood Insurance Studies and automating the process of flood delineation with a Geographic Information System (GIS); increases in accuracy and detail result from the use of very-high-accuracy elevation data and automated delineation; and the resulting digital data sets contain valuable ancillary information such as flood depth, as well as greatly facilitating map storage and utility. The method consists of creating stage-discharge relations from the archived output of the existing hydraulic model, using these relations to create updated flood stages for recalculated flood discharges, and using a GIS to automate the map generation process. Many of the effective flood maps were created in the late 1970?s and early 1980?s, and suffer from a number of well recognized deficiencies such as out-of-date or inaccurate estimates of discharges for selected recurrence intervals, changes in basin characteristics, and relatively low quality elevation data used for flood delineation. FEMA estimates that 45 percent of effective maps are over 10 years old (FEMA, 1997). Consequently, Congress has mandated the updating and periodic review of existing maps, which have cost the Nation almost 3 billion (1997) dollars. The need to update maps and the cost of doing so were the primary motivations for piloting a more cost-effective and efficient updating method. New technologies such as Geographic Information Systems and LIDAR (Light Detection and Ranging) elevation mapping are key to improving the efficiency of flood map updating, but they also improve the accuracy, detail, and usefulness of the resulting digital flood maps. GISs produce digital maps without manual estimation of inundated areas between

  11. 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.

  12. Effect of Contrast Inversion Enhancement on the Accuracy of Endodontic File Length Determination in Digital Radiography

    PubMed Central

    Farhadi, Nastaran; Mehdizadeh, Mojdeh

    2015-01-01

    Objective The aim of this ex vivo study was to evaluate the accuracy of endodontic file length measurement on digital periapical radiographs after application of contrast inversion digital enhancement. Materials and Methods Forty single-rooted single-canal mature permanent human teeth with canals measuring 20-24 mm in length were used in this study. ISO #08 K-files were placed in the root canals of the teeth. The file lengths were measured with a digital caliper as the gold standard. Standard periapical digital images were obtained with the Digora storage phosphor plates and Digora Optime scanner as the original images. The contrast inversion option of Scanora software program version 5.1 was used to produce enhanced images. Three radiologists and three endodontists measured file lengths on the original and enhanced images. The measurements were compared using repeated measures ANOVA and Bonferroni tests (α=0.05). Results There were significant differences between the measurement accuracy of the original and enhanced images (p<0.05). The enhanced images exhibited longer measurements compared to the original images. However, the two sets of digital radiographs provided significantly longer measurements compared to the gold standard (p<0.05). Conclusion The contrast inversion tool of Scanora software program decreases measurement accuracy of the length of small endodontic files on digital periapical radiographs. It is suggested that contrast inversion should not be used in determining the lengths of small endodontic files. PMID:26155552

  13. Digital Elevation Models From ground-Based GPS As Validation For Satellite Altimetry On The Greenland Inland Ice

    NASA Astrophysics Data System (ADS)

    Stober, Manfred; Hepperle, Jorg; Rawiel, Paul

    2011-02-01

    A long-term geodetic project on the Greenland inland ice is performed in order to determine elevations, elevation change, flow velocity, and deformation of the ice surface in the western part of the Greenland ice sheet. There are two main research areas: Swiss Camp (ETH/CU-Camp) which was started in 1991, and ST2, started in 2004. Until 2008 a total of 10 measuring campaigns were carried out at Swiss Camp. The 3D-coordinates of the snow and ice surfaces were measured by ground-based static and kinematical GPS survey. As a result very precise digital elevation models of the research areas are available. The digital terrain models can be used as ground control areas for satellite altimetry. As an example, they were used for validation of ICESat satellite elevation data. Height comparisons along one track show in average a discrepancy of 0.13 m ± 0.06 m. Due to their very high accuracy, the measured areas can also be used as control areas for CryoSat. The next field measurements are planned in summer 2011. The location of the ground measurements will be coordinated with predicted tracks for CryoSat.

  14. Investigation of potential sea level rise impact on the Nile Delta, Egypt using digital elevation models.

    PubMed

    Hasan, Emad; Khan, Sadiq Ibrahim; Hong, Yang

    2015-10-01

    In this study, the future impact of Sea Level Rise (SLR) on the Nile Delta region in Egypt is assessed by evaluating the elevations of two freely available Digital Elevation Models (DEMs): the SRTM and the ASTER-GDEM-V2. The SLR is a significant worldwide dilemma that has been triggered by recent climatic changes. In Egypt, the Nile Delta is projected to face SLR of 1 m by the end of the 21th century. In order to provide a more accurate assessment of the future SLR impact on Nile Delta's land and population, this study corrected the DEM's elevations by using linear regression model with ground elevations from GPS survey. The information for the land cover types and future population numbers were derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and the Gridded Population of the Worlds (GPWv3) datasets respectively. The DEM's vertical accuracies were assessed using GPS measurements and the uncertainty analysis revealed that the SRTM-DEM has positive bias of 2.5 m, while the ASTER-GDEM-V2 showed a positive bias of 0.8 m. The future inundated land cover areas and the affected population were illustrated based on two SLR scenarios of 0.5 m and 1 m. The SRTM DEM data indicated that 1 m SLR will affect about 3900 km(2) of cropland, 1280 km(2) of vegetation, 205 km(2) of wetland, 146 km(2) of urban areas and cause more than 6 million people to lose their houses. The overall vulnerability assessment using ASTER-GDEM-V2 indicated that the influence of SLR will be intense and confined along the coastal areas. For instance, the data indicated that 1 m SLR will inundate about 580 Km(2) (6%) of the total land cover areas and approximately 887 thousand people will be relocated. Accordingly, the uncertainty analysis of the DEM's elevations revealed that the ASTER-GDEM-V2 dataset product was considered the best to determine the future impact of SLR on the Nile Delta region. PMID:26410824

  15. What's in an elevation difference? Accuracy and corrections of satellite elevation data sets for quantification of glacier changes

    NASA Astrophysics Data System (ADS)

    Nuth, C.; Kääb, A.

    2010-10-01

    There is an increasing number of DEMs available worldwide for deriving elevation differences over time, including vertical changes on glaciers. Most of these DEMs are heavily post-processed or merged, so that physical error modelling becomes impossible and statistical error modelling is required instead. We propose a three-step methodological framework for assessing and correcting DEMs to quantify glacier elevation changes: remove DEM shifts, check for elevation-dependent biases, and check for higher-order, sensor-specific biases. An analytic, simple and robust method to co-register elevation data is presented in regions where stable terrain is either plentiful (case study New Zealand) or limited (case study Svalbard). The method is exemplified using the three global elevation data sets available, SRTM, ICESat and the ASTER GDEM, and with automatically generated DEMs from satellite stereo instruments of ASTER and SPOT5-HRS. After three-dimensional co-registration, significant biases related to elevation were found in some of the stereoscopic DEMs. Biases related to the satellite acquisition geometry (along/cross track) were detected at two frequencies in the automatically generated ASTER DEMs. The higher frequency bias seems to be related to satellite emph{jitter}, most effective in the back-looking pass of the satellite. The origins of the more significant lower frequency bias is uncertain. ICESat-derived elevations are found to be the most consistent globally available elevation data set available so far. Before performing regional-scale glacier elevation change studies or mosaicking DEMs from multiple individual tiles (e.g. ASTER GDEM), we recommend to co-register all elevation data to ICESat as a global vertical reference system. The proposed methodological framework is exemplified for elevation changes on the Fox, Franz Joseph, Tasman and Murchison glaciers of New Zealand and the glaciers of central Spitsbergen, Svalbard.

  16. Accuracy, security, and processing time comparisons of biometric fingerprint recognition system using digital and optical enhancements

    NASA Astrophysics Data System (ADS)

    Alsharif, Salim; El-Saba, Aed; Jagapathi, Rajendarreddy

    2011-06-01

    Fingerprint recognition is one of the most commonly used forms of biometrics and has been widely used in daily life due to its feasibility, distinctiveness, permanence, accuracy, reliability, and acceptability. Besides cost, issues related to accuracy, security, and processing time in practical biometric recognition systems represent the most critical factors that makes these systems widely acceptable. Accurate and secure biometric systems often require sophisticated enhancement and encoding techniques that burdens the overall processing time of the system. In this paper we present a comparison between common digital and optical enhancementencoding techniques with respect to their accuracy, security and processing time, when applied to biometric fingerprint systems.

  17. "Battleship Numberline": A Digital Game for Improving Estimation Accuracy on Fraction Number Lines

    ERIC Educational Resources Information Center

    Lomas, Derek; Ching, Dixie; Stampfer, Eliane; Sandoval, Melanie; Koedinger, Ken

    2011-01-01

    Given the strong relationship between number line estimation accuracy and math achievement, might a computer-based number line game help improve math achievement? In one study by Rittle-Johnson, Siegler and Alibali (2001), a simple digital game called "Catch the Monster" provided practice in estimating the location of decimals on a number line.…

  18. [Assessment of precision and accuracy of digital surface photogrammetry with the DSP 400 system].

    PubMed

    Krimmel, M; Kluba, S; Dietz, K; Reinert, S

    2005-03-01

    The objective of the present study was to evaluate the precision and accuracy of facial anthropometric measurements obtained through digital 3-D surface photogrammetry with the DSP 400 system in comparison to traditional 2-D photogrammetry. Fifty plaster casts of cleft infants were imaged and 21 standard anthropometric measurements were obtained. For precision assessment the measurements were performed twice in a subsample. Accuracy was determined by comparison of direct measurements and indirect 2-D and 3-D image measurements. Precision of digital surface photogrammetry was almost as good as direct anthropometry and clearly better than 2-D photogrammetry. Measurements derived from 3-D images showed better congruence to direct measurements than from 2-D photos. Digital surface photogrammetry with the DSP 400 system is sufficiently precise and accurate for craniofacial anthropometric examinations. PMID:15832575

  19. Accuracy assessment of the U.S. Geological Survey National Elevation Dataset, and comparison with other large-area elevation datasets: SRTM and ASTER

    USGS Publications Warehouse

    Gesch, Dean B.; Oimoen, Michael J.; Evans, Gayla A.

    2014-01-01

    The National Elevation Dataset (NED) is the primary elevation data product produced and distributed by the U.S. Geological Survey. The NED provides seamless raster elevation data of the conterminous United States, Alaska, Hawaii, U.S. island territories, Mexico, and Canada. The NED is derived from diverse source datasets that are processed to a specification with consistent resolutions, coordinate system, elevation units, and horizontal and vertical datums. The NED serves as the elevation layer of The National Map, and it provides basic elevation information for earth science studies and mapping applications in the United States and most of North America. An important part of supporting scientific and operational use of the NED is provision of thorough dataset documentation including data quality and accuracy metrics. The focus of this report is on the vertical accuracy of the NED and on comparison of the NED with other similar large-area elevation datasets, namely data from the Shuttle Radar Topography Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER).

  20. Shoreline extraction from light detection and ranging digital elevation model data and aerial images

    NASA Astrophysics Data System (ADS)

    Yousef, Amr; Iftekharuddin, Khan M.; Karim, Mohammad A.

    2014-01-01

    There is an increased demand for understanding the accurate position of the shorelines. The automatic extraction of shorelines utilizing the digital elevation models (DEMs) obtained from light detection and ranging (LiDAR), aerial images, and multispectral images has become very promising. In this article, we develop two innovative algorithms that can effectively extract shorelines depending on the available data sources. The first is a multistep morphological technique that works on LiDAR DEM with respect to a tidal datum, whereas the second depends on the availability of training data to extract shorelines from LiDAR DEM fused with aerial images. Unlike similar techniques, the morphological approach detects and eliminates the outliers that result from waves, etc., by means of an anomaly test with neighborhood constraints. Additionally, it eliminates docks, bridges, and fishing piers along the extracted shorelines by means of Hough transform. The second approach extracts the shoreline by means of color space conversion of the aerial images and the support vector machines classifier to segment the fused data into water and land. We perform Monte-Carlo simulations to estimate the confidence interval for the error in shoreline position. Compared with other relevant techniques in literature, the proposed methods offer better accuracy in shoreline extraction.

  1. Topographic Phase Recovery from Stacked ERS Interferometry and a Low-Resolution Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.; Sichoix, Lydie; Frey, Herbert V. (Technical Monitor)

    2000-01-01

    A hybrid approach to topographic recovery from ERS interferometry is developed and assessed. Tropospheric/ionospheric artifacts, imprecise orbital information, and layover are key issues in recovering topography and surface deformation from repeat-pass interferometry. Previously, we developed a phase gradient approach to stacking interferograms to reduce these errors and also to reduce the short-wavelength phase noise (see Sandwell arid Price [1998] and Appendix A). Here the method is extended to use a low-resolution digital elevation model to constrain long-wavelength phase errors and an iteration scheme to minimize errors in the computation of phase gradient. We demonstrate the topographic phase recovery on 16-m postings using 25 ERS synthetic aperture radar images from an area of southern California containing 2700 m of relief. On the basis of a comparison with 81 GPS monuments, the ERS derived topography has a typical absolute accuracy of better than 10 m except in areas of layover. The resulting topographic phase enables accurate two-pass, real-time interferometry even in mountainous areas where traditional phase unwrapping schemes fail. As an example, we form a topography-free (127-m perpendicular baseline) interferogram spanning 7.5 years; fringes from two major earthquakes and a seismic slip on the San Andreas Fault are clearly isolated.

  2. Predicting Bed Grain Size in Threshold Channels Using Lidar Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Snyder, N. P.; Nesheim, A. O.; Wilkins, B. C.; Edmonds, D. A.

    2011-12-01

    Over the past 20 years, researchers have developed GIS-based algorithms to extract channel networks and measure longitudinal profiles from digital elevation models (DEMs), and have used these to study stream morphology in relation to tectonics, climate and ecology. The accuracy of stream elevations from traditional DEMs (10-50 m pixels) is typically limited by the contour interval (3-20 m) of the rasterized topographic map source. This is a particularly severe limitation in low-relief watersheds, where 3 m of channel elevation change may occur over several km. Lidar DEMs (~1 m pixels) allow researchers to resolve channel elevation changes of ~0.5 m, enabling reach-scale calculations of gradient, which is the most important parameter for understanding channel processes at that scale. Lidar DEMs have the additional advantage of allowing users to make estimates of channel width. We present a process-based model that predicts median bed grain size in threshold gravel-bed channels from lidar slope and width measurements using the Shields and Manning equations. We compare these predictions to field grain size measurements in segments of three Maine rivers. Like many paraglacial rivers, these have longitudinal profiles characterized by relatively steep (gradient >0.002) and flat (gradient <0.0005) segments, with length scales of several km. This heterogeneity corresponds to strong variations in channel form, sediment supply, bed grain size, and aquatic habitat characteristics. The model correctly predicts bed sediment size within a factor of two in ~70% of the study sites. The model works best in single-thread channels with relatively low sediment supply, and poorly in depositional, multi-thread and/or fine (median grain size <20 mm) reaches. We evaluate the river morphology (using field and lidar measurements) in the context of the Parker et al. (2007) hydraulic geometry relations for single-thread gravel-bed rivers, and find correspondence in the locations where both

  3. 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.

  4. Analysis of the influence of the digital elevation model characteristics on hydrodynamic simulations: the case of the Tagus River

    NASA Astrophysics Data System (ADS)

    Falcão, Ana Paula; Pestana, Rita; Matias, Magda P.; Gonçalves, Alexandre; Heleno, Sandra

    2014-05-01

    Floods are one of the major and hazardous natural events, with the potential to cause fatalities, displacement of people and damage to the environment, to severely compromise economic development and to undermine the economic activities, as the Floods Directive of the European Union clearly recalls (Directive 2007/60/EC). This Directive establishes a framework for the assessment and management of flood risks. As such, it relies on hydrodynamic simulation of floods. For this a single digital elevation model valid for the whole study area is a requirement and its construction usually implies the use of topographic and bathymetric data collected by distinct equipment and methods, at different times and acquired with a variety of spatial resolutions and accuracies. In this paper we present a comparison of hydrodynamic simulation results, in flood extension and water elevation level, of a Tagus River flood event cover the period between 5pm of December 29th, 2000 until 1am of January 9th, 2001, by using the combined digital elevation model resampled at a cell size of 15m, 30m and 50m. The study area is a section of 70 km of the Tagus River, between Tramagal and Santarém. The Tagus River is the longest of the Iberian Peninsula and is responsible for periodical floods in one of the most important agricultural areas in Portugal. For this area a digital elevation model acquired in 2008 by advanced interferometric techniques is available (5m of spatial resolution), accurate in the floodplain area but with no information in river channel since the radar signal has no ability to penetrate into water, and 29 cross-sections acquired by eco-sounder equipment in 2012, with 3km intervals are available. In order to analyse and validate those differences, a dataset with SAR imagery, provided by ESA, and the water levels measured at Almourol hydrometric station were used.

  5. Synergetic merging of Cartosat-1 and RAMP to generate improved digital elevation model of Schirmacher oasis, east Antarctica

    NASA Astrophysics Data System (ADS)

    Jawak, S. D.; Luis, A. J.

    2014-11-01

    Available digital elevation models (DEMs) of Antarctic region generated by using radar altimetry and the Antarctic digital database (ADD) indicate elevation variations of up to hundreds of meters, which necessitates the generation of local DEM and its validation by using ground reference. An enhanced digital elevation model (eDEM) of the Schirmacher oasis region, east Antarctica, is generated synergistically by using Cartosat-1 stereo pair-derived photogrammetric DEM (CartoDEM)-based point elevation dataset and multitemporal radarsat Antarctic mapping project version 2 (RAMPv2) DEM-based point elevation dataset. In this study, we analyzed suite of interpolation techniques for constructing a DEM from RAMPv2 and CartoDEM-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 improves the elevation accuracy of DEM from synergistically fused RAMPv2 and CartoDEM point elevation datasets. RAMPv2 points and CartoDEM points were used as primary data for various interpolation techniques such as ordinary kriging (OK), simple kriging (SK), universal kriging (UK), disjunctive kriging (DK) techniques, inverse distance weighted (IDW), global polynomial (GP) with power 1 and 2, local polynomial (LP) and radial basis functions (RBF). Cokriging of 2 variables with second dataset was used for ordinary cokriging (OCoK), simple cokriging (SCoK), universal cokriging (UCoK) and disjunctive cokriging (DCoK). The IDW, GP, LP, RBF, and kriging methods were applied to one variable, while Cokriging experiments were employed on two variables. The experiment of dataset and its combination produced two types of point elevation map categorized as (1) one variable (RAMPv2 Point maps and CartoDEM Point maps) and (2) two variables (RAMPv2 Point maps + CartoDEM Point maps). Interpolated surfaces were evaluated with the help of differential global positioning system

  6. Development and Utilization of High Precision Digital Elevation Data taken by Airborne Laser Scanner

    NASA Astrophysics Data System (ADS)

    Akutsu, Osamu; Ohta, Masataka; Isobe, Tamio; Ando, Hisamitsu, Noguchi, Takahiro; Shimizu, Masayuki

    2005-03-01

    Disasters caused by heavy rain in urban areas bring a damage such as chaos in the road and railway transport systems, power failure, breakdown of the telephone system and submersion of built up areas, subways and underground shopping arcades, etc. It is important to obtain high precision elevation data which shows the detailed landform because a slight height difference affects damages by flood very considerably. Therefore, The Geographical Survey Institute (GSI) is preparing 5m grid digital terrain model (DTM) based on precise ground elevation data taken by using airborne laser scanner. This paper describes the process and an example of the use of a 5m grid digital data set.

  7. Elevating student potential: creating digital video to teach neurotransmission.

    PubMed

    Jarvinen, Michael K; Jarvinen, Lamis Z

    2012-01-01

    Students today have unprecedented access to technology, the Internet, and social media. Their nearly ubiquitous use of these platforms is well documented. Given that today's students may be primed to learn using a different medium, incorporating various technological elements into the classroom in a manner compatible with traditional approaches to teaching becomes a challenge. We recently designed and implemented a strategy that capitalized on this knowledge. Students in their first neuroscience course were required to create a 3-5 minute digital video using video-making freeware available on any Mac or PC. They used images, text, animation, as well as downloaded music to describe the fundamental process of neurotransmission as it applies to a topic of their choice. In comparison to students taught using other more traditional approaches to demonstrate the process of neurotransmission, we observed that students who took part in the video-making project exhibited better understanding of the neurological process at multiple levels, as defined by Bloom's revised taxonomy. This was true even of students who had no aspirations of pursuing a Neuroscience career, thus suggesting that there was an overall increased level of student engagement regardless of personal career interests. The utility of our approach was validated by both direct and indirect assessments. Importantly, this particular strategy to teaching difficult concepts offers a high degree of flexibility allowing it to potentially be incorporated into any upper-level Neuroscience course. PMID:23493934

  8. Accuracy of a Digital Weight Scale Relative to the Nintendo Wii in Measuring Limb Load Asymmetry

    PubMed Central

    Kumar, NS Senthil; Omar, Baharudin; Joseph, Leonard H; Hamdan, Nor; Htwe, Ohnmar; Hamidun, Nursalbiyah

    2014-01-01

    [Purpose] The aim of the present study was to investigate the accuracy of a digital weight scale relative to the Wii in limb loading measurement during static standing. [Methods] This was a cross-sectional study conducted at a public university teaching hospital. The sample consisted of 24 participants (12 with osteoarthritis and 12 healthy) recruited through convenient sampling. Limb loading measurements were obtained using a digital weight scale and the Nintendo Wii in static standing with three trials under an eyes-open condition. The limb load asymmetry was computed as the symmetry index. [Results] The accuracy of measurement with the digital weight scale relative to the Nintendo Wii was analyzed using the receiver operating characteristic (ROC) curve and Kolmogorov-Smirnov test (K-S test). The area under the ROC curve was found to be 0.67. Logistic regression confirmed the validity of digital weight scale relative to the Nintendo Wii. The D statistics value from the K-S test was found to be 0.16, which confirmed that there was no significant difference in measurement between the equipment. [Conclusion] The digital weight scale is an accurate tool for measuring limb load asymmetry. The low price, easy availability, and maneuverability make it a good potential tool in clinical settings for measuring limb load asymmetry. PMID:25202181

  9. Object representations at multiple scales from digital elevation models.

    PubMed

    Drăguţ, Lucian; Eisank, Clemens

    2011-06-15

    In the last decade landform classification and mapping has developed as one of the most active areas of geomorphometry. However, translation from continuous models of elevation and its derivatives (slope, aspect, and curvatures) to landform divisions (landforms and landform elements) is filtered by two important concepts: scale and object ontology. Although acknowledged as being important, these two issues have received surprisingly little attention.This contribution provides an overview and prospects of object representation from DEMs as a function of scale. Relationships between object delineation and classification or regionalization are explored, in the context of differences between general and specific geomorphometry. A review of scales issues in geomorphometry-ranging from scale effects to scale optimization techniques-is followed by an analysis of pros and cons of using cells and objects in DEM analysis. Prospects for coupling multi-scale analysis and object delineation are then discussed. Within this context, we propose discrete geomorphometry as a possible approach between general and specific geomorphometry. Discrete geomorphometry would apply to and describe land-surface divisions defined solely by the criteria of homogeneity in respect to a given land-surface parameter or a combination of several parameters. Homogeneity, in its turn, should always be relative to scale. PMID:21760655

  10. Object representations at multiple scales from digital elevation models

    PubMed Central

    Drăguţ, Lucian; Eisank, Clemens

    2011-01-01

    In the last decade landform classification and mapping has developed as one of the most active areas of geomorphometry. However, translation from continuous models of elevation and its derivatives (slope, aspect, and curvatures) to landform divisions (landforms and landform elements) is filtered by two important concepts: scale and object ontology. Although acknowledged as being important, these two issues have received surprisingly little attention. This contribution provides an overview and prospects of object representation from DEMs as a function of scale. Relationships between object delineation and classification or regionalization are explored, in the context of differences between general and specific geomorphometry. A review of scales issues in geomorphometry—ranging from scale effects to scale optimization techniques—is followed by an analysis of pros and cons of using cells and objects in DEM analysis. Prospects for coupling multi-scale analysis and object delineation are then discussed. Within this context, we propose discrete geomorphometry as a possible approach between general and specific geomorphometry. Discrete geomorphometry would apply to and describe land-surface divisions defined solely by the criteria of homogeneity in respect to a given land-surface parameter or a combination of several parameters. Homogeneity, in its turn, should always be relative to scale. PMID:21760655

  11. The Landcover Impact on the Aspect/Slope Accuracy Dependence of the SRTM-1 Elevation Data for the Humboldt Range

    PubMed Central

    Miliaresis, George C.

    2008-01-01

    The U.S. National Landcover Dataset (NLCD) and the U.S National Elevation Dataset (NED) (bare earth elevations) were used in an attempt to assess to what extent the directional and slope dependency of the Shuttle Radar Topography Mission (SRTM) finished digital elevation model is affected by landcover. Four landcover classes: forest, shrubs, grass and snow cover, were included in the study area (Humboldt Range in NW portion of Nevada, USA). Statistics, rose diagrams, and frequency distributions of the elevation differences (NED-SRTM) per landcover class per geographic direction were used. The decomposition of elevation differences on the basis of aspect and slope terrain classes identifies a) over-estimation of elevation by the SRTM instrument along E, NE and N directions (negative elevation difference that decreases linearly with slope) while b) underestimation is evident towards W, SW and S directions (positive elevation difference increasing with slope). The aspect/slope/landcover elevation differences modelling overcome the systematic errors evident in the SRTM dataset and revealed vegetation height information and the snow penetration capability of the SRTM instrument. The linear regression lines per landcover class might provide means of correcting the systematic error (aspect/slope dependency) evident in SRTM dataset.

  12. Influence of scanning strategies on the accuracy of digital intraoral scanning systems.

    PubMed

    Ender, A; Mehl, A

    2013-01-01

    The digital intraoral impression is a central part in today's CAD/CAM dentistry. With its possibilities, new treatment options for the patient is provided and the prosthetic workflow is accelerated. Nowadays, the major issue with intraoral scanning systems is to gain more accuracy especially for larger scan areas and to simplify clinical handling for the dentist. The aim of this study was to investigate different scanning strategies regardingtheir accuracy with full arch scans in an in-vitro study design. A reference master model was used for the digital impressions with the Lava COS, the Cerec Bluecam and a powderfree intraoral scanning system, Cadent iTero. The trueness and precision of each scanning protocol was measured. Lava COS provides the a trueness of 45.8 microm with the scanning protocol recommended from the manufacturer. A different scanning protocol shows significantly lower accuracy (trueness +/- 90.2 microm). Cerec Bluecam also benefits from an optimal scanning protocol with a trueness of +/- 23.3 microm compared to +/- 52.5 microm with a standard protocol. The powderfree impression system Cadent iTero shows also a high accurate full-arch scan with a trueness of +/- 35.0 microm and a precision of +/- 30.9 microm. With the current intraoral scanning systems, full arch dental impressions are possible with a high accuracy, if adequate scan strategies are used. The powderfree scanning system provides the same level of accuracy compared to scanning systems with surface pretreatment. PMID:23641661

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

    USGS Publications Warehouse

    Haugerud, Ralph A.

    1999-01-01

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

  14. 90-METER DIGITAL ELEVATION MODEL (DEM) FOR THE MID-ATLANTIC INTEGRATED ASSESSMENT (MAIA) STUDY AREA

    EPA Science Inventory

    This data set is a geographic information system (GIS) coverage of the 90-meter digital elevation model (DEM) for the United States Environmental Protection Agency (USEPA) Mid-Atlantic Integrated Assessment (MAIA) Project region. The coverage was produced using US Geological Su...

  15. Lunar Topography and Basins Mapped Using a Clementine Stereo Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Cook, A. C.; Spudis, P. D.; Robinson, M. S.; Watters, T. R.

    2002-01-01

    Planet-wide (1 km/pixel and 5 km/pixel) Digital Elevation Models (DEM) of the Moon have been produced using Clementine UVVIS (Ultraviolet-Visible) stereo. Six new basins have been discovered, two suspected basins have been confirmed, and the dimensions of existing basins better defined. Additional information is contained in the original extended abstract.

  16. Digital core based transmitted ultrasonic wave simulation and velocity accuracy analysis

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Shan, Rui

    2016-06-01

    Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation (LESS), although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.

  17. Comparison of dimensional accuracy of digital dental models produced from scanned impressions and scanned stone casts

    NASA Astrophysics Data System (ADS)

    Subeihi, Haitham

    Introduction: Digital models of dental arches play a more and more important role in dentistry. A digital dental model can be generated by directly scanning intraoral structures, by scanning a conventional impression of oral structures or by scanning a stone cast poured from the conventional impression. An accurate digital scan model is a fundamental part for the fabrication of dental restorations. Aims: 1. To compare the dimensional accuracy of digital dental models produced by scanning of impressions versus scanning of stone casts. 2. To compare the dimensional accuracy of digital dental models produced by scanning of impressions made of three different materials (polyvinyl siloxane, polyether or vinyl polyether silicone). Methods and Materials: This laboratory study included taking addition silicone, polyether and vinyl polyether silicone impressions from an epoxy reference model that was created from an original typodont. Teeth number 28 and 30 on the typodont with a missing tooth number 29 were prepared for a metal-ceramic three-unit fixed dental prosthesis with tooth #29 being a pontic. After tooth preparation, an epoxy resin reference model was fabricated by duplicating the typodont quadrant that included the tooth preparations. From this reference model 12 polyvinyl siloxane impressions, 12 polyether impressions and 12 vinyl polyether silicone impressions were made. All 36 impressions were scanned before pouring them with dental stone. The 36 dental stone casts were, in turn, scanned to produce digital models. A reference digital model was made by scanning the reference model. Six groups of digital models were produced. Three groups were made by scanning of the impressions obtained with the three different materials, the other three groups involved the scanning of the dental casts that resulted from pouring the impressions made with the three different materials. Groups of digital models were compared using Root Mean

  18. High accuracy digital aging monitor based on PLL-VCO circuit

    NASA Astrophysics Data System (ADS)

    Yuejun, Zhang; Zhidi, Jiang; Pengjun, Wang; Xuelong, Zhang

    2015-01-01

    As the manufacturing process is scaled down to the nanoscale, the aging phenomenon significantly affects the reliability and lifetime of integrated circuits. Consequently, the precise measurement of digital CMOS aging is a key aspect of nanoscale aging tolerant circuit design. This paper proposes a high accuracy digital aging monitor using phase-locked loop and voltage-controlled oscillator (PLL-VCO) circuit. The proposed monitor eliminates the circuit self-aging effect for the characteristic of PLL, whose frequency has no relationship with circuit aging phenomenon. The PLL-VCO monitor is implemented in TSMC low power 65 nm CMOS technology, and its area occupies 303.28 × 298.94 μm2. After accelerating aging tests, the experimental results show that PLL-VCO monitor improves accuracy about high temperature by 2.4% and high voltage by 18.7%.

  19. Accuracy Comparison of Digital Surface Models Created by Unmanned Aerial Systems Imagery and Terrestrial Laser Scanner

    NASA Astrophysics Data System (ADS)

    Naumann, M.; Geist, M.; Bill, R.; Niemeyer, F.; Grenzdörffer, G.

    2013-08-01

    The main focus of the paper is a comparative study in which we have investigated, whether automatically generated digital surface models (DSM) obtained from unmanned aerial systems (UAS) imagery are comparable with DSM obtained from terrestrial laser scanning (TLS). The research is conducted at a pilot dike for coastal engineering. The effort and the achievable accuracy of both DSMs are compared. The error budgets of these two methods are investigated and the models obtained in each case compared against each other.

  20. Accuracy assessment of high frequency 3D ultrasound for digital impression-taking of prepared teeth

    NASA Astrophysics Data System (ADS)

    Heger, Stefan; Vollborn, Thorsten; Tinschert, Joachim; Wolfart, Stefan; Radermacher, Klaus

    2013-03-01

    Silicone based impression-taking of prepared teeth followed by plaster casting is well-established but potentially less reliable, error-prone and inefficient, particularly in combination with emerging techniques like computer aided design and manufacturing (CAD/CAM) of dental prosthesis. Intra-oral optical scanners for digital impression-taking have been introduced but until now some drawbacks still exist. Because optical waves can hardly penetrate liquids or soft-tissues, sub-gingival preparations still need to be uncovered invasively prior to scanning. High frequency ultrasound (HFUS) based micro-scanning has been recently investigated as an alternative to optical intra-oral scanning. Ultrasound is less sensitive against oral fluids and in principal able to penetrate gingiva without invasively exposing of sub-gingival preparations. Nevertheless, spatial resolution as well as digitization accuracy of an ultrasound based micro-scanning system remains a critical parameter because the ultrasound wavelength in water-like media such as gingiva is typically smaller than that of optical waves. In this contribution, the in-vitro accuracy of ultrasound based micro-scanning for tooth geometry reconstruction is being investigated and compared to its extra-oral optical counterpart. In order to increase the spatial resolution of the system, 2nd harmonic frequencies from a mechanically driven focused single element transducer were separated and corresponding 3D surface models were calculated for both fundamentals and 2nd harmonics. Measurements on phantoms, model teeth and human teeth were carried out for evaluation of spatial resolution and surface detection accuracy. Comparison of optical and ultrasound digital impression taking indicate that, in terms of accuracy, ultrasound based tooth digitization can be an alternative for optical impression-taking.

  1. Determination of the accuracy and operating constants in a digitally biased ring core magnetometer

    USGS Publications Warehouse

    Green, A.W., Jr.

    1990-01-01

    By using a very stable voltage reference and a high precision digital-to-analog converter to set bias in digital increments, the inherently high stability and accuracy of a ring core magnetometer can be significantly enhanced. In this case it becomes possible to measure not only variations about the bias level, but to measure the entire value of the field along each magnetometer sensing axis in a nearly absolute sense. To accomplish this, one must accurately determine the value of the digital bias increment for each axis, the zero field offset value for each axis, the scale values, and the transfer coefficients (or nonorthogonality angles) for pairs of axes. This determination can be carried out very simply, using only the Earth's field, a proton magnetometer, and a tripod-mounted fixture which is capable of rotations about two axes that are mutually perpendicular to the Earth's magnetic field vector. ?? 1990.

  2. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models

    NASA Astrophysics Data System (ADS)

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-06-01

    Mapping or "delimiting" landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  3. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models

    PubMed Central

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-01-01

    Mapping or “delimiting” landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  4. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models.

    PubMed

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-06-01

    Mapping or "delimiting" landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  5. Digital elevation model based geomorphological mapping in the lower River Boyne valley, Ireland

    NASA Astrophysics Data System (ADS)

    Foster, Gez; Turner, Jonathan; Gallagher, Colman; Lewis, Helen

    2010-05-01

    Interpretation of digital elevation models (DEMs) is rapidly becoming a valuable extension to field-based geomorphic mapping. High-resolution LiDAR data (Light Detection and Ranging; point spacing 1m, vertical accuracy 0.1m) is ideally-suited for mapping areas of complex and subtle geomorphology, such as fluvial landscapes. This poster outlines how LiDAR data are being used to map and characterise the postglacial fluvial terraces of the lower Boyne valley, Co. Meath, Ireland. Comprehensive mapping, together with longitudinal profiles, demonstrate that the valley contains a suite, or ‘staircase', of six main fluvial terraces, spanning an altitude range of ca. 20m. These terraces represent a chronosequence of ‘palaeo' floodplains, with the highest (T1) being the oldest level, and the lowest (T6) the youngest. The evolution of the valley has thus involved progressive erosion, punctuated by episodes of vertical stability or re-filling. Classified maps of the river terrace sequence indicate that terrace T1 is closely associated with glacial landforms, while T2 exhibits multiple channels with large bar-forms, and could mark a braided river system that conveyed huge water and sediment loads during deglaciation ca. 20-17 ka BP. The ‘modern' floodplain (T6) is ubiquitous, and preliminary field studies have dated two of its palaeochannels to >1,000 cal. BP. The LiDAR based model of geomorphic evolution in the lower Boyne valley is being used to underpin field-based geomorphological and sediment studies, focusing on the acquisition of OSL and radiocarbon dates to secure the timing of river terrace formation and to assess the relationships between fluvial development and environmental change since the Late Glacial period.

  6. Reliability and accuracy of digital templating for the humeral component of total shoulder arthroplasty

    PubMed Central

    Davis, Shane M; Lane, Christianne J; Koonce, Ryan C; Hartman, Andrew P; Ball, Kenneth; Esch, James C

    2014-01-01

    Background This experimental study evaluated the interobserver reliability and accuracy of pre-operative digital templating for humeral head size, stem size and neck angle for total shoulder arthroplasty. Methods Twenty-five patients underwent a total shoulder arthroplasty with a single prosthesis. Four independent, blinded surgeons (two experienced shoulder surgeons and two PGY-6 fellows) used pre-operative radiographs and templating software to generate templates of the humeral head, stem and neck for each patient. Interobserver reliability was calculated using weighted kappa (κ) analysis. Accuracy was assessed by comparing templates to actual implant sizes. Results Interobserver reliability was fair to substantial (κ = 0.26 to 0.71) for head size, fair to substantial (κ = 0.39 to 0.72) for stem size and slight to fair (κ = 0.16 to 0.34) for neck angle. Templated head size, stem size and neck angle had accuracies of 53%, 77% and 68% within one size variation, respectively. Experience did not affect accuracy (p = 0.11 to 0.48). Conclusions Digital templating is not a useful guide for pre-operative surgical planning and should not be used to select a prosthesis.

  7. Digital elevation data as an aid to land use and land cover classification

    USGS Publications Warehouse

    Colvocoresses, Alden P.

    1981-01-01

    In relatively well mapped areas such as the United States and Europe, digital data can be developed from topographic maps or from the stereo aerial photographic movie. For poorer mapped areas (which involved most of the world's land areas), a satellite designed to obtain stereo data offers the best hope for a digital elevation database. Such a satellite, known as Mapsat, has been defined by the U.S. Geological Survey. Utilizing modern solid state technology, there is no reason why such stereo data cannot be acquired simultaneously with the multispectral response, thus simplifying the overall problem of land use and land cover classification.

  8. Lossless data compression of grid-based digital elevation models: A png image format evaluation

    NASA Astrophysics Data System (ADS)

    Scarmana, G.

    2014-05-01

    At present, computers, lasers, radars, planes and satellite technologies make possible very fast and accurate topographic data acquisition for the production of maps. However, the problem of managing and manipulating this data efficiently remains. One particular type of map is the elevation map. When stored on a computer, it is often referred to as a Digital Elevation Model (DEM). A DEM is usually a square matrix of elevations. It is like an image, except that it contains a single channel of information (that is, elevation) and can be compressed in a lossy or lossless manner by way of existing image compression protocols. Compression has the effect of reducing memory requirements and speed of transmission over digital links, while maintaining the integrity of data as required. In this context, this paper investigates the effects of the PNG (Portable Network Graphics) lossless image compression protocol on floating-point elevation values for 16-bit DEMs of dissimilar terrain characteristics. The PNG is a robust, universally supported, extensible, lossless, general-purpose and patent-free image format. Tests demonstrate that the compression ratios and run decompression times achieved with the PNG lossless compression protocol can be comparable to, or better than, proprietary lossless JPEG variants, other image formats and available lossless compression algorithms.

  9. Topogrid Derived 10 Meter Resolution Digital Elevation Model of Charleston, and Parts of Berkeley, Colleton, Dorchester and Georgetown Counties, South Carolina

    USGS Publications Warehouse

    Chirico, Peter G.

    2005-01-01

    EXPLANATION The purpose of developing a new 10m resolution digital elevation model (DEM) of the Charleston Region was to more accurately depict geologic structure, surfical geology, and landforms of the Charleston County Region. Previously, many areas northeast and southwest of Charleston were originally mapped with a 20 foot contour interval. As a result, large areas within the National Elevation Dataset (NED) depict flat terraced topography where there was a lack of higher resolution elevation data. To overcome these data voids, the new DEM is supplemented with additional elevation data and break-lines derived from aerial photography and topographic maps. The resultant DEM is stored as a raster grid at uniform 10m horizontal resolution. The elevation model contained in this publication was prodcued utilizing the ANUDEM algorthim. ANUDEM allows for the inclusion of contours, streams, rivers, lake and water body polygons as well as spot height data to control the development of the elevation model. A preliminary statistical analysis using over 788 vertical elevation check points, primarily located in the northeastern part of the study area, derived from USGS 7.5 Minute Topographic maps reveals that the final DEM, has a vertical accuracy of ?3.27 meters. A table listing the elevation comparison between the elevation check points and the final DEM is provided.

  10. Rapid calculation of terrain parameters for radiation modeling from digital elevation data

    NASA Technical Reports Server (NTRS)

    Dozier, Jeff; Frew, James

    1990-01-01

    Digital elevation models are now widely used to calculate terrain parameters to determine incoming solar and longwave radiation for use in surface climate models, interpretation of remote-sensing data, and parameters in hydrologic models. Because of the large number of points in an elevation grid, fast algorithms are useful to save computation time. A description is given of rapid methods for calculating slope and azimuth, solar illumination angle, horizons, and view factors for radiation from sky and terrain. Calculation time is reduced by fast algorithms and lookup tables.

  11. 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.

  12. Validating Flood Mapping Products Using a Digital Elevation Model Comparison Technique

    NASA Astrophysics Data System (ADS)

    Fayne, J.

    2014-12-01

    This preliminary study assessed the validity of a pixel analysis elevation comparison technique and determined necessary steps for improvement. The pixel analysis sought to assess the probability of a flood occurring in a particular area by comparing the spatial extent of flood mapping products to the local elevation. The method was developed to determine if the physical relationship between elevation and floods as shown in satellite images is accurately represented in a flood mapping product. The data incorporated in this study are raster digital elevation model (DEM) tiles, a scene from Landsat 5 during a flood period, and a scene from the NASA DEVELOP Flood Disasters Team Flood Product. Pixels representing flooded areas were compared to the elevation height pixels using horizontal transect lines to create pixel value profiles across a 727 km transect of Vietnam and Cambodia. The elevation model comparison validates the Flood Product by depicting water presence in alignment with areas of low elevation. Initial findings indicate that the technique can be used to improve the assessment of flood mapping products in transects less than 10 km. Future research will focus on streamlining the pixel analysis process to yield comprehensive results for larger areas.

  13. Analyzing remote sensing geobotanical trends in Quetico Provincial Park, Ontario, Canada, using digital elevation data

    NASA Technical Reports Server (NTRS)

    Warner, Timothy A.; Campagna, David J.; Levandowski, Don W.; Cetin, Haluk; Evans, Carla S.

    1991-01-01

    A 10 x 13-km area in Quetico Provincial Park, Canada has been studied using a digital elevation model to separate different drainage classes and to examine the influence of site factors and lithology on vegetation. Landsat Thematic Mapper data have been classified into six forest classes of varying deciduous-coniferous cover through nPDF, a procedure based on probability density functions. It is shown that forests growing on mafic lithologies are enriched in deciduous species, compared to those growing on granites. Of the forest classes found on mafics, the highest coniferous component was on north facing slopes, and the highest deciduous component on south facing slopes. Granites showed no substantial variation between site classes. The digital elevation derived site data is considered to be an important tool in geobotanical investigations.

  14. 1:100,000-scale topographic contours derived from digital elevation models, San Francisco Bay region, California: a digital database

    USGS Publications Warehouse

    Wright, Heather M.; Wentworth, Carl M.

    2001-01-01

    This report presents a consistent set of 1:100,000-scale vector topographic contours for all eleven 30x60-minute quadrangles in the San Francisco Bay region for use in visualizing the topography and preparing maps of the region. The contours were prepared by contouring an areally continuous 30-m altitude grid (National Elevation Dataset, Jan., 1999), and differ from USGS hypsographic DLG's (available for only part of the region). The report consists of 26 numbered parts, which represent text, spatial data, and 1:100,000-scale map graphics. Most of the files are provided in two or three different digital formats. All files are available for download here.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Building precise and up-to-date coastal DEMs is a prerequisite for accurate modeling and forecasting of hydrodynamic processes at local scale. Marine flooding, originating from tsunamis, storm surges or waves, is one of them. Some high resolution DEMs are being generated for multiple coast configurations (gulf, embayment, strait, estuary, harbor approaches, low-lying areas…) along French Atlantic and Channel coasts. This work is undertaken within the framework of the TANDEM project (Tsunamis in the Atlantic and the English ChaNnel: Definition of the Effects through numerical Modeling) (2014-2017). DEMs boundaries were defined considering the vicinity of French civil nuclear facilities, site effects considerations and potential tsunamigenic sources. Those were identified from available historical observations. Seamless integrated topographic and bathymetric coastal DEMs will be used by institutions taking part in the study to simulate expected wave height at regional and local scale on the French coasts, for a set of defined scenarii. The main tasks were (1) the development of a new capacity of production of DEM, (2) aiming at the release of high resolution and precision digital field models referred to vertical reference frameworks, that require (3) horizontal and vertical datum conversions (all source elevation data need to be transformed to a common datum), on the basis of (4) the building of (national and/or local) conversion grids of datum relationships based on known measurements. Challenges in coastal DEMs development deal with good practices throughout model development that can help minimizing uncertainties. This is particularly true as scattered elevation data with variable density, from multiple sources (national hydrographic services, state and local government agencies, research organizations and private engineering companies) and from many different types (paper fieldsheets to be digitized, single beam echo sounder, multibeam sonar, airborne laser

  16. The conservation value of elevation data accuracy and model sophistication in reserve design under sea-level rise.

    PubMed

    Zhu, Mingjian; Hoctor, Tom; Volk, Mike; Frank, Kathryn; Linhoss, Anna

    2015-10-01

    Many studies have explored the value of using more sophisticated coastal impact models and higher resolution elevation data in sea-level rise (SLR) adaptation planning. However, we know little about to what extent the improved models and data could actually lead to better conservation outcomes under SLR. This is important to know because high-resolution data are likely to not be available in some data-poor coastal areas in the world and running more complicated coastal impact models is relatively time-consuming, expensive, and requires assistance by qualified experts and technicians. We address this research question in the context of identifying conservation priorities in response to SLR. Specifically, we investigated the conservation value of using more accurate light detection and ranging (Lidar)-based digital elevation data and process-based coastal land-cover change models (Sea Level Affecting Marshes Model, SLAMM) to identify conservation priorities versus simple "bathtub" models based on the relatively coarse National Elevation Dataset (NED) in a coastal region of northeast Florida. We compared conservation outcomes identified by reserve design software (Zonation) using three different model dataset combinations (Bathtub-NED, Bathtub-Lidar, and SLAMM-Lidar). The comparisons show that the conservation priorities are significantly different with different combinations of coastal impact models and elevation dataset inputs. The research suggests that it is valuable to invest in more accurate coastal impact models and elevation datasets in SLR adaptive conservation planning because this model-dataset combination could improve conservation outcomes under SLR. Less accurate coastal impact models, including ones created using coarser Digital Elevation Model (DEM) data can still be useful when better data and models are not available or feasible, but results need to be appropriately assessed and communicated. A future research priority is to investigate how

  17. Wound Area Measurement with Digital Planimetry: Improved Accuracy and Precision with Calibration Based on 2 Rulers

    PubMed Central

    Foltynski, Piotr

    2015-01-01

    Introduction In the treatment of chronic wounds the wound surface area change over time is useful parameter in assessment of the applied therapy plan. The more precise the method of wound area measurement the earlier may be identified and changed inappropriate treatment plan. Digital planimetry may be used in wound area measurement and therapy assessment when it is properly used, but the common problem is the camera lens orientation during the taking of a picture. The camera lens axis should be perpendicular to the wound plane, and if it is not, the measured area differ from the true area. Results Current study shows that the use of 2 rulers placed in parallel below and above the wound for the calibration increases on average 3.8 times the precision of area measurement in comparison to the measurement with one ruler used for calibration. The proposed procedure of calibration increases also 4 times accuracy of area measurement. It was also showed that wound area range and camera type do not influence the precision of area measurement with digital planimetry based on two ruler calibration, however the measurements based on smartphone camera were significantly less accurate than these based on D-SLR or compact cameras. Area measurement on flat surface was more precise with the digital planimetry with 2 rulers than performed with the Visitrak device, the Silhouette Mobile device or the AreaMe software-based method. Conclusion The calibration in digital planimetry with using 2 rulers remarkably increases precision and accuracy of measurement and therefore should be recommended instead of calibration based on single ruler. PMID:26252747

  18. Digital phase-locked-loop speed sensor for accuracy improvement in analog speed controls. [feedback control and integrated circuits

    NASA Technical Reports Server (NTRS)

    Birchenough, A. G.

    1975-01-01

    A digital speed control that can be combined with a proportional analog controller is described. The stability and transient response of the analog controller were retained and combined with the long-term accuracy of a crystal-controlled integral controller. A relatively simple circuit was developed by using phase-locked-loop techniques and total error storage. The integral digital controller will maintain speed control accuracy equal to that of the crystal reference oscillator.

  19. Implications of different digital elevation models and preprocessing techniques to delineate debris flow inundation hazard zones in El Salvador

    NASA Astrophysics Data System (ADS)

    Anderson, E. R.; Griffin, R.; Irwin, D.

    2013-12-01

    Heavy rains and steep, volcanic slopes in El Salvador cause numerous landslides every year, posing a persistent threat to the population, economy and environment. Although potential debris inundation hazard zones have been delineated using digital elevation models (DEMs), some disparities exist between the simulated zones and actual affected areas. Moreover, these hazard zones have only been identified for volcanic lahars and not the shallow landslides that occur nearly every year. This is despite the availability of tools to delineate a variety of landslide types (e.g., the USGS-developed LAHARZ software). Limitations in DEM spatial resolution, age of the data, and hydrological preprocessing techniques can contribute to inaccurate hazard zone definitions. This study investigates the impacts of using different elevation models and pit filling techniques in the final debris hazard zone delineations, in an effort to determine which combination of methods most closely agrees with observed landslide events. In particular, a national DEM digitized from topographic sheets from the 1970s and 1980s provide an elevation product at a 10 meter resolution. Both natural and anthropogenic modifications of the terrain limit the accuracy of current landslide hazard assessments derived from this source. Global products from the Shuttle Radar Topography Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM (ASTER GDEM) offer more recent data but at the cost of spatial resolution. New data derived from the NASA Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in 2013 provides the opportunity to update hazard zones at a higher spatial resolution (approximately 6 meters). Hydrological filling of sinks or pits for current hazard zone simulation has previously been achieved through ArcInfo spatial analyst. Such hydrological processing typically only fills pits and can lead to drastic modifications of original elevation values

  20. Measuring the accuracy and precision of quantitative coronary angiography using a digitally simulated test phantom

    NASA Astrophysics Data System (ADS)

    Morioka, Craig A.; Whiting, James S.; LeFree, Michelle T.

    1998-06-01

    Quantitative coronary angiography (QCA) diameter measurements have been used as an endpoint measurement in clinical studies involving therapies to reduce coronary atherosclerosis. The accuracy and precision of the QCA measure can affect the sample size and study conclusions of a clinical study. Measurements using x-ray test phantoms can underestimate the precision and accuracy of the actual arteries in clinical digital angiograms because they do not contain complex patient structures. Determining the clinical performance of QCA algorithms under clinical conditions is difficult because: (1) no gold standard test object exists in clinical images, (2) phantom images do not have any structured background noise. We purpose the use of computer simulated arteries as a replacement for traditional angiographic test phantoms to evaluate QCA algorithm performance.

  1. Comparative Analysis of Global Digital Elevation Models and Ultra-Prominent Mountain Peaks

    NASA Astrophysics Data System (ADS)

    Grohmann, Carlos H.

    2016-06-01

    Global Digital Elevation Models (GDEMs) are datasets of vital importance for regional-scale analysis in areas such as geomorphology, [paleo]climatology, oceanography and biodiversity. In this work I present a comparative assessment of the datasets ETOPO1 (1' resolution), GTOPO30, GLOBE, SRTM30 PLUS, GMTED2010 and ACE2 (30") against the altitude of the world's ultra prominent peaks. GDEMs' elevations show an expected tendency of underestimating the peak's altitude, but differences reach 3,500 m. None of the GDEMs captures the full range of elevation on Earth and they do not represent well the altitude of the most prominent peaks. Some of these problems could be addressed with the release of NASADEM, but the smoothing effect caused by moving-window resampling can only be tackled by using new techniques, such as scale-adaptative kernels and curvature-based terrain generalisation.

  2. Camera model and calibration process for high-accuracy digital image metrology of inspection planes

    NASA Astrophysics Data System (ADS)

    Correia, Bento A. B.; Dinis, Joao

    1998-10-01

    High accuracy digital image based metrology must rely on an integrated model of image generation that is able to consider simultaneously the geometry of the camera vs. object positioning, and the conversion of the optical image on the sensor into an electronic digital format. In applications of automated visual inspection involving the analysis of approximately plane objects these models are generally simplified in order to facilitate the process of camera calibration. In this context, the lack of rigor in the determination of the intrinsic parameters in such models is particularly relevant. Aiming at the high accuracy metrology of contours of objects lying on an analysis plane, and involving sub-pixel measurements, this paper presents a three-stage camera model that includes an extrinsic component of perspective distortion and the intrinsic components of radial lens distortion and sensor misalignment. The later two factors are crucial in applications of machine vision that rely on the use of low cost optical components. A polynomial model for the negative radial lens distortion of wide field of view CCTV lenses is also established.

  3. Appraisal of digital terrain elevation data for low-altitude flight

    NASA Technical Reports Server (NTRS)

    Zelenka, Richard E.; Swenson, Harry N.

    1992-01-01

    The use of terrain elevation databases in advanced guidance and navigation systems has greatly expanded. However, the limitations and accuracies of these databases must be considered and established prior to safe system flight evaluation. A simple approach to quantify reasonable flight limits is presented and evaluated for a helicopter guidance system dependent on a terrain database. The flight test evaluated involved a helicopter equipped with a Global Positioning System (GPS) receiver and radar altimeter, and a ground station GPS receiver which provided improved helicopter positioning. The precision navigation and radar altimeter data was acquired while flying low-altitude missions in south-central Pennsylvania. The aircraft-determined terrain elevations were compared with the terrain predicted by the Defense Mapping Agency (DMA) Level 1 terrain elevation data for the same area. The results suggest a safe set clearance altitude of 220 ft for flight testing of a DMA-based guidance avionic in the same area.

  4. Digital reader vs print media: the role of digital technology in reading accuracy in age-related macular degeneration

    PubMed Central

    Gill, K; Mao, A; Powell, A M; Sheidow, T

    2013-01-01

    Purpose To compare patient satisfaction, reading accuracy, and reading speed between digital e-readers (Sony eReader, Apple iPad) and standard paper/print media for patients with stable wet age-related macular degeneration (AMD). Methods Patients recruited for the study were patients with stable wet AMD, in one or both eyes, who would benefit from a low-vision aid. The selected text sizes by patients reflected the spectrum of low vision in regard to their macular disease. Stability of macular degeneration was assessed on a clinical examination with stable visual acuity. Patients recruited for the study were assessed for reading speeds on both digital readers and standard paper text. Standardized and validated texts for reading speeds were used. Font sizes in the study reflected a spectrum from newsprint to large print books. Patients started with the smallest print size they could read on the standardized paper text. They then used digital readers to read the same size standardized text. Reading speed was calculated as words per minute by the formula (correctly read words/reading time (s)·60). The visual analog scale was completed by patients after reading each passage. These included their assessment on ‘ease of use' and ‘clarity of print' for each device and the print paper. Results A total of 27 patients were used in the study. Patients consistently read faster (P<0.0003) on the Apple iPad with larger text sizes (size 24 or greater) when compared with paper, and also on the paper compared with the Sony eReader (P<0.03) in all text group sizes. Patients chose the iPad to have the best clarity and the print paper as the easiest to use. Conclusions This study has demonstrated that digital devices may have a use in visual rehabilitation for low-vision patients. Devices that have larger display screens and offer high contrast ratios will benefit AMD patients who require larger texts to read. PMID:23492860

  5. Application of Digital Image Correlation Method to Improve the Accuracy of Aerial Photo Stitching

    NASA Astrophysics Data System (ADS)

    Tung, Shih-Heng; Jhou, You-Liang; Shih, Ming-Hsiang; Hsiao, Han-Wei; Sung, Wen-Pei

    2016-04-01

    Satellite images and traditional aerial photos have been used in remote sensing for a long time. However, there are some problems with these images. For example, the resolution of satellite image is insufficient, the cost to obtain traditional images is relatively high and there is also human safety risk in traditional flight. These result in the application limitation of these images. In recent years, the control technology of unmanned aerial vehicle (UAV) is rapidly developed. This makes unmanned aerial vehicle widely used in obtaining aerial photos. Compared to satellite images and traditional aerial photos, these aerial photos obtained using UAV have the advantages of higher resolution, low cost. Because there is no crew in UAV, it is still possible to take aerial photos using UAV under unstable weather conditions. Images have to be orthorectified and their distortion must be corrected at first. Then, with the help of image matching technique and control points, these images can be stitched or used to establish DEM of ground surface. These images or DEM data can be used to monitor the landslide or estimate the volume of landslide. For the image matching, we can use such as Harris corner method, SIFT or SURF to extract and match feature points. However, the accuracy of these methods for matching is about pixel or sub-pixel level. The accuracy of digital image correlation method (DIC) during image matching can reach about 0.01pixel. Therefore, this study applies digital image correlation method to match extracted feature points. Then the stitched images are observed to judge the improvement situation. This study takes the aerial photos of a reservoir area. These images are stitched under the situations with and without the help of DIC. The results show that the misplacement situation in the stitched image using DIC to match feature points has been significantly improved. This shows that the use of DIC to match feature points can actually improve the accuracy of

  6. Accuracy of Conventional and Digital Radiography in Detecting External Root Resorption

    PubMed Central

    Mesgarani, Abbas; Haghanifar, Sina; Ehsani, Maryam; Yaghub, Samereh Dokhte; Bijani, Ali

    2014-01-01

    Introduction: External root resorption (ERR) is associated with physiological and pathological dissolution of mineralized tissues by clastic cells and radiography is one of the most important methods in its diagnosis. The aim of this experimental study was to evaluate the accuracy of conventional intraoral radiography (CR) in comparison with digital radiographic techniques, i.e. charge-coupled device (CCD) and photo-stimulable phosphor (PSP) sensors, in detection of ERR. Methods and Materials: This study was performed on 80 extracted human mandibular premolars. After taking separate initial periapical radiographs with CR technique, CCD and PSP sensors, the artificial defects resembling ERR with variable sizes were created in apical half of the mesial, distal and buccal surfaces of the teeth. Ten teeth were used as control samples without any resorption. The radiographs were then repeated with 2 different exposure times and the images were observed by 3 observers. Data were analyzed using SPSS version 17 and chi-squared and Cohen’s Kappa tests with 95% confidence interval (CI=95%). Result: The CCD had the highest percentage of correct assessment compared to the CR and PSP sensors, although the difference was not significant (P=0.39). It was shown that the higher dosage of radiation increases the accuracy of diagnosis; however, it was only significant for CCD sensor (P=0.02). Also, the accuracy of diagnosis increased with the increase in the size of lesion (P=0.001). Conclusion: Statistically significant difference was not observed for accurate detection of ERR by conventional and digital radiographic techniques. PMID:25386202

  7. Digital elevation model of King Edward VII Peninsula, West Antarctica, from SAR interferometry and ICESat laser altimetry

    USGS Publications Warehouse

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

    2005-01-01

    We present a digital elevation model (DEM) of King Edward VII Peninsula, Sulzberger Bay, West Antarctica, developed using 12 European Remote Sensing (ERS) synthetic aperture radar (SAR) scenes and 24 Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles. We employ differential interferograms from the ERS tandem mission SAR scenes acquired in the austral fall of 1996, and four selected ICESat laser altimetry profiles acquired in the austral fall of 2004, as ground control points (GCPs) to construct an improved geocentric 60-m resolution DEM over the grounded ice region. We then extend the DEM to include two ice shelves using ICESat profiles via Kriging. Twenty additional ICESat profiles acquired in 2003-2004 are used to assess the accuracy of the DEM. After accounting for radar penetration depth and predicted surface changes, including effects due to ice mass balance, solid Earth tides, and glacial isostatic adjustment, in part to account for the eight-year data acquisition discrepancy, the resulting difference between the DEM and ICESat profiles is -0.57 ?? 5.88 m. After removing the discrepancy between the DEM and ICESat profiles for a final combined DEM using a bicubic spline, the overall difference is 0.05 ?? 1.35 m. ?? 2005 IEEE.

  8. Digital Elevation Models of TYCHO Crater and the Lunar Polar Regions

    NASA Astrophysics Data System (ADS)

    Margot, J. L.; Campbell, D. B.; Jurgens, R. F.; Slade, M. A.

    1998-09-01

    Earth-based radar interferometry [1] has been used to map the lunar polar regions and Tycho Crater at high spatial ( ~ 100 m) and height ( ~ 50 m) resolutions. Compared to existing topographic data sets, the radar observations offer digital elevation models with dense horizontal spacing and improved height resolution. Earth-based radars can also provide measurements of the largely unknown topography in the polar regions. Elevation data and radar imagery obtained with the Goldstone X-band system (lambda = 3.5 cm) are presented for the Tycho Crater area, with a spatial resolution of 200 m and a height resolution of 30 m. A careful comparison of the radar-derived topography with Clementine altimetry points [2] reveals a very good agreement between the two techniques. Rms deviations between the radar-derived heights and 87 Clementine points available over the 200 x 200 km scene are ~ 100 m. The digital elevation model allows detailed morphometry of the 85 km diameter crater: the floor of Tycho lies 3970 m below a 1738 km radius sphere, and the crater's central peak rises 2400 m above the floor. The average rim crest elevation is 730 m above the 1738 km datum, giving a mean rim to floor depth of 4700 m. The floor has two distinct units with the western section being higher in elevation by ~ 200 m. This dichotomy is consistent with an asymmetry in the crater shape which reveals that maximum wall slumping occured in the western and southwestern regions of the crater. Digital elevation models of the polar regions are being used to estimate the location of permanently shadowed areas which may harbor ice deposits [3]. The range of illumination conditions over the lunar polar regions could be sampled by an imaging instrument in a polar orbit during a full terrestrial year. Alternatively, topographic maps obtained with Earth-based radar can be used to model the illumination conditions over the entire solar illumination cycle. [1] I. I. Shapiro et al. (1972). Science, 178, 939

  9. Error analysis in the digital elevation model of Kuwait desert derived from repeat pass synthetic aperture radar interferometry

    NASA Astrophysics Data System (ADS)

    Rao, Kota S.; Al Jassar, Hala K.

    2010-09-01

    The aim of this paper is to analyze the errors in the Digital Elevation Models (DEMs) derived through repeat pass SAR interferometry (InSAR). Out of 29 ASAR images available to us, 8 are selected for this study which has unique data set forming 7 InSAR pairs with single master image. The perpendicular component of baseline (B highmod) varies between 200 to 400 m to generate good quality DEMs. The Temporal baseline (T) varies from 35 days to 525 days to see the effect of temporal decorrelation. It is expected that all the DEMs be similar to each other spatially with in the noise limits. However, they differ very much with one another. The 7 DEMs are compared with the DEM of SRTM for the estimation of errors. The spatial and temporal distribution of errors in the DEM is analyzed by considering several case studies. Spatial and temporal variability of precipitable water vapour is analysed. Precipitable water vapour (PWV) corrections to the DEMs are implemented and found to have no significant effect. The reasons are explained. Temporal decorrelation of phases and soil moisture variations seem to have influence on the accuracy of the derived DEM. It is suggested that installing a number of corner reflectors (CRs) and the use of Permanent Scatter approach may improve the accuracy of the results in desert test sites.

  10. A flooding algorithm for extracting drainage networks from unprocessed digital elevation models

    NASA Astrophysics Data System (ADS)

    Rueda, Antonio; Noguera, José M.; Martínez-Cruz, Carmen

    2013-09-01

    A new method for extracting the drainage network from a digital elevation model (DEM) is presented. It is based on the well-known D8 approach that simulates the overland flow but uses a more elaborate water transfer model that is inspired by the natural behaviour of water. The proposed solution has several advantages: it works on unprocessed DEMs avoiding the problems caused by pits and flats, can generate watercourses with a width greater than one cell and detects fluvial landforms like lakes, marshes or river islands that are not directly handled by most previous solutions.

  11. Geomorphological feature extraction from a digital elevation model through fuzzy knowledge-based classification

    NASA Astrophysics Data System (ADS)

    Argialas, Demetre P.; Tzotsos, Angelos

    2003-03-01

    The objective of this research was the investigation of advanced image analysis methods for geomorphological mapping. Methods employed included multiresolution segmentation of the Digital Elevation Model (DEM) GTOPO30 and fuzzy knowledge based classification of the segmented DEM into three geomorphological classes: mountain ranges, piedmonts and basins. The study area was a segment of the Basin and Range Physiographic Province in Nevada, USA. The implementation was made in eCognition. In particular, the segmentation of GTOPO30 resulted into primitive objects. The knowledge-based classification of the primitive objects based on their elevation and shape parameters, resulted in the extraction of the geomorphological features. The resulted boundaries in comparison to those by previous studies were found satisfactory. It is concluded that geomorphological feature extraction can be carried out through fuzzy knowledge based classification as implemented in eCognition.

  12. 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.

  13. State of Texas - Highlighting Low-Lying Areas Derived from USGS Digital Elevation Data

    USGS Publications Warehouse

    Kosovich, John J.

    2008-01-01

    In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts a color shaded relief representation of Texas and a grayscale relief of the surrounding areas. The first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands, which highlight low-elevation areas at a coarse spatial resolution. Standard USGS National Elevation Dataset (NED) 1 arc-second (nominally 30-meter) digital elevation model (DEM) data are the basis for the map, which is designed to be used at a broad scale and for informational purposes only. The NED data were derived from the original 1:24,000-scale USGS topographic map bare-earth contours, which were converted into gridded quadrangle-based DEM tiles at a constant post spacing (grid cell size) of either 30 meters (data before the mid-1990s) or 10 meters (mid-1990s and later data). These individual-quadrangle DEMs were then converted to spherical coordinates (latitude/longitude decimal degrees) and edge-matched to ensure seamlessness. The NED source data for this map consists of a mixture of 30-meter- and 10-meter-resolution DEMs. State and county boundary, hydrography, city, and road layers were modified from USGS National Atlas data downloaded in 2003. The NED data were downloaded in 2002. Shaded relief over Mexico was obtained from the USGS National Atlas.

  14. Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas

    NASA Astrophysics Data System (ADS)

    Leitão, João P.; Moy de Vitry, Matthew; Scheidegger, Andreas; Rieckermann, Jörg

    2016-04-01

    Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is

  15. A Combined SRTM Digital Elevation Model for Zanjan State of Iran Based on the Corrective Surface Idea

    NASA Astrophysics Data System (ADS)

    Kiamehr, Ramin

    2016-04-01

    One arc-second high resolution version of the SRTM model recently published for the Iran by the US Geological Survey database. Digital Elevation Models (DEM) is widely used in different disciplines and applications by geoscientist. It is an essential data in geoid computation procedure, e.g., to determine the topographic, downward continuation (DWC) and atmospheric corrections. Also, it can be used in road location and design in civil engineering and hydrological analysis. However, a DEM is only a model of the elevation surface and it is subject to errors. The most important parts of errors could be comes from the bias in height datum. On the other hand, the accuracy of DEM is usually published in global sense and it is important to have estimation about the accuracy in the area of interest before using of it. One of the best methods to have a reasonable indication about the accuracy of DEM is obtained from the comparison of their height versus the precise national GPS/levelling data. It can be done by the determination of the Root-Mean-Square (RMS) of fitting between the DEM and leveling heights. The errors in the DEM can be approximated by different kinds of functions in order to fit the DEMs to a set of GPS/levelling data using the least squares adjustment. In the current study, several models ranging from a simple linear regression to seven parameter similarity transformation model are used in fitting procedure. However, the seven parameter model gives the best fitting with minimum standard division in all selected DEMs in the study area. Based on the 35 precise GPS/levelling data we obtain a RMS of 7 parameter fitting for SRTM DEM 5.5 m, The corrective surface model in generated based on the transformation parameters and included to the original SRTM model. The result of fitting in combined model is estimated again by independent GPS/leveling data. The result shows great improvement in absolute accuracy of the model with the standard deviation of 3.4 meter.

  16. Comparison of the diagnostic accuracy of direct digital radiography system, filtered images, and subtraction radiography

    PubMed Central

    Takeshita, Wilton Mitsunari; Vessoni Iwaki, Lilian Cristina; Da Silva, Mariliani Chicarelli; Filho, Liogi Iwaki; Queiroz, Alfredo De Franco; Geron, Lucas Bachegas Gomes

    2013-01-01

    Background: To compare the diagnostic accuracy of three different imaging systems: Direct digital radiography system (DDR-CMOS), four types of filtered images, and a priori and a posteriori registration of digital subtraction radiography (DSR) in the diagnosis of proximal defects. Materials and Methods: The teeth were arranged in pairs in 10 blocks of vinyl polysiloxane, and proximal defects were performed with drills of 0.25, 0.5, and 1 mm diameter. Kodak RVG 6100 sensor was used to capture the images. A posteriori DSR registrations were done with Regeemy 0.2.43 and subtraction with Image Tool 3.0. Filtered images were obtained with Kodak Dental Imaging 6.1 software. Images (n = 360) were evaluated by three raters, all experts in dental radiology. Results: Sensitivity and specificity of the area under the receiver operator characteristic (ROC) curve (Az) were higher for DSR images with all three drills (Az = 0.896, 0.979, and 1.000 for drills 0.25, 0.5, and 1 mm, respectively). The highest values were found for 1-mm drills and the lowest for 0.25-mm drills, with negative filter having the lowest values of all (Az = 0.631). Conclusion: The best method of diagnosis was by using a DSR. The negative filter obtained the worst results. Larger drills showed the highest sensitivity and specificity values of the area under the ROC curve. PMID:24124300

  17. Accuracy of digital periapical radiography and cone-beam computed tomography in detecting external root resorption

    PubMed Central

    Geha, Hassem; Sankar, Vidya; Teixeira, Fabricio B.; McMahan, Clyde Alex; Noujeim, Marcel

    2015-01-01

    Purpose The purpose of this study was to evaluate and compare the efficacy of cone-beam computed tomography (CBCT) and digital intraoral radiography in diagnosing simulated small external root resorption cavities. Materials and Methods Cavities were drilled in 159 roots using a small spherical bur at different root levels and on all surfaces. The teeth were imaged both with intraoral digital radiography using image plates and with CBCT. Two sets of intraoral images were acquired per tooth: orthogonal (PA) which was the conventional periapical radiograph and mesioangulated (SET). Four readers were asked to rate their confidence level in detecting and locating the lesions. Receiver operating characteristic (ROC) analysis was performed to assess the accuracy of each modality in detecting the presence of lesions, the affected surface, and the affected level. Analysis of variation was used to compare the results and kappa analysis was used to evaluate interobserver agreement. Results A significant difference in the area under the ROC curves was found among the three modalities (P=0.0002), with CBCT (0.81) having a significantly higher value than PA (0.71) or SET (0.71). PA was slightly more accurate than SET, but the difference was not statistically significant. CBCT was also superior in locating the affected surface and level. Conclusion CBCT has already proven its superiority in detecting multiple dental conditions, and this study shows it to likewise be superior in detecting and locating incipient external root resorption. PMID:26389057

  18. Comparison of the accuracy of digitally fabricated polyurethane model and conventional gypsum model

    PubMed Central

    Kim, So-Yeun; Lee, So-Hyoun; Cho, Seong-Keun; Jeong, Chang-Mo; Jeon, Young-Chan; Yun, Mi-Jung

    2014-01-01

    PURPOSE The accuracy of a gypsum model (GM), which was taken using a conventional silicone impression technique, was compared with that of a polyurethane model (PM), which was taken using an iTero™ digital impression system. MATERIALS AND METHODS The maxillary first molar artificial tooth was selected as the reference tooth. The GMs were fabricated through a silicone impression of a reference tooth, and PMs were fabricated by a digital impression (n=9, in each group). The reference tooth and experimental models were scanned using a 3 shape convince™ scan system. Each GM and PM image was superimposed on the registered reference model (RM) and 2D images were obtained. The discrepancies of the points registered on the superimposed images were measured and defined as GM-RM group and PM-RM group. Statistical analysis was performed using a Student's T-test (α=0.05). RESULTS A comparison of the absolute value of the discrepancy revealed a significant difference between the two groups only at the occlusal surface. The GM group showed a smaller mean discrepancy than the PM group. Significant differences in the GM-RM group and PM-RM group were observed in the margins (point a and f), mesial mid-axial wall (point b) and occlusal surfaces (point c and d). CONCLUSION Under the conditions examined, the digitally fabricated polyurethane model showed a tendency for a reduced size in the margin than the reference tooth. The conventional gypsum model showed a smaller discrepancy on the occlusal surface than the polyurethane model. PMID:24605199

  19. Diagnostic Accuracy of Inverted and Unprocessed Digitized Periapical Radiographs for Detection of Peri-Implant Defects

    PubMed Central

    Pourhashemi, Seyed Jalal; Kiani, Mohammad Taghi; Emami, Raheleh; Kharazifard, Mohamad Javad

    2015-01-01

    Objectives: This study aimed to compare the diagnostic accuracy of inverted and unprocessed digitized periapical radiographs for detection of peri-implant defects. Materials and Methods: A total of 30 osteotomy sites were prepared in three groups of control, study group 1 with 0.425 mm defects and study group 2 with 0.725 mm defects using the SIC and Astra Tech drill systems with 4.25mm and 4.85mm diameters. Small and large defects were randomly created in the coronal 8mm of 20 implant sites; implants (3.4mm diameter, 14.5mm length) were then placed. Thirty periapical (PA) radiographs were obtained using Digora imaging system (Soredex Corporation, Helsinki, Finland), size 2 photostimulable storage phosphor (PSP) plate sensors (40.0mm×30.0mm) and Scanora software. Unprocessed images were inverted using Scanora software by applying image inversion and a total of 60 images were obtained and randomly evaluated by four oral and maxillofacial radiologists. Data were analyzed using the t-test. Results: Significant differences were observed in absolute and complete sensitivity and specificity of the two imaging modalities for detection of small and large defects (P<0.05). Unprocessed digital images had a higher mean in terms of absolute sensitivity for detection of small defects, complete sensitivity for detection of large peri-implant defects and definite rule out of defects compared with inverted images. Conclusion: Unprocessed digital images have a higher diagnostic value for detection of small and large peri-implant defects and also for definite rule out of defects compared with inverted images. PMID:27123016

  20. Delineating small karst watersheds based on digital elevation model and eco-hydrogeological principles

    NASA Astrophysics Data System (ADS)

    Jie Luo, Guang; Jie Wang, Shi; Bai, Xiao Yong; Liu, Xiu Ming; Cheng, An Yun

    2016-03-01

    Dominated by specific eco-hydrogeological backgrounds, a small watershed delineated by using the traditional method is always inauthentic in karst regions because it cannot accurately reflect the eco-hydrological process of the dual structure of the surface and subsurface. This study proposes a new method for the delineation of small watersheds based on digital elevation models (DEMs) and eco-hydrogeological principles in karst regions. This method is applied to one section of the tributary area (Sancha River) of the Yangtze River in China. By comparing the quantity, shape, superimposition, and characteristics of the internal hydrological process of a small watershed extracted by using the digital elevation model with that extracted by using the proposed method of this study, we conclude that the small karst watersheds extracted by the new method accurately reflect the hydrological process of the river basin. Furthermore, we propose that the minimum unit of the river basin in karst regions should be the watershed, whose exit is the corrosion and corrasion baselevel and a further division of watershed may cause a significant inconsistency with the true eco-hydrological process.

  1. Construction of a 3-arcsecond digital elevation model for the Gulf of Maine

    USGS Publications Warehouse

    Twomey, Erin R.; Signell, Richard P.

    2013-01-01

    A system-wide description of the seafloor topography is a basic requirement for most coastal oceanographic studies. The necessary detail of the topography obviously varies with application, but for many uses, a nominal resolution of roughly 100 m is sufficient. Creating a digital bathymetric grid with this level of resolution can be a complex procedure due to a multiplicity of data sources, data coverages, datums and interpolation procedures. This report documents the procedures used to construct a 3-arcsecond (approximately 90-meter grid cell size) digital elevation model for the Gulf of Maine (71°30' to 63° W, 39°30' to 46° N). We obtained elevation and bathymetric data from a variety of American and Canadian sources, converted all data to the North American Datum of 1983 for horizontal coordinates and the North American Vertical Datum of 1988 for vertical coordinates, used a combination of automatic and manual techniques for quality control, and interpolated gaps using a surface-fitting routine.

  2. Perspectives on open access high resolution digital elevation models to produce global flood hazard layers

    NASA Astrophysics Data System (ADS)

    Sampson, Christopher; Smith, Andrew; Bates, Paul; Neal, Jeffrey; Trigg, Mark

    2015-12-01

    Global flood hazard models have recently become a reality thanks to the release of open access global digital elevation models, the development of simplified and highly efficient flow algorithms, and the steady increase in computational power. In this commentary we argue that although the availability of open access global terrain data has been critical in enabling the development of such models, the relatively poor resolution and precision of these data now limit significantly our ability to estimate flood inundation and risk for the majority of the planet's surface. The difficulty of deriving an accurate 'bare-earth' terrain model due to the interaction of vegetation and urban structures with the satellite-based remote sensors means that global terrain data are often poorest in the areas where people, property (and thus vulnerability) are most concentrated. Furthermore, the current generation of open access global terrain models are over a decade old and many large floodplains, particularly those in developing countries, have undergone significant change in this time. There is therefore a pressing need for a new generation of high resolution and high vertical precision open access global digital elevation models to allow significantly improved global flood hazard models to be developed.

  3. Estimating net solar radiation using Landsat Thematic Mapper and digital elevation data

    NASA Technical Reports Server (NTRS)

    Dubayah, R.

    1992-01-01

    A radiative transfer algorithm is combined with digital elevation and satellite reflectance data to model spatial variability in net solar radiation at fine spatial resolution. The method is applied to the tall-grass prairie of the 16 x 16 sq km FIFE site (First ISLSCP Field Experiment) of the International Satellite Land Surface Climatology Project. Spectral reflectances as measured by the Landsat Thematic Mapper (TM) are corrected for atmospheric and topographic effects using field measurements and accurate 30-m digital elevation data in a detailed model of atmosphere-surface interaction. The spectral reflectances are then integrated to produce estimates of surface albedo in the range 0.3-3.0 microns. This map of albedo is used in an atmospheric and topographic radiative transfer model to produce a map of net solar radiation. A map of apparent net solar radiation is also derived using only the TM reflectance data, uncorrected for topography, and the average field-measured downwelling solar irradiance. Comparison with field measurements at 10 sites on the prairie shows that the topographically derived radiation map accurately captures the spatial variability in net solar radiation, but the apparent map does not.

  4. Quantification of soil losses from tourist trails - use of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Tomczyk, Aleksandra

    2010-05-01

    Tourism impacts in protected mountain areas are one of the main concerns for land managers. Impact to environment is most visible at locations of highly concentrated activities like tourist trails, campsites etc. The main indicators of the tourist trail degradation are: vegetation loss (trampling of vegetation cover), change of vegetation type and composition, widening of the trails, muddiness and soil erosion. The last one is especially significant, since it can cause serious transformation of the land surface. Such undesirable changes cannot be repaired without high-cost management activities, and, in some cases they can made the trails difficult and unsafe to use. Scientific understanding of soil erosion related to human impact can be useful for more effective management of the natural protected areas. The aim of this study was to use of digital elevation models (DEMs) to precisely quantify of soil losses from tourist trails. In the study precise elevation data were gathered in several test fields of 4 by 5 m spatial dimension. Measurements were taken in 13 test fields, located in two protected natural areas in south Poland: Gorce National Park and Popradzki Landscape Park. The measuring places were located on trails characterized by different slope, type of vegetation and type of use. Each test field was established by four special marks, firmly dug into the ground. Elevation data were measured with the electronic total station. Irregular elevation points were surveying with essential elements of surrounding terrain surface being included. Moreover, surveys in fixed profile lines were done. For each test field a set of 30 measurements in control points has been collected and these data provide the base for verification of digital elevation models. Average density of the surveying was 70 points per square meter (1000 - 1500 elevation points per each test fields). Surveys in each test field were carried out in August and September of 2008, June 2009 and August

  5. State of Louisiana - Highlighting Low-Lying Areas Derived from USGS Digital Elevation Data

    USGS Publications Warehouse

    Kosovich, John J.

    2008-01-01

    In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts a color shaded relief representation highlighting the State of Louisiana and depicts the surrounding areas using muted elevation colors. The first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands, which highlight low-elevation areas at a coarse spatial resolution. Areas below sea level typically are surrounded by levees or some other type of flood-control structures. Standard USGS National Elevation Dataset (NED) 1 arc-second (nominally 30-meter) digital elevation model (DEM) data are the basis for the map, which is designed to be used at a broad scale and for informational purposes only. The NED data are a mixture of data and were derived from the original 1:24,000-scale USGS topographic map bare-earth contours, which were converted into gridded quadrangle-based DEM tiles at a constant post spacing (grid cell size) of either 30 meters (data before the mid-1990s) or 10 meters (mid-1990s and later data). These individual-quadrangle DEMs were then converted to spherical coordinates (latitude/longitude decimal degrees) and edge-matched to ensure seamlessness. Approximately one-half of the area shown on this map has DEM source data at a 30-meter resolution, with the remaining half consisting of mostly 10-meter contour-derived DEM data and some small areas of higher-resolution LIght Detection And Ranging (LIDAR) data along parts of the coastline. Areas below sea level typically are surrounded by levees or some other type of flood-control structures. State and parish boundary, hydrography, city, and road layers were modified from USGS National Atlas data downloaded in 2003. The NED data were downloaded in 2007.

  6. Mapping elevations of tidal wetland restoration sites in San Francisco Bay: Comparing accuracy of aerial lidar with a singlebeam echosounder

    USGS Publications Warehouse

    Athearn, N.D.; Takekawa, J.Y.; Jaffe, B.; Hattenbach, B.J.; Foxgrover, A.C.

    2010-01-01

    The southern edge of San Francisco Bay is surrounded by former salt evaporation ponds, where tidal flow has been restricted since the mid to late 1890s. These ponds are now the focus of a large wetland restoration project, and accurate measurement of current pond bathymetry and adjacent mud flats has been critical to restoration planning. Aerial light detection and ranging (lidar) has become a tool for mapping surface elevations, but its accuracy had rarely been assessed for wetland habitats. We used a singlebeam echosounder system we developed for surveying shallow wetlands to map submerged pond bathymetry in January of 2004 and compared those results with aerial lidar surveys in two ponds that were dry in May of 2004. From those data sets, we compared elevations for 5164 (Pond E9, 154 ha) and 2628 (Pond E14, 69 ha) echosounder and lidar points within a 0.375-m radius of each other (0.750-m diameter lidar spot size). We found that mean elevations of the lidar points were lower than the echosounder results by 5 ?? 0.1 cm in Pond E9 and 2 ?? 0.2 cm in Pond E14. Only a few points (5% in Pond E9, 2% in Pond E14) differed by more than 20 cm, and some of these values may be explained by residual water in the ponds during the lidar survey or elevation changes that occurred between surveys. Our results suggest that aerial lidar may be a very accurate and rapid way to assess terrain elevations for wetland restoration projects. ?? 2010 Coastal Education and Research Foundation.

  7. Application of Low-Cost Digital Elevation Models to Detect Change in Forest Carbon Sequestration Projects

    SciTech Connect

    Kenneth Glenn MacDicken

    2007-07-31

    This two-year study evaluated advanced multispectral digital imagery applications for assessment of forest carbon stock change. A series of bench and field studies in North Carolina and Ohio tested aerial assessments of forest change between two time periods using two software packages (ERDAS and TERREST) for Digital Elevation Model (DEM) creation, automated classification software (eCognition) for canopy segmentation and a multiple ranging laser designed to improve quality of elevation data. Results of the DEM software comparison showed that while TERREST has the potential to produce much higher resolution DEM than ERDAS, it is unable to resolve crucial canopy features adequately. Lab tests demonstrated that additional laser data improves image registration and Z-axis DEM quality. Data collected in the field revealed difficult challenges in correctly modeling the location of laser strike and subsequently determining elevations in both software packages. Automated software segmentation of tree canopies provided stem diameter and biomass carbon estimates that were within 3% of comparable ground based estimates in the Ohio site and produced similar biomass estimates for a limited number of plots in the Duke forest. Tree height change between time periods and canopy segmentation from multispectral imagery allowed calculation of forest carbon stock change at costs that are comparable to those for ground-based methods. This work demonstrates the potential of lower cost imagery systems enhanced with laser data to collect high quality imagery and paired laser data for forestry and environmental applications. Additional research on automated canopy segmentation and multi-temporal image registration is needed to refine these methods for commercial use.

  8. 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.

  9. Spatial disaggregation of satellite-derived irradiance using a high-resolution digital elevation model

    SciTech Connect

    Ruiz-Arias, Jose A.; Tovar-Pescador, Joaquin; Cebecauer, Tomas; Suri, Marcel

    2010-09-15

    Downscaling of the Meteosat-derived solar radiation ({proportional_to}5 km grid resolution) is based on decomposing the global irradiance and correcting the systematic bias of its components using the elevation and horizon shadowing that are derived from the SRTM-3 digital elevation model (3 arc sec resolution). The procedure first applies the elevation correction based on the difference between coarse and high spatial resolution. Global irradiance is split into direct, diffuse circumsolar and diffuse isotropic components using statistical models, and then corrections due to terrain shading and sky-view fraction are applied. The effect of reflected irradiance is analysed only in the theoretical section. The method was applied in the eastern Andalusia, Spain, and the validation was carried out for 22 days on April, July and December 2006 comparing 15-min estimates of the satellite-derived solar irradiance and observations from nine ground stations. Overall, the corrections of the satellite estimates in the studied region strongly reduced the mean bias of the estimates for clear and cloudy days from roughly 2.3% to 0.4%. (author)

  10. Three-dimensional displays for natural hazards analysis, using classified Landsat Thematic Mapper digital data and large-scale digital elevation models

    NASA Technical Reports Server (NTRS)

    Butler, David R.; Walsh, Stephen J.; Brown, Daniel G.

    1991-01-01

    Methods are described for using Landsat Thematic Mapper digital data and digital elevation models for the display of natural hazard sites in a mountainous region of northwestern Montana, USA. Hazard zones can be easily identified on the three-dimensional images. Proximity of facilities such as highways and building locations to hazard sites can also be easily displayed. A temporal sequence of Landsat TM (or similar) satellite data sets could also be used to display landscape changes associated with dynamic natural hazard processes.

  11. Evaluating a CCD film digitizer: comparing interpretation accuracy with original film readings

    NASA Astrophysics Data System (ADS)

    Gitlin, Joseph N.; Scott, William W., Jr.; Bell, Kathryn; Narayan, Anand

    2002-04-01

    The purpose of the study was to determine if there were differences between the interpretations of radiographic images resulting from digitizing films using a recently developed CCD unit, and the readings of the original films. The general hypothesis to be tested was that there were no significant differences in the measures of accuracy, sensitivity, specificity and ROC analyses when the interpretations related to the two modes were compared. The authors selected 120 radiographic examinations for the study from departmental teaching files, which included chest, abdomen, extremity and other cases that were considered difficult to interpret. The authors also selected six specific abnormalities visualized on 60 of the cases as true positives to classify the reports. After anonymizing the patient identification, the films were digitized and independently interpreted by four board-certified radiologists. Each reader read all of the examinations, half on film alternators and the other half on a high-resolution soft-copy workstation. No reader interpreted the same examination more than once. As of this date, the preliminary results indicate that the hypothesis will be accepted, but more analyses of the data must be performed to confirm the early findings. The additional work will include complete verification of data entry and classification of interpretations, a detailed review of perceived image quality and completion of the ROC analysis by pairs of readers. If the results are confirmed, radiologists, other physicians and administrators will have another reliable option to conventional film practice through increased access to remote primary diagnosis and consultation using high-speed telecommunication media.

  12. Gulf of Mexico Region - Highlighting Low-Lying Areas Derived from USGS Digital Elevation Data

    USGS Publications Warehouse

    Kosovich, John J.

    2008-01-01

    In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts a color shaded relief representation of the area surrounding the Gulf of Mexico. The first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands, which highlight low-elevation areas at a coarse spatial resolution. Standard USGS National Elevation Dataset (NED) 1 arc-second (nominally 30-meter) digital elevation model (DEM) data are the basis for the map, which is designed to be used at a broad scale and for informational purposes only. The NED data were derived from the original 1:24,000-scale USGS topographic map bare-earth contours, which were converted into gridded quadrangle-based DEM tiles at a constant post spacing (grid cell size) of either 30 meters (data before the mid-1990s data) or 10 meters (mid-1990s and later data). These individual-quadrangle DEMs were then converted to spherical coordinates (latitude/longitude decimal degrees) and edge-matched to ensure seamlessness. Approximately one-half of the area shown on this map has DEM source data at a 30-meter resolution, with the remaining half consisting of 10-meter contour-derived DEM data or higher-resolution LIDAR data. Areas below sea level typically are surrounded by levees or some other type of flood-control structures. State and county boundary, hydrography, city, and road layers were modified from USGS National Atlas data downloaded in 2003. The NED data were downloaded in 2005.

  13. Side-specific effect of yolk testosterone elevation on second-to-fourth digit ratio in a wild passerine.

    PubMed

    Nagy, Gergely; Blázi, György; Hegyi, Gergely; Török, János

    2016-02-01

    Second-to-fourth digit ratio is a widely investigated sexually dimorphic morphological trait in human studies and could reliably indicate the prenatal steroid environment. Conducting manipulative experiments to test this hypothesis comes up against ethical limits in humans. However, oviparous tetrapods may be excellent models to experimentally investigate the effects of prenatal steroids on offspring second-to-fourth digit ratio. In this field study, we injected collared flycatcher (Ficedula albicollis) eggs with physiological doses of testosterone. Fledglings from eggs with elevated yolk testosterone, regardless of their sex, had longer second digits on their left feet than controls, while the fourth digit did not differ between groups. Therefore, second-to-fourth digit ratio was higher in the testosterone-injected group, but only on the left foot. This is the first study which shows experimentally that early testosterone exposure can affect second-to-fourth digit ratio in a wild population of a passerine bird. PMID:26732381

  14. Side-specific effect of yolk testosterone elevation on second-to-fourth digit ratio in a wild passerine

    NASA Astrophysics Data System (ADS)

    Nagy, Gergely; Blázi, György; Hegyi, Gergely; Török, János

    2016-02-01

    Second-to-fourth digit ratio is a widely investigated sexually dimorphic morphological trait in human studies and could reliably indicate the prenatal steroid environment. Conducting manipulative experiments to test this hypothesis comes up against ethical limits in humans. However, oviparous tetrapods may be excellent models to experimentally investigate the effects of prenatal steroids on offspring second-to-fourth digit ratio. In this field study, we injected collared flycatcher ( Ficedula albicollis) eggs with physiological doses of testosterone. Fledglings from eggs with elevated yolk testosterone, regardless of their sex, had longer second digits on their left feet than controls, while the fourth digit did not differ between groups. Therefore, second-to-fourth digit ratio was higher in the testosterone-injected group, but only on the left foot. This is the first study which shows experimentally that early testosterone exposure can affect second-to-fourth digit ratio in a wild population of a passerine bird.

  15. The research of digital circuit system for high accuracy CCD of portable Raman spectrometer

    NASA Astrophysics Data System (ADS)

    Yin, Yu; Cui, Yongsheng; Zhang, Xiuda; Yan, Huimin

    2013-08-01

    The Raman spectrum technology is widely used for it can identify various types of molecular structure and material. The portable Raman spectrometer has become a hot direction of the spectrometer development nowadays for its convenience in handheld operation and real-time detection which is superior to traditional Raman spectrometer with heavy weight and bulky size. But there is still a gap for its measurement sensitivity between portable and traditional devices. However, portable Raman Spectrometer with Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) technology can enhance the Raman signal significantly by several orders of magnitude, giving consideration in both measurement sensitivity and mobility. This paper proposed a design and implementation of driver and digital circuit for high accuracy CCD sensor, which is core part of portable spectrometer. The main target of the whole design is to reduce the dark current generation rate and increase signal sensitivity during the long integration time, and in the weak signal environment. In this case, we use back-thinned CCD image sensor from Hamamatsu Corporation with high sensitivity, low noise and large dynamic range. In order to maximize this CCD sensor's performance and minimize the whole size of the device simultaneously to achieve the project indicators, we delicately designed a peripheral circuit for the CCD sensor. The design is mainly composed with multi-voltage circuit, sequential generation circuit, driving circuit and A/D transition parts. As the most important power supply circuit, the multi-voltage circuits with 12 independent voltages are designed with reference power supply IC and set to specified voltage value by the amplifier making up the low-pass filter, which allows the user to obtain a highly stable and accurate voltage with low noise. What's more, to make our design easy to debug, CPLD is selected to generate sequential signal. The A/D converter chip consists of a correlated

  16. The Application of Digital Pathology to Improve Accuracy in Glomerular Enumeration in Renal Biopsies

    PubMed Central

    Troost, Jonathan P.; Gasim, Adil; Bagnasco, Serena; Avila-Casado, Carmen; Johnstone, Duncan; Hodgin, Jeffrey B.; Conway, Catherine; Gillespie, Brenda W.; Nast, Cynthia C.; Barisoni, Laura; Hewitt, Stephen M.

    2016-01-01

    Background In renal biopsy reporting, quantitative measurements, such as glomerular number and percentage of globally sclerotic glomeruli, is central to diagnostic accuracy and prognosis. The aim of this study is to determine the number of glomeruli and percent globally sclerotic in renal biopsies by means of registration of serial tissue sections and manual enumeration, compared to the numbers in pathology reports from routine light microscopic assessment. Design We reviewed 277 biopsies from the Nephrotic Syndrome Study Network (NEPTUNE) digital pathology repository, enumerating 9,379 glomeruli by means of whole slide imaging. Glomerular number and the percentage of globally sclerotic glomeruli are values routinely recorded in the official renal biopsy pathology report from the 25 participating centers. Two general trends in reporting were noted: total number per biopsy or average number per level/section. Both of these approaches were assessed for their accuracy in comparison to the analogous numbers of annotated glomeruli on WSI. Results The number of glomeruli annotated was consistently higher than those reported (p<0.001); this difference was proportional to the number of glomeruli. In contrast, percent globally sclerotic were similar when calculated on total glomeruli, but greater in FSGS when calculated on average number of glomeruli (p<0.01). The difference in percent globally sclerotic between annotated and those recorded in pathology reports was significant when global sclerosis is greater than 40%. Conclusions Although glass slides were not available for direct comparison to whole slide image annotation, this study indicates that routine manual light microscopy assessment of number of glomeruli is inaccurate, and the magnitude of this error is proportional to the total number of glomeruli. PMID:27310011

  17. Accuracy, precision and response time of consumer bimetal and digital thermometers for cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three models each of consumer instant-read bimetal and digital thermometers were tested for accuracy, precision and response time compared to a calibrated thermocouple in cooked 80 percent and 90 percent lean ground beef patties and boneless and bone-in split chicken breasts. At the recommended inse...

  18. Digital Elevation Model Creation Using SfM on High-Altitude Snow-Covered Surfaces at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Millstein, J. D.; Hawley, R. L.

    2015-12-01

    Structure from Motion (SfM) provides a means through which a digital elevation model (DEM) can be constructed with data acquired at a relatively low cost when compared to other current alternatives. Using an Unmanned Aerial Vehicle (UAV), a large area can be efficiently covered at high spatial resolution to quantify regional topography. Structure from Motion applied to photogrammetric techniques from a UAV has proven to be a successful tool, but challenges to UAV-based SfM include high-altitude locations with few distinctive surface features and minor textural differences. In June 2015, we piloted a small UAV (Quest) in order to conduct a topographical survey of Summit Camp, Greenland using SfM. Summit Camp sits at a surface elevation of 3200 meters above sea level, and occupies a snow-covered surface. The flat, very uniform terrain proved to be a challenge when flying the UAV and processing imagery using SfM techniques. In this presentation we discuss the issues both with operating a UAV instrument platform at high-altitude in the polar regions and interpreting the resulting DEM from a snow-covered region. The final DEM of Summit Camp covers a large portion of the surface area directly impacted by camp activities. In particular, volume calculations of drifting snow gauge an estimate of the equipment hours that will be required to clear and unearth structures. Investigation of surface roughness at multiple length scales can similarly provide insight on the accuracy of the DEM when observing texturally uniform surfaces.

  19. Bathymetry and digital elevation models of Coyote Creek and Alviso Slough, South San Francisco Bay, California

    USGS Publications Warehouse

    Foxgrover, Amy C.; Finlayson, David P.; Jaffe, Bruce E.; Fregoso, Theresa A.

    2011-01-01

    The bathymetry surveys were conducted using the state-of-the-art research vessel R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping in extremely shallow water. We provide high-resolution bathymetric data collected by the USGS. For the 2010 baseline survey we have merged the bathymetry with aerial lidar data that were collected for the USGS during the same time period to create a seamless, high-resolution digital elevation model (DEM) of the study area. The series of bathymetry datasets are provided at 1 m resolution and the 2010 bathymetric/topographic DEM at 2 m resolution. The data are formatted as both X, Y, Z text files and ESRI Arc ASCII files that are accompanied by FGDC compliant metadata.

  20. Synthetic Aperture Radar Interferometry for Digital Elevation Model of Kuwait Desert - Analysis of Errors

    NASA Astrophysics Data System (ADS)

    Jassar, H. K. Al; Rao, K. S.

    2012-07-01

    Using different combinations of 29 Advanced Synthetic Aperture Radar (ASAR) images, 43 Digital Elevations Models (DEM) were generated adopting SAR Interferometry (InSAR) technique. Due to sand movement in desert terrain, there is a poor phase correlation between different SAR images. Therefore, suitable methodology for generating DEMs of Kuwait desert terrain using InSAR technique were worked out. Time series analysis was adopted to derive the best DEM out of 43 DEMs. The problems related to phase de-correlation over desert terrain are discussed. Various errors associated with the DEM generation are discussed which include atmospheric effects, penetration into soil medium, sand movement. The DEM of Shuttle Radar Topography Mission (SRTM) is used as a reference. The noise levels of DEM of SRTM are presented.

  1. Hydrologic analysis of a flood based on a new Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Nishio, M.; Mori, M.

    2015-06-01

    These The present study aims to simulate the hydrologic processes of a flood, based on a new, highly accurate Digital Elevation Model (DEM). The DEM is provided by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, and has a spatial resolution of five meters. It was generated by the new National Project in 2012. The Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) is used to simulate the hydrologic process of a flood of the Onga River in Iizuka City, Japan. A large flood event in the typhoon season in 2003 caused serious damage around the Iizuka City area. Precise records of rainfall data from the Automated Meteorological Data Acquisition System (AMeDAS) were input into the HEC-HMS. The estimated flood area of the simulation results by HEC-HMS was identical to the observed flood area. A watershed aggregation map is also generated by HEC-HMS around the Onga River.

  2. Extracting low-resolution river networks from high-resolution digital elevation models

    USGS Publications Warehouse

    Olivera, F.; Lear, M.S.; Famiglietti, J.S.; Asante, Kwasi

    2002-01-01

    Including a global river network in the land component of global climate models (GCMs) is necessary in order to provide a more complete representation of the hydrologic cycle. The process of creating these networks is called river network upscaling and consists of lowering the resolution of already available fine networks to make them compatible with GCMs. Fine-resolution river networks have a level of detail appropriate for analysis at the watershed scale but are too intensive for global hydrologic studies. A river network upscaling algorithm, which processes fine-resolution digital elevation models to determine the flow directions that best describe the flow patterns in a coarser user-defined scale, is presented. The objectives of this study were to develop an algorithm that advances the previous work in the field by being applicable at a global scale, allowing for the upscaling to be performed in a projected environment, and generating evenly distributed flow directions.

  3. A digital elevation model of the Greenland ice sheet and validation with airborne laser altimeter data

    NASA Technical Reports Server (NTRS)

    Bamber, Jonathan L.; Ekholm, Simon; Krabill, William B.

    1997-01-01

    A 2.5 km resolution digital elevation model (DEM) of the Greenland ice sheet was produced from the 336 days of the geodetic phase of ERS-1. During this period the altimeter was operating in ice-mode over land surfaces providing improved tracking around the margins of the ice sheet. Combined with the high density of tracks during the geodetic phase, a unique data set was available for deriving a DEM of the whole ice sheet. The errors present in the altimeter data were investigated via a comparison with airborne laser altimeter data obtained for the southern half of Greenland. Comparison with coincident satellite data showed a correlation with surface slope. An explanation for the behavior of the bias as a function of surface slope is given in terms of the pattern of surface roughness on the ice sheet.

  4. Vegetation Cover Mapping Based on Remote Sensing and Digital Elevation Model Data

    NASA Astrophysics Data System (ADS)

    Korets, M. A.; Ryzhkova, V. A.; Danilova, I. V.; Prokushkin, A. S.

    2016-06-01

    An algorithm of forest cover mapping based on combined GIS-based analysis of multi-band satellite imagery, digital elevation model, and ground truth data was developed. Using the classification principles and an approach of Russian forest scientist Kolesnikov, maps of forest types and forest growing conditions (FGC) were build. The first map is based on RS-composite classification, while the second map is constructed on the basis of DEM-composite classification. The spatial combination of this two layers were also used for extrapolation and mapping of ecosystem carbon stock values (kgC/m2). The proposed approach was applied for the test site area (~3600 km2), located in the Northern Siberia boreal forests of Evenkia near Tura settlement.

  5. Alluvial Fan Delineation from SAR and LIDAR-Derived Digital Elevation Models in the Philippines

    NASA Astrophysics Data System (ADS)

    Aquino, D. T.; Ortiz, I.; Timbas, N.; Gacusan, R.; Montalbo, K.; Eco, R. C.; Lagmay, A.

    2013-12-01

    Occurrence of floods and debris flows leading to the formation of alluvial fans at the base of mountains naturally improve fertility of alluvial plains. However, these formations also have detrimental effects to communities within these zones like the case of Barangay (village) Andap, New Bataan, Compostela Valley where the whole village was wiped out by debris flow when it was hit by Supertyphoon Bopha in 2012. Hence, demarcating the boundaries of alluvial fans is crucial in disaster preparedness and mitigation. This study describes a method to delineate alluvial fans through contour maps from SAR and LiDAR-derived digital elevation models. Based on this data, we used hydrographic apex point polygons to plot the outflow points of upstream watersheds. The watershed and alluvial fan polygons were used to simulate debris flows in the study sites. The fans generated from the flood simulation were consistent with the polygons delineated from the digital elevation model. Satellite imagery and evidences of alluvial deposits found on site revealed 392 alluvial fans in the country. Widest among these is the sprawling 760 sq km fan identified in Cagayan Valley threatening about 434,329 persons at risk of debris flow. Other fans include those identified in Calapan, Mindoro (531 sq km), Kaliwanagan, Pangasinan (436 sq km), Pampanga Alluvial Fan (325 sq km), Mina, Iloilo (315 sq km), Lamsugod, S. Cotabato (286 sq km), in Tignaman, Oton and Alimodian in Iloilo (272 sq km), and the bajada, a series of alluvial fan coalescing to form a larger fan, identified in Ilocos Norte (218 sq km).

  6. A Digital Elevation Model for Seaside, Oregon: Procedures, Data Sources, and Analysis

    NASA Astrophysics Data System (ADS)

    Venturato, A. J.

    2004-12-01

    As part of a pilot study to modernize Flood Insurance Rate Maps for the Federal Emergency Management Agency (FEMA), a digital elevation model (DEM) was developed for the purpose of modeling tsunami inundation for Seaside, Oregon. The DEM consists of elevation data values with a horizontal grid spacing of 1/3 arc seconds, or approximately 10 meters. The DEM was generated from several topographic and bathymetric data sources, requiring significant processing challenges. These challenges included conversion to a single specified projection, units, horizontal datum, and vertical datum; analysis and removal of errant data from hydrographic, topographic, and LIDAR surveys; and a point-by-point analysis of overlapping data sources. Data were collected from the National Oceanic and Atmospheric Administration National Ocean Service and National Geophysical Data Center, the U.S. Geological Survey, the Oregon Geospatial Data Center, the University of Oregon, and the Oregon Department of Geology and Mineral Industries. Data were converted into formats compatible with ESRI ArcGIS 3.3 software. ArcGIS was used for spatial analysis, error correction, and surface grid development using triangular irregular networking. Post-processing involved a consistency analysis and comparison with original data and control data sources. The final DEM was compared with a previous DEM developed for tsunami inundation modeling in 1997. Significant shoreline differences were found between the DEMs, resulting in an analysis of the shoreline changes around the mouth of the Necanicum River. The shoreline analysis includes a spatial analysis of digital orthophotos over the recent past and a review of historical accretion and erosion rates along the Columbia River littoral cell.

  7. New Techniques and Metrics for Describing Rivers Using High Resolution Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Bailey, P.; McKean, J. A.; Poulsen, F.; Ochoski, N.; Wheaton, J. M.

    2013-12-01

    Techniques for collecting high resolution digital elevation models (DEMs) of fluvial environments are cheaper and more widely accessible than ever before. These DEMs improve over traditional transect-based approaches because they represent the channel bed as a continuous surface. Advantages beyond the obvious more accurate representations of channel area and volume include the three dimensional representation of geomorphic features that directly influence the behavior of river organisms. It is possible to identify many of these habitats using topography alone, but when combined with the spatial arrangement of these areas within the channel, a more holistic view of biologic existence can be gleaned from the three dimensional representation of the channel. We present a new approach for measuring and describing channels that leverages the continuous nature of digital elevation model surfaces. Delivered via the River Bathymetry Toolkit (RBT) this approach is capable of not only reproducing the traditional transect-based metrics, but also includes novel techniques for generating stage independent channel measurements, regardless of the flow that occurred at the time of data capture. The RBT also possesses the capability of measuring changes over time, accounting for uncertainty using approaches adopted from the Geomorphic Change Detection (GCD) literature and producing maps and metrics for erosion and deposition. This new approach is available via the River Bathymetry Toolit that is structured to enable repeat systematic measurements over an unlimited number of sites. We present how this approach has been applied to over 500 sites in the Pacific Northwest as part of the Columbia Habitat Mapping Program (CHaMP). We demonstrate the new channel metrics for a range of these sites, both at the observed and simulated flows as well as examples of changes in channel morphology over time. We present an analysis comparing these new metrics against traditional transect based

  8. Accuracy of Computerized Vertical Measurements on Digital Orthopantomographs: Posterior Mandibular Region

    PubMed Central

    Assaf, Mohammad; Gharbyah, Alaa’ Z. Abu

    2014-01-01

    Objectives: Orthopantomographs are commonly used for diagnosis in clinical dentistry. Although the manufacturers claim a constant magnification effect, the reliability of measuring dimensions on the panoramic radiographs is not clear. The aim of this study was to evaluate the accuracy of measuring vertical dimensions in the posterior mandibular area on digital orthopantomographs. Materials and Methods: A retrospective survey of 20 orthopantomographs with unrestored implants (only with cover screw) in the mandibular posterior region (molars and premolars) was conducted. All radiographs were taken using the same machine by skilled technicians. Two examiners were asked to measure the vertical dimension of the implants seen on the radiographs viewed using two differently sized display screens. Inter-examiner and intra-examiner reliability tests were performed. Differences between the measured length and the actual length using each screen type were compared. Results: High coefficients of reliability were observed on intra- and inter-examiner correlation. The overall reliability of measuring the vertical dimensions of implants between both examiners for the large screen and the small screen were 97.4% (Cronbach's alpha 0.993) and 94.0% (Cronbach's alpha 0.984), respectively. There were no significant differences between the errors seen with either the large screen or the small screen, when each of them was compared to the original length (P = 0.146). Conclusion: This study shows that vertical dimensions in the posterior mandibular region (molar and premolars) can be reliably measured on an orthopantomograph using a calibrated machine and special software. PMID:25806135

  9. High accuracy digital image correlation powered by GPU-based parallel computing

    NASA Astrophysics Data System (ADS)

    Zhang, Lingqi; Wang, Tianyi; Jiang, Zhenyu; Kemao, Qian; Liu, Yiping; Liu, Zejia; Tang, Liqun; Dong, Shoubin

    2015-06-01

    A sub-pixel digital image correlation (DIC) method with a path-independent displacement tracking strategy has been implemented on NVIDIA compute unified device architecture (CUDA) for graphics processing unit (GPU) devices. Powered by parallel computing technology, this parallel DIC (paDIC) method, combining an inverse compositional Gauss-Newton (IC-GN) algorithm for sub-pixel registration with a fast Fourier transform-based cross correlation (FFT-CC) algorithm for integer-pixel initial guess estimation, achieves a superior computation efficiency over the DIC method purely running on CPU. In the experiments using simulated and real speckle images, the paDIC reaches a computation speed of 1.66×105 POI/s (points of interest per second) and 1.13×105 POI/s respectively, 57-76 times faster than its sequential counterpart, without the sacrifice of accuracy and precision. To the best of our knowledge, it is the fastest computation speed of a sub-pixel DIC method reported heretofore.

  10. Malingering in Toxic Exposure. Classification Accuracy of Reliable Digit Span and WAIS-III Digit Span Scaled Scores

    ERIC Educational Resources Information Center

    Greve, Kevin W.; Springer, Steven; Bianchini, Kevin J.; Black, F. William; Heinly, Matthew T.; Love, Jeffrey M.; Swift, Douglas A.; Ciota, Megan A.

    2007-01-01

    This study examined the sensitivity and false-positive error rate of reliable digit span (RDS) and the WAIS-III Digit Span (DS) scaled score in persons alleging toxic exposure and determined whether error rates differed from published rates in traumatic brain injury (TBI) and chronic pain (CP). Data were obtained from the files of 123 persons…

  11. 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.

  12. Comparison of Multi-Scale Digital Elevation Models for Defining Waterways and Catchments Over Large Areas

    NASA Astrophysics Data System (ADS)

    Harris, B.; McDougall, K.; Barry, M.

    2012-07-01

    Digital Elevation Models (DEMs) allow for the efficient and consistent creation of waterways and catchment boundaries over large areas. Studies of waterway delineation from DEMs are usually undertaken over small or single catchment areas due to the nature of the problems being investigated. Improvements in Geographic Information Systems (GIS) techniques, software, hardware and data allow for analysis of larger data sets and also facilitate a consistent tool for the creation and analysis of waterways over extensive areas. However, rarely are they developed over large regional areas because of the lack of available raw data sets and the amount of work required to create the underlying DEMs. This paper examines definition of waterways and catchments over an area of approximately 25,000 km2 to establish the optimal DEM scale required for waterway delineation over large regional projects. The comparative study analysed multi-scale DEMs over two test areas (Wivenhoe catchment, 543 km2 and a detailed 13 km2 within the Wivenhoe catchment) including various data types, scales, quality, and variable catchment input parameters. Historic and available DEM data was compared to high resolution Lidar based DEMs to assess variations in the formation of stream networks. The results identified that, particularly in areas of high elevation change, DEMs at 20 m cell size created from broad scale 1:25,000 data (combined with more detailed data or manual delineation in flat areas) are adequate for the creation of waterways and catchments at a regional scale.

  13. Digital Elevation Models and Derived Products from Lroc Nac Stereo Observations

    NASA Astrophysics Data System (ADS)

    Burns, K. N.; Speyerer, E. J.; Robinson, M. S.; Tran, T.; Rosiek, M. R.; Archinal, B. A.; Howington-Kraus, E.; the LROC Science Team

    2012-08-01

    One of the primary objectives of the Lunar Reconnaissance Orbiter Camera (LROC) is to acquire stereo observations with the Narrow Angle Camera (NAC) to enable production of high resolution digital elevation models (DEMs). This work describes the processes and techniques used in reducing the NAC stereo observations to DEMs through a combination of USGS integrated Software for Imagers and Spectrometers (ISIS) and SOCET SET® from BAE Systems by a team at Arizona State University (ASU). LROC Science Operations Center personnel have thus far reduced 130 stereo observations to DEMs of more than 130 stereo pairs for 11 Constellation Program (CxP) sites and 53 other regions of scientific interest. The NAC DEM spatial sampling is typically 2 meters, and the vertical precision is 1-2 meters. Such high resolution provides the three-dimensional view of the lunar surface required for site selection, hazard avoidance and planning traverses that minimize resource consumption. In addition to exploration analysis, geologists can measure parameters such as elevation, slope, and volume to place constraints on composition and geologic history. The NAC DEMs are released and archived through NASA's Planetary Data System.

  14. High Resolution Photogrammetric Digital Elevation Models Across Calving Fronts and Meltwater Channels in Greenland

    NASA Astrophysics Data System (ADS)

    Le Bel, D. A.; Brown, S.; Zappa, C. J.; Bell, R. E.; Frearson, N.; Tinto, K. J.

    2014-12-01

    Photogrammetric digital elevation models (DEMs) are a powerful approach for understanding elevation change and dynamics along the margins of the large ice sheets. The IcePod system, mounted on a New York Air National Guard LC-130, can measure high-resolution surface elevations with a Riegl VQ580 scanning laser altimeter and Imperx Bobcat IGV-B6620 color visible-wavelength camera (6600x4400 resolution); the surface temperature with a Sofradir IRE-640L infrared camera (spectral response 7.7-9.5 μm, 640x512 resolution); and the structure of snow and ice with two radar systems. We show the use of IcePod imagery to develop DEMs across calving fronts and meltwater channels in Greenland. Multiple over-flights of the Kangerlussaq Airport ramp have provided a test of the technique at a location with accurate, independently-determined elevation. Here the photogrammetric DEM of the airport, constrained by ground control measurements, is compared with the Lidar results. In July 2014 the IcePod ice-ocean imaging system surveyed the calving fronts of five outlet glaciers north of Jakobshavn Isbrae. We used Agisoft PhotoScan to develop a DEM of each calving front using imagery captured by the IcePod systems. Adjacent to the ice sheet, meltwater plumes foster mixing in the fjord, moving warm ocean water into contact with the front of the ice sheet where it can undercut the ice front and trigger calving. The five glaciers provide an opportunity to examine the calving front structure in relation to ocean temperature, fjord circulation, and spatial scale of the meltwater plumes. The combination of the accurate DEM of the calving front and the thermal imagery used to constrain the temperature and dynamics of the adjacent plume provides new insights into the ice-ocean interactions. Ice sheet margins provide insights into the connections between the surface meltwater and the fate of the water at the ice sheet base. Surface meltwater channels are visualized here for the first time using

  15. Morphological convexity measures for terrestrial basins derived from digital elevation models

    NASA Astrophysics Data System (ADS)

    Lim, Sin Liang; Daya Sagar, B. S.; Chet Koo, Voon; Tien Tay, Lea

    2011-09-01

    Geophysical basins of terrestrial surfaces have been quantitatively characterized through a host of indices such as topological quantities (e.g. channel bifurcation and length ratios), allometric scaling exponents (e.g. fractal dimensions), and other geomorphometric parameters (channel density, Hack's and Hurst exponents). Channel density, estimated by taking the ratio between the length of channel network ( L) and the area of basin ( A) in planar form, provides a quantitative index that has hitherto been related to various geomorphologically significant processes. This index, computed by taking the planar forms of channel network and its corresponding basin, is a kind of convexity measure in the two-dimensional case. Such a measure - estimated in general as a function of basin area and channel network length, where the important elevation values of the topological region within a basin and channel network are ignored - fails to capture the spatial variability between homotopic basins possessing different altitude-ranges. Two types of convexity measures that have potential to capture the terrain elevation variability are defined as the ratio of (i) length of channel network function and area of basin function and (ii) areas of basin and its convex hull functions. These two convexity measures are estimated in three data sets that include (a) synthetic basin functions, (b) fractal basin functions, and (c) realistic digital elevation models (DEMs) of two regions of peninsular Malaysia. It is proven that the proposed convexity measures are altitude-dependent and that they could capture the spatial variability across the homotopic basins of different altitudes. It is also demonstrated on terrestrial DEMs that these convexity measures possess relationships with other quantitative indexes such as fractal dimensions and complexity measures (roughness indexes).

  16. 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.

  17. Bathymetric survey and digital elevation model of Little Holland Tract, Sacramento-San Joaquin Delta, California

    USGS Publications Warehouse

    Snyder, Alexander G.; Lacy, Jessica R.; Stevens, Andrew W.; Carlson, Emily M.

    2016-01-01

    The U.S. Geological Survey conducted a bathymetric survey in Little Holland Tract, a flooded agricultural tract, in the northern Sacramento-San Joaquin Delta (the “Delta”) during the summer of 2015. The new bathymetric data were combined with existing data to generate a digital elevation model (DEM) at 1-meter resolution. Little Holland Tract (LHT) was historically diked off for agricultural uses and has been tidally inundated since an accidental levee breach in 1983. Shallow tidal regions such as LHT have the potential to improve habitat quality in the Delta. The DEM of LHT was developed to support ongoing studies of habitat quality in the area and to provide a baseline for evaluating future geomorphic change. The new data comprise 138,407 linear meters of real-time-kinematic (RTK) Global Positioning System (GPS) elevation data, including both bathymetric data collected from personal watercraft and topographic elevations collected on foot at low tide. A benchmark (LHT15_b1) was established for geodetic control of the survey. Data quality was evaluated both by comparing results among surveying platforms, which showed systematic offsets of 1.6 centimeters (cm) or less, and by error propagation, which yielded a mean vertical uncertainty of 6.7 cm. Based on the DEM and time-series measurements of water depth, the mean tidal prism of LHT was determined to be 2,826,000 cubic meters. The bathymetric data and DEM are available at http://dx.doi.org/10.5066/F7RX9954. 

  18. A Comparative Study on Diagnostic Accuracy of Colour Coded Digital Images, Direct Digital Images and Conventional Radiographs for Periapical Lesions – An In Vitro Study

    PubMed Central

    Mubeen; K.R., Vijayalakshmi; Bhuyan, Sanat Kumar; Panigrahi, Rajat G; Priyadarshini, Smita R; Misra, Satyaranjan; Singh, Chandravir

    2014-01-01

    Objectives: The identification and radiographic interpretation of periapical bone lesions is important for accurate diagnosis and treatment. The present study was undertaken to study the feasibility and diagnostic accuracy of colour coded digital radiographs in terms of presence and size of lesion and to compare the diagnostic accuracy of colour coded digital images with direct digital images and conventional radiographs for assessing periapical lesions. Materials and Methods: Sixty human dry cadaver hemimandibles were obtained and periapical lesions were created in first and second premolar teeth at the junction of cancellous and cortical bone using a micromotor handpiece and carbide burs of sizes 2, 4 and 6. After each successive use of round burs, a conventional, RVG and colour coded image was taken for each specimen. All the images were evaluated by three observers. The diagnostic accuracy for each bur and image mode was calculated statistically. Results: Our results showed good interobserver (kappa > 0.61) agreement for the different radiographic techniques and for the different bur sizes. Conventional Radiography outperformed Digital Radiography in diagnosing periapical lesions made with Size two bur. Both were equally diagnostic for lesions made with larger bur sizes. Colour coding method was least accurate among all the techniques. Conclusion: Conventional radiography traditionally forms the backbone in the diagnosis, treatment planning and follow-up of periapical lesions. Direct digital imaging is an efficient technique, in diagnostic sense. Colour coding of digital radiography was feasible but less accurate however, this imaging technique, like any other, needs to be studied continuously with the emphasis on safety of patients and diagnostic quality of images. PMID:25584318

  19. Visual and Statistical Analysis of Digital Elevation Models Generated Using Idw Interpolator with Varying Powers

    NASA Astrophysics Data System (ADS)

    Asal, F. F.

    2012-07-01

    Digital elevation data obtained from different Engineering Surveying techniques is utilized in generating Digital Elevation Model (DEM), which is employed in many Engineering and Environmental applications. This data is usually in discrete point format making it necessary to utilize an interpolation approach for the creation of DEM. Quality assessment of the DEM is a vital issue controlling its use in different applications; however this assessment relies heavily on statistical methods with neglecting the visual methods. The research applies visual analysis investigation on DEMs generated using IDW interpolator of varying powers in order to examine their potential in the assessment of the effects of the variation of the IDW power on the quality of the DEMs. Real elevation data has been collected from field using total station instrument in a corrugated terrain. DEMs have been generated from the data at a unified cell size using IDW interpolator with power values ranging from one to ten. Visual analysis has been undertaken using 2D and 3D views of the DEM; in addition, statistical analysis has been performed for assessment of the validity of the visual techniques in doing such analysis. Visual analysis has shown that smoothing of the DEM decreases with the increase in the power value till the power of four; however, increasing the power more than four does not leave noticeable changes on 2D and 3D views of the DEM. The statistical analysis has supported these results where the value of the Standard Deviation (SD) of the DEM has increased with increasing the power. More specifically, changing the power from one to two has produced 36% of the total increase (the increase in SD due to changing the power from one to ten) in SD and changing to the powers of three and four has given 60% and 75% respectively. This refers to decrease in DEM smoothing with the increase in the power of the IDW. The study also has shown that applying visual methods supported by statistical

  20. Product Accuracy Effect of Oblique and Vertical Non-Metric Digital Camera Utilization in Uav-Photogrammetry to Determine Fault Plane

    NASA Astrophysics Data System (ADS)

    Amrullah, C.; Suwardhi, D.; Meilano, I.

    2016-06-01

    This study aims to see the effect of non-metric oblique and vertical camera combination along with the configuration of the ground control points to improve the precision and accuracy in UAV-Photogrammetry project. The field observation method is used for data acquisition with aerial photographs and ground control points. All data are processed by digital photogrammetric process with some scenarios in camera combination and ground control point configuration. The model indicates that the value of precision and accuracy increases with the combination of oblique and vertical camera at all control point configuration. The best products of the UAV-Photogrammetry model are produced in the form of Digital Elevation Model (DEM) compared to the LiDAR DEM. Furthermore, DEM from UAV-Photogrammetry and LiDAR are used to define the fault plane by using cross-section on the model and interpretation to determine the point at the extreme height of terrain changes. The result of the defined fault planes indicate that two models do not show any significant difference.

  1. Improved estimation of flood parameters by combining space based SAR data with very high resolution digital elevation data

    NASA Astrophysics Data System (ADS)

    Zwenzner, H.; Voigt, S.

    2009-05-01

    Severe flood events turned out to be the most devastating catastrophes for Europe's population, economy and environment during the past decades. The total loss caused by the August 2002 flood is estimated to be 10 billion Euros for Germany alone. Due to their capability to present a synoptic view of the spatial extent of floods, remote sensing technology, and especially synthetic aperture radar (SAR) systems, have been successfully applied for flood mapping and monitoring applications. However, the quality and accuracy of the flood masks and derived flood parameters always depends on the scale and the geometric precision of the original data as well as on the classification accuracy of the derived data products. The incorporation of auxiliary information such as elevation data can help to improve the plausibility and reliability of the derived flood masks as well as higher level products. This paper presents methods to improve the matching of flood masks with very high resolution digital elevation models as derived from LiDAR measurements for example. In the following, a cross section approach is presented that allows the dynamic fitting of the position of flood mask profiles according to the underlying terrain information from the DEM. This approach is tested in two study areas, using different input data sets. The first test area is part of the Elbe River (Germany) where flood masks derived from Radarsat-1 and IKONOS during the 2002 flood are used in combination with a LiDAR DEM of 1 m spatial resolution. The other test data set is located on the River Severn (UK) and flood masks derived from the TerraSAR-X satellite and aerial photos acquired during the 2007 flood are used in combination with a LiDAR DEM of 2 m pixel spacing. By means of these two examples the performance of the matching technique and the scaling effects are analysed and discussed. Furthermore, the systematic flood mapping capability of the different imaging systems are examined. It could be

  2. Improved estimation of flood parameters by combining space based SAR data with very high resolution digital elevation data

    NASA Astrophysics Data System (ADS)

    Zwenzner, H.; Voigt, S.

    2008-10-01

    Severe flood events turned out to be the most devastating catastrophes for Europe's population, economy and environment during the past decades. The total loss caused by the August 2002 flood is estimated to be 10 billion Euros for Germany alone. Due to their capability to present a synoptic view of the spatial extent of floods, remote sensing technology, and especially synthetic aperture radar (SAR) systems, have been successfully applied for flood mapping and monitoring applications. However, the quality and accuracy of the flood masks and derived flood parameters always depends on the scale and the geometric precision of the original data as well as on the classification accuracy of the derived data products. The incorporation of auxiliary information such as elevation data can help to improve the plausibility and reliability of the derived flood masks as well as higher level products. This paper presents methods to improve the matching of flood masks with very high resolution digital elevation models as derived from LiDAR measurements for example. In the following, a cross section approach is presented that allows the dynamic fitting of the position of flood mask profiles according to the underlying terrain information from the DEM. This approach is tested in two study areas, using different input data sets. The first test area is part of the Elbe River (Germany) where flood masks derived from Radarsat-1 and IKONOS during the 2002 flood are used in combination with a LiDAR DEM of 1 m spatial resolution. The other test data set is located on the River Severn (UK) and flood masks derived from the TerraSAR-X satellite and aerial photos acquired during the 2007 flood are used in combination with a LiDAR DEM of 2 m pixel spacing. By means of these two examples the performance of the matching technique and the scaling effects are analysed and discussed. Furthermore, the systematic flood mapping capability of the different imaging systems are examined. It could be

  3. Using Selective Drainage Methods to Extract Continuous Surface Flow from 1-Meter Lidar-Derived Digital Elevation Data

    USGS Publications Warehouse

    Poppenga, Sandra K.; Worstell, Bruce B.; Stoker, Jason M.; Greenlee, Susan K.

    2010-01-01

    Digital elevation data commonly are used to extract surface flow features. One source for high-resolution elevation data is light detection and ranging (lidar). Lidar can capture a vast amount of topographic detail because of its fine-scale ability to digitally capture the surface of the earth. Because elevation is a key factor in extracting surface flow features, high-resolution lidar-derived digital elevation models (DEMs) provide the detail needed to consistently integrate hydrography with elevation, land cover, structures, and other geospatial features. The U.S. Geological Survey has developed selective drainage methods to extract continuous surface flow from high-resolution lidar-derived digital elevation data. The lidar-derived continuous surface flow network contains valuable information for water resource management involving flood hazard mapping, flood inundation, and coastal erosion. DEMs used in hydrologic applications typically are processed to remove depressions by filling them. High-resolution DEMs derived from lidar can capture much more detail of the land surface than courser elevation data. Therefore, high-resolution DEMs contain more depressions because of obstructions such as roads, railroads, and other elevated structures. The filling of these depressions can significantly affect the DEM-derived surface flow routing and terrain characteristics in an adverse way. In this report, selective draining methods that modify the elevation surface to drain a depression through an obstruction are presented. If such obstructions are not removed from the elevation data, the filling of depressions to create continuous surface flow can cause the flow to spill over an obstruction in the wrong location. Using this modified elevation surface improves the quality of derived surface flow and retains more of the true surface characteristics by correcting large filled depressions. A reliable flow surface is necessary for deriving a consistently connected drainage

  4. Evaluation of the geometric stability and the accuracy potential of digital cameras — Comparing mechanical stabilisation versus parameterisation

    NASA Astrophysics Data System (ADS)

    Rieke-Zapp, D.; Tecklenburg, W.; Peipe, J.; Hastedt, H.; Haig, Claudia

    Recent tests on the geometric stability of several digital cameras that were not designed for photogrammetric applications have shown that the accomplished accuracies in object space are either limited or that the accuracy potential is not exploited to the fullest extent. A total of 72 calibrations were calculated with four different software products for eleven digital camera models with different hardware setups, some with mechanical fixation of one or more parts. The calibration procedure was chosen in accord to a German guideline for evaluation of optical 3D measuring systems [VDI/VDE, VDI/VDE 2634 Part 1, 2002. Optical 3D Measuring Systems-Imaging Systems with Point-by-point Probing. Beuth Verlag, Berlin]. All images were taken with ringflashes which was considered a standard method for close-range photogrammetry. In cases where the flash was mounted to the lens, the force exerted on the lens tube and the camera mount greatly reduced the accomplished accuracy. Mounting the ringflash to the camera instead resulted in a large improvement of accuracy in object space. For standard calibration best accuracies in object space were accomplished with a Canon EOS 5D and a 35 mm Canon lens where the focusing tube was fixed with epoxy (47 μm maximum absolute length measurement error in object space). The fixation of the Canon lens was fairly easy and inexpensive resulting in a sevenfold increase in accuracy compared with the same lens type without modification. A similar accuracy was accomplished with a Nikon D3 when mounting the ringflash to the camera instead of the lens (52 μm maximum absolute length measurement error in object space). Parameterisation of geometric instabilities by introduction of an image variant interior orientation in the calibration process improved results for most cameras. In this case, a modified Alpa 12 WA yielded the best results (29 μm maximum absolute length measurement error in object space). Extending the parameter model with Fi

  5. ASTER-Derived 30-Meter-Resolution Digital Elevation Models of Afghanistan

    USGS Publications Warehouse

    Chirico, Peter G.; Warner, Michael B.

    2007-01-01

    INTRODUCTION The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging instrument aboard the Terra satellite, launched on December 19, 1999, as part of the National Aeronautics and Space Administration's (NASA) Earth Observing System (EOS). The ASTER sensor consists of three subsystems: the visible and near infrared (VNIR), the shortwave infrared (SWIR), and the thermal infrared (TIR), each with a different spatial resolution (VNIR, 15 meters; SWIR, 30 meters, TIR 90 meters). The VNIR system has the capability to generate along-track stereo images that can be used to create digital elevation models (DEMs) at 30-meter resolution. Currently, the only available DEM dataset for Afghanistan is the 90-meter-resolution Shuttle Radar Topography Mission (SRTM) data. This dataset is appropriate for macroscale DEM analysis and mapping. However, ASTER provides a low cost opportunity to generate higher resolution data. For this publication, study areas were identified around populated areas and areas where higher resolution elevation data were desired to assist in natural resource assessments. The higher resolution fidelity of these DEMs can also be used for other terrain analysis including landform classification and geologic structure analysis. For this publication, ASTER scenes were processed and mosaicked to generate 36 DEMs which were created and extracted using PCI Geomatics' OrthoEngine 3D Stereo software. The ASTER images were geographically registered to Landsat data with at least 15 accurate and well distributed ground control points with a root mean square error (RMSE) of less that one pixel (15 meters). An elevation value was then assigned to each ground control point by extracting the elevation from the 90-meter SRTM data. The 36 derived DEMs demonstrate that the software correlated on nearly flat surfaces and smooth slopes accurately. Larger errors occur in cloudy and snow-covered areas, lakes, areas with steep slopes, and

  6. Quantifying depression storage of snowmelt runoff over frozen ground using aerial photography and digital elevation model

    NASA Astrophysics Data System (ADS)

    Hayashi, M.; Donovan, K.; Sjogren, D.

    2004-05-01

    The northern prairie region of North America is characterized by undulating terrains with very low regional gradient, underlain by clay-rich glacial tills. The soils derived from clay-rich tills have very low permeability when they are frozen. As a result a large amount of snowmelt runoff is generated over frozen ground. Numerous depressions on the undulating terrains trap snowmelt water and focus the infiltration flux under the depressions. Therefore, the depressions have important hydrologic functions regarding runoff retention and groundwater recharge. Previous studies have investigated the storage of snowmelt runoff and subsequent infiltration at a scale of each depression (102-103 m2). However, to understand the roles of depressions in regional hydrology, depression storage needs to be evaluated at a much larger scale. Our ultimate goal is to quantify depression storage at the scale of watersheds (102-103km 2) and represent it properly in a large-scale hydrologic model. As the first step towards this goal, we quantified depression storage at 1-km2 scale using infrared (IR) aerial photographs and digital elevation model combined with the measurement of water depth in depressions. Two parcels of land were selected for the study in the watershed of West Nose Creek, located immediately north of Calgary, Alberta, Canada. Each site contained a subsection of native prairie grass and cultivated field. Snow surveys were conducted at each site to estimate the average snow water equivalent (SWE) on the ground prior to melt. SWE ranged between 26 mm and 39 mm. Water depth was measured in 111 depressions when they were filled up to the peak level, and IR photographs were taken simultaneously at a scale of 1:10,000. The soil was frozen to a depth of 1 m or greater as indicated by several thermocouple arrays installed at the site. Detailed elevation survey was conducted in summer using a total station and differential global positioning system for 10 selected depressions to

  7. Volume Change Rates of Southeast Alaskan Icefields from Stacked Digital Elevation Models, 2000-2009/2010

    NASA Astrophysics Data System (ADS)

    Melkonian, A. K.; Elliott, J.; Willis, M. J.; Pritchard, M. E.

    2012-12-01

    We derive volume change rates (dV/dt) for the three major temperate icefields of Southeast Alaska. The Juneau, Stikine, and Glacier Bay icefields cover approximately 14,300 km2 and have recently been contributing disproportionately to sea level rise. In this study we provide estimates of volume change rates between 2000 and 2009/2010 based on near-complete spatial coverage from stacked digital elevations models (DEMs) acquired by the Shuttle Radar Topography Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Our method applies a weighted linear regression to elevations on a pixel-by-pixel basis over each icefield, and we filter out elevations based on deviation from the first elevation (which is SRTM about 90% of the time) to exclude ASTER elevations influenced by clouds, shadow, etc. The maximum positive deviation allowed is ~5 m a-1, which comes from estimates of precipitation in this region and probably overestimates the amount of thickening actually occurring. This large positive constraint means our volume change rates are likely more representative of lower bounds on volume loss. All three icefields are losing volume - the combined rate is approximately -7.7±0.9 km3 a-1, equivalent to a mass loss rate of 6.9±0.8 Gt a-1 assuming a density of 900 kg m3 for the lost material. The area-averaged elevation change rate (dh/dt) is -0.44±0.05 m a-1 w.e., with most loss occurring at the Glacier Bay and Stikine Icefields. Juneau Icefield (~3,900 km2) has a small dV/dt, at -0.3±0.1 km3 a-1. This is due to the positive dV/dt of the Taku Glacier, the largest outlet glacier of the Juneau Icefield. Our results are consistent with previous studies that document the recent advance of Taku and its status as the glacier with the highest positive volume change rate in Alaska. The dh/dt pattern we observe elsewhere over the Juneau Icefield is similar to previous studies, with practically every outlet glacier except Taku experiencing

  8. New Enhancements of an ERS1-2 + ICESat Digital Elevation Model of West Antarctica Using MODIS Imagery, Shapelets, and Kriging

    NASA Astrophysics Data System (ADS)

    Haran, T. M.; Scambos, T. A.; Fahnestock, M. A.; Csatho, B. M.

    2008-12-01

    An image enhancement approach is used to develop a new digital elevation map of West Antarctica, combining multiple MODIS images and both radar altimetry and ICESat laser altimetry Digital Elevation Model (DEM) data. The method combines the wide image coverage of MODIS, and its high radiometric sensitivity (which equates to high sunward slope sensitivity), with the high precision and accuracy of ICESat and combined ICESat and radar altimetry DEMs. ICESat (as of September 2008) has acquired a series of fourteen near-repeat observational campaigns over the Antarctic during the period September 2003 to March 2008, covering the continent to 86 deg S. ICESat data are acquired as a series of spot elevations, averaging a ~60m diameter surface region every ~172m. However, ICESat track paths have spacings wide enough (2 km at 85 deg; 20 - 50 km at 75 deg) that some surface ice dynamical features (e.g. flowlines, undulations, ice rises) are missed by the track data used to construct the ICESat DEM. Radar altimetry can provide some of the missing data north of 81.5 deg, but only to a maximum resolution of about 5 km. A set of cloud-cleared MODIS band 1 data from both the Aqua and Terra platforms acquired during the 2003-2004 austral summer, used in generating the Mosaic of Antarctica (MOA) surface morphology image map, were used for the image enhancement. Past analyses of the slope-brightness relationship for MODIS have shown ice surface slope precisions of +/- 0.00015. ICESat spot elevations have nominal precisions of ~5 cm under ideal conditions, although thin-cloud effects and mislocation errors can magnify these. Only cloud-free areas of MODIS scenes that also meet specific slope, grain-size, solar zenith, brightness, latitude, and elevation criteria are used for image enhancement. We calibrate brightness-to-slope relationships for several MODIS images of the central West Antarctic using a smoothed version of the combined DEM. Using the calibrations, we then create a

  9. Scoria cones on Mars: Detailed investigation of morphometry based on high-resolution digital elevation models

    NASA Astrophysics Data System (ADS)

    Brož, Petr; Čadek, Ondřej; Hauber, Ernst; Rossi, Angelo Pio

    2015-09-01

    We analyze the shapes of 28 hypothesized scoria cones in three regions on Mars, i.e., Ulysses and Hydraotes Colles and Coprates Chasma. Using available High-Resolution Imaging Science Experiment and Context Camera (CTX) digital elevation models, we determine the basic morphometric characteristics of the cones and estimate from ballistic modeling the physical parameters of volcanic eruptions that could have formed them. When compared to terrestrial scoria cones, most of the studied cones show larger volumes (up to 4.2 × 109 m3), larger heights (up to 573 m), and smaller average slopes. The average slopes of the Ulysses, Hydraotes, and Coprates cones range between 7° and 25°, and the maximum slopes only rarely exceed 30°, which suggests only a minor role of scoria redistribution by avalanching. Ballistic analysis indicates that all cones were formed in a similar way, and their shapes are consistent with an ejection velocity about 2 times larger and a particle size about 20 times smaller than on Earth. Our results support the hypothesis that the investigated edifices were formed by low-energy Strombolian volcanic eruptions and hence are equivalent to terrestrial scoria cones. The cones in Hydraotes Colles and Coprates Chasma are on average smaller and steeper than the cones in Ulysses Colles, which is likely due to the difference in topographic elevation and the associated difference in atmospheric pressure. This study provides the expected morphometric characteristics of Martian scoria cones, which can be used to identify landforms consistent with this type of activity elsewhere on Mars and distinguish them from other conical edifices.

  10. Accuracy of EAARL lidar ground elevations using a bare-earth algorithm in marsh and beach grasses on the Chandeleur Islands, Louisiana

    USGS Publications Warehouse

    Doran, Kara S.; Sallenger, Asbury H.; Reynolds, Billy J.; Wright, C. Wayne

    2010-01-01

    The NASA Experimental Advanced Airborne Lidar (EAARL) is an airborne lidar (light detection and ranging) instrument designed to map coastal topography and bathymetry. The EAARL system has the capability to capture each laser-pulse return over a large signal range and can digitize the full waveform of the backscattered energy. Because of this ability to capture the full waveform, the EAARL system can map features such as coral reefs, beaches, coastal vegetation, and trees, where extreme variations in the laser backscatter are caused by different physical and optical characteristics. Post-processing of the EAARL data is accomplished using the Airborne Lidar Processing System (ALPS) (Nayegandhi and others, 2009). In ALPS, the waveform of the lidar is analyzed and split into first and last returns. The 'first returns' are indicative of vegetation-canopy height, or bare ground in the absence of vegetation, whereas 'last returns' typically represent 'bare-earth' elevations under vegetation. To test the accuracy of the first-return and bare-earth EAARL data, topographic and vegetation height surveys were conducted in the Chandeleur Islands, concurrent with an EAARL lidar survey and an aerial oblique-photographic survey from September 20 to 27, 2006. The Chandeleur Islands are a north-south-oriented chain of low-lying islands located approximately 100 kilometers east of the city of New Orleans, Louisiana. The islands are narrow north-south strips of land with marsh on the landward (west sides) and sandy beaches on their gulfward (east sides). Prior to Hurricane Katrina, which made landfall at Buras, Louisiana, as a Category 3 storm on August 29, 2005, prominent, 3- to 4-meter-high sand dunes were present in the northern Chandeleurs. The storm removed them, leaving post-storm island elevations of generally less than 2 meters above 0.0 NAVD88. This report is part of a study of the impact of Hurricane Katrina on the Chandeleur Islands using pre-storm and post-storm lidar

  11. A high-accuracy digital star tracker for advanced planetary missions.

    NASA Technical Reports Server (NTRS)

    Salomon, P. M.; Crawford, W. E.

    1972-01-01

    The digital star tracker represents a novel departure from previous analog designs in terms of circuit implementation and operational capabilities. As an element of an all-digital spacecraft control system, it combines proven low-level analog signal processing with digital error control and command functions. Additional capabilities that are obtainable with the digital circuitry include programmable intensity threshold gates, commanded electronic pointing control, and an acquisition/control algorithm which minimizes the effects of straylight disturbances. The capabilities inherent in the implementation have been successfully demonstrated in a laboratory model of the instrument.

  12. A high-accuracy digital star tracker for advanced planetary missions

    NASA Technical Reports Server (NTRS)

    Salomon, P. M.; Crawford, W. E.

    1973-01-01

    The digital star tracker represents a novel departure from previous analog designs in terms of circuit implementation and operational capabilities. As an element of an all-digital spacecraft control system, it combines proven low-level analog signal processing with digital error control and command functions. Additional capabilities that are obtainable with the digital circuitry include programmable intensity threshold gates, commanded electronic pointing control, and an acquisition/control algorithm which minimizes the effects of straylight disturbances. The capabilities inherent in the implementation have been successfully demonstrated in a laboratory model of the instrument.

  13. Computation of spatial significance of mountain objects extracted from multiscale digital elevation models

    NASA Astrophysics Data System (ADS)

    Sathyamoorthy, Dinesh

    2014-06-01

    The derivation of spatial significance is an important aspect of geospatial analysis and hence, various methods have been proposed to compute the spatial significance of entities based on spatial distances with other entities within the cluster. This paper is aimed at studying the spatial significance of mountain objects extracted from multiscale digital elevation models (DEMs). At each scale, the value of spatial significance index SSI of a mountain object is the minimum number of morphological dilation iterations required to occupy all the other mountain objects in the terrain. The mountain object with the lowest value of SSI is the spatially most significant mountain object, indicating that it has the shortest distance to the other mountain objects. It is observed that as the area of the mountain objects reduce with increasing scale, the distances between the mountain objects increase, resulting in increasing values of SSI. The results obtained indicate that the strategic location of a mountain object at the centre of the terrain is more important than its size in determining its reach to other mountain objects and thus, its spatial significance.

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

    NASA Astrophysics Data System (ADS)

    Maire, C.; Datcu, M.

    2004-09-01

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

  15. The Need of Nested Grids for Aerial and Satellite Images and Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Villa, G.; Mas, S.; Fernández-Villarino, X.; Martínez-Luceño, J.; Ojeda, J. C.; Pérez-Martín, B.; Tejeiro, J. A.; García-González, C.; López-Romero, E.; Soteres, C.

    2016-06-01

    Usual workflows for production, archiving, dissemination and use of Earth observation images (both aerial and from remote sensing satellites) pose big interoperability problems, as for example: non-alignment of pixels at the different levels of the pyramids that makes it impossible to overlay, compare and mosaic different orthoimages, without resampling them and the need to apply multiple resamplings and compression-decompression cycles. These problems cause great inefficiencies in production, dissemination through web services and processing in "Big Data" environments. Most of them can be avoided, or at least greatly reduced, with the use of a common "nested grid" for mutiresolution production, archiving, dissemination and exploitation of orthoimagery, digital elevation models and other raster data. "Nested grids" are space allocation schemas that organize image footprints, pixel sizes and pixel positions at all pyramid levels, in order to achieve coherent and consistent multiresolution coverage of a whole working area. A "nested grid" must be complemented by an appropriate "tiling schema", ideally based on the "quad-tree" concept. In the last years a "de facto standard" grid and Tiling Schema has emerged and has been adopted by virtually all major geospatial data providers. It has also been adopted by OGC in its "WMTS Simple Profile" standard. In this paper we explain how the adequate use of this tiling schema as common nested grid for orthoimagery, DEMs and other types of raster data constitutes the most practical solution to most of the interoperability problems of these types of data.

  16. TERRAIN: A computer program to process digital elevation models for modeling surface flow

    SciTech Connect

    Schwartz, P.M.; Levine, D.A.; Hunsaker, C.T.; Timmins, S.P.

    1995-08-01

    This document provides a step by step procedure, TERRAIN, for processing digital elevation models to calculate overland flow paths, watershed boundaries, slope, and aspect. The algorithms incorporated into TERRAIN have been used at two different geographic scales: first for small research watersheds where surface wetness measurements are made, and second for regional water modeling for entire counties. For small areas methods based on flow distribution may be more desirable, especially if time-dependent flow models are to be used. The main improvement in TERRAIN compared with earlier programs on which it is based is that it combines the conditioning routines, which remove depressions to avoid water storage, into a single process. Efficiency has also been improved, reducing run times as much as 10:1 and enabling the processing of very large grids in strips for regional modeling. Additionally, the ability to calculate the nutrient load delivered any cell in a watershed has been added. These improvements make TERRAIN a powerful tool for modeling surface flow.

  17. Prediction of Wind Speeds Based on Digital Elevation Models Using Boosted Regression Trees

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Etienne, C.; Tian, J.; Krauß, T.

    2015-12-01

    In this paper a new approach is presented to predict maximum wind speeds using Gradient Boosted Regression Trees (GBRT). GBRT are a non-parametric regression technique used in various applications, suitable to make predictions without having an in-depth a-priori knowledge about the functional dependancies between the predictors and the response variables. Our aim is to predict maximum wind speeds based on predictors, which are derived from a digital elevation model (DEM). The predictors describe the orography of the Area-of-Interest (AoI) by various means like first and second order derivatives of the DEM, but also higher sophisticated classifications describing exposure and shelterness of the terrain to wind flux. In order to take the different scales into account which probably influence the streams and turbulences of wind flow over complex terrain, the predictors are computed on different spatial resolutions ranging from 30 m up to 2000 m. The geographic area used for examination of the approach is Switzerland, a mountainious region in the heart of europe, dominated by the alps, but also covering large valleys. The full workflow is described in this paper, which consists of data preparation using image processing techniques, model training using a state-of-the-art machine learning algorithm, in-depth analysis of the trained model, validation of the model and application of the model to generate a wind speed map.

  18. Grid digital elevation model based algorithms for determination of hillslope width functions through flow distance transforms

    NASA Astrophysics Data System (ADS)

    Liu, Jintao; Chen, Xi; Zhang, Xingnan; Hoagland, Kyle D.

    2012-04-01

    Recently developed hillslope storage dynamics theory can represent the essential physical behavior of a natural system by accounting explicitly for the plan shape of a hillslope in an elegant and simple way. As a result, this theory is promising for improving catchment-scale hydrologic modeling. In this study, grid digital elevation model (DEM) based algorithms for determination of hillslope geometric characteristics (e.g., hillslope units and width functions in hillslope storage dynamics models) are presented. This study further develops a method for hillslope partitioning, established by Fan and Bras (1998), by applying it on a grid network. On the basis of hillslope unit derivation, a flow distance transforms method (TD∞) is suggested in order to decrease the systematic error of grid DEM-based flow distance calculation caused by flow direction approximation to streamlines. Hillslope width transfer functions are then derived to convert the probability density functions of flow distance into hillslope width functions. These algorithms are applied and evaluated on five abstract hillslopes, and detailed tests and analyses are carried out by comparing the derivation results with theoretical width functions. The results demonstrate that the TD∞ improves estimations of the flow distance and thus hillslope width function. As the proposed procedures are further applied in a natural catchment, we find that the natural hillslope width function can be well fitted by the Gaussian function. This finding is very important for applying the newly developed hillslope storage dynamics models in a real catchment.

  19. 2010 bathymetric survey and digital elevation model of Corte Madera Bay, California

    USGS Publications Warehouse

    Foxgrover, Amy C.; Finlayson, David P.; Jaffe, Bruce E.; Takekawa, John Y.; Thorne, Karen M.; Spragens, Kyle A.

    2011-01-01

    A high-resolution bathymetric survey of Corte Madera Bay, California, was collected in early 2010 in support of a collaborative research project initiated by the San Francisco Bay Conservation and Development Commission and funded by the U.S. Environmental Protection Agency. The primary objective of the Innovative Wetland Adaptation in the Lower Corte Madera Creek Watershed Project is to develop shoreline adaptation strategies to future sea-level rise based upon sound science. Fundamental to this research was the development of an of an up-to-date, high-resolution digital elevation model (DEM) extending from the subtidal environment through the surrounding intertidal marsh. We provide bathymetric data collected by the U.S. Geological Survey and have merged the bathymetry with a 1-m resolution aerial lidar data set that was collected by the National Oceanic and Atmospheric Administration during the same time period to create a seamless, high-resolution DEM of Corte Madera Bay and the surrounding topography. The bathymetric and DEM surfaces are provided at both 1 m and 10 m resolutions formatted as both X, Y, Z text files and ESRI Arc ASCII files, which are accompanied by Federal Geographic Data Committee compliant metadata.

  20. Automated delineation of karst sinkholes from LiDAR-derived digital elevation models

    NASA Astrophysics Data System (ADS)

    Wu, Qiusheng; Deng, Chengbin; Chen, Zuoqi

    2016-08-01

    Sinkhole mapping is critical for understanding hydrological processes and mitigating geological hazards in karst landscapes. Current methods for identifying sinkholes are primarily based on visual interpretation of low-resolution topographic maps and aerial photographs with subsequent field verification, which is labor-intensive and time-consuming. The increasing availability of high-resolution LiDAR-derived digital elevation data allows for an entirely new level of detailed delineation and analyses of small-scale geomorphologic features and landscape structures at fine scales. In this paper, we present a localized contour tree method for automated extraction of sinkholes in karst landscapes. One significant advantage of our automated approach for sinkhole extraction is that it may reduce inconsistencies and alleviate repeatability concerns associated with visual interpretation methods. In addition, the proposed method has contributed to improving the sinkhole inventory in several ways: (1) detection of non-inventoried sinkholes; (2) identification of previously inventoried sinkholes that have been filled; (3) delineation of sinkhole boundaries; and (4) characterization of sinkhole morphometric properties. We applied the method to Fillmore County in southeastern Minnesota, USA, and identified three times as many sinkholes as the existing database for the same area. The results suggest that previous visual interpretation method might significantly underestimate the number of potential sinkholes in the region. Our method holds great potential for creating and updating sinkhole inventory databases at a regional scale in a timely manner.

  1. A marked point process of rectangles and segments for automatic analysis of digital elevation models.

    PubMed

    Ortner, Mathias; Descombe, Xavier; Zerubia, Josiane

    2008-01-01

    This work presents a framework for automatic feature extraction from images using stochastic geometry. Features in images are modeled as realizations of a spatial point process of geometrical shapes. This framework allows the incorporation of a priori knowledge on the spatial repartition of features. More specifically, we present a model based on the superposition of a process of segments and a process of rectangles. The former is dedicated to the detection of linear networks of discontinuities, while the latter aims at segmenting homogeneous areas. An energy is defined, favoring connections of segments, alignments of rectangles, as well as a relevant interaction between both types of objects. The estimation is performed by minimizing the energy using a simulated annealing algorithm. The proposed model is applied to the analysis of Digital Elevation Models (DEMs). These images are raster data representing the altimetry of a dense urban area. We present results on real data provided by the IGN (French National Geographic Institute) consisting in low quality DEMs of various types. PMID:18000328

  2. Assessment of high resolution digital elevation model for deep humus-rich sediments delineation at a plot scale

    NASA Astrophysics Data System (ADS)

    Penížek, Vít; Zádorová, Tereza

    2014-05-01

    Resolution and quality of digital elevation models is a key factor in erosion modeling. Spatial estimates of erosion and sedimentation rates are important for soil organic carbon stocks prediction or delineation of newly formed soil cover by degradation and sedimentation of soil material. Such analysis can be sensitive to DEM vertical accuracy and horizontal resolution. LIDAR data can provide very precise DEMs with very high resolution. In our study we used ground based LIDAR data with 10cm pixel. At such resolution, not only naturally formed terrain features are observed, but also anthropogenic features are depicted. Anthropogenic features are represented by more significant objects like hedges or ditches that can significantly influence the water and sediment movement in the landscape on one hand, on the other hand less significant anthropogenic impact can influence the terrain surface. Plot management forms a regular network consisting of parallel linear features given by plowing operations. At our research plot, such features depicted by DEM form specific flow direction (drainage) pattern over the area comparing to coarser resolution DEMs. We focused on comparison of differently preprocessed DEMs for deep humus-rich sediments depth prediction. We compared success rate of prediction models based on original DEM, DEMs with different resampling (resolution) and modeling of original DEM adding random noise given by size of plowing based terrain pattern. The study showed that original high resolution DEM significantly decreases the possibility of soil depth prediction. The actual very precise surface description is not very relevant for GIS modeling due to sensitivity of the models. DEMs depicting the wider constellations of the terrain were more successful in the prediction. The study was supported by grant nr. 13-07516P of the Czech science foundation and by grant nr. QJ1230319 of the Ministry of Agriculture.

  3. Accuracy of Repetition of Digitized and Synthesized Speech for Young Children in Background Noise

    ERIC Educational Resources Information Center

    Drager, Kathryn D. R.; Clark-Serpentine, Elizabeth A.; Johnson, Kate E.; Roeser, Jennifer L.

    2006-01-01

    Purpose: The present study investigated the intelligibility of digitized and synthesized speech output in background noise for children 3-5 years old. The purpose of the study was to determine whether there was a difference in the intelligibility (ability to repeat) of 3 types of speech output (digitized, DECTalk synthesized, and MacinTalk…

  4. 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.

  5. A method for the processing and analysis of digital terrain elevation data. [Shiprock and Gallup Quadrangles, Arizona and New Mexico

    NASA Technical Reports Server (NTRS)

    Junkin, B. G. (Principal Investigator)

    1979-01-01

    A method is presented for the processing and analysis of digital topography data that can subsequently be entered in an interactive data base in the form of slope, slope length, elevation, and aspect angle. A discussion of the data source and specific descriptions of the data processing software programs are included. In addition, the mathematical considerations involved in the registration of raw digitized coordinate points to the UTM coordinate system are presented. Scale factor considerations are also included. Results of the processing and analysis are illustrated using the Shiprock and Gallup Quadrangle test data.

  6. The use of Digital Elevation Models for sediment connectivity assessment: state of the art and perspectives

    NASA Astrophysics Data System (ADS)

    Cavalli, Marco; Borselli, Lorenzo; Crema, Stefano; Marchi, Lorenzo; Vigiak, Olga

    2015-04-01

    Geomorphic coupling, i.e. linkages between geomorphic system components, and sediment connectivity, i.e. the degree of linkage that controls sediment fluxes throughout landscape, have important implications for the behavior of geomorphic systems and have become key issues in the study of sediment transfer processes. The detailed characterization of the topographic surface plays a fundamental role for studying sediment dynamics in a catchment. Digital Elevation Models (DEMs) can both improve geomorphological interpretation (e.g. individuation of sediment source areas) and enable the quantitative modeling of sediment fluxes and connectivity. In particular, the availability of LiDAR-derived high-resolution Digital Terrain Models (DTMs), exploited using geomorphometric analysis, extends the applicability and potentialities of topography-based modeling approaches. Indeed, geomorphometry allows to derive detailed characterization of drainage pattern and surface roughness, which are two of the most important parameters in the study of sediment delivery. Since the late 1990s, some GIS-based approaches mainly based on stream-power have been developed for modeling the topographic potential for erosion and deposition and evaluating the impedance to sediment conveyance. But it is in the more recent years that an increasing interest for the quantitative characterization of the linkage between landscape units can be observed in literature. The development of geomorphometric indices, such as the sediment connectivity index (IC) by Borselli et al. (2008) and the version of IC proposed by Cavalli et al. (2013), and related freeware applications, has certainly contributed to this increased interest. In this work, the state of the art on the use of DEMs for sediment connectivity assessment, with a specific focus on the sediment connectivity index and following applications, will be presented. Future perspectives will be also discussed. References Borselli L., Cassi P., Torri D., 2008

  7. Building a 2.5D Digital Elevation Model from 2D Imagery

    NASA Technical Reports Server (NTRS)

    Padgett, Curtis W.; Ansar, Adnan I.; Brennan, Shane; Cheng, Yang; Clouse, Daniel S.; Almeida, Eduardo

    2013-01-01

    When projecting imagery into a georeferenced coordinate frame, one needs to have some model of the geographical region that is being projected to. This model can sometimes be a simple geometrical curve, such as an ellipse or even a plane. However, to obtain accurate projections, one needs to have a more sophisticated model that encodes the undulations in the terrain including things like mountains, valleys, and even manmade structures. The product that is often used for this purpose is a Digital Elevation Model (DEM). The technology presented here generates a high-quality DEM from a collection of 2D images taken from multiple viewpoints, plus pose data for each of the images and a camera model for the sensor. The technology assumes that the images are all of the same region of the environment. The pose data for each image is used as an initial estimate of the geometric relationship between the images, but the pose data is often noisy and not of sufficient quality to build a high-quality DEM. Therefore, the source imagery is passed through a feature-tracking algorithm and multi-plane-homography algorithm, which refine the geometric transforms between images. The images and their refined poses are then passed to a stereo algorithm, which generates dense 3D data for each image in the sequence. The 3D data from each image is then placed into a consistent coordinate frame and passed to a routine that divides the coordinate frame into a number of cells. The 3D points that fall into each cell are collected, and basic statistics are applied to determine the elevation of that cell. The result of this step is a DEM that is in an arbitrary coordinate frame. This DEM is then filtered and smoothed in order to remove small artifacts. The final step in the algorithm is to take the initial DEM and rotate and translate it to be in the world coordinate frame [such as UTM (Universal Transverse Mercator), MGRS (Military Grid Reference System), or geodetic] such that it can be saved in

  8. Differences in topographic characteristics computed from 100- and 1000-m resolution digital elevation model data

    USGS Publications Warehouse

    Wolock, D.M.; McCabe, G.J.

    2000-01-01

    Topographic characteristics computed from 100- and 1000-m resolution digital elevation model (DEM) data are compared for 50 locations representing varied terrain in the conterminous USA. The topographic characteristics are three parameters used extensively in hydrological research and modelling - slope (S), specific catchment area (A(s)) and a wetness index computed as the logarithm of the specific catchment area divided by slope [ln(A(s)/S)]. Slope values computed from 1000-m DEMs are smaller than those computed from 100-m DEMs; specific catchment area and the wetness index are larger for the 1000-m DEMs compared with the 100-m DEMs. Most of the differences between the 100- and 1000-m resolution DEMs can be attributed to terrain-discretization effects in the computation of the topographic characteristics and are not the result of smoothing or loss of terrain detail in the coarse data. In general, the terrain-discretization effects are greatest on flat terrain with long length-scale features, and the smoothing effects are greatest on steep terrain with short length-scale features. For the most part, the differences in the average values of the topographic characteristics computed from 100- and 1000-m resolution DEMs are predictable; that is, biases in the mean values for the characteristics computed from a 1000-m DEM can be corrected with simple linear equations. Copyright (C) 2000 John Wiley and Sons, Ltd.Topographic characteristics computed from 100- and 1000-m resolution digital elevation model (DEM) data are compared for 50 locations representing varied terrain in the conterminous USA. The topographic characteristics are three parameters used extensively in hydrological research and modelling - slope (S), specific catchment area (As) and a wetness index computed as the logarithm of the specific catchment area divided by slope [In(As/S)]. Slope values computed from 1000-m DEMs are smaller than those computed from 100-m DEMs; specific catchment area and the

  9. 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

  10. Structural analysis of Turtle Mountain (Alberta) using digital elevation model: Toward a progressive failure

    NASA Astrophysics Data System (ADS)

    Jaboyedoff, Michel; Couture, Réjean; Locat, Pascal

    2009-01-01

    In 1903, the eastern slope of Turtle Mountain (Alberta) was affected by a 30 M m 3-rockslide named Frank Slide that resulted in more than 70 casualties. Assuming that the main discontinuity sets, including bedding, control part of the slope morphology, the structural features of Turtle Mountain were investigated using a digital elevation model (DEM). Using new landscape analysis techniques, we have identified three main joint and fault sets. These results are in agreement with those sets identified through field observations. Landscape analysis techniques, using a DEM, confirm and refine the most recent geology model of the Frank Slide. The rockslide was initiated along bedding and a fault at the base of the slope and propagated up slope by a regressive process following a surface composed of pre-existing discontinuities. The DEM analysis also permits the identification of important geological structures along the 1903 slide scar. Based on the so called Sloping Local Base Level (SLBL) an estimation was made of the present unstable volumes in the main scar delimited by the cracks, and around the south area of the scar (South Peak). The SLBL is a method permitting a geometric interpretation of the failure surface based on a DEM. Finally we propose a failure mechanism permitting the progressive failure of the rock mass that considers gentle dipping wedges (30°). The prisms or wedges defined by two discontinuity sets permit the creation of a failure surface by progressive failure. Such structures are more commonly observed in recent rockslides. This method is efficient and is recommended as a preliminary analysis prior to field investigation.

  11. Hazard Mapping of Structurally Controlled Landslide in Southern Leyte, Philippines Using High Resolution Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Luzon, Paul Kenneth; Rochelle Montalbo, Kristina; Mahar Francisco Lagmay, Alfredo

    2014-05-01

    The 2006 Guinsaugon landslide in St. Bernard, Southern Leyte is the largest known mass movement of soil in the Philippines. It consisted of a 15 million m3 rockslide-debris avalanche from an approximately 700 m high escarpment produced by continuous movement of the Philippine fault at approximately 2.5 cm/year. The landslide was preceded by continuous heavy rainfall totaling 571.2 mm from February 8 to 12, 2006. The catastrophic landslide killed more than 1,000 people and displaced 19,000 residents over its 6,400 km path. To investigate the present-day morphology of the scar and potential failure that may occur, an analysis of a high-resolution digital elevation model (10 m resolution Synthetic Aperture Radar images in 2013) was conducted, leading to the generation of a structurally controlled landslide hazard map of the area. Discontinuity sets that could contribute to any failure mechanism were identified using Coltop 3D software which uses a unique lower Schmidt-Lambert color scheme for any given dip and dip direction. Thus, finding main morpho-structural orientations became easier. Matterocking, a software designed for structural analysis, was used to generate possible planes that could slide due to the identified discontinuity sets. Conefall was then utilized to compute the extent to which the rock mass will run out. The results showed potential instabilities in the scarp area of the 2006 Guinsaguon landslide and in adjacent slopes because of the presence of steep discontinuities that range from 45-60°. Apart from the 2006 Guinsaugon potential landslides, conefall simulation generated farther rock mass extent in adjacent slopes. In conclusion, there is a high probability of landslides in the municipality of St. Bernard Leyte, where the 2006 Guinsaugon Landslide occurred. Concerned agencies may use maps produced from this study for disaster preparedness and to facilitate long-term recovery planning for hazardous areas.

  12. The geometric signature: Quantifying landslide-terrain types from digital elevation models

    USGS Publications Warehouse

    Pike, R.J.

    1988-01-01

    Topography of various types and scales can be fingerprinted by computer analysis of altitude matrices (digital elevation models, or DEMs). The critical analytic tool is the geometric signature, a set of measures that describes topographic form well enough to distinguish among geomorphically disparate landscapes. Different surficial processes create topography with diagnostic forms that are recognizable in the field. The geometric signature abstracts those forms from contour maps or their DEMs and expresses them numerically. This multivariate characterization enables once-in-tractable problems to be addressed. The measures that constitute a geometric signature express different but complementary attributes of topographic form. Most parameters used here are statistical estimates of central tendency and dispersion for five major categories of terrain geometry; altitude, altitude variance spectrum, slope between slope reversals, and slope and its curvature at fixed slope lengths. As an experimental application of geometric signatures, two mapped terrain types associated with different processes of shallow landsliding in Marin County, California, were distinguished consistently by a 17-variable description of topography from 21??21 DEMs (30-m grid spacing). The small matrix is a statistical window that can be used to scan large DEMs by computer, thus potentially automating the mapping of contrasting terrain types. The two types in Marin County host either (1) slow slides: earth flows and slump-earth flows, or (2) rapid flows: debris avalanches and debris flows. The signature approach should adapt to terrain taxonomy and mapping in other areas, where conditions differ from those in Central California. ?? 1988 International Association for Mathematical Geology.

  13. Submarine Melting of Icebergs from Repeat High-Resolution Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Enderlin, E. M.; Hamilton, G. S.; Straneo, F.; Cenedese, C.

    2014-12-01

    Icebergs calved from tidewater glaciers act as distributed freshwater sources as they transit through fjords to the surrounding ocean basins. Glacier discharge estimates provide a crude approximation of the total iceberg discharge on inter-annual timescales, but the liquid freshwater flux from icebergs in glacial fjords is largely unknown. Here we use repeat high-resolution digital elevation models (DEMs) to derive meltwater fluxes for 18 icebergs in Sermilik Fjord, East Greenland, during the 2011-2013 boreal summers, and for 33 comparably-sized icebergs in Ilulissat Fjord, West Greenland, during March-April 2011 and July 2012. We find that iceberg melt rates for Sermilik Fjord are in good agreement with simulated melt rates along the vertical terminus of Helheim Glacier in winter, i.e. when melting at the glacier front is not enhanced by subglacial discharge, providing an independent validation of our technique. Variations in meltwater fluxes from icebergs are primarily related to differences in the submerged area of individual icebergs, which is consistent with theory. The stratification of water masses in fjords has a noticeable effect on summertime-derived melt estimates, with lower melt rates (and meltwater fluxes) observed in the relatively cold and fresh Polar Water layer and higher melt rates in the underlying warmer and more saline Atlantic Water layer. The meltwater flux dependence on submerged area, particularly within the deeper Atlantic Water layer, suggests that changes in the characteristics of icebergs (size/shape/keel-depth) calved from a tidewater glacier will alter the magnitude and distribution of meltwater fluxes within the fjord, which may in turn influence fjord circulation and the heat content delivered to the glacier terminus.

  14. A robust interpolation method for constructing digital elevation models from remote sensing data

    NASA Astrophysics Data System (ADS)

    Chen, Chuanfa; Liu, Fengying; Li, Yanyan; Yan, Changqing; Liu, Guolin

    2016-09-01

    A digital elevation model (DEM) derived from remote sensing data often suffers from outliers due to various reasons such as the physical limitation of sensors and low contrast of terrain textures. In order to reduce the effect of outliers on DEM construction, a robust algorithm of multiquadric (MQ) methodology based on M-estimators (MQ-M) was proposed. MQ-M adopts an adaptive weight function with three-parts. The weight function is null for large errors, one for small errors and quadric for others. A mathematical surface was employed to comparatively analyze the robustness of MQ-M, and its performance was compared with those of the classical MQ and a recently developed robust MQ method based on least absolute deviation (MQ-L). Numerical tests show that MQ-M is comparative to the classical MQ and superior to MQ-L when sample points follow normal and Laplace distributions, and under the presence of outliers the former is more accurate than the latter. A real-world example of DEM construction using stereo images indicates that compared with the classical interpolation methods, such as natural neighbor (NN), ordinary kriging (OK), ANUDEM, MQ-L and MQ, MQ-M has a better ability of preserving subtle terrain features. MQ-M replaces thin plate spline for reference DEM construction to assess the contribution to our recently developed multiresolution hierarchical classification method (MHC). Classifying the 15 groups of benchmark datasets provided by the ISPRS Commission demonstrates that MQ-M-based MHC is more accurate than MQ-L-based and TPS-based MHCs. MQ-M has high potential for DEM construction.

  15. Coupling of digital elevation model and rainfall-runoff model in storm drainage network design

    NASA Astrophysics Data System (ADS)

    Gumbo, Bekithemba; Munyamba, Nelson; Sithole, George; Savenije, Hubert H. G.

    Often planners and engineers are faced with various options and questions in storm drainage network design e.g. flow pattern, direction, runoff quantity and therefore size of drain, or scenario after a road, airfield or building has been constructed. In most instances planning without drainage in mind has caused failure or extensive damage to property including the storm water drains which channel the water away. With the advent of various modelling and geographic information systems (GIS) tools this problem can be averted. The University of Zimbabwe’s (UZ) main campus had its storm drainage network reconstructed at a cost of about US$100 000, because of persistent flooding. This paper describes a method of assessing the effectiveness of storm drainage networks by combining a digital elevation model (DEM) with a rainfall-runoff model based on the Soil Conservation Service South African manual (SCS-SA). The UZ campus was used as the test site. The DEM was generated from aerial photographs and the data imported into ArcView. The 3.0 km 2 basin was then delineated into sub-catchments using ArcView Hydro extension tools. The land-use, watershed and soil map of the UZ were merged in ArcView and initial curve numbers (CN) assigned. Using three years of daily rainfall data, runoff and peak flows were calculated for each sub-catchment. By overlaying the natural flow lines derived from the DEM with the reconstructed physical drains a comparison of the flow direction and the orientation of the drains was achieved. Peak flows where calculated for each delineated watershed and the results used to check the adequacy of the trapezoidal concrete lined drains. A combination of a DEM and rainfall-runoff model within a GIS platform proves to be useful in estimating runoff on partly urbanised watersheds and in determining the size and orientation of storm drains. It is particularly useful for new areas where development is being contemplated.

  16. Testing 3D landform quantification methods with synthetic drumlins in a real digital elevation model

    NASA Astrophysics Data System (ADS)

    Hillier, John K.; Smith, Mike J.

    2012-06-01

    Metrics such as height and volume quantifying the 3D morphology of landforms are important observations that reflect and constrain Earth surface processes. Errors in such measurements are, however, poorly understood. A novel approach, using statistically valid ‘synthetic' landscapes to quantify the errors is presented. The utility of the approach is illustrated using a case study of 184 drumlins observed in Scotland as quantified from a Digital Elevation Model (DEM) by the ‘cookie cutter' extraction method. To create the synthetic DEMs, observed drumlins were removed from the measured DEM and replaced by elongate 3D Gaussian ones of equivalent dimensions positioned randomly with respect to the ‘noise' (e.g. trees) and regional trends (e.g. hills) that cause the errors. Then, errors in the cookie cutter extraction method were investigated by using it to quantify these ‘synthetic' drumlins, whose location and size is known. Thus, the approach determines which key metrics are recovered accurately. For example, mean height of 6.8 m is recovered poorly at 12.5 ± 0.6 (2σ) m, but mean volume is recovered correctly. Additionally, quantification methods can be compared: A variant on the cookie cutter using an un-tensioned spline induced about twice (× 1.79) as much error. Finally, a previously reportedly statistically significant (p = 0.007) difference in mean volume between sub-populations of different ages, which may reflect formational processes, is demonstrated to be only 30-50% likely to exist in reality. Critically, the synthetic DEMs are demonstrated to realistically model parameter recovery, primarily because they are still almost entirely the original landscape. Results are insensitive to the exact method used to create the synthetic DEMs, and the approach could be readily adapted to assess a variety of landforms (e.g. craters, dunes and volcanoes).

  17. Digital Elevation Models Aid the Analysis of Flows at Hrad Vallis, Mars

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.; Hamilton, C.; Garbeil, H.

    2015-12-01

    We have identified several landforms in the Hrad Vallis region of Mars (33.0o - 35.5oN, 216o - 218oW), which suggest that this area was covered by an ice sheet concurrent with volcanic eruptions. Using digital elevation models derived from High Resolution Imaging Science (HiRISE) and Context Camera (CTX) data, a reexamination of the area reveals a complex history including flow inflation and topographic control by transient topographic barriers. Among Amazonian-age outflow channels, Hrad Vallis is exceptional as it exhibits good evidence of magma/water interactions. It is inferred to have formed in association with a shallow igneous sill that melted part of the martian cryosphere and/or released water from an extensive aquifer to produce enormous lahar-like mud flows. Exposed ~30 m high dikes, 20 m high eroded mounds, and flow paths that are inconsistent with present-day topographic gradients, lead us to speculate that this area was covered by at least ~40 m of material (eolian deposits or ice) at the time of volcanic dike intrusion and flow emplacement. This material was subsequently removed leaving no clear morphologic signs (e.g., wind streaks, if eolian material; moraines, if ice). We favor the ice model because if this area was once ice-covered, it offers a plausible mode of formation (as pingoes) for some enigmatic 30 m high domes in the vicinity. At least one 120 km long flow from Hrad Vallis was emplaced as a pahoehoe-like flow that was confined by topographic obstacles and subsequently inflated to thickness of ~45 m. Although the direct relationship between this flow and Hrad Vallis remains to be determined, the inflated flow suggests a longer period of eruption/emplacement at a slower effusion rate than was previously believed.

  18. Combining MESSENGER Data in Production and Analysis of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Becker, K. J.; Howington-Kraus, E.; Thomas, O. H.; Neumann, G. A.; Mazarico, E.; Kirk, R. L.; Weller, L. A.; Edmundson, K. L.; Stephens, J. S.; Sawyers, R. J.; Robinson, M. S.; Solomon, S. C.

    2012-12-01

    The U.S. Geological Survey is combining image and laser altimetry data of Mercury acquired from instruments on the MESSENGER [1] spacecraft for the production and analysis of digital elevation models (DEMs). Precise image measurements that tie Mercury Laser Altimeter (MLA) [2] point data to Mercury Dual Imaging System (MDIS) [3] stereo pairs are obtained using the SOCET SET (®BAE Systems) digital photogrammetry software suite. These measurements will be added to existing Integrated Software for Imagers and Spectrometers [4] control networks used to produce global cartographic basemaps and a global DEM [5]. The MLA points serve as three-dimensional control points in a least-squares bundle adjustment [6] that improves image attitude and/or position parameters and generates improved triangulated ground coordinates for all tie and control points. The resulting point cloud is used to create an updated global DEM controlled to the MLA data. The MLA-to-MDIS image comparison also provides the boresight relationship between the two instruments. For quality assurance, several regional DEMs are created with SOCET SET for selected sites on Mercury that provide variation in terrain and observation conditions. These sites are used in the analysis and comparison of DEMs produced with a variety of methods and data sources (photogrammetry, photoclinometry, stereo techniques, and MLA), similar to comparisons that have been done for HRSC [7] and LRO [8] DEMs. Ultimately orthorectified cartographic products will be created by projecting MDIS images using the highest quality shape model available. [1] Solomon, S.C. et al., 2001. The MESSENGER mission to Mercury: Scientific objectives and implementation, Planet. Space Sci., 49, 1445-1465. [2] Zuber, M.T. et al., 2011. Orbital observations of Mercury with the Mercury Laser Altimeter, EPSC-DPS Joint Meeting, 6, abstract EPSC-DPS2011-278. [3] Hawkins, S.E. III et al., 2007. The Mercury Dual Imaging System on the MESSENGER spacecraft

  19. The use of UAV to document sloping landscapes to produce digital elevation models to examine environmental degradation

    NASA Astrophysics Data System (ADS)

    Themistocleous, K.; Agapiou, A.; Papadavid, G.; Christoforou, M.; Hadjimitsis, D. G.

    2015-10-01

    This paper focuses on the use of Unmanned Aerial Vehicles (UAVs) over the study area of Pissouri in Cyprus to document the sloping landscapes of the area. The study area has been affected by overgrazing, which has led to shifts in the vegetation patterns and changing microtopography of the soil. The UAV images were used to generate digital elevation models (DEMs) to examine the changes in microtopography. Next to that orthophotos were used to detect changes in vegetation patterns. The combined data of the digital elevation models and the orthophotos will be used to detect the occurrence of catastrophic shifts and mechanisms for desertification in the study area due to overgrazing. This study is part of the "CASCADE- Catastrophic shifts in dryland" project.

  20. A new method for the determination of flow directions and upslope areas in grid digital elevation models

    NASA Astrophysics Data System (ADS)

    Tarboton, David G.

    A new procedure for the representation of flow directions and calculation of upslope areas using rectangular grid digital elevation models is presented. The procedure is based on representing flow direction as a single angle taken as the steepest downward slope on the eight triangular facets centered at each grid point. Upslope area is then calculated by proportioning flow between two downslope pixels according to how close this flow direction is to the direct angle to the downslope pixel. This procedure offers improvements over prior procedures that have restricted flow to eight possible directions (introducing grid bias) or proportioned flow according to slope (introducing unrealistic dispersion). The new procedure is more robust than prior procedures based on fitting local planes while retaining a simple grid based structure. Detailed algorithms are presented and results are demonstrated through test examples and application to digital elevation data sets.

  1. 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

  2. In vivo accuracy of conventional and digital radiographic methods in confirming root canal working length determination by Root ZX

    PubMed Central

    OROSCO, Fernando Accorsi; BERNARDINELI, Norberti; GARCIA, Roberto Brandão; BRAMANTE, Clovis Monteiro; DUARTE, Marco Antonio Húngaro; de MORAES, Ivaldo Gomes

    2012-01-01

    Objectives To compare, in vivo, the accuracy of conventional and digital radiographic methods in determining root canal working length. Material and Methods Twenty-five maxillary incisor or canine teeth from 22 patients were used in this study. Considering the preoperative radiographs as the baseline, a 25 K file was inserted into the root canal to the point where the Root ZX electronic apex locator indicated the APEX measurement in the screen. From this measurement, 1 mm was subtracted for positioning the file. The radiographic measurements were made using a digital sensor (Digora 1.51) or conventional type-E films, size 2, following the paralleling technique, to determine the distance of the file tip and the radiographic apex. Results The Student "t" test indicated mean distances of 1.11 mm to conventional and 1.20 mm for the digital method and indicated a significant statistical difference (p<0.05). Conclusions The conventional radiographic method was found to be superior to the digital one in determining the working length of the root canal. PMID:23138737

  3. High-accuracy fit of the poles of spectroscopy amplifiers designed for mixed analog-digital filtering

    SciTech Connect

    Bittanti, S.; Gatti, E.; Ripamonti, G.; Savaresi, S.M.

    1997-04-01

    In this paper, a method for the identification of the poles` and zeros` position of an analog amplifier for nuclear spectroscopy used as a prefilter for a subsequent digital filter setup is presented. The proposed technique is based upon a subspace-based system state-space identification (4SID) method, which is well suited to a data set constituted by a noisy measurement of the sampled impulse response of the circuit. The algorithm runs unassisted and does not require skills by the operator. The experiments confirm that by using the so-obtained pole values, the shape of the impulse response of the amplifier can be fit with much better than 1% accuracy. Consequently, the overall filtering (analog + digital) can have finite duration and a top with a flatness much better than 1%.

  4. Accuracy of Digital Bitewing Radiography versus Different Views of Digital Panoramic Radiography for Detection of Proximal Caries

    PubMed Central

    Abdinian, Mehrdad; Razavi, Sayed Mohammad; Samety, Amir Abbas; Faghihian, Elham

    2015-01-01

    Objectives: Dental caries are common and have a high incidence among populations. Radiographs are essential for detecting proximal caries. The best technique should be recognized for accurate detection of caries. The aim of this study was to compare the accuracy of detection of proximal caries using intraoral bitewing, extraoral bitewing, improved interproximal panoramic, improved orthogonality panoramic and conventional panoramic radiographs. Materials and Methods: In this descriptive cross sectional study, 100 extracted human teeth with and without proximal caries were used. Intra and extraoral radiographs were taken. Images were evaluated and scored by two observers. Scores were compared with the histological gold standard. The diagnostic accuracy of radiographs was assessed by means of receiver operating characteristic (ROC) curve analysis (P<0.05). Results: Microscopic evaluation of proximal surfaces revealed that 54.8% of the surfaces were sound and 45.2% were carious (with different depths). The differences in the area under the ROC curve (Az value) among the five techniques were not statistically significant. Conclusion: Improved interproximal panoramic and extraoral bitewing radiographs were superior to conventional panoramic radiography for detection of proximal caries ex vivo and should be considered for patients with contraindications for intraoral radiographs. PMID:26622284

  5. WAIS Digit Span-Based Indicators of Malingered Neurocognitive Dysfunction: Classification Accuracy in Traumatic Brain Injury

    ERIC Educational Resources Information Center

    Heinly, Matthew T.; Greve, Kevin W.; Bianchini, Kevin J.; Love, Jeffrey M.; Brennan, Adrianne

    2005-01-01

    The present study determined specificity and sensitivity to malingered neurocognitive dysfunction (MND) in traumatic brain injury (TBI) for several Wechsler Adult Intelligence Scale (WAIS) Digit Span scores. TBI patients (n = 344) were categorized into one of five groups: no incentive, incentive only, suspect, probable MND, and definite MND.…

  6. Increasing the accuracy and automation of fractional vegetation cover estimation from digital photographs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of automated methods to estimate canopy cover (CC) from digital photographs has increased in recent years given its potential to produce accurate, fast and inexpensive CC measurements. Wide acceptance has been delayed because of the limitations of these methods. This work introduces a novel ...

  7. Impact of Computer-Aided Detection Systems on Radiologist Accuracy With Digital Mammography

    PubMed Central

    Cole, Elodia B.; Zhang, Zheng; Marques, Helga S.; Hendrick, R. Edward; Yaffe, Martin J.; Pisano, Etta D.

    2014-01-01

    OBJECTIVE The purpose of this study was to assess the impact of computer-aided detection (CAD) systems on the performance of radiologists with digital mammograms acquired during the Digital Mammographic Imaging Screening Trial (DMIST). MATERIALS AND METHODS Only those DMIST cases with proven cancer status by biopsy or 1-year follow-up that had available digital images were included in this multireader, multicase ROC study. Two commercially available CAD systems for digital mammography were used: iCAD SecondLook, version 1.4; and R2 ImageChecker Cenova, version 1.0. Fourteen radiologists interpreted, without and with CAD, a set of 300 cases (150 cancer, 150 benign or normal) on the iCAD SecondLook system, and 15 radiologists interpreted a different set of 300 cases (150 cancer, 150 benign or normal) on the R2 ImageChecker Cenova system. RESULTS The average AUC was 0.71 (95% CI, 0.66–0.76) without and 0.72 (95% CI, 0.67–0.77) with the iCAD system (p = 0.07). Similarly, the average AUC was 0.71 (95% CI, 0.66–0.76) without and 0.72 (95% CI 0.67–0.77) with the R2 system (p = 0.08). Sensitivity and specificity differences without and with CAD for both systems also were not significant. CONCLUSION Radiologists in our studies rarely changed their diagnostic decisions after the addition of CAD. The application of CAD had no statistically significant effect on radiologist AUC, sensitivity, or specificity performance with digital mammograms from DMIST. PMID:25247960

  8. The effects of digital elevation model resolution on the calculation and predictions of topographic wetness indices.

    SciTech Connect

    Drover, Damion, Ryan

    2011-12-01

    One of the largest exports in the Southeast U.S. is forest products. Interest in biofuels using forest biomass has increased recently, leading to more research into better forest management BMPs. The USDA Forest Service, along with the Oak Ridge National Laboratory, University of Georgia and Oregon State University are researching the impacts of intensive forest management for biofuels on water quality and quantity at the Savannah River Site in South Carolina. Surface runoff of saturated areas, transporting excess nutrients and contaminants, is a potential water quality issue under investigation. Detailed maps of variable source areas and soil characteristics would therefore be helpful prior to treatment. The availability of remotely sensed and computed digital elevation models (DEMs) and spatial analysis tools make it easy to calculate terrain attributes. These terrain attributes can be used in models to predict saturated areas or other attributes in the landscape. With laser altimetry, an area can be flown to produce very high resolution data, and the resulting data can be resampled into any resolution of DEM desired. Additionally, there exist many maps that are in various resolutions of DEM, such as those acquired from the U.S. Geological Survey. Problems arise when using maps derived from different resolution DEMs. For example, saturated areas can be under or overestimated depending on the resolution used. The purpose of this study was to examine the effects of DEM resolution on the calculation of topographic wetness indices used to predict variable source areas of saturation, and to find the best resolutions to produce prediction maps of soil attributes like nitrogen, carbon, bulk density and soil texture for low-relief, humid-temperate forested hillslopes. Topographic wetness indices were calculated based on the derived terrain attributes, slope and specific catchment area, from five different DEM resolutions. The DEMs were resampled from LiDAR, which is a

  9. Digital Elevation Models Aid the Analysis of Double Layered Ejecta (DLE) Impact Craters on Mars

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.; Boyce, J. M.; Garbeil, H.

    2014-12-01

    Considerable debate has recently taken place concerning the origin of the inner and outer ejecta layers of double layered ejecta (DLE) craters on Mars. For craters in the diameter range ~10 to ~25 km, the inner ejecta layer of DLE craters displays characteristic grooves extending from the rim crest, and has led investigators to propose three hypotheses for their formation: (1) deposition of the primary ejecta and subsequent surface scouring by either atmospheric vortices or a base surge; (2) emplacement through a landslide of the near-rim crest ejecta; and (3) instabilities (similar to Gortler vortices) generated by high flow-rate, and high granular temperatures. Critical to resolving between these models is the topographic expression of both the ejecta layer and the groove geometry. To address this problem, we have made several digital elevation models (DEMs) from CTX and HiRISE stereo pairs using the Ames Stereo Pipeline at scales of 24 m/pixel and 1 m/pixel, respectively. These DEMs allow several key observations to be made that bear directly upon the origin of the grooves associated with DLE craters: (1) Grooves formed on the sloping ejecta layer surfaces right up to the preserved crater rim; (2) There is clear evidence that grooves traverse the topographic boundary between the inner and outer ejecta layers; and (3) There are at least two different sets of radial grooves, with smaller grooves imprinted upon the larger grooves. There are "deep-wide" grooves that have a width of ~200 m and a depth of ~10 m, and there are "shallow-narrow" grooves with a width of <50 m and depth <5 m. These two scales of grooves are not consistent with their formation analogous to a landslide. Two different sets of grooves would imply that, simultaneously, two different depths to the flow would have to exist if the grooves were formed by shear within the flow, something that is not physically possible. All three observations can only be consistent with a model of groove formation

  10. Stable isotopes and Digital Elevation Models to study nutrient inputs in high-Arctic lakes

    NASA Astrophysics Data System (ADS)

    Calizza, Edoardo; Rossi, David; Costantini, Maria Letizia; Careddu, Giulio; Rossi, Loreto

    2016-04-01

    Ice cover, run-off from the watershed, aquatic and terrestrial primary productivity, guano deposition from birds are key factors controlling nutrient and organic matter inputs in high-Arctic lakes. All these factors are expected to be significantly affected by climate change. Quantifying these controls is a key baseline step to understand what combination of factors subtends the biological productivity in Arctic lakes and will drive their ecological response to environmental change. Basing on Digital Elevation Models, drainage maps, and C and N elemental content and stable isotope analysis in sediments, aquatic vegetation and a dominant macroinvertebrate species (Lepidurus arcticus Pallas 1973) belonging to Tvillingvatnet, Storvatnet and Kolhamna, three lakes located in North Spitsbergen (Svalbard), we propose an integrated approach for the analysis of (i) nutrient and organic matter inputs in lakes; (ii) the role of catchment hydro-geomorphology in determining inter-lake differences in the isotopic composition of sediments; (iii) effects of diverse nutrient inputs on the isotopic niche of Lepidurus arcticus. Given its high run-off and large catchment, organic deposits in Tvillingvatnet where dominated by terrestrial inputs, whereas inputs were mainly of aquatic origin in Storvatnet, a lowland lake with low potential run-off. In Kolhamna, organic deposits seem to be dominated by inputs from birds, which actually colonise the area. Isotopic signatures were similar between samples within each lake, representing precise tracers for studies on the effect of climate change on biogeochemical cycles in lakes. The isotopic niche of L. aricticus reflected differences in sediments between lakes, suggesting a bottom-up effect of hydro-geomorphology characterizing each lake on nutrients assimilated by this species. The presented approach proven to be an effective research pathway for the identification of factors subtending to nutrient and organic matter inputs and transfer

  11. Calibration of Watershed Lag Time Equation for Philippine Hydrology using RADARSAT Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Cipriano, F. R.; Lagmay, A. M. A.; Horritt, M.; Mendoza, J.; Sabio, G.; Punay, K. N.; Taniza, H. J.; Uichanco, C.

    2015-12-01

    Widespread flooding is a major problem in the Philippines. The country experiences heavy amount of rainfall throughout the year and several areas are prone to flood hazards because of its unique topography. Human casualties and destruction of infrastructure are just some of the damages caused by flooding and the Philippine government has undertaken various efforts to mitigate these hazards. One of the solutions was to create flood hazard maps of different floodplains and use them to predict the possible catastrophic results of different rain scenarios. To produce these maps with accurate output, different input parameters were needed and one of those is calculating hydrological components from topographical data. This paper presents how a calibrated lag time (TL) equation was obtained using measurable catchment parameters. Lag time is an essential input in flood mapping and is defined as the duration between the peak rainfall and peak discharge of the watershed. The lag time equation involves three measurable parameters, namely, watershed length (L), maximum potential retention (S) derived from the curve number, and watershed slope (Y), all of which were available from RADARSAT Digital Elevation Models (DEM). This approach was based on a similar method developed by CH2M Hill and Horritt for Taiwan, which has a similar set of meteorological and hydrological parameters with the Philippines. Rainfall data from fourteen water level sensors covering 67 storms from all the regions in the country were used to estimate the actual lag time. These sensors were chosen by using a screening process that considers the distance of the sensors from the sea, the availability of recorded data, and the catchment size. The actual lag time values were plotted against the values obtained from the Natural Resource Conservation Management handbook lag time equation. Regression analysis was used to obtain the final calibrated equation that would be used to calculate the lag time

  12. Geomorphic Map of Worcester County, Maryland, Interpreted from a LIDAR-Based, Digital Elevation Model

    USGS Publications Warehouse

    Newell, Wayne L.; Clark, Inga

    2008-01-01

    A recently compiled mosaic of a LIDAR-based digital elevation model (DEM) is presented with geomorphic analysis of new macro-topographic details. The geologic framework of the surficial and near surface late Cenozoic deposits of the central uplands, Pocomoke River valley, and the Atlantic Coast includes Cenozoic to recent sediments from fluvial, estuarine, and littoral depositional environments. Extensive Pleistocene (cold climate) sandy dune fields are deposited over much of the terraced landscape. The macro details from the LIDAR image reveal 2 meter-scale resolution of details of the shapes of individual dunes, and fields of translocated sand sheets. Most terrace surfaces are overprinted with circular to elliptical rimmed basins that represent complex histories of ephemeral ponds that were formed, drained, and overprinted by younger basins. The terrains of composite ephemeral ponds and the dune fields are inter-shingled at their margins indicating contemporaneous erosion, deposition, and re-arrangement and possible internal deformation of the surficial deposits. The aggregate of these landform details and their deposits are interpreted as the products of arid, cold climate processes that were common to the mid-Atlantic region during the Last Glacial Maximum. In the Pocomoke valley and its larger tributaries, erosional remnants of sandy flood plains with anastomosing channels indicate the dynamics of former hydrology and sediment load of the watershed that prevailed at the end of the Pleistocene. As the climate warmed and precipitation increased during the transition from late Pleistocene to Holocene, dune fields were stabilized by vegetation, and the stream discharge increased. The increased discharge and greater local relief of streams graded to lower sea levels stimulated down cutting and created the deeply incised valleys out onto the continental shelf. These incised valleys have been filling with fluvial to intertidal deposits that record the rising sea

  13. High-resolution digital elevation models of the Flade Iceblink feature in NE Greenland

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Juntunen, T.; Porter, C. C.; Morin, P. J.

    2013-12-01

    We produce a time series of high-resolution digital elevation models (DEM) to examine the recent evolution of an 8.7 km2 sub-glacial lake collapse feature near the southern summit of the 8500 km2 Flade Isblink Ice Cap (FIIC) in northeastern Greenland [Figure 1]. Visible imagery from the MODerate-resolution Imaging Spectroradiometer (MODIS) indicates the collapse occurred between August 16th and September 6th, 2011 at the site of a recurring moulin. DEMs are extracted using the NASA Ames Stereo Pipeline for the period between June 2012 and late 2013 from 0.5 m resolution along-track stereo image pairs available via the NGA commercial imagery program. The DEMs are compared to a 1996 ERS InSAR derived DEM [Palmer et al., 2010], and to a contemporary airborne laser altimeter swath flown by NASA Icebridge in mid-April 2013 to derive the volume of the feature and the uncertainties on the high-resolution DEMs. The 'mitten' shaped feature is bounded by crevasses on three sides, with a shallow ramp to the south. It is ~70 m deep, 3.7 km north-to-south and 3 km east-to-west and has a volume of ~0.3 km3. Ice penetrating radar from a nearby Icebridge mission in May 2011, indicates the ice is approximately 550 m thick and that the bed is very flat and smooth about 1 km to the southeast of the feature. The nearby bed topography, local geology and lack of recorded seismicity in the area indicate it is unlikely that the feature is the result of either subglacial volcanic activity or the collapse of a limestone karst feature below the ice cap - the neighboring Princess Elizabeth Alps are composed of 420 Ma Caledonide fold belt gneisses. The presence of recurring supraglacial meltwater streams and drainage into the feature, its rapid formation and its steep sided nature instead suggest that it formed during the rapid drainage of a sub-glacial lake - which is, as far as we are aware, the first recorded instance of such an occurrence in Greenland. Meltwater observed using 250 m

  14. Effect of modulation frequency bandwidth on measurement accuracy and precision for digital diffuse optical spectroscopy (dDOS)

    NASA Astrophysics Data System (ADS)

    Jung, Justin; Istfan, Raeef; Roblyer, Darren

    2014-03-01

    Near-infrared (NIR) frequency-domain Diffuse Optical Spectroscopy (DOS) is an emerging technology with a growing number of potential clinical applications. In an effort to reduce DOS system complexity and improve portability, we recently demonstrated a direct digital sampling method that utilizes digital signal generation and detection as a replacement for more traditional analog methods. In our technique, a fast analog-to-digital converter (ADC) samples the detected time-domain radio frequency (RF) waveforms at each modulation frequency in a broad-bandwidth sweep (50- 300MHz). While we have shown this method provides comparable results to other DOS technologies, the process is data intensive as digital samples must be stored and processed for each modulation frequency and wavelength. We explore here the effect of reducing the modulation frequency bandwidth on the accuracy and precision of extracted optical properties. To accomplish this, the performance of the digital DOS (dDOS) system was compared to a gold standard network analyzer based DOS system. With a starting frequency of 50MHz, the input signal of the dDOS system was swept to 100, 150, 250, or 300MHz in 4MHz increments and results were compared to full 50-300MHz networkanalyzer DOS measurements. The average errors in extracted μa and μs' with dDOS were lowest for the full 50-300MHz sweep (less than 3%) and were within 3.8% for frequency bandwidths as narrow as 50-150MHz. The errors increased to as much as 9.0% when a bandwidth of 50-100MHz was tested. These results demonstrate the possibility for reduced data collection with dDOS without critical compensation of optical property extraction.

  15. Accuracy of consumer bimetal and digital thermometers in cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The only way to determine if meat products have been cooked to an internal temperature necessary to inactivate pathogens is to use a thermometer. To date, the accuracy and reliability of consumer instant-read thermometers have only been evaluated in water-baths, not in meat products. Ten units of th...

  16. Topographic analysis for tectonic geomorphology using digital image processing of elevation data from the Mississippi embayment and adjacent areas

    SciTech Connect

    Mayer, L. . Dept. of Geology)

    1993-03-01

    Image processing of digital elevation data provides a framework within which to evaluate the relative importance of tectonic and erosional signatures on the landscape. Shaded relief imaging of the elevation data illuminates regional topographic features coincident with the physiographic provinces bounding the Mississippi embayment portion of the Coastal Plain: the Ozark Plateaus and Ouachitas on the west, the Central Lowland on the north, and the Interior Low Plateaus on the east. Grayscale or colors from custom color lookup tables are assigned based on elevation. Stretching can be used to enhance a particular elevation range while spatial convolution kernels can be used to provide a robust and rapid means of designing high- and low-pass filters for the purpose of restricting the frequency range examined. Thresholding the elevation ranges and assigning boundaries of the resultant binary images allow for the rapid delineation of topographic contour lines and permits quantization of planform geometry. Forty one-degree by 30-minute quadrangles have been imaged for the purpose of delineating topographic features of possible tectonic origin.

  17. High-resolution digital elevation model of lower Cowlitz and Toutle Rivers, adjacent to Mount St. Helens, Washington, based on an airborne lidar survey of October 2007

    USGS Publications Warehouse

    Mosbrucker, Adam

    2015-01-01

    Castle and Coldwater Lakes. Final results averaged about two laser last-return points per square meter. As reported by Watershed Sciences, Inc., vertical accuracy is 10 centimeters (cm) at the 95-percent confidence interval on bare road surfaces; however, over natural terrain, USGS found vertical accuracy to be 10–50 cm. This USGS data series contains the bare-earth lidar data as 1- and 10-meter (m) resolution Esri grid files. Digital-elevation data can be downloaded (1m_DEM.zip and 10m_DEM.zip), as well as a 1-m resolution hillshade image with pyramids (1m_hillshade.zip). These geospatial data files require geographic information system (GIS) software for viewing.

  18. High-resolution digital elevation model of Mount St. Helens crater and upper North Fork Toutle River basin, Washington, based on an airborne lidar survey of September 2009

    USGS Publications Warehouse

    Mosbrucker, Adam

    2014-01-01

    -return points per square meter. As reported by Watershed Sciences, Inc., vertical accuracy is 10 centimeters (cm) at the 95-percent confidence interval on bare road surfaces; however, over natural terrain, USGS found vertical accuracy to be 10–50 cm. This USGS data series contains the bare-earth lidar data as 1- and 10-meter (m) resolution Esri grid files. Digital-elevation data can be downloaded (1m_DEM.zip and 10m_DEM.zip), as well as a 1-m resolution hillshade image with pyramids (1m_hillshade.zip). These geospatial data files require geographic information system (GIS) software for viewing.

  19. Accuracy of CBCT, Digital Radiography and Cross-Sectioning for the Evaluation of Mandibular Incisor Root Canals

    PubMed Central

    Assadian, Hadi; Dabbaghi, Arash; Gooran, Morteza; Eftekhar, Behrouz; Sharifi, Sanaz; Shams, Nassim; Dehghani Najvani, Ali; Tabesh, Hamed

    2016-01-01

    Introduction: The aim of this study was to compare the accuracy of cone-beam computed tomography (CBCT), digital radiography and tooth sectioning in evaluating root canal morphology of mandibular incisors in an in vitro setting. Methods and Materials: A total of 76 samples were imaged using CBCT, and digital radiography in straight and angled views. The samples were then sectioned at different distances from the apex for further visualization under stereomicroscope. The agreement between the observers was statistically analyzed by kappa correlation coefficient and the chi-square test. Results: The results showed that the majority of the samples had a single canal (Vertucci’s Type I). CBCT analysis reported more frequent multi-canal roots in comparison with the other techniques. In pairwise comparisons, the highest agreement was found between digital radiographic imaging and microscopic cross-sectioning both in terms of canal configuration and the number of root canals. Conclusion: None of the used imaging techniques per se could adequately show the exact internal anatomical configuration in accordance with the gold standard. PMID:27141217

  20. Experience in reading digital images may decrease observer accuracy in mammography

    NASA Astrophysics Data System (ADS)

    Rawashdeh, Mohammad A.; Lewis, Sarah J.; Lee, Warwick; Mello-Thoms, Claudia; Reed, Warren M.; McEntee, Mark; Tapia, Kriscia; Brennan, Patrick C.

    2015-03-01

    Rationale and Objectives: To identify parameters linked to higher levels of performance in screening mammography. In particular we explored whether experience in reading digital cases enhances radiologists' performance. Methods: A total of 60 cases were presented to the readers, of which 20 contained cancers and 40 showed no abnormality. Each case comprised of four images and 129 breast readers participated in the study. Each reader was asked to identify and locate any malignancies using a 1-5 confidence scale. All images were displayed using 5MP monitors, supported by radiology workstations with full image manipulation capabilities. A jack-knife free-response receiver operating characteristic, figure of merit (JAFROC, FOM) methodology was employed to assess reader performance. Details were obtained from each reader regarding their experience, qualifications and breast reading activities. Spearman and Mann Whitney U techniques were used for statistical analysis. Results: Higher performance was positively related to numbers of years professionally qualified (r= 0.18; P<0.05), number of years reading breast images (r= 0.24; P<0.01), number of mammography images read per year (r= 0.28; P<0.001) and number of hours reading mammographic images per week (r= 0.19; P<0.04). Unexpectedly, higher performance was inversely linked to previous experience with digital images (r= - 0.17; p<0.05) and further analysis, demonstrated that this finding was due to changes in specificity. Conclusion: This study suggests suggestion that readers with experience in digital images reporting may exhibit a reduced ability to correctly identify normal appearances requires further investigation. Higher performance is linked to number of cases read per year.

  1. Accuracy Assessment of Digital Surface Models Based on WorldView-2 and ADS80 Stereo Remote Sensing Data

    PubMed Central

    Hobi, Martina L.; Ginzler, Christian

    2012-01-01

    Digital surface models (DSMs) are widely used in forest science to model the forest canopy. Stereo pairs of very high resolution satellite and digital aerial images are relatively new and their absolute accuracy for DSM generation is largely unknown. For an assessment of these input data two DSMs based on a WorldView-2 stereo pair and a ADS80 DSM were generated with photogrammetric instruments. Rational polynomial coefficients (RPCs) are defining the orientation of the WorldView-2 satellite images, which can be enhanced with ground control points (GCPs). Thus two WorldView-2 DSMs were distinguished: a WorldView-2 RPCs-only DSM and a WorldView-2 GCP-enhanced RPCs DSM. The accuracy of the three DSMs was estimated with GPS measurements, manual stereo-measurements, and airborne laser scanning data (ALS). With GCP-enhanced RPCs the WorldView-2 image orientation could be optimised to a root mean square error (RMSE) of 0.56 m in planimetry and 0.32 m in height. This improvement in orientation allowed for a vertical median error of −0.24 m for the WorldView-2 GCP-enhanced RPCs DSM in flat terrain. Overall, the DSM based on ADS80 images showed the highest accuracy of the three models with a median error of 0.08 m over bare ground. As the accuracy of a DSM varies with land cover three classes were distinguished: herb and grass, forests, and artificial areas. The study suggested the ADS80 DSM to best model actual surface height in all three land cover classes, with median errors <1.1 m. The WorldView-2 GCP-enhanced RPCs model achieved good accuracy, too, with median errors of −0.43 m for the herb and grass vegetation and −0.26 m for artificial areas. Forested areas emerged as the most difficult land cover type for height modelling; still, with median errors of −1.85 m for the WorldView-2 GCP-enhanced RPCs model and −1.12 m for the ADS80 model, the input data sets evaluated here are quite promising for forest canopy modelling. PMID:22778645

  2. Digital Archive of UKRVO: The Positional Accuracy of Minor Planets Determinations

    NASA Astrophysics Data System (ADS)

    Golovnya, V.; Andruk, V.

    Scanning and astrometric processing of two 30x30 cm photographic plates with images of minor planets were conducted. The plates were obtained at the double wide-angle astrograph (DWAA, 400/2000) on the program of photographic sky survey and the program of small planets' observations. The plates were digitized using a flatbed scanner Epson Expression 10000XL. Images were obtained in the gray range of 16 -bits with a resolution of 1200dpi (> 11,000 pix along the one of the axies) and included into the UkrVO Joint Digital Archive (JDA). The plates are related to GUA040C observational archive. Image processing has been carried out in software package LINUS/MID AS/ROM AFOT. Topocentric equatorial coordinates for the second exposition minor planet images were obtained with a single measurement error ± 0.1 " and ± 0.3" for coordinate and ± 0.2m for magnitudes in the Tycho-2 catalog as reference.

  3. Elevation contours of the bedrock surface, North Platte 1- by 2-degree Quadrangle, Nebraska, digitized from a published 1:250,000-scale geologic map

    USGS Publications Warehouse

    Zelt, Ronald B.

    1995-01-01

    A geologic map showing the configuration of the bedrock surface for the North Platte, Nebraska, 1- by 2-degree quadrangle was published at a scale of 1:250,000 in 1991. This report describes the conversion of the bedrock-surface elevation map into a digital geographic data set and includes those data at a nominal scale of 1:500,000. A film separation of the published elevation contours was scanned to produce a file of digital graphics data. The digital graphics data were processed further to produce a digital geographic data set. Geographic feature attributes and data-set documentation also are included in the digital data set. The digital geographic data are formatted for distribution in accordance with the Spatial Data Transfer Standard approved by the U.S. National Institute of Standards and Technology.

  4. Optimization of computer-based technology of creating large reservoir's Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Shikunova, Ekaterina; Pavlovsky, Andrew; Zemlyanov, Igor; Gorelits, Olga

    2010-05-01

    Using Digital Elevation Model of bottom and coastal zone for large-scale anthropogenic water reservoirs is very important for sustainable water management in actual conditions of Global Climate Change. DEM is unified monitoring base for different types of reservoirs in varied types of ecosystems in various environmental and economical conditions. It may be used for getting current morphometric characteristics, pollution and biodiversity analysis, monitoring bottom relief changing and making management decisions. In 2008-2009 State Oceanography Institute (SOI) carried out the DEMs for reservoirs of Volga river system. In 2008 in SOI was created DEM of Uglichsky reservoir, which is typical Russian reservoir. Methodology and computer-based technology were developed and evaluated. In 2009 in SOI were created DEMs of Gorkovsky, Volgogradsky and six reservoirs of Moscow region. Such result was achieved by optimization of DEM's creating process. Initially we used complex of GIS programs, which include GIS Map-2008 Panorama, ArcMap v.9.3.1, ArcView v.3.2a, Golden Surfer v.8, Global Mapper v.10. The input data are bathymetric survey data, large-scale maps (scale 1:10 000, 1:25 000) and remote sensing data of high resolution. Office analysis consists of several main milestones. 1. Vectorization of coastline and relief data from maps and remote sensing data using GIS Map-2008 by Panorama; ArcView v.3.2a. 2. Maps data elaboration with using bathymetric survey data. Because some maps are longstanding it is necessary to renew them. 3. Creating point's array including all data from maps, RSD and bathymetric survey. 4. Separation small calculation zones including four survey cross-sections. 5. Determine of anisotropy parameters, which depend on channel orientation. 6. Create shapes for clipping of correct grid zones. Each shape includes 2 cross-sections. Milestones 2-6 realize in ArcView v.3.2a. 7. Creating grid's array using Golden Surfer v.8 for each zone by interpolation method

  5. Multiplexing image detector method for digital sun sensors with arc-second class accuracy and large FOV.

    PubMed

    Wei, Minsong; Xing, Fei; You, Zheng; Wang, Geng

    2014-09-22

    To improve the accuracy of digital sun sensors (DSS) to the level of arc-second while maintaining a large field of view (FOV), a multiplexing image detector method was proposed. Based on a single multiplexing detector, a dedicated mask with different groups of encoding apertures was utilized to divide the whole FOV into several sub-FOVs, every of which would cover the whole detector. In this paper, we present a novel method to analyze and optimize the diffraction effect and the parameters of the aperture patterns in the dedicated mask, including the aperture size, focal length, FOV, as well as the clearance between adjacent apertures. Based on the simulation, a dedicated mask with 13 × 13 various groups of apertures was designed and fabricated; furthermore a prototype of DSS with a single multiplexing detector and 13 × 13 sub-FOVs was built and test. The results indicated that the DSS prototype could reach the accuracy of 5 arc-second (3σ) within a 105° × 105° FOV. Using this method, the sun sensor still keeps the original features of low power consumption, small size and high dynamic range when it realizes both high accuracy and large FOV. PMID:25321780

  6. Topogrid Derived 10 Meter Resolution Digital Elevation Model of the Shenandoah National Park and Surrounding Region, Virginia

    USGS Publications Warehouse

    Chirico, Peter G.; Tanner, Seth D.

    2004-01-01

    Explanation The purpose of developing a new 10m resolution DEM of the Shenandoah National Park Region was to more accurately depict geologic structure, surfical geology, and landforms of the Shenandoah National Park Region in preparation for automated landform classification. Previously, only a 30m resolution DEM was available through the National Elevation Dataset (NED). During production of the Shenandoah10m DEM of the Park the Geography Discipline of the USGS completed a revised 10m DEM to be included into the NED. However, different methodologies were used to produce the two similar DEMs. The ANUDEM algorithm was used to develop the Shenadoah DEM data. This algorithm allows for the inclusion of contours, streams, rivers, lake and water body polygons as well as spot height data to control the elevation model. A statistical analysis using over 800 National Geodetic Survey (NGS) first and second order vertical control points reveals that the Shenandoah10m DEM, produced as a part of the Appalachian Blue Ridge Landscape project, has a vertical accuracy of ?4.87 meters. The metadata for the 10m NED data reports a vertical accuracy of ?7m. A table listing the NGS control points, the elevation comparison, and the RMSE for the Shenandoah10m DEM is provided. The process of automated terrain classification involves developing statistical signatures from the DEM for each type of surficial deposit and landform type. The signature will be a measure of several characteristics derived from the elevation data including slope, aspect, planform curvature, and profile curvature. The quality of the DEM is of critical importance when extracting terrain signatures. The highest possible horizontal and vertical accuracy is required. The more accurate Shenandoah 10m DEM can now be analyzed and integrated with the geologic observations to yield statistical correlations between the two in the development of landform and surface geology mapping projects.

  7. Determining the Suitability of Different Digital Elevation Models and Satellite Images for Fancy Maps. An Example of Cyprus

    NASA Astrophysics Data System (ADS)

    Drachal, J.; Kawel, A. K.

    2016-06-01

    The article describes the possibility of developing an overall map of the selected area on the basis of publicly available data. Such a map would take the form designed by the author with the colors that meets his expectations and a content, which he considers to be appropriate. Among the data available it was considered the use of satellite images of the terrain in real colors and, in the form of shaded relief, digital terrain models with different resolutions of the terrain mesh. Specifically the considered data were: MODIS, Landsat 8, GTOPO-30, SRTM-30, SRTM-1, SRTM-3, ASTER. For the test area the island of Cyprus was chosen because of the importance in tourism, a relatively small area and a clearly defined boundary. In the paper there are shown and discussed various options of the Cyprus terrain image obtained synthetically from variants of Modis, Landsat and digital elevation models of different resolutions.

  8. Evaluating the Effects of Reductions in LiDAR Data on the Visual and Statistical Characteristics of the Created Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Asal, F. F.

    2016-06-01

    With continuous developments in LiDAR technologies high point cloud densities have been attainable but accompanied by challenges for processing big volumes of data. Reductions in high point cloud densities are expected to lower data acquisition and data processing costs; however this could affect the characteristics of the generated Digital Elevation Models (DEMs). This research aimed to evaluate the effects of reductions in airborne LiDAR point cloud data densities on the visual and statistical characteristics of the generated DEMs. DEMs have been created from a dataset which constitutes last returns of raw LiDAR data that was acquired at bare lands for Gilmer County, USA between March and April 2004, where qualitative and quantitative testing analyses have been performed. Visual analysis has shown that the DEM can withstand a considerable degree of quality with reduced densities down to 0.128 pts/m2 (47 % of the data remaining), however degradations in the DEM visual characteristics appeared in coarser tones and rougher textures have occurred with more reductions. Additionally, the statistical analysis has indicated that the standard deviations of the DEM elevations have decreased by only 22 % of the total decrease with data density reductions down to 0.101 pts/m2 (37 % of the data remaining) while greater rate of decreasing in the standard deviations has occurred with more reductions referring to greater rate of surface smoothing and elevation approximating. Furthermore, the accuracy analysis testing has given that the DEM accuracy has degraded by only 4.83 % of the total degradations with data density reductions down to 0.128 pts/m2, however great deteriorations in the DEM accuracy have occurred with more data reductions. Finally, it is recommended that LiDAR data can withstand point density reductions down to 0.128 pts/m2 (about 50 % of the data) without big deteriorations in the visual and

  9. Broadband fully automated digitally assisted coaxial bridge for high accuracy impedance ratio measurements

    NASA Astrophysics Data System (ADS)

    Overney, Frédéric; Lüönd, Felix; Jeanneret, Blaise

    2016-06-01

    This paper describes the principle of a new fully automated digitally assisted coaxial bridge having a large bandwidth ranging from 60 Hz to 50 kHz. The performance of the bridge is evaluated making 1:1 comparisons between calculable ac resistors. The agreement between the calculated and the measured frequency dependence of the resistors is better than 5\\cdot {{10}-8} at frequencies up to 5 kHz, better than 1\\cdot {{10}-7} up to 20 kHz and better than 0.8\\cdot {{10}-6} up to 50 kHz. This bridge is particularly well suited to investigate the ac transport properties of graphene in the quantum Hall regime.

  10. Josephson-based full digital bridge for high-accuracy impedance comparisons

    NASA Astrophysics Data System (ADS)

    Overney, Frédéric; Flowers-Jacobs, Nathan E.; Jeanneret, Blaise; Rüfenacht, Alain; Fox, Anna E.; Underwood, Jason M.; Koffman, Andrew D.; Benz, Samuel P.

    2016-08-01

    This paper describes a Josephson-based full digital impedance bridge capable of comparing any two impedances, regardless of type (R-C, R-L, or L-C), over a large frequency range (from 1 kHz to 20 kHz). At the heart of the bridge are two Josephson arbitrary waveform synthesizer systems that offer unprecedented flexibility in high-precision impedance calibration, that is, it can compare impedances with arbitrary ratios and phase angles. Thus this single bridge can fully cover the entire complex plane. In the near future, this type of instrument will considerably simplify the realization and maintenance of the various impedance scales in many National Metrology Institutes around the world. Contribution of the National Institute of Standards and Technology, US Department of Commerce, not subject to copyright in the United States.

  11. Influence of scanning system and dentist's level of training in the accuracy of digital impressions

    NASA Astrophysics Data System (ADS)

    Hategan, Simona; Gabor, Alin; Zaharia, Cristian; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Jivanescu, Anca

    2016-03-01

    Background: The principal aim of our study was to evaluate digital impressions, taken with spray powder and powderfree scan systems, in order to determine the influence of the dentist's commitment to training as a critical factor regarding quality. Material and method: Two digital intraoral impression systems from the same manufacture (Sirona) : Apollo DI and CEREC Omnicam, were used to scan 16 crown preparations on teeth on a typodont maxillary model. Because an Apollo Di intraoral camera is a powder system, an adhesive was applied before using the powder spray. Three groups were used to scan the crown preparations in order to determine coating thickness homogeneity. One group consisted of senior year dental students, a second consisted of prosthodontics residents, and the third consisted of prosthodontics specialists. The same procedure was applied with a CEREC Omnicam intraoral camera, which is a powder-free system. By using the two systems software parameters we were able to determine the scanning precision. Results: Homogeneity scores for Apollo Di regarding the spray layer was significantly thinner for all dental surfaces in the first group, while the second group had thinner coatings for buccal and distal surfaces. For the third group, the crown preparations were coated more homogeneously than the first two groups. The powder-free system CEREC Omnicam can, to a degree, mask the lack of experience in direct optical impressions by avoiding the poor quality coating, which can lead to defective marginal adaptation of definitive restoration. Conclusions: The dentist's lack of experience can be mitigated, and partially avoided, by using powder-free systems. At the same time, the dentist can give more time towards learning how to integrate computerized fabricated restoration into the practice. The commitment to training is a critical factor in the successful integration of the technology. In

  12. Decadal region-wide and glacier-wide mass balances derived from multi-temporal ASTER satellite digital elevation models. Validation over the Mont-Blanc area

    NASA Astrophysics Data System (ADS)

    Berthier, Etienne; Cabot, Vincent; Vincent, Christian; Six, Delphine

    2016-06-01

    Since 2000, a vast archive of stereo-images has been built by the Advanced Spaceborne Thermal Emission and Reflection (ASTER) satellite. Several studies already extracted glacier mass balances from multi-temporal ASTER digital elevation models (DEMs) but they lacked accurate independent data for validation. Here, we apply a linear regression to a time series of 3D-coregistered ASTER DEMs to estimate the rate of surface elevation changes (dh/dtASTER) and geodetic mass balances of Mont-Blanc glaciers (155 km²) between 2000 and 2014. Validation using field and spaceborne geodetic measurements reveals large errors at the individual pixel level (> 1 m a-1) and an accuracy of 0.2-0.3 m a-1 for dh/dtASTER averaged over areas larger than 1 km². For all Mont-Blanc glaciers, the ASTER region-wide mass balance (-1.05±0.37 m water equivalent (w.e.) a-1) agrees remarkably with the one measured using Spot5 and Pléiades DEMs (-1.06±0.23 m w.e. a-1) over their common 2003-2012 period. This multi-temporal ASTER DEM strategy leads to smaller errors than the simple differencing of two ASTER DEMs. By extrapolating dh/dtASTER to mid-February 2000, we infer a mean penetration depth of about 9±3 m for the C-band Shuttle Radar Topographic Mission (SRTM) radar signal, with a strong altitudinal dependency (range 0-12 m). This methodology thus reveals the regional pattern of glacier surface elevation changes and improves our knowledge of the penetration of the radar signal into snow and ice.

  13. Assessing the quality of Digital Elevation Models obtained from mini-Unmanned Aerial Vehicles for overland flow modelling in urban areas

    NASA Astrophysics Data System (ADS)

    Leitão, J. P.; Moy de Vitry, M.; Scheidegger, A.; Rieckermann, J.

    2015-06-01

    Precise and detailed Digital Elevation Models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of Unmanned Aerial Vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, fourteen UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch and (iv) weather conditions. In addition, we compared the best quality UAV DEM to a conventional Light Detection and Ranging (LiDAR)-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to LiDAR-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g., buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional LiDAR-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is their flexibility that enables more frequent

  14. Rediscovery and Revival of Analytical Refractometry for Protein Determination: Recombining Simplicity With Accuracy in the Digital Era.

    PubMed

    Anderle, Heinz; Weber, Alfred

    2016-03-01

    Among "vintage" methods of protein determination, quantitative analytical refractometry has received far less attention than well-established pharmacopoeial techniques based on protein nitrogen content, such as Dumas combustion (1831) and Kjeldahl digestion (1883). Protein determination by quantitative refractometry dates back to 1903 and has been extensively investigated and characterized in the following 30 years, but has since vanished into a few niche applications that may not require the degree of accuracy and precision essential for pharmaceutical analysis. However, because high-resolution and precision digital refractometers have replaced manual instruments, reducing time and resource consumption, the method appears particularly attractive from an economic, ergonomic, and environmental viewpoint. The sample solution can be measured without dilution or other preparation procedures than the separation of the protein-free matrix by ultrafiltration, which might even be omitted for a constant matrix and excipient composition. PMID:26886312

  15. Accuracy of conventional digital palpation and ultrasound of the cricothyroid membrane in obese women in labour.

    PubMed

    You-Ten, K E; Desai, D; Postonogova, T; Siddiqui, N

    2015-11-01

    Success of cricothyroidotomy depends on accurate identification of anatomical neck landmarks. Anaesthetists palpated the cricothyroid membrane of 28 obese and 28 non-obese women in labour (cut-off BMI 30 kg.m(-2) ) and marked the entry point for device insertion with an ultraviolet invisible pen. Ultrasonography was used to mark the midpoint of the cricothyroid membrane and the distance between the two marks was measured. The median (IQR [range]) distance between the two marks was significantly greater in the obese than the non-obese patients (5 (2-9.5 [0-34]) mm vs 1.8 (0.1-6 [0-15]) mm, respectively; p = 0.02). The cricothyroid membrane was accurately identified with digital palpation in only 39% (11/28) of obese compared with 71% (20/28) of non-obese patients (p = 0.03). Increased neck circumference in obese patients was significantly associated with inaccuracy in locating the cricothyroid membrane. Percutaneous identification of the cricothyroid membrane in obese women in labour was poor. Pre-procedural ultrasound may help improved the identification of neck landmarks for cricothyroidotomy. PMID:26186092

  16. A computational-grid based system for continental drainage network extraction using SRTM digital elevation models

    NASA Technical Reports Server (NTRS)

    Curkendall, David W.; Fielding, Eric J.; Pohl, Josef M.; Cheng, Tsan-Huei

    2003-01-01

    We describe a new effort for the computation of elevation derivatives using the Shuttle Radar Topography Mission (SRTM) results. Jet Propulsion Laboratory's (JPL) SRTM has produced a near global database of highly accurate elevation data. The scope of this database enables computing precise stream drainage maps and other derivatives on Continental scales. We describe a computing architecture for this computationally very complex task based on NASA's Information Power Grid (IPG), a distributed high performance computing network based on the GLOBUS infrastructure. The SRTM data characteristics and unique problems they present are discussed. A new algorithm for organizing the conventional extraction algorithms [1] into a cooperating parallel grid is presented as an essential component to adapt to the IPG computing structure. Preliminary results are presented for a Southern California test area, established for comparing SRTM and its results against those produced using the USGS National Elevation Data (NED) model.

  17. On the methods for the construction of seabed digital elevation models (using the example of the White Sea)

    NASA Astrophysics Data System (ADS)

    Nikiforov, S. L.; Koshel, S. M.; Frol, V. V.; Popov, O. E.; Levchenko, O. V.

    2015-03-01

    A digital elevation model (DEM) of the White Sea has been constructed based on navigational maps on different scales. The maps have been scanned, and their raster images have been processed. The isobaths have been vectorized, and attribute tables have been created. The vector layers have been transformed from map projections to geographical coordinates. The sheets have been edited and stapled. The geometry and attributes have been corrected. When constructing a DEM, it is important to choose an algorithm that will make it possible to maintain the bed forms expressed in the raw isobaths with maximum detail in the model. An original algorithm developed and implemented by the authors is used. It is based on the fast computation of the distances to the two nearest isobaths at different levels. Its main feature is the interpretation of the contour lines as linear vector objects. The comparison of the depths based on the constructed seabed DEM with depths measured during echo sounding in natural conditions shows their good agreement. Currently, not only the constructed seabed digital elevation model but also methodical and methodological bases of numerical simulations, including the new classification approaches to the terrain description, are relevant.

  18. Accuracy Assessment of Lidar-Derived Digital Terrain Model (dtm) with Different Slope and Canopy Cover in Tropical Forest Region

    NASA Astrophysics Data System (ADS)

    Salleh, M. R. M.; Ismail, Z.; Rahman, M. Z. A.

    2015-10-01

    Airborne Light Detection and Ranging (LiDAR) technology has been widely used recent years especially in generating high accuracy of Digital Terrain Model (DTM). High density and good quality of airborne LiDAR data promises a high quality of DTM. This study focussing on the analysing the error associated with the density of vegetation cover (canopy cover) and terrain slope in a LiDAR derived-DTM value in a tropical forest environment in Bentong, State of Pahang, Malaysia. Airborne LiDAR data were collected can be consider as low density captured by Reigl system mounted on an aircraft. The ground filtering procedure use adaptive triangulation irregular network (ATIN) algorithm technique in producing ground points. Next, the ground control points (GCPs) used in generating the reference DTM and these DTM was used for slope classification and the point clouds belong to non-ground are then used in determining the relative percentage of canopy cover. The results show that terrain slope has high correlation for both study area (0.993 and 0.870) with the RMSE of the LiDAR-derived DTM. This is similar to canopy cover where high value of correlation (0.989 and 0.924) obtained. This indicates that the accuracy of airborne LiDAR-derived DTM is significantly affected by terrain slope and canopy caver of study area.

  19. A computer simulation study comparing lesion detection accuracy with digital mammography, breast tomosynthesis, and cone-beam CT breast imaging

    SciTech Connect

    Gong Xing; Glick, Stephen J.; Liu, Bob; Vedula, Aruna A.; Thacker, Samta

    2006-04-15

    Although conventional mammography is currently the best modality to detect early breast cancer, it is limited in that the recorded image represents the superposition of a three-dimensional (3D) object onto a 2D plane. Recently, two promising approaches for 3D volumetric breast imaging have been proposed, breast tomosynthesis (BT) and CT breast imaging (CTBI). To investigate possible improvements in lesion detection accuracy with either breast tomosynthesis or CT breast imaging as compared to digital mammography (DM), a computer simulation study was conducted using simulated lesions embedded into a structured 3D breast model. The computer simulation realistically modeled x-ray transport through a breast model, as well as the signal and noise propagation through a CsI based flat-panel imager. Polyenergetic x-ray spectra of Mo/Mo 28 kVp for digital mammography, Mo/Rh 28 kVp for BT, and W/Ce 50 kVp for CTBI were modeled. For the CTBI simulation, the intensity of the x-ray spectra for each projection view was determined so as to provide a total average glandular dose of 4 mGy, which is approximately equivalent to that given in conventional two-view screening mammography. The same total dose was modeled for both the DM and BT simulations. Irregular lesions were simulated by using a stochastic growth algorithm providing lesions with an effective diameter of 5 mm. Breast tissue was simulated by generating an ensemble of backgrounds with a power law spectrum, with the composition of 50% fibroglandular and 50% adipose tissue. To evaluate lesion detection accuracy, a receiver operating characteristic (ROC) study was performed with five observers reading an ensemble of images for each case. The average area under the ROC curves (A{sub z}) was 0.76 for DM, 0.93 for BT, and 0.94 for CTBI. Results indicated that for the same dose, a 5 mm lesion embedded in a structured breast phantom was detected by the two volumetric breast imaging systems, BT and CTBI, with statistically

  20. Accuracy of food portion size estimation from digital pictures acquired by a chest-worn camera

    PubMed Central

    Jia, Wenyan; Chen, Hsin-Chen; Yue, Yaofeng; Li, Zhaoxin; Fernstrom, John; Bai, Yicheng; Li, Chengliu; Sun, Mingui

    2014-01-01

    Objective Accurate estimation of food portion size is of paramount importance in dietary studies. We have developed a small, chest-worn electronic device called eButton which automatically takes pictures of consumed foods for objective dietary assessment. From the acquired pictures, the food portion size can be calculated semi-automatically with the help of computer software. The aim of the present study is to evaluate the accuracy of the calculated food portion size (volumes) from eButton pictures. Design Participants wore an eButton during their lunch. The volume of food in each eButton picture was calculated using software. For comparison, three raters estimated the food volume by viewing the same picture. The actual volume was determined by physical measurement using seed displacement. Setting Dining room and offices in a research laboratory. Subjects Seven lab member volunteers. Results Images of 100 food samples (fifty Western and fifty Asian foods) were collected and each food volume was estimated from these images using software. The mean relative error between the estimated volume and the actual volume over all the samples was −2.8 % (95 % CI −6.8 %, 1.2%) with SD of 20.4 %. For eighty-five samples, the food volumes determined by computer differed by no more than 30 % from the results of actual physical measurements. When the volume estimates by the computer and raters were compared, the computer estimates showed much less bias and variability. Conclusions From the same eButton pictures, the computer-based method provides more objective and accurate estimates of food volume than the visual estimation method. PMID:24476848

  1. Optimization of the resolution of remotely sensed digital elevation model to facilitate the simulation and spatial propagation of flood events in flat areas

    NASA Astrophysics Data System (ADS)

    Karapetsas, Nikolaos; Skoulikaris, Charalampos; Katsogiannos, Fotis; Zalidis, George; Alexandridis, Thomas

    2013-04-01

    The use of satellite remote sensing products, such as Digital Elevation Models (DEMs), under specific computational interfaces of Geographic Information Systems (GIS) has fostered and facilitated the acquisition of data on specific hydrologic features, such as slope, flow direction and flow accumulation, which are crucial inputs to hydrology or hydraulic models at the river basin scale. However, even though DEMs of different resolution varying from a few km up to 20m are freely available for the European continent, these remotely sensed elevation data are rather coarse in cases where large flat areas are dominant inside a watershed, resulting in an unsatisfactory representation of the terrain characteristics. This scientific work aims at implementing a combing interpolation technique for the amelioration of the analysis of a DEM in order to be used as the input ground model to a hydraulic model for the assessment of potential flood events propagation in plains. More specifically, the second version of the ASTER Global Digital Elevation Model (GDEM2), which has an overall accuracy of around 20 meters, was interpolated with a vast number of aerial control points available from the Hellenic Mapping and Cadastral Organization (HMCO). The uncertainty that was inherent in both the available datasets (ASTER & HMCO) and the appearance of uncorrelated errors and artifacts was minimized by incorporating geostatistical filtering. The resolution of the produced DEM was approximately 10 meters and its validation was conducted with the use of an external dataset of 220 geodetic survey points. The derived DEM was then used as an input to the hydraulic model InfoWorks RS, whose operation is based on the relief characteristics contained in the ground model, for defining, in an automated way, the cross section parameters and simulating the flood spatial distribution. The plain of Serres, which is located in the downstream part of the Struma/Strymon transboundary river basin shared

  2. 3D-geological structures with digital elevation models using GPU programming

    NASA Astrophysics Data System (ADS)

    Mateo Lázaro, Jesús; Sánchez Navarro, José Ángel; García Gil, Alejandro; Edo Romero, Vanesa

    2014-09-01

    We present an application that visualises three-dimensional geological structures with digital terrain models. The three-dimensional structures are displayed as their intersections with two-dimensional surfaces that may be defined analytically (e.g., sections) or with grid meshes in the case of irregular surfaces such as the digital terrain models. The process begins with classic techniques of terrain visualisation using hypsometric shading with textures. Then, geometric transformations that are easily conceived and programmed are added, thus representing the three-dimensional structures with their location and orientation. Functions of three variables are used to define the geological structures, and data from digital terrain models are used as one of the variables. This provides a simple source code and results in a short calculation time. Additionally, the process of generating new textures can be performed by a Graphics Processing Unit (GPU), thereby making real-time processing very effective and providing the possibility of displaying the simulation of geological structures in motion.

  3. Landslide-susceptibility analysis using light detection and ranging-derived digital elevation models and logistic regression models: a case study in Mizunami City, Japan

    NASA Astrophysics Data System (ADS)

    Wang, Liang-Jie; Sawada, Kazuhide; Moriguchi, Shuji

    2013-01-01

    To mitigate the damage caused by landslide disasters, different mathematical models have been applied to predict landslide spatial distribution characteristics. Although some researchers have achieved excellent results around the world, few studies take the spatial resolution of the database into account. Four types of digital elevation model (DEM) ranging from 2 to 20 m derived from light detection and ranging technology to analyze landslide susceptibility in Mizunami City, Gifu Prefecture, Japan, are presented. Fifteen landslide-causative factors are considered using a logistic-regression approach to create models for landslide potential analysis. Pre-existing landslide bodies are used to evaluate the performance of the four models. The results revealed that the 20-m model had the highest classification accuracy (71.9%), whereas the 2-m model had the lowest value (68.7%). In the 2-m model, 89.4% of the landslide bodies fit in the medium to very high categories. For the 20-m model, only 83.3% of the landslide bodies were concentrated in the medium to very high classes. When the cell size decreases from 20 to 2 m, the area under the relative operative characteristic increases from 0.68 to 0.77. Therefore, higher-resolution DEMs would provide better results for landslide-susceptibility mapping.

  4. Semi-automated Technique to Extract Boundary of Valley/mountain Glaciers using Glacio-morphological Information from Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Chakraborty, M.; Panigrahy, S.; Kundu, S.

    2014-11-01

    A semi automated technique has been developed to extract the spatial extension of valleys and mountain glaciers. The method is based on morphological properties of glaciated area extracted from Digital Elevation Model (DEM). Identification of glacial boundary based on spectral information from optical remote sensing imageries produces errors due to misclassification of debris-covered ablation area with surrounding rocky terrain and perennially snow-covered slope with debris free glaciated area. Elevation information DEM of Shuttle Radar Topography Mission (SRTM), CartoDEM and ASTER DEM have been used. A part of western Himalayas was selected as the study area that contains large glaciated basins, e.g., Bhagirathi, Baspa, Chandra basin. First order derivatives, slope aspect, and second order derivatives like, profile and plan curvatures are computed from the DEM. The derivatives are used to quantify and characterise the morphological aspects of the glaciated area and used in the decision rule models to generate the glacial boundaries. The ridge lines of the study areas are also generated from the plan curvature and used in the model to delineate the catchments areas of the glaciers. The slope based boundary is checked for consistency with the boundary from profile curvature and combined manually to generate the final glacier boundary. Area and length under the derived boundary of Gangotri glacier of Bhagirathi catchments are 90.25 sq km and 30.5 km. The result has been checked with high resolution optical data. This objective approach is important to delineate glaciated area, measure the length, width and area and generate glacial hypsometry, concentration factor of the glaciers. Accuracy of the result depends up on the quality of the DEM. DEM generated by SAR interferometric technique is found superior over DEM generated from other interpolation techniques.

  5. A comparison of lesion detection accuracy using digital mammography and flat-panel CT breast imaging (Honorable Mention Poster Award)

    NASA Astrophysics Data System (ADS)

    Gong, Xing; Vedula, Aruna A.; Thacker, Samta; Glick, Stephen J.

    2005-04-01

    Although conventional mammography is currently the best modality to detect early breast cancer, it is limited in that the recorded image represents the superposition of a 3D object onto a 2D plane. As an alternative, cone-beam CT breast imaging with a CsI based flat-panel imager (CTBI) has been proposed with the ability to provide 3D visualization of breast tissue. To investigate possible improvements in lesion detection accuracy using CTBI over digital mammography (DM), a computer simulation study was conducted using simulated lesions embedded into a structured 3D breast model. The computer simulation realistically modeled x-ray transport through a breast model, as well as the signal and noise propagation through the flat-panel imager. Polyenergetic x-ray spectra of W/Al 50 kVp for CTBI and Mo/Mo 28 kVp for DM were modeled. For the CTBI simulation, the intensity of the x-ray spectra for each projection view was determined so as to provide a total mean glandular dose (MGD) of 4 mGy, which is approximately equivalent to that given in a conventional two-view screening mammography study. Since only one DM view was investigated here, the intensity of the DM x-ray spectra was defined to give 2 mGy MGD. Irregular lesions were simulated by using a stochastic growth algorithm providing lesions with an effective diameter of 5 mm. Breast tissue was simulated by generating an ensemble of backgrounds with a power law spectrum. To evaluate lesion detection accuracy, a receiver operating characteristic (ROC) study was performed with 4 observers reading an ensemble of images for each case. The average area under the ROC curves (Az) was 0.94 for CTBI, and 0.81 for DM. Results indicate that a 5 mm lesion embedded in a structured breast phantom can be detected by CT breast imaging with statistically significant higher confidence than with digital mammography.

  6. A fast topographic characterization of seismic station locations in Iran through integrated use of digital elevation models and GIS

    NASA Astrophysics Data System (ADS)

    Karimzadeh, Sadra; Miyajima, Masakatsu; Kamel, Batoul; Pessina, Vera

    2015-10-01

    We present topographic slope positions of seismic stations within four independent networks (IGUT, IIEES, GSI, and BHRC) in Iran through integrated use of digital elevation models and GIS. Since topographic amplification factor (TAF) due to ground surface irregularity could be one of the reasons of earthquake wave amplification and unexpected damage of structures located on the top of ridges in many previous studies, the ridge stations in the study area are recognized using topographic position index (TPI) as a spatial-based scale-dependent approach that helps in classification of topographic positions. We also present the correlation between local topographic positions and V {/s 30} along with Voronoi tiles of two networks (IGUT and IIEES). The obtained results can be profitably used in seismology to establish homogeneous subnetworks based on Voronoi tiles with precise feedback and in the formulation of new ground motion prediction equations with respect to topographic position and topographic amplification factor.

  7. An automated approach for extracting Barrier Island morphology from digital elevation models

    NASA Astrophysics Data System (ADS)

    Wernette, Phillipe; Houser, Chris; Bishop, Michael P.

    2016-06-01

    The response and recovery of a barrier island to extreme storms depends on the elevation of the dune base and crest, both of which can vary considerably alongshore and through time. Quantifying the response to and recovery from storms requires that we can first identify and differentiate the dune(s) from the beach and back-barrier, which in turn depends on accurate identification and delineation of the dune toe, crest and heel. The purpose of this paper is to introduce a multi-scale automated approach for extracting beach, dune (dune toe, dune crest and dune heel), and barrier island morphology. The automated approach introduced here extracts the shoreline and back-barrier shoreline based on elevation thresholds, and extracts the dune toe, dune crest and dune heel based on the average relative relief (RR) across multiple spatial scales of analysis. The multi-scale automated RR approach to extracting dune toe, dune crest, and dune heel based upon relative relief is more objective than traditional approaches because every pixel is analyzed across multiple computational scales and the identification of features is based on the calculated RR values. The RR approach out-performed contemporary approaches and represents a fast objective means to define important beach and dune features for predicting barrier island response to storms. The RR method also does not require that the dune toe, crest, or heel are spatially continuous, which is important because dune morphology is likely naturally variable alongshore.

  8. Accuracy of direct digital radiography for detecting occlusal caries in primary teeth compared with conventional radiography and visual inspection: an in vitro study

    PubMed Central

    Dias da Silva, P R; Martins Marques, M; Steagall, W; Medeiros Mendes, F; Lascala, C A

    2010-01-01

    Objectives The diagnosis of caries lesions is still a matter of concern in dentistry. The diagnosis of dental caries by digital radiography has a number of advantages over conventional radiography; however, this method has not been explored fully in the field of paediatric dentistry. This in vitro research evaluated the accuracy of direct digital radiography compared with visual inspection and conventional radiography in the diagnosis of occlusal caries lesions in primary molars. Methods 50 molars were selected and evaluated under standardized conditions by 2 previously calibrated examiners according to 3 diagnostic methods (visual inspection, conventional radiography and direct digital radiography). Direct digital radiographs were obtained with the Dixi3 system (Planmeca, Helsinki, Finland) and the conventional radiographs with InSight film (Kodak Eastman Co., Rochester, NY). The images were scored and a reference standard was obtained histologically. The interexaminer reliability was calculated using Cohen's kappa test and the specificity, sensitivity and accuracy of the methods were calculated. Results Examiner reliability was good. For lesions limited to the enamel, visual inspection showed significantly higher sensitivity and accuracy than both radiographic methods, but no significant difference was found in specificity. For teeth with dentinal caries, no significant differences were found for any parameter when comparing visual and radiographic evaluation. Conclusions Although less accurate than the visual method for detecting caries lesions confined to the enamel, the direct digital radiographic method is as effective as conventional radiographic examination and visual inspection of primary teeth with occlusal caries when the dentine is involved. PMID:20729186

  9. Extracting topographic structure from digital elevation data for geographic information-system analysis

    USGS Publications Warehouse

    Jenson, Susan K.; Domingue, Julia O.

    1988-01-01

    The first phase of analysis is a conditioning phase that generates three data sets: the original OEM with depressions filled, a data set indicating the flow direction for each cell, and a flow accumulation data set in which each cell receives a value equal to the total number of cells that drain to it. The original OEM and these three derivative data sets can then be processed in a variety of ways to optionally delineate drainage networks, overland paths, watersheds for userspecified locations, sub-watersheds for the major tributaries of a drainage network, or pour point linkages between watersheds. The computer-generated drainage lines and watershed polygons and the pour point linkage information can be transferred to vector-based geographic information systems for futher analysis. Comparisons between these computergenerated features and their manually delineated counterparts generally show close agreement, indicating that these software tools will save analyst time spent in manual interpretation and digitizing.

  10. Accuracy, precision and response time of consumer fork, remote digital probe and disposable indicator thermometers for cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nine different commercially available instant-read consumer thermometers (forks, remotes, digital probe and disposable color change indicators) were tested for accuracy and precision compared to a calibrated thermocouple in 80 percent and 90 percent lean ground beef patties, and boneless and bone-in...

  11. Pharmacokinetic digital phantoms for accuracy assessment of image-based dosimetry in 177Lu-DOTATATE peptide receptor radionuclide therapy

    NASA Astrophysics Data System (ADS)

    Brolin, Gustav; Gustafsson, Johan; Ljungberg, Michael; Sjögreen Gleisner, Katarina

    2015-08-01

    Patient-specific image-based dosimetry is considered to be a useful tool to limit toxicity associated with peptide receptor radionuclide therapy (PRRT). To facilitate the establishment and reliability of absorbed-dose response relationships, it is essential to assess the accuracy of dosimetry in clinically realistic scenarios. To this end, we developed pharmacokinetic digital phantoms corresponding to patients treated with 177Lu-DOTATATE. Three individual voxel phantoms from the XCAT population were generated and assigned a dynamic activity distribution based on a compartment model for 177Lu-DOTATATE, designed specifically for this purpose. The compartment model was fitted to time-activity data from 10 patients, primarily acquired using quantitative scintillation camera imaging. S values for all phantom source-target combinations were calculated based on Monte-Carlo simulations. Combining the S values and time-activity curves, reference values of the absorbed dose to the phantom kidneys, liver, spleen, tumours and whole-body were calculated. The phantoms were used in a virtual dosimetry study, using Monte-Carlo simulated gamma-camera images and conventional methods for absorbed-dose calculations. The characteristics of the SPECT and WB planar images were found to well represent those of real patient images, capturing the difficulties present in image-based dosimetry. The phantoms are expected to be useful for further studies and optimisation of clinical dosimetry in 177Lu PRRT.

  12. Research on high-accuracy two-dimensional digital image correlation hardware measurement systems used in the engineering practice

    NASA Astrophysics Data System (ADS)

    Chen, Guang; Ding, Keqin; Feng, Qibo

    2014-11-01

    Digital image correlation (DIC) method is a rapid development of photomechanics technology. The basic principle of the method is calculated the correlation between before and after deformation of the specimen surface speckle images, which is used to determine displacement and deformation. DIC measurement system includes hardware and software system. The former is the speckle image acquisition system, the latter are speckle image analysis algorithm and implementation procedures. Because the software analysis algorithm can achieve sub-pixel accuracy or even more, most of scholars have focused on the speckle image analysis algorithms. The system performance caused by the composition of hardware system has been less introduced. The hardware system mainly included the camera, lenses, lighting and other components. If hardware system is not perfect and stable, it will bring hundreds or even thousands of micro strain measurement error. These unfavorable factors make 2D-DIC inaccurate in small deformation tests. To some extent, it limits the application of 2D-DIC in the engineering practice. This paper analyzed that the various components of DIC hardware system impacted on the system performance, It was given that how to reasonably select the various components in the typical cases, as well as involved that the selection of 2D-DIC measurement system is applied to the actual engineering measurements in high temperature environment. These can provide support that 2D-DIC measurement system is better applied to the engineering practice.

  13. Pharmacokinetic digital phantoms for accuracy assessment of image-based dosimetry in (177)Lu-DOTATATE peptide receptor radionuclide therapy.

    PubMed

    Brolin, Gustav; Gustafsson, Johan; Ljungberg, Michael; Gleisner, Katarina Sjögreen

    2015-08-01

    Patient-specific image-based dosimetry is considered to be a useful tool to limit toxicity associated with peptide receptor radionuclide therapy (PRRT). To facilitate the establishment and reliability of absorbed-dose response relationships, it is essential to assess the accuracy of dosimetry in clinically realistic scenarios. To this end, we developed pharmacokinetic digital phantoms corresponding to patients treated with (177)Lu-DOTATATE. Three individual voxel phantoms from the XCAT population were generated and assigned a dynamic activity distribution based on a compartment model for (177)Lu-DOTATATE, designed specifically for this purpose. The compartment model was fitted to time-activity data from 10 patients, primarily acquired using quantitative scintillation camera imaging. S values for all phantom source-target combinations were calculated based on Monte-Carlo simulations. Combining the S values and time-activity curves, reference values of the absorbed dose to the phantom kidneys, liver, spleen, tumours and whole-body were calculated. The phantoms were used in a virtual dosimetry study, using Monte-Carlo simulated gamma-camera images and conventional methods for absorbed-dose calculations. The characteristics of the SPECT and WB planar images were found to well represent those of real patient images, capturing the difficulties present in image-based dosimetry. The phantoms are expected to be useful for further studies and optimisation of clinical dosimetry in (177)Lu PRRT. PMID:26215085

  14. A Digital Elevation Model of the Greenland Ice Sheet based on Envisat and CryoSat-2 Radar Altimetry

    NASA Astrophysics Data System (ADS)

    Levinsen, J. F.; Smith, B. E.; Sandberg Sørensen, L.; Khvorostovsky, K.; Forsberg, R.

    2014-12-01

    With the launch of the first radar altimeter by ESA in 1992, more than two decades of radar altimetry data are now available. Therefore, one goal of ESA's Ice Sheet Climate Change Initiative is the estimation of surface elevation changes of the Greenland Ice Sheet (GrIS) based on ERS-1, -2, Envisat, CryoSat-2, and, in the longer term, Sentinel-3 data. This will create a data record from 1992 until present date. In addition to elevation-change records, such data can be processed to produce digital elevation models, or DEMs, of the ice sheets. The DEMs can be used to correct radar altimetry data for slope-induced errors resulting from the large footprint (e.g. 2-10 km for Envisat vs. 60 m for ICESat laser altimetry) or to correct for the underlying surface topography when applying the repeat-track method. DEMs also provide key information in e.g. SAR remote sensing of ice velocities to remove the interferograms' topographic signal or in regional climate modeling. This work focuses on the development of a GrIS DEM from Envisat and CryoSat-2 altimetry, corrected with temporally and spatially coincident NASA ICESat, ATM, and LVIS laser data. The spatial resolution is 2 x 2 km and the reference year 2010. It is based on 2009 and 2010 data, the 2009 data adjusted to 2010 by accounting for the intermediate elevation changes. This increases the spatial data coverage and reduces data errors. The GIMP DEM has been corrected for negative elevations and errors in the north, and used to constrain the final DEM. The recently acquired observations and increased data coverage give a strong advantage to this DEM relative to previous models, based on lower-resolution, more temporally scattered data (e.g. a decade of observations or only ICESat data, limited to three annual 35-day acquisition periods). Furthermore, as surface changes occur continuously, an up-to-date DEM is necessary to correctly constrain the observations, thereby ensuring an accurate change detection or modeling

  15. A digital elevation model of the Greenland Ice Sheet derived from combined laser and radar altimetry data

    NASA Astrophysics Data System (ADS)

    Fredenslund Levinsen, Joanna; Smith, Ben; Sørensen, Louise S.; Forsberg, René

    2014-05-01

    When estimating elevation changes of ice-covered surfaces from radar altimetry, it is important to correct for slope-induced errors. They cause the reflecting point of the pulse to move up-slope and thus return estimates in the wrong coordinates. Slope-induced errors can be corrected for by introducing a Digital Elevation Model (DEM). In this work, such a DEM is developed for the Greenland Ice Sheet using a combination of Envisat radar and ICESat laser altimetry. If time permits, CryoSat radar altimetry will be included as well. The reference year is 2010 and the spatial resolution 2.5 x 2.5 km. This is in accordance with the results obtained in the ESA Ice Sheets CCI project showing that a 5 x 5 km grid spacing is reasonable for ice sheet-wide change detection (Levinsen et al., 2013). Separate DEMs will be created for the given data sets, and the geostatistical spatial interpolation method collocation will be used to merge them, thus adjusting for potential inter-satellite biases. The final DEM is validated with temporally and spatially agreeing airborne lidar data acquired in the NASA IceBridge and ESA CryoVex campaigns. The motivation for developing a new DEM is based on 1) large surface changes presently being observed, and mainly in margin regions, hence necessitating updated topography maps for accurately deriving and correcting surface elevation changes, and 2) although radar altimetry is subject to surface penetration of the signal into the snowpack, data is acquired continuously in time. This is not the case with e.g. ICESat, where laser altimetry data were obtained in periods of active lasers, i.e. three times a year with a 35-day repeat track. Previous DEMs e.g. have 2007 as the nominal reference year, or they are built merely from ICESat data. These have elevation errors as small as 10 cm, which is lower than for Envisat and CryoSat. The advantage of an updated DEM consisting of combined radar and laser altimetry therefore is the possibility of

  16. Effects of Orbit and Pointing Geometry of a Spaceborne Formation for Monostatic-Bistatic Radargrammetry on Terrain Elevation Measurement Accuracy

    PubMed Central

    Renga, Alfredo; Moccia, Antonio

    2009-01-01

    During the last decade a methodology for the reconstruction of surface relief by Synthetic Aperture Radar (SAR) measurements – SAR interferometry – has become a standard. Different techniques developed before, such as stereo-radargrammetry, have been experienced from space only in very limiting geometries and time series, and, hence, branded as less accurate. However, novel formation flying configurations achievable by modern spacecraft allow fulfillment of SAR missions able to produce pairs of monostatic-bistatic images gathered simultaneously, with programmed looking angles. Hence it is possible to achieve large antenna separations, adequate for exploiting to the utmost the stereoscopic effect, and to make negligible time decorrelation, a strong liming factor for repeat-pass stereo-radargrammetric techniques. This paper reports on design of a monostatic-bistatic mission, in terms of orbit and pointing geometry, and taking into account present generation SAR and technology for accurate relative navigation. Performances of different methods for monostatic-bistatic stereo-radargrammetry are then evaluated, showing the possibility to determine the local surface relief with a metric accuracy over a wide range of Earth latitudes. PMID:22389594

  17. Use of TOPSAR digital elevation data to determine the 3-dimensional shape of an alluvial fan

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.

    1995-01-01

    Landforms in arid regions record the interplay between tectonic forces and climate. Alluvial fans are a common landform in desert regions where the rate of uplift is greater than weathering or sedimentation. Changes in uplift rate or climatic conditions can lead to isolation of the currently forming fan surface through entrenchment and construction of another fan either further from the mountain front (decreased uplift or increased runoff) or closer to the mountain front (increased uplift or decreased runoff). Thus, many alluvial fans are made up of a mosaic of fan units of different age, some older than 1 million years. For this reason, determination of the stages of fan evolution can lead to a history of uplift and runoff. In an attempt to separate the effects of tectonic (uplift) and climatic (weathering, runoff, sedimentation) processes on the shapes of alluvial fan units, a modified conic equation developed by Troeh (1965) was fitted to TOPSAR digital topographic data for the Trail Canyon alluvial fan in Death Valley, California. This allows parameters for the apex position, slope, and radial curvature to be compared with unit age.

  18. Determination of fractal dimensions of digital elevation models for the watershed of Lake Jocasse, South Carolina

    SciTech Connect

    Wagenseil, R.

    1991-01-01

    There are persistent difficulties in monitoring nonpoint source pollution and in the related field of hydrology. The problems stem from variations in spatial distribution which are poorly understood and difficult to model with established methods. Two recent developments may offer a solution, if they are combined with care. The first development is the increasing capability of computer mapping, called geographic information systems (GIS). These systems can store, retrieve, and manipulate data with an explicit spatial structure. The second development is the field of fractal mathematics. Fractal mathematics includes geometric sets which have simple descriptions, despite complex appearances. One family of such fractal sets are the Brownian surfaces, which capture many of the qualities of natural land surfaces in a simple statistical model. Up until now, the Brownian models have been constrained by the assumption that the same statistical relationship holds over the entire surface. This is called the constraint of stationarity. The need to study how the landscape differs by location leads to relaxing the constraint of stationarity. This, in turn, causes some profound changes in the model. A special computer program applies the new model to a set of three-dimensional digital maps of natural terrain (DEMs). The model performs well, and highlights differences in landforms. This suggests several new approaches to spatial variation.

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

    NASA Astrophysics Data System (ADS)

    Markwick, P. J.

    2001-12-01

    The past surface relief of the Earth is an essential boundary condition for computer-based atmosphere and ocean modeling. It also provides the geographic context for understanding surface processes and biotic distributions and interactions. However, with increased model resolution and the addition of vegetation, soil (weathering) and chemical modules, there is now a need for more robust, detailed paleo-topographies and bathymetries that are fully integrated with the processes being modeled, especially the hydrological system (hydrologically correct). Here I present a new GIS-based, hydrologically correct, paleo-DEM for the Maastrichtian (Late Cretaceous). This project was initiated in 1995 while the author was a graduate at the University of Chicago using the plate reconstructions of Rowley (1995, unpublished). The Maastrichtian paleogeography used in this study is one of a series of 27 global maps, representing the Cretaceous and Cenozoic, being compiled simultaneously to ensure continuity between each time interval. Each map is generated at a scale of 1:30 million in ArcView GIS and ArcInfo, using data from the author's own databases of lithologic, tectonic and fossil information, the lithologic databases of the Paleogeographic Atlas Project (The University of Chicago), a survey of published literature, and DSDP / ODP data. Interpretations of elevation are derived following the methods outlined in Ziegler et al (1985), an understanding of the tectonic regime and evolution of each geographic feature, and the age-depth relationship for the ocean. The Maastrichtian has been completed first to provide the boundary conditions for a coupled atmosphere-ocean experiment. The hydrologically correct global DEM was derived using the elevation contours from the paleogeography and the suite of hydrological tools now available in ArcInfo GRID. The DEM has been constrained by defining areas of paleo-internal drainage, paleo-river mouths and known paleo-river courses. When

  20. Drainage networks and watersheds delineation derived from TIN-based digital elevation models

    NASA Astrophysics Data System (ADS)

    Freitas, Henrique Rennó de Azeredo; Freitas, Corina da Costa; Rosim, Sergio; Oliveira, João Ricardo de Freitas

    2016-07-01

    Triangulated Irregular Networks (TIN) efficiently define terrain models from which drainage networks and watersheds can be extracted with important applications in hydrology. In this work, the TIN model is represented by a constrained Delaunay triangulation obtained from contour lines and sampled points. Paths of steepest descent calculated from the TIN are connected by processing the triangles according to an associated priority, then forming a drainage graph structure proposed to generate drainage networks from accumulated flows. Major problems such as flat areas and pits that create inconsistencies in the terrain model and discontinuities in flows are removed with procedures that interpolate the elevation values of particular points on the TIN. Drainage networks are defined by arbitrary threshold values, and their associated watersheds and subwatersheds are then delineated. TIN results are qualitatively and quantitatively compared to an available reference drainage network, and also to regular grid results generated with the TerraHidro system. The drainage networks automatically obtained from the drainage graph highly agree to the main courses of water on the terrain, indicating that the TIN is an attractive alternative terrain model for hydrological purposes, and that the proposed drainage graph can be used for the automatic extraction of drainage networks that are consistent with real-world hydrological patterns.

  1. Deep Neural Networks for Above-Ground Detection in Very High Spatial Resolution Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Marmanis, D.; Adam, F.; Datcu, M.; Esch, T.; Stilla, U.

    2015-03-01

    Deep Learning techniques have lately received increased attention for achieving state-of-the-art results in many classification problems, including various vision tasks. In this work, we implement a Deep Learning technique for classifying above-ground objects within urban environments by using a Multilayer Perceptron model and VHSR DEM data. In this context, we propose a novel method called M-ramp which significantly improves the classifier's estimations by neglecting artefacts, minimizing convergence time and improving overall accuracy. We support the importance of using the M-ramp model in DEM classification by conducting a set of experiments with both quantitative and qualitative results. Precisely, we initially train our algorithm with random DEM tiles and their respective point-labels, considering less than 0.1% over the test area, depicting the city center of Munich (25 km2). Furthermore with no additional training, we classify two much larger unseen extents of the greater Munich area (424 km2) and Dongying city, China (257 km2) and evaluate their respective results for proving knowledge-transferability. Through the use of M-ramp, we were able to accelerate the convergence by a magnitude of 8 and achieve a decrease in above-ground relative error by 24.8% and 5.5% over the different datasets.

  2. Digital Elevation Models of Differences (DODs): implementation for assessment of soil erosion on recreational trails.

    NASA Astrophysics Data System (ADS)

    Tomczyk, A.; Ewertowski, M.

    2012-04-01

    Introduction: Tourism's negative impact on protected mountain areas is one of the main concerns for land managers. The impact on the natural environment is the most visible at locations of highly concentrated activities such as tourist trails, campsites, etc. The main indicators of the tourist trail degradation are vegetation loss (trampling of vegetation cover), change of vegetation type and composition, trail widening, muddiness and soil erosion. The last one is especially significant, since it can cause serious transformation to the land surface. Such undesirable changes cannot be repaired without high-cost management activities and in some cases they can made the trails difficult and unsafe to use. The scientific understanding of soil erosion in relation to human impact can be useful for a more effective management of protected natural areas (PNAs). The main objectives of this study are: (1) to analyse the spatial aspect of surface changes in microscale; (2) to quantify precisely the short-term rate of soil loss and deposition. Study area and methods: To gather precise and objective elevation data, an electronic total station with microprism were used. Measurements were taken in 12 test fields, located in two protected natural areas in south Poland: the Gorce National Park and Popradzki Landscape Park. The measuring places were located on the trails characterized by different slope, types of vegetation, and types of use. Each of the test fields was established by four special marks, firmly dug into the ground. Five sessions of measurement was carried out for each test field: August/September 2008, June 2009, August/September 2009, June 2010, August/September 2010. Generated DEMs (based on field surveys' results) were subtracted from each other, and thus we obtained a spatial picture of the loss or deposition of soil in each cell of the model, from one survey session to another. The subtraction of DEMs from subsequent time periods (DEMs of Difference - DoDs gave

  3. Channel profiles around Himalayan river anticlines: Constraints on their formation from digital elevation model analysis

    NASA Astrophysics Data System (ADS)

    Robl, JöRg; Stüwe, Kurt; Hergarten, Stefan

    2008-06-01

    We present a comparison between measured and numerically modeled channel profiles of rivers in two important drainage basins of Central Nepal: the Kali-Gandaki and the Arun drainage basins. Modeled channel profiles are based on a simple stream power approach using best fit exponents defining the nonlinearities in the relative contributions of local channel gradient and water flux to erosion rate. Our analysis of the stream power in the whole river network confirms the work of other authors that a 50- to 80-km-wide zone, roughly corresponding to the High Himalayan topography, is subjected to rapid rock uplift. We suggest a model where the uplift of this zone is driven by erosion and isostatic response, so that centers of maximum uplift are located within the main channels of the north-south draining rivers. We also suggest that the rate of uplift slows down with increasing distance to the main channels. Such a spatial distribution of the uplift leads ultimately to the formation of river anticlines as observed along all major Himalayan rivers. We propose that the formation of river anticlines along south draining Himalayan rivers was accelerated by a sudden increase of the drainage area and discharge when the rivers captured orogen-parallel drainages on the north side of the range. This may follow successive headward cutting into the Tibetan Plateau. The model is confirmed by differences between main channels and east-west running tributaries. Time-dependent numerical models predict that capture events cause strongly elevated erosion rates in the main channel.

  4. Effect of optical digitizer selection on the application accuracy of a surgical localization system-a quantitative comparison between the OPTOTRAK and flashpoint tracking systems

    NASA Technical Reports Server (NTRS)

    Li, Q.; Zamorano, L.; Jiang, Z.; Gong, J. X.; Pandya, A.; Perez, R.; Diaz, F.

    1999-01-01

    Application accuracy is a crucial factor for stereotactic surgical localization systems, in which space digitization camera systems are one of the most critical components. In this study we compared the effect of the OPTOTRAK 3020 space digitization system and the FlashPoint Model 3000 and 5000 3D digitizer systems on the application accuracy for interactive localization of intracranial lesions. A phantom was mounted with several implantable frameless markers which were randomly distributed on its surface. The target point was digitized and the coordinates were recorded and compared with reference points. The differences from the reference points represented the deviation from the "true point." The root mean square (RMS) was calculated to show the differences, and a paired t-test was used to analyze the results. The results with the phantom showed that, for 1-mm sections of CT scans, the RMS was 0.76 +/- 0. 54 mm for the OPTOTRAK system, 1.23 +/- 0.53 mm for the FlashPoint Model 3000 3D digitizer system, and 1.00 +/- 0.42 mm for the FlashPoint Model 5000 system. These preliminary results showed that there is no significant difference between the three tracking systems, and, from the quality point of view, they can all be used for image-guided surgery procedures. Copyright 1999 Wiley-Liss, Inc.

  5. Delineation of Flood Prone Areas using Digital Elevation Models: Scale Dependence

    NASA Astrophysics Data System (ADS)

    di Leo, M.; Manfreda, S.; Sole, A.; Fiorentino, M.

    2009-04-01

    The delineation of the areas subject to flood inundations raises complex problems regarding the definition of hydrological forcing and the parametrization of models for flood wave propagation (e.g., Horritt & Bates, 2000, 2002). The increasing availability of new technologies for the measurement of surface elevation (eg GPS, SAR interferometry, radar and laser altimetry) led to an increase in the attraction of DEM-based procedures for the delineation of floodplains. In recent years, much effort has gone into the identification of flood prone areas through the use of hydrological and hydraulic studies carried out by River Basin Authorities (public institutions dedicated to river basins management). These studies are generally based on topographic surveys and numerical modelling for the flood wave propagation providing an enormous database rarely used for post processing. Manfreda et al. (2006) have recently used the technical documentation, produced during the definition of Hydrogeological Management Plan by the River Basin Authorities, to define a synthetic procedure for the delineation of flood inundation exposure. The relevance of such techniques lies in the ability to characterize, at least at first approximation, portions of the territory where is not possible to run expensive hydrological-hydraulic simulations. The development of simplified methodologies is taken further in the present study to investigate the relationship between areas exposed to flood inundation and the geomorphologic characteristics of the terrain (contributing area, local slope of the surface, curvature, TOPMODEL topographic index) showing a strong correlation with the TOPMODEL topographic index. Manfreda et al. (2006) also defined a new expression of the topographical index more suited to the task of delineating flood exposure directly from a DEM analysis. This permitted the definition of a fast procedure for the calculation of flood inundation areas using a threshold level (ITms) to

  6. The Assessment of Orthophoto Quality with Respect to the Structure of Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Modiri, M.; Enayati, H.; Ebrahimikia, M.

    2015-12-01

    producing instruction and the accuracy of the DEM which are mostly related to its density, the suitable resolution for producing different scale orthophotos at each kind of topographic class have been calculated from mentioned methods consequences and shown as a final result.

  7. Validating continuous digital light processing (cDLP) additive manufacturing accuracy and tissue engineering utility of a dye-initiator package.

    PubMed

    Wallace, Jonathan; Wang, Martha O; Thompson, Paul; Busso, Mallory; Belle, Vaijayantee; Mammoser, Nicole; Kim, Kyobum; Fisher, John P; Siblani, Ali; Xu, Yueshuo; Welter, Jean F; Lennon, Donald P; Sun, Jiayang; Caplan, Arnold I; Dean, David

    2014-03-01

    This study tested the accuracy of tissue engineering scaffold rendering via the continuous digital light processing (cDLP) light-based additive manufacturing technology. High accuracy (i.e., <50 µm) allows the designed performance of features relevant to three scale spaces: cell-scaffold, scaffold-tissue, and tissue-organ interactions. The biodegradable polymer poly (propylene fumarate) was used to render highly accurate scaffolds through the use of a dye-initiator package, TiO2 and bis (2,4,6-trimethylbenzoyl)phenylphosphine oxide. This dye-initiator package facilitates high accuracy in the Z dimension. Linear, round, and right-angle features were measured to gauge accuracy. Most features showed accuracies between 5.4-15% of the design. However, one feature, an 800 µm diameter circular pore, exhibited a 35.7% average reduction of patency. Light scattered in the x, y directions by the dye may have reduced this feature's accuracy. Our new fine-grained understanding of accuracy could be used to make further improvements by including corrections in the scaffold design software. Successful cell attachment occurred with both canine and human mesenchymal stem cells (MSCs). Highly accurate cDLP scaffold rendering is critical to the design of scaffolds that both guide bone regeneration and that fully resorb. Scaffold resorption must occur for regenerated bone to be remodeled and, thereby, achieve optimal strength. PMID:24429508

  8. Extraction of cross sections from digital elevation model for one-dimensional dam-break wave propagation in mountain valleys

    NASA Astrophysics Data System (ADS)

    Pilotti, Marco

    2016-01-01

    Shallow Water Equations (SWE) provide a fundamental component for the quantification and mapping of hydraulic hazard. In steep mountain valleys, the use of one-dimensional SWE (also known as St. Venant Equations, SVE) is often legitimate and computationally competitive against two-dimensional solvers. However, in the same environment, the solution of SVE is hindered by the need of an accurate bathymetric reconstruction, which implies a number of cross sections which cannot be readily acquired by conventional field surveys. On the other hand, Digital Elevation Models (DEM) with resolution adequate for studies of flood propagation are available in many areas of the world. In this paper, I propose to compute cross sections automatically by operating along the channel network derived from a valley's raster DEM, on the basis of algorithms that hitherto have been used for geomorphological and hydrological purposes. The extraction process can be refined by varying cross section inter-distance and width, in order to prevent superimpositions that might occur due to the sinuosity of the thalweg and to better capture the valley's local topography. At the end of this process, the geometric functions needed by SVE solvers can be computed for each cross section. A software tool that implements the described algorithm is provided to the scientific community.

  9. An efficient variant of the Priority-Flood algorithm for filling depressions in raster digital elevation models

    NASA Astrophysics Data System (ADS)

    Zhou, Guiyun; Sun, Zhongxuan; Fu, Suhua

    2016-05-01

    Depressions are common features in raster digital elevation models (DEMs) and they are usually filled for the automatic extraction of drainage networks. Among existing algorithms for filling depressions, the Priority-Flood algorithm substantially outperforms other algorithms in terms of both time complexity and memory requirement. The Priority-Flood algorithm uses a priority queue to process cells. This study proposes an efficient variant of the Priority-Flood algorithm, which considerably reduces the number of cells processed by the priority queue by using region-growing procedures to process the majority of cells not within depressions or flat regions. We present three implementations of the proposed variant: two-pass implementation, one-pass implementation and direct implementation. Experiments are conducted on thirty DEMs with a resolution of 3m. All three implementations run faster than existing variants of the algorithm for all tested DEMs. The one-pass implementation runs the fastest and the average speed-up over the fastest existing variant is 44.6%.

  10. A fast and robust bulk-loading algorithm for indexing very large digital elevation datasets: I. Algorithm

    NASA Astrophysics Data System (ADS)

    Rodríguez, Félix R.; Barrena, Manuel

    2011-07-01

    Digital elevation models (DEMs) constitute a valuable source of data for a number of geoscience-related applications. The Shuttle Radar Topography Mission (SRTM) collected and made available to the public the world's largest DEM (composed of billions of points) until that date. The SRTM DEM is stored on the NASA repository as a well-organized collection of flat files. The retrieval of this stored topographic information about a region of interest involves one selection of a proper list of files, their downloading, data filtering in the desired region, and their processing according to user needs. With the aim to provide an easier and faster access to this data by improving its further analysis and processing, we have indexed the SRTM DEM by means of a spatial indexing based on the kd-tree data structure, called the Q-tree. This paper is the first in a two-part series that describes the method followed to build an index on such huge amounts of data, minimizing the number of insert operations. We demonstrate that our method can build a very efficient space-partitioning index, with good performance in both point and range queries on the spatial data. To the best of our knowledge, this is the only successful spatial indexing proposal in the literature that deals with such a huge volume of data.

  11. Using X-band Weather Radar Measurements to Monitor the Integrity of Digital Elevation Models for Synthetic Vision Systems

    NASA Technical Reports Server (NTRS)

    Young, Steve; UijtdeHaag, Maarten; Sayre, Jonathon

    2003-01-01

    Synthetic Vision Systems (SVS) provide pilots with displays of stored geo-spatial data representing terrain, obstacles, and cultural features. As comprehensive validation is impractical, these databases typically have no quantifiable level of integrity. Further, updates to the databases may not be provided as changes occur. These issues limit the certification level and constrain the operational context of SVS for civil aviation. Previous work demonstrated the feasibility of using a realtime monitor to bound the integrity of Digital Elevation Models (DEMs) by using radar altimeter measurements during flight. This paper describes an extension of this concept to include X-band Weather Radar (WxR) measurements. This enables the monitor to detect additional classes of DEM errors and to reduce the exposure time associated with integrity threats. Feature extraction techniques are used along with a statistical assessment of similarity measures between the sensed and stored features that are detected. Recent flight-testing in the area around the Juneau, Alaska Airport (JNU) has resulted in a comprehensive set of sensor data that is being used to assess the feasibility of the proposed monitor technology. Initial results of this assessment are presented.

  12. Evaluation of the effects of the seasonal variation of solar elevation angle and azimuth on the processes of digital filtering and thematic classification of relief units

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Novo, E. M. L. M.

    1983-01-01

    The effects of the seasonal variation of illumination over digital processing of LANDSAT images are evaluated. Two sets of LANDSAT data referring to the orbit 150 and row 28 were selected with illumination parameters varying from 43 deg to 64 deg for azimuth and from 30 deg to 36 deg for solar elevation respectively. IMAGE-100 system permitted the digital processing of LANDSAT data. Original images were transformed by means of digital filtering so as to enhance their spatial features. The resulting images were used to obtain an unsupervised classification of relief units. Topographic variables (declivity, altitude, relief range and slope length) were used to identify the true relief units existing on the ground. The LANDSAT over pass data show that digital processing is highly affected by illumination geometry, and there is no correspondence between relief units as defined by spectral features and those resulting from topographic features.

  13. Comparison of the accuracy of digital stereophotogrammetry and projection moiré profilometry for three-dimensional imaging of the face.

    PubMed

    Artopoulos, A; Buytaert, J A N; Dirckx, J J J; Coward, T J

    2014-05-01

    The aim of this study was to compare the three-dimensional (3D) imaging accuracy between a digital stereophotogrammetry device and a projection moiré profilometry setup using anatomical models in conjunction with surface matching software. Twenty-two 3D surface models of the middle third of the face derived from computed tomography (CT) scans were used to fabricate photopolymer models by rapid prototyping. These were digitized using digital stereophotogrammetry and projection moiré profilometry. The 3D surface models acquired were compared for shape differences with the original CT models using surface matching software. Global registration between each pair of corresponding models was carried out using an iterative closest point algorithm. The mean surface deviations following registration were used to calculate Bland-Altman limits of agreement between the two methods. The distributions of measured surface differences were used to calculate L-moments. Paired t-tests were carried out for hypothesis testing. Correlation between difference and mean was -0.3, and 95% limits of agreement were -0.084mm and 0.064mm. No statistically significant differences in mean measurement error (L1 moments) were observed (P=0.1882). The experimental moiré profilometry setup employed produced 3D models of facial anatomy of comparable accuracy to a widely used commercialized digital stereophotogrammetry device. PMID:24225265

  14. UAV-based photogrammetry combination of the elevational outcrop and digital surface models: an example of Sanyi active fault in western Taiwan

    NASA Astrophysics Data System (ADS)

    Hsieh, Cheng-En; Huang, Wen-Jeng; Chang, Ping-Yu; Lo, Wei

    2016-04-01

    An unmanned aerial vehicle (UAV) with a digital camera is an efficient tool for geologists to investigate structure patterns in the field. By setting ground control points (GCPs), UAV-based photogrammetry provides high-quality and quantitative results such as a digital surface model (DSM) and orthomosaic and elevational images. We combine the elevational outcrop 3D model and a digital surface model together to analyze the structural characteristics of Sanyi active fault in Houli-Fengyuan area, western Taiwan. Furthermore, we collect resistivity survey profiles and drilling core data in the Fengyuan District in order to build the subsurface fault geometry. The ground sample distance (GSD) of an elevational outcrop 3D model is 3.64 cm/pixel in this study. Our preliminary result shows that 5 fault branches are distributed 500 meters wide on the elevational outcrop and the width of Sanyi fault zone is likely much great than this value. Together with our field observations, we propose a structural evolution model to demonstrate how the 5 fault branches developed. The resistivity survey profiles show that Holocene gravel was disturbed by the Sanyi fault in Fengyuan area.

  15. Computing the LS factor for the Revised Universal Soil Loss Equation through array-based slope processing of digital elevation data using a C++ executable

    NASA Astrophysics Data System (ADS)

    Van Remortel, R. D.; Maichle, R. W.; Hickey, R. J.

    2004-11-01

    Until the mid-1990s, a major limitation of using the Universal Soil Loss Equation and Revised Universal Soil Loss Equation erosion models at regional landscape scales was the difficulty in estimating LS factor (slope length and steepness) values suitable for use in geographic information systems applications. A series of ArcInfo™ Arc Macro Language scripts was subsequently created that enabled the production of either USLE- or RUSLE-based LS factor raster grids using a digital elevation model input data set. These scripts have functioned exceptionally well for both single- and multiple-watershed applications within targeted study areas. However, due to the nature and complexity of flowpath processing necessary to compute cumulative slope length, the scripts have not taken advantage of available computing resources to the extent possible. It was determined that the speed of the computer runs could be significantly increased without sacrificing accuracy in the final results by performing the majority of the elevation data processing in a two-dimensional array framework outside the ArcInfo environment. This paper describes the evolution of a major portion of the original RUSLE-based AML processing code to an array-based executable program using ANSI C++™ software. Examples of the relevant command-line arguments are provided and comparative results from several AML-vs.-executable time trials are also presented. In wide-ranging areas of the United States where it has been tested, the new RUSLE-based executable has produced LS-factor values that mimic those generated by the original AML as well as the RUSLE Handbook estimates. Anticipated uses of the executable program include water quality assessment, landscape ecology, land-use change detection studies, and decision support activities. This research has now given users the option of either running the executable file alone to process a single watershed reporting unit or running a supporting AML shell program that

  16. Sequential digital elevation models of active lava flows from ground-based stereo time-lapse imagery

    NASA Astrophysics Data System (ADS)

    James, M. R.; Robson, S.

    2014-11-01

    We describe a framework for deriving sequences of digital elevation models (DEMs) for the analysis of active lava flows using oblique stereo-pair time-lapse imagery. A photo-based technique was favoured over laser-based alternatives due to low equipment cost, high portability and capability for network expansion, with images of advancing flows captured by digital SLR cameras over durations of up to several hours. However, under typical field scale scenarios, relative camera orientations cannot be rigidly maintained (e.g. through the use of a stereo bar), preventing the use of standard stereo time-lapse processing software. Thus, we trial semi-automated DEM-sequence workflows capable of handling the small camera motions, variable image quality and restricted photogrammetric control that result from the practicalities of data collection at remote and hazardous sites. The image processing workflows implemented either link separate close-range photogrammetry and traditional stereo-matching software, or are integrated in a single software package based on structure-from-motion (SfM). We apply these techniques in contrasting case studies from Kilauea volcano, Hawaii and Mount Etna, Sicily, which differ in scale, duration and image texture. On Kilauea, the advance direction of thin fluid lava lobes was difficult to forecast, preventing good distribution of control. Consequently, volume changes calculated through the different workflows differed by ∼10% for DEMs (over ∼30 m2) that were captured once a minute for 37 min. On Mt. Etna, more predictable advance (∼3 m h-1 for ∼3 h) of a thicker, more viscous lava allowed robust control to be deployed and volumetric change results were generally within 5% (over ∼500 m2). Overall, the integrated SfM software was more straightforward to use and, under favourable conditions, produced results comparable to those from the close-range photogrammetry pipeline. However, under conditions with limited options for photogrammetric

  17. Accuracy of Bolton analysis measured in laser scanned digital models compared with plaster models (gold standard) and cone-beam computer tomography images

    PubMed Central

    Kim, Jooseong

    2016-01-01

    Objective The aim of this study was to compare the accuracy of Bolton analysis obtained from digital models scanned with the Ortho Insight three-dimensional (3D) laser scanner system to those obtained from cone-beam computed tomography (CBCT) images and traditional plaster models. Methods CBCT scans and plaster models were obtained from 50 patients. Plaster models were scanned using the Ortho Insight 3D laser scanner; Bolton ratios were calculated with its software. CBCT scans were imported and analyzed using AVIZO software. Plaster models were measured with a digital caliper. Data were analyzed with descriptive statistics and the intraclass correlation coefficient (ICC). Results Anterior and overall Bolton ratios obtained by the three different modalities exhibited excellent agreement (> 0.970). The mean differences between the scanned digital models and physical models and between the CBCT images and scanned digital models for overall Bolton ratios were 0.41 ± 0.305% and 0.45 ± 0.456%, respectively; for anterior Bolton ratios, 0.59 ± 0.520% and 1.01 ± 0.780%, respectively. ICC results showed that intraexaminer error reliability was generally excellent (> 0.858 for all three diagnostic modalities), with < 1.45% discrepancy in the Bolton analysis. Conclusions Laser scanned digital models are highly accurate compared to physical models and CBCT scans for assessing the spatial relationships of dental arches for orthodontic diagnosis. PMID:26877978

  18. Projection of Stabilized Aerial Imagery Onto Digital Elevation Maps for Geo-Rectified and Jitter-Free Viewing

    NASA Technical Reports Server (NTRS)

    Ansar, Adnan I.; Brennan, Shane; Clouse, Daniel S.

    2012-01-01

    As imagery is collected from an airborne platform, an individual viewing the images wants to know from where on the Earth the images were collected. To do this, some information about the camera needs to be known, such as its position and orientation relative to the Earth. This can be provided by common inertial navigation systems (INS). Once the location of the camera is known, it is useful to project an image onto some representation of the Earth. Due to the non-smooth terrain of the Earth (mountains, valleys, etc.), this projection is highly non-linear. Thus, to ensure accurate projection, one needs to project onto a digital elevation map (DEM). This allows one to view the images overlaid onto a representation of the Earth. A code has been developed that takes an image, a model of the camera used to acquire that image, the pose of the camera during acquisition (as provided by an INS), and a DEM, and outputs an image that has been geo-rectified. The world coordinate of the bounds of the image are provided for viewing purposes. The code finds a mapping from points on the ground (DEM) to pixels in the image. By performing this process for all points on the ground, one can "paint" the ground with the image, effectively performing a projection of the image onto the ground. In order to make this process efficient, a method was developed for finding a region of interest (ROI) on the ground to where the image will project. This code is useful in any scenario involving an aerial imaging platform that moves and rotates over time. Many other applications are possible in processing aerial and satellite imagery.

  19. Digital elevation models in 10 minute time steps - a status report on 4D monitoring of an active erosional scar

    NASA Astrophysics Data System (ADS)

    Kaiser, Andreas; Neugirg, Fabian; Hass, Erik; Jose, Steffen; Haas, Florian; Schmidt, Jürgen

    2016-04-01

    In erosional research a variety of processes are well understood and have been mimicked under laboratory conditions. In complex natural systems such as Alpine environments a multitude of influencing factors tend to superimpose single processes in a mixed signal which impedes a reliable interpretation. These mixed signals can already be captured by geoscientific research approaches such as sediment collectors, erosion pins or remote sensing surveys. Nevertheless, they fail to distinguish between single processes and their individual impact on slope morphology. Throughout the last two years a highly active slope of unsorted glacial deposits in the northern Alps has been monitored by repeated terrestrial laser scans roughly every three months. Resulting high resolution digital elevation models of difference were produced to identify possible seasonal patterns. By reproducing the TLS results with a physically based erosion model (EROSION 3D) ran with in situ input data from rainfall simulations and a climate station a better understanding of individual mechanism could be achieved. However, the already elaborate combination of soil science and close range remote sensing could not answer all questions concerning the slopes behaviour, especially not for freeze and thaw cycles and the winter period. Therefore, an array of three fully automatic synchronised cameras was setup to generate continuous 3D surface models. Among the main challenges faced for the system were the energy supply and durability, perspectives of the cameras to avoid shadowing and to guarantee sufficient overlap, a certain robustness to withstand rough alpine weather conditions, the scaling of each 3D model by tracked ground control points and the automatic data handling. First results show individual processes sculpting the slope's morphology but further work is required to improve automatic point cloud creation and change monitoring.

  20. An approach of crater automatic recognition based on contour digital elevation model from Chang'E Missions

    NASA Astrophysics Data System (ADS)

    Zuo, W.; Li, C.; Zhang, Z.; Li, H.; Feng, J.

    2015-12-01

    In order to provide fundamental information for exploration and related scientific research on the Moon and other planets, we propose a new automatic method to recognize craters on the lunar surface based on contour data extracted from a digital elevation model (DEM). First, we mapped 16-bits DEM to 256 gray scales for data compression, then for the purposes of better visualization, the grayscale is converted into RGB image. After that, a median filter is applied twice to DEM for data optimization, which produced smooth, continuous outlines for subsequent construction of contour plane. Considering the fact that the morphology of crater on contour plane can be approximately expressed as an ellipse or circle, we extract the outer boundaries of contour plane with the same color(gray value) as targets for further identification though a 8- neighborhood counterclockwise searching method. Then, A library of training samples is constructed based on above targets calculated from some sample DEM data, from which real crater targets are labeled as positive samples manually, and non-crater objects are labeled as negative ones. Some morphological feathers are calculated for all these samples, which are major axis (L), circumference(C), area inside the boundary(S), and radius of the largest inscribed circle(R). We use R/L, R/S, C/L, C/S, R/C, S/L as the key factors for identifying craters, and apply Fisher discrimination method on the sample library to calculate the weight of each factor and determine the discrimination formula, which is then applied to DEM data for identifying lunar craters. The method has been tested and verified with DEM data from CE-1 and CE-2, showing strong recognition ability and robustness and is applicable for the recognition of craters with various diameters and significant morphological differences, making fast and accurate automatic crater recognition possible.

  1. Size Distribution for Potentially Unstable Rock Masses and In Situ Rock Blocks Using LIDAR-Generated Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Mavrouli, O.; Corominas, J.; Jaboyedoff, M.

    2015-07-01

    In this paper, two analytical procedures which are independent from the existence of empirical data are presented for the calculation of (1) the size distribution of potentially unstable rock masses that expresses the potential rockfall size distribution, including big volumes corresponding to potential rare events with low susceptibility of failure and (2) the in situ block distribution on the slope face. Two approaches are, respectively, used. The first one involves the detection of kinematically unstable surfaces on a digital elevation model (DEM) and on orthophotos and the calculation of the volumes resting on them. For the second one the in situ block volumes formed by the intersection of the existing discontinuity sets are calculated using a high-resolution DEM. The procedures are presented through an application example at the country of Andorra and in particular at the chute of Forat Negre. The results from the first procedure indicate that it is kinematically possible to have mobilized volumes of some thousands of cubic meters; however, these are considered rare events with low susceptibility of failure. The size distribution of potentially unstable rock masses for big volume events was well fitted by a power law with an exponent of -0.5. The in situ block distribution on the slope face from the second procedure, assuming three types of intersection between the joints of the existing discontinuity sets and two extreme cases of discontinuity persistence, was also found to follow a power law, but with an exponent of -1.3. The comparison with the observed in the field block volume distribution on the slope face indicates that in reality discontinuities have a very high persistence and that considering only their visible trace length overestimates volumes, which is conservative.

  2. Monitoring fine-sediment volume in the Colorado River ecosystem, Arizona: construction and analysis of digital elevation models

    USGS Publications Warehouse

    Kaplinski, Matt; Hazel, Joseph E., Jr.; Grams, Paul E.; Davis, Philip A.

    2014-01-01

    Digital elevation models (DEMs) of eleven 2–5 kilometer reaches of the Colorado River ecosystem (CRE) in Grand Canyon were constructed from repeat bathymetric and topographic surveys collected between August 2000 and December 2004. The DEMs will be used by researchers to study the effects of Glen Canyon Dam (GCD) operations on the sediment resources of the CRE in Grand Canyon by quantifying morphological changes and sediment transfer within and among the study reaches. Airborne surveys collected light detection and ranging (lidar) and photogrammetric data, whereas ground topographic and bathymetric data were collected simultaneously on river trips. Surveys were conducted in August 2000, September 2000, May 2002, May 2004, November 2004, and December 2004. The aerial lidar and photogrammetric data were merged with the ground topographic and bathymetric data to create DEMs of the study areas with a grid resolution of 1 meter. For each survey period, the vertical component of uncertainty (specifically, reproducibility or precision) was estimated for each data type (lidar/photogrammetry, ground surveys, bathymetry) and for two different types of bed-surface texture (smooth and rough). The resulting DEMs from this study are a valuable contribution to ongoing efforts in assessing the effects of GCD operations on the CRE. The DEMs can be used to map the spatial characteristics of geomorphic change within the study reaches and to estimate sediment budgets for different time periods by calculating the difference in sediment volume between surveys. In addition, the DEMs provide essential boundary conditions for numerical models of sediment transport and deposition, as well as help define the spatial distribution of habitat for fisheries investigations.

  3. A multi-directional and multi-scale roughness filter to detect lineament segments on digital elevation models - analyzing spatial objects in R

    NASA Astrophysics Data System (ADS)

    Baumann, Sebastian; Robl, Jörg; Wendt, Lorenz; Willingshofer, Ernst; Hilberg, Sylke

    2016-04-01

    Automated lineament analysis on remotely sensed data requires two general process steps: The identification of neighboring pixels showing high contrast and the conversion of these domains into lines. The target output is the lineaments' position, extent and orientation. We developed a lineament extraction tool programmed in R using digital elevation models as input data to generate morphological lineaments defined as follows: A morphological lineament represents a zone of high relief roughness, whose length significantly exceeds the width. As relief roughness any deviation from a flat plane, defined by a roughness threshold, is considered. In our novel approach a multi-directional and multi-scale roughness filter uses moving windows of different neighborhood sizes to identify threshold limited rough domains on digital elevation models. Surface roughness is calculated as the vertical elevation difference between the center cell and the different orientated straight lines connecting two edge cells of a neighborhood, divided by the horizontal distance of the edge cells. Thus multiple roughness values depending on the neighborhood sizes and orientations of the edge connecting lines are generated for each cell and their maximum and minimum values are extracted. Thereby negative signs of the roughness parameter represent concave relief structures as valleys, positive signs convex relief structures as ridges. A threshold defines domains of high relief roughness. These domains are thinned to a representative point pattern by a 3x3 neighborhood filter, highlighting maximum and minimum roughness peaks, and representing the center points of lineament segments. The orientation and extent of the lineament segments are calculated within the roughness domains, generating a straight line segment in the direction of least roughness differences. We tested our algorithm on digital elevation models of multiple sources and scales and compared the results visually with shaded relief map

  4. Use of Digital Elevation Models to understand map landforms and history of the magmatism Khibiny Massif (Kola Peninsula, Russia)

    NASA Astrophysics Data System (ADS)

    Chesalova, Elena; Asavin, Alex

    2016-04-01

    This work presents an improved geomorphological methodology that uses 3D model of relief, remotely-sensed data, geological, geophysical maps and tools of Geographical Information Systems. On the basis of maps of 1: 50,000 and 1: 200,000 the Digital Elevation model (DEM) of Khibiny massif was developed. We used software ARC / INFO v10.2 ESRI. A DEM was used for analyzing landform by extracting the slope gradient, curvature, valley pro?les, slope, aspect and so on. The results were gradually re?ned from the interpretation of satellite imagery and geological map Geomorphological analysis will allow us to determine spatial regularities in inner massive construction. We try to found areas where gas emissions (CH4/H2) enrich, according to morphometry, geology, tectonic and other environments. The main regional blocks were de?ned by different morphological evidences: impression zone, similar to subsidence caldera; uplift zone, domed area (located in the highest part of massif and zone of intersection of main faults) and others. It says that there are the few stages in the development of the Khibiny massif. There is no common concept of the consequence of intrudes magmatic phases now. And we hope that our geomorphical analysis take a new evidences about this problems. Locations of the blocks' borders (tectonic zones) were recognized by lineament analysis of valleys and tectonic faults presented in relief. Erosion system is represented by valleys of 4 ranks. It inherits the zone of tectonic disturbances 3 groups of faults were recognized: 1) Global lineament system cross whole peninsula - existing before Khibiny massif intrusion; 2) Faults associated with the formation of the intrusive phases sequence and magma differentiation and with later collision history during magma cooling; 3) Crack system related to neotectonic process. We believed that if different magmatic phases intrude in similar tectonic environment, the common spatial system of faults will be formed. Really we

  5. The use of LANDSAT-4 MSS digital data in temporal data sets and the evaluation of scene-to-scene registration accuracy

    NASA Technical Reports Server (NTRS)

    Anderson, J. E. (Principal Investigator)

    1983-01-01

    The MSS sensor on LANDSAT 4 is, in certain performance aspects, different from those on LANDSATS 1 through 3. These differences created some concern in the NASA research community as to whether individual data sets can be registered accurately enough to produce acceptable data sets for multitemporal data analysis. The use of LANDSAT 4 MSS digital data in temporal data sets is examined and a method is presented for estimating temporal registration accuracy based on the use of an X-Y digitizer and grey tone electrostatic plots. Results indicate that the RMS temporal registration errors are not significantly different from the temporal data sets generated using LANDSAT 4 and LANDSAT 2 data (33.35 meters) and the temporal data set constructed from two LANDSAT 2 data sets (33.61 meters). A derivation of the model used to evaluate the temporal registration is included.

  6. The use of Landsat-4 MSS digital data in temporal data sets and the evaluation of scene-to-scene registration accuracy

    NASA Technical Reports Server (NTRS)

    Anderson, J. E.

    1985-01-01

    The MSS sensor on Landsat 4 is, in certain performance aspects, diferent from those of Landsats 1 through 3. These differences created some concern in the NASA research community as to whether individual data sets can be registered accurately enough to produce acceptable data sets for multitemporal data analysis. The use of Landsat 4 MSS digital data in temporal data sets is examined and a method is presented for estimating temporal registration accuracy based on the use of an X-Y digitizer and grey tone electrostatic plots. Results indicate that the RMS temporal registration errors are not significantly different from the temporal data sets generated using Landsat 4 and Landsat 2 data (33.35 meters) and the temporal data set constructed from two Landsat 2 data sets (33.61 meters). A derivation of the model used to evaluate the temporal registration is included.

  7. A critical source area phosphorus index with topographic transport factors using high resolution LiDAR digital elevation models

    NASA Astrophysics Data System (ADS)

    Thomas, Ian; Murphy, Paul; Fenton, Owen; Shine, Oliver; Mellander, Per-Erik; Dunlop, Paul; Jordan, Phil

    2015-04-01

    A new phosphorus index (PI) tool is presented which aims to improve the identification of critical source areas (CSAs) of phosphorus (P) losses from agricultural land to surface waters. In a novel approach, the PI incorporates topographic indices rather than watercourse proximity as proxies for runoff risk, to account for the dominant control of topography on runoff-generating areas and P transport pathways. Runoff propensity and hydrological connectivity are modelled using the Topographic Wetness Index (TWI) and Network Index (NI) respectively, utilising high resolution digital elevation models (DEMs) derived from Light Detection and Ranging (LiDAR) to capture the influence of micro-topographic features on runoff pathways. Additionally, the PI attempts to improve risk estimates of particulate P losses by incorporating an erosion factor that accounts for fine-scale topographic variability within fields. Erosion risk is modelled using the Unit Stream Power Erosion Deposition (USPED) model, which integrates DEM-derived upslope contributing area and Universal Soil Loss Equation (USLE) factors. The PI was developed using field, sub-field and sub-catchment scale datasets of P source, mobilisation and transport factors, for four intensive agricultural catchments in Ireland representing different agri-environmental conditions. Datasets included soil test P concentrations, degree of P saturation, soil attributes, land use, artificial subsurface drainage locations, and 2 m resolution LiDAR DEMs resampled from 0.25 m resolution data. All factor datasets were integrated within a Geographical Information System (GIS) and rasterised to 2 m resolution. For each factor, values were categorised and assigned relative risk scores which ranked P loss potential. Total risk scores were calculated for each grid cell using a component formulation, which summed the products of weighted factor risk scores for runoff and erosion pathways. Results showed that the new PI was able to predict

  8. Testing Pixel Translation Digital Elevation Models to Reconstruct Slip Histories: An Example from the Agua Blanca Fault, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Wilson, J.; Wetmore, P. H.; Malservisi, R.; Ferwerda, B. P.; Teran, O.

    2012-12-01

    We use recently collected slip vector and total offset data from the Agua Blanca fault (ABF) to constrain a pixel translation digital elevation model (DEM) to reconstruct the slip history of this fault. This model was constructed using a Perl script that reads a DEM file (Easting, Northing, Elevation) and a configuration file with coordinates that define the boundary of each fault segment. A pixel translation vector is defined as a magnitude of lateral offset in an azimuthal direction. The program translates pixels north of the fault and prints their pre-faulting position to a new DEM file that can be gridded and displayed. This analysis, where multiple DEMs are created with different translation vectors, allows us to identify areas of transtension or transpression while seeing the topographic expression in these areas. The benefit of this technique, in contrast to a simple block model, is that the DEM gives us a valuable graphic which can be used to pose new research questions. We have found that many topographic features correlate across the fault, i.e. valleys and ridges, which likely have implications for the age of the ABF, long term landscape evolution rates, and potentially provide conformation for total slip assessments The ABF of northern Baja California, Mexico is an active, dextral strike slip fault that transfers Pacific-North American plate boundary strain out of the Gulf of California and around the "Big Bend" of the San Andreas Fault. Total displacement on the ABF in the central and eastern parts of the fault is 10 +/- 2 km based on offset Early-Cretaceous features such as terrane boundaries and intrusive bodies (plutons and dike swarms). Where the fault bifurcates to the west, the northern strand (northern Agua Blanca fault or NABF) is constrained to 7 +/- 1 km. We have not yet identified piercing points on the southern strand, the Santo Tomas fault (STF), but displacement is inferred to be ~4 km assuming that the sum of slip on the NABF and STF is

  9. Accuracy of Answers Provided by Digital/Face-to-Face Reference Services in Japanese Public Libraries and Q & A Sites

    ERIC Educational Resources Information Center

    Tsuji, Keita; To, Haruna; Hara, Atsuyuki

    2011-01-01

    We asked the same 60 questions using DRS (digital reference services) in Japanese public libraries, face-to-face reference services and Q & A (question and answer) sites. It was found that: (1) The correct answer ratio of DRS is higher than that of Q & A sites; (2) DRS takes longer to provide answers as compared to Q & A sites; and (3) The correct…

  10. Automatic and Objective Detection of Shallow Landslides from Lidar-Derived High-Resolution Digital Elevation Models Using a Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Reeder, W. J.; McKean, J. A.; Tonina, D.

    2012-12-01

    An accurate and detailed inventory map of existing shallow landslides is a necessary component of shallow landslide risk assessment. Traditional methods for creating landslide inventory maps include visual interpretation of aerial photographs, visual analysis of topographic maps and field surveys. The visual methods tend to be subjective and can be greatly hampered by the presence of forests or other dense vegetation. Field surveying is time consuming and can be limited by access to steep or heavily vegetated terrain. Shallow slides are also often only reported as point locations with no recorded information about size or even two-dimensional footprint. The increasing availability of high resolution, LiDAR-derived digital elevation models (DEMs), showing bare earth topography even beneath forest canopies, has created new opportunities to improve and automate the shallow landslide mapping process. Here we introduce the Automated Shallow Landslide Detection (ASLD) method, which is an integrated set of Matlab® utilities that, uses a two-dimensional continuous Morlet wavelet transform in an automated and largely unsupervised manner, to analyze high resolution terrain data and map the locations and footprints of shallow landslides. The terrain data are filtered to remove the finest scale of roughness and then the Morlet wavelet transform is applied to the terrain model. The Morlet wavelet is directionally selective and effectively steered to align with the aspect at each node in the DEM. This reduces confusion with other, likely non-landslide generated, topographic features that are not aligned with the local slope direction. Convex-upward features are then eliminated, as the polarity of their wavelet transform will be reversed. Finally, simple user-defined rules for the general shape of shallow landslides are applied to further eliminate false positives. The capabilities of ASLD are demonstrated in two different drainages. Buckhorn Creek is tributary to the South Fork

  11. Accuracy of consumer fork, remote, and digital probe thermometers in cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Use of a thermometer is the only way to determine if meat products have been cooked to an internal temperature necessary to inactivate pathogens. To date, the accuracy and reliability of consumer instant-read thermometers have only been evaluated in water-baths, not in meat products. For each of the...

  12. Use of Digital Elevation Models to understand map landforms and history of the magmatism Khibiny Massif (Kola Peninsula, Russia)

    NASA Astrophysics Data System (ADS)

    Chesalova, Elena; Asavin, Alex

    2016-04-01

    This work presents an improved geomorphological methodology that uses 3D model of relief, remotely-sensed data, geological, geophysical maps and tools of Geographical Information Systems. On the basis of maps of 1: 50,000 and 1: 200,000 the Digital Elevation model (DEM) of Khibiny massif was developed. We used software ARC / INFO v10.2 ESRI. A DEM was used for analyzing landform by extracting the slope gradient, curvature, valley pro?les, slope, aspect and so on. The results were gradually re?ned from the interpretation of satellite imagery and geological map Geomorphological analysis will allow us to determine spatial regularities in inner massive construction. We try to found areas where gas emissions (CH4/H2) enrich, according to morphometry, geology, tectonic and other environments. The main regional blocks were de?ned by different morphological evidences: impression zone, similar to subsidence caldera; uplift zone, domed area (located in the highest part of massif and zone of intersection of main faults) and others. It says that there are the few stages in the development of the Khibiny massif. There is no common concept of the consequence of intrudes magmatic phases now. And we hope that our geomorphical analysis take a new evidences about this problems. Locations of the blocks' borders (tectonic zones) were recognized by lineament analysis of valleys and tectonic faults presented in relief. Erosion system is represented by valleys of 4 ranks. It inherits the zone of tectonic disturbances 3 groups of faults were recognized: 1) Global lineament system cross whole peninsula - existing before Khibiny massif intrusion; 2) Faults associated with the formation of the intrusive phases sequence and magma differentiation and with later collision history during magma cooling; 3) Crack system related to neotectonic process. We believed that if different magmatic phases intrude in similar tectonic environment, the common spatial system of faults will be formed. Really we

  13. Landscape unit based digital elevation model development for the freshwater wetlands within the Arthur C. Marshall Loxahatchee National Wildlife Refuge, Southeastern Florida

    USGS Publications Warehouse

    Xie, Zhixiao; Liu, Zhongwei; Jones, John W.; Higer, Aaron L.; Telis, Pamela A.

    2011-01-01

    The hydrologic regime is a critical limiting factor in the delicate ecosystem of the greater Everglades freshwater wetlands in south Florida that has been severely altered by management activities in the past several decades. "Getting the water right" is regarded as the key to successful restoration of this unique wetland ecosystem. An essential component to represent and model its hydrologic regime, specifically water depth, is an accurate ground Digital Elevation Model (DEM). The Everglades Depth Estimation Network (EDEN) supplies important hydrologic data, and its products (including a ground DEM) have been well received by scientists and resource managers involved in Everglades restoration. This study improves the EDEN DEMs of the Loxahatchee National Wildlife Refuge, also known as Water Conservation Area 1 (WCA1), by adopting a landscape unit (LU) based interpolation approach. The study first filtered the input elevation data based on newly available vegetation data, and then created a separate geostatistical model (universal kriging) for each LU. The resultant DEMs have encouraging cross-validation and validation results, especially since the validation is based on an independent elevation dataset (derived by subtracting water depth measurements from EDEN water surface elevations). The DEM product of this study will directly benefit hydrologic and ecological studies as well as restoration efforts. The study will also be valuable for a broad range of wetland studies.

  14. Expected accuracy of tilt measurements on a novel hexapod-based digital zenith camera system: a Monte-Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Hirt, Christian; Papp, Gábor; Pál, András; Benedek, Judit; Szũcs, Eszter

    2014-08-01

    Digital zenith camera systems (DZCS) are dedicated astronomical-geodetic measurement systems for the observation of the direction of the plumb line. A DZCS key component is a pair of tilt meters for the determination of the instrumental tilt with respect to the plumb line. Highest accuracy (i.e., 0.1 arc-seconds or better) is achieved in practice through observation with precision tilt meters in opposite faces (180° instrumental rotation), and application of rigorous tilt reduction models. A novel concept proposes the development of a hexapod (Stewart platform)-based DZCS. However, hexapod-based total rotations are limited to about 30°-60° in azimuth (equivalent to ±15° to ±30° yaw rotation), which raises the question of the impact of the rotation angle between the two faces on the accuracy of the tilt measurement. The goal of the present study is the investigation of the expected accuracy of tilt measurements to be carried out on future hexapod-based DZCS, with special focus placed on the role of the limited rotation angle. A Monte-Carlo simulation study is carried out in order to derive accuracy estimates for the tilt determination as a function of several input parameters, and the results are validated against analytical error propagation. As the main result of the study, limitation of the instrumental rotation to 60° (30°) deteriorates the tilt accuracy by a factor of about 2 (4) compared to a 180° rotation between the faces. Nonetheless, a tilt accuracy at the 0.1 arc-second level is expected when the rotation is at least 45°, and 0.05 arc-second (about 0.25 microradian) accurate tilt meters are deployed. As such, a hexapod-based DZCS can be expected to allow sufficiently accurate determination of the instrumental tilt. This provides supporting evidence for the feasibility of such a novel instrumentation. The outcomes of our study are not only relevant to the field of DZCS, but also to all other types of instruments where the instrumental tilt

  15. An approach to regional wetland digital elevation model development using a differential global positioning system and a custom-built helicopter-based surveying system

    USGS Publications Warehouse

    Jones, J.W.; Desmond, G.B.; Henkle, C.; Glover, R.

    2012-01-01

    Accurate topographic data are critical to restoration science and planning for the Everglades region of South Florida, USA. They are needed to monitor and simulate water level, water depth and hydroperiod and are used in scientific research on hydrologic and biologic processes. Because large wetland environments and data acquisition challenge conventional ground-based and remotely sensed data collection methods, the United States Geological Survey (USGS) adapted a classical data collection instrument to global positioning system (GPS) and geographic information system (GIS) technologies. Data acquired with this instrument were processed using geostatistics to yield sub-water level elevation values with centimetre accuracy (??15 cm). The developed database framework, modelling philosophy and metadata protocol allow for continued, collaborative model revision and expansion, given additional elevation or other ancillary data. ?? 2012 Taylor & Francis.

  16. Automatic identification of fault surfaces through Object Based Image Analysis of a Digital Elevation Model in the submarine area of the North Aegean Basin

    NASA Astrophysics Data System (ADS)

    Argyropoulou, Evangelia

    2015-04-01

    The current study was focused on the seafloor morphology of the North Aegean Basin in Greece, through Object Based Image Analysis (OBIA) using a Digital Elevation Model. The goal was the automatic extraction of morphologic and morphotectonic features, resulting into fault surface extraction. An Object Based Image Analysis approach was developed based on the bathymetric data and the extracted features, based on morphological criteria, were compared with the corresponding landforms derived through tectonic analysis. A digital elevation model of 150 meters spatial resolution was used. At first, slope, profile curvature, and percentile were extracted from this bathymetry grid. The OBIA approach was developed within the eCognition environment. Four segmentation levels were created having as a target "level 4". At level 4, the final classes of geomorphological features were classified: discontinuities, fault-like features and fault surfaces. On previous levels, additional landforms were also classified, such as continental platform and continental slope. The results of the developed approach were evaluated by two methods. At first, classification stability measures were computed within eCognition. Then, qualitative and quantitative comparison of the results took place with a reference tectonic map which has been created manually based on the analysis of seismic profiles. The results of this comparison were satisfactory, a fact which determines the correctness of the developed OBIA approach.

  17. Mapping mine wastes and analyzing areas affected by selenium-rich water runoff in southeast Idaho using AVIRIS imagery and digital elevation data

    USGS Publications Warehouse

    Mars, J.C.; Crowley, J.K.

    2003-01-01

    Remotely sensed hyperspectral and digital elevation data from southeastern Idaho are combined in a new method to assess mine waste contamination. Waste rock from phosphorite mining in the area contains selenium, cadmium, vanadium, and other metals. Toxic concentrations of selenium have been found in plants and soils near some mine waste dumps. Eighteen mine waste dumps and five vegetation cover types in the southeast Idaho phosphate district were mapped by using Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) imagery and field data. The interaction of surface water runoff with mine waste was assessed by registering the AVIRIS results to digital elevation data, enabling determinations of (1) mine dump morphologies, (2) catchment watershed areas above each mine dump, (3) flow directions from the dumps, (4) stream gradients, and (5) the extent of downstream wetlands available for selenium absorption. Watersheds with the most severe selenium contamination, such as the South Maybe Canyon watershed, are associated with mine dumps that have large catchment watershed areas, high stream gradients, a paucity of downstream wetlands, and dump forms that tend to obstruct stream flow. Watersheds associated with low concentrations of dissolved selenium, such as Angus Creek, have mine dumps with small catchment watershed areas, low stream gradients, abundant wetlands vegetation, and less obstructing dump morphologies. ?? 2002 Elsevier Science Inc. All rights reserved.

  18. Comparison of Diagnostic Accuracy of Conventional Intraoral Periapical and Direct Digital Radiographs in Detecting Interdental Bone Loss

    PubMed Central

    Suragimath, Girish; Jaishankar, H.P.; Kulkarni, Prasad; Bijjaragi, Shobha C.; Sangle, Varsha Ajit

    2015-01-01

    Background: Periodontitis is an inflammatory disease of the supporting tissues of the teeth caused by specific microorganisms, resulting in destruction of the periodontal ligament and alveolar bone. Progressive loss of alveolar bone is the salient feature of periodontal disease. Accurate detection of periodontal disease with the use of radiographs helps in diagnosis, treatment and prognosis. Aims: The present study aims to compare the efficacy of conventional intraoral periapical (IOPA) and direct digital radiographs (RVG) in detecting interdental alveolar bone loss using intrasurgical (IS) measurements as the gold standard. Materials and Methods: Thirty patients elected to undergo periodontal flap surgery with periodontitis computing to 60 interdental alveolar defects on mandibular first molars were considered. IOPA and RVG were captured using standardized techniques. Bone loss measurements in IOPA and RVG were compared to the IS measurements. Statistical Analysis: Statistical analysis was carried out using student t test and ANOVA with the help of SPSS software and p-value <0.05 was considered as significant. Results: Both IOPA and RVG underestimated the bone loss measurements when compared to IS measurements which was statistically significant (p<0.0001). Bone loss measurements in RVG were closer to IS measurements than IOPA. Conclusion: Both the radiographic techniques IOPA and RVG underestimated bone loss by 1.5–2.5 mm. RVG was superior to IOPA for the detection of interdental bone loss due to reduced time and radiation exposure to obtain the same diagnostic information. PMID:25859522

  19. A semi-automated tool for reducing the creation of false closed depressions from a filled LIDAR-derived digital elevation model

    USGS Publications Warehouse

    Waller, John S.; Doctor, Daniel H.; Terziotti, Silvia

    2015-01-01

    Closed depressions on the land surface can be identified by ‘filling’ a digital elevation model (DEM) and subtracting the filled model from the original DEM. However, automated methods suffer from artificial ‘dams’ where surface streams cross under bridges and through culverts. Removal of these false depressions from an elevation model is difficult due to the lack of bridge and culvert inventories; thus, another method is needed to breach these artificial dams. Here, we present a semi-automated workflow and toolbox to remove falsely detected closed depressions created by artificial dams in a DEM. The approach finds the intersections between transportation routes (e.g., roads) and streams, and then lowers the elevation surface across the roads to stream level allowing flow to be routed under the road. Once the surface is corrected to match the approximate location of the National Hydrologic Dataset stream lines, the procedure is repeated with sequentially smaller flow accumulation thresholds in order to generate stream lines with less contributing area within the watershed. Through multiple iterations, artificial depressions that may arise due to ephemeral flow paths can also be removed. Preliminary results reveal that this new technique provides significant improvements for flow routing across a DEM and minimizes artifacts within the elevation surface. Slight changes in the stream flow lines generally improve the quality of flow routes; however some artificial dams may persist. Problematic areas include extensive road ditches, particularly along divided highways, and where surface flow crosses beneath road intersections. Limitations do exist, and the results partially depend on the quality of data being input. Of 166 manually identified culverts from a previous study by Doctor and Young in 2013, 125 are within 25 m of culverts identified by this tool. After three iterations, 1,735 culverts were identified and cataloged. The result is a reconditioned

  20. Long-term stability of peneplains and landscape evolution in southern Tibet inferred from field data, cosmogenic nuclides, and digital elevation models

    NASA Astrophysics Data System (ADS)

    Strobl, M.; Hetzel, R.; Ding, L.; Zhang, L.

    2010-05-01

    Peneplains constitute a widespread and well developed geomorphic element on the Tibetan Plateau, nevertheless little is known about their formation and the subsequent landscape evolution. In southern Tibet, north of Nam Co (~31° 20'N, 90° E), a particularly well-preserved peneplain occurs at an elevation of ~5350 m in Cretaceous granitoids. The main planation surface has been incised by small streams that formed additional small low-relief surfaces at lower elevations. Fluvial incision of the main peneplain has generated a local relief of up to ~700 m. The progressive incision has led to hillslope gradients that increase with decreasing elevation, i.e. from the main peneplain at ~5350 m down to the current base level at ~4650 m, as revealed by field observations and the analysis of digital elevation model. In order to quantify the landscape evolution of the peneplain region we determined local and catchment-wide erosion rates from the concentration of in situ-produced cosmogenic 10Be. Local erosion rates on the main peneplain and the low-relief bedrock surfaces at lower elevation range from 6 to 12 m Ma-1 and indicate that the geomorphic surfaces are stable over long periods of time. Spatially integrated erosion rates of small river systems that are incising and eroding headwards into the main peneplain are only slightly higher and range from 11 to 18 m Ma-1. Even if river incision has proceeded at a rate that is 2-4 times higher than the catchment-wide erosion rates, i.e. at 30 to 60 m Ma-1, it would take about 10 to 20 Ma to generate the local relief of ~700 m observed today. This demonstrates that the major peneplain is a very stable geomorphic element with a minimum age of 10 to 20 Ma and that the landscape in the region has barely been modified by erosion in the last millions of years.

  1. Evaluation of diagnostic accuracy of conventional and digital periapical radiography, panoramic radiography, and cone-beam computed tomography in the assessment of alveolar bone loss

    PubMed Central

    Takeshita, Wilton Mitsunari; Vessoni Iwaki, Lilian Cristina; Da Silva, Mariliani Chicarelli; Tonin, Renata Hernandes

    2014-01-01

    Background: To evaluate the diagnostic accuracy of different radiographic methods in the assessment of proximal alveolar bone loss (ABL). Materials and Methods: ABL, the distance between cement-enamel junction and alveolar bone crest, was measured in 70 mandibular human teeth – directly on the mandibles (control), using conventional periapical radiography with film holders (Rinn XCP and Han-Shin), digital periapical radiography with complementary metal-oxide semiconductor sensor, conventional panoramic, and cone-beam computed tomography (CBCT). Three programs were used to measure ABL on the images: Image tool 3.0 (University of Texas Health Sciences Center, San Antonio, Texas, USA), Kodak Imaging 6.1 (Kodak Dental Imaging 6.1, Carestream Health®, Rochester, NY, USA), and i-CAT vision 1.6.20. Statistical analysis used ANOVA and Tukey's test at 5% significance level. Results: The tomographic images showed the highest means, whereas the lowest were found for periapical with Han-Shin. Controls differed from periapical with Han-Shin (P < 0.0001). CBCT differed from panoramic (P = 0.0130), periapical with Rinn XCP (P = 0.0066), periapical with Han-Shin (P < 0.0001), and digital periapical (P = 0.0027). Conventional periapicals with film holders differed from each other (P = 0.0007). Digital periapical differed from conventional periapical with Han-Shin (P = 0.0004). Conclusions: Conventional periapical with Han-Shin film holder was the only method that differed from the controls. CBCT had the closest means to the controls. PMID:25191066

  2. Digital Elevations and Extents of Regional Hydrogeologic Units in the Northern Atlantic Coastal Plain Aquifer System From Long Island, New York, to North Carolina

    USGS Publications Warehouse

    Pope, Jason P.; David C. Andreasen; Mcfarland, E. Randolph; Watt, Martha K.

    2016-01-01

    Digital geospatial datasets of the extents and top elevations of the regional hydrogeologic units of the Northern Atlantic Coastal Plain aquifer system from Long Island, New York, to northeastern North Carolina were developed to provide an updated hydrogeologic framework to support analysis of groundwater resources. The 19 regional hydrogeologic units were delineated by elevation grids and extent polygons for 20 layers: the land and bathymetric surface at the top of the unconfined surficial aquifer, the upper surfaces of 9 confined aquifers and 9 confining units, and the bedrock surface that defines the base of all Northern Atlantic Coastal Plain sediments. The delineation of the regional hydrogeologic units relied on the interpretive work from source reports for New York, New Jersey, Delaware and Maryland, Virginia, and North Carolina rather than from re-analysis of fundamental hydrogeologic data. This model of regional hydrogeologic unit geometries represents interpolation, extrapolation, and generalization of the earlier interpretive work. Regional units were constructed from available digital data layers from the source studies in order to extend units consistently across political boundaries and approximate units in offshore areas.Though many of the Northern Atlantic Coastal Plain hydrogeologic units may extend eastward as far as the edge of the Atlantic Continental Shelf, the modeled boundaries of all regional hydrogeologic units in this study were clipped to an area approximately defined by the furthest offshore extent of fresh to brackish water in any part of the aquifer system, as indicated by chloride concentrations of 10,000 milligrams per liter. Elevations and extents of units that do not exist onshore in Long Island, New York, were not included north of New Jersey. Hydrogeologic units in North Carolina were included primarily to provide continuity across the Virginia-North Carolina State boundary, which was important for defining the southern edge of

  3. On the Standardization of Vertical Accuracy Figures in Dems

    NASA Astrophysics Data System (ADS)

    Casella, V.; Padova, B.

    2013-01-01

    Digital Elevation Models (DEMs) play a key role in hydrological risk prevention and mitigation: hydraulic numeric simulations, slope and aspect maps all heavily rely on DEMs. Hydraulic numeric simulations require the used DEM to have a defined accuracy, in order to obtain reliable results. Are the DEM accuracy figures clearly and uniquely defined? The paper focuses on some issues concerning DEM accuracy definition and assessment. Two DEM accuracy definitions can be found in literature: accuracy at the interpolated point and accuracy at the nodes. The former can be estimated by means of randomly distributed check points, while the latter by means of check points coincident with the nodes. The two considered accuracy figures are often treated as equivalent, but they aren't. Given the same DEM, assessing it through one or the other approach gives different results. Our paper performs an in-depth characterization of the two figures and proposes standardization coefficients.

  4. Regional glacier mass loss estimated by ICESat-GLAS data and SRTM digital elevation model in the West Kunlun Mountains, Tibetan Plateau, 2003-2009

    NASA Astrophysics Data System (ADS)

    Wu, Hongbo; Wang, Ninglian; Guo, Zhongming; Wu, Yuwei

    2014-01-01

    The Ice, Cloud and land Elevation Satellite (ICESat) altimetry and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data are used to estimate glacier mass loss changes in the West Kunlun Mountains, Tibetan Plateau (TP), 2003 to 2009. We integrated Landsat thematic mapper (TM)/enhanced TM images and GIS spatial analysis to map glacier surface elevation changes during 2003 to 2009. The ICESat-GLAS data can be used as baselines for surface elevation changes in altimetry as well as for TM imagery changes for depicting glacier area. Least-squares regression of an ICESat-derived thickness series shows the regional glacier mass decreased at an average rate of 1.41±0.23 km3/year water equivalent from 2003 to 2009, during the period of 2003 to 2009, the trend in thickness change became weaker. The ICESat-GLAS and SRTM DEM elevation differences between February 2003 and October 2009 show that the glacier surface elevations were decreasing below 5800 m but increased by 1.1±0.7 m above 6000 m a.s.l. region over that period. Thickness changes in the lower reaches of the glaciers indicate that the glacier ice ablation was mainly due to the summer temperature increases of 0.23°C and the summer precipitation decreases of 47.8 mm as measured at four stations, as well as the effects of sand and dust sources from the Tarim Basin. Meanwhile, in the upper parts of the glaciers (above 5800 m a.s.l.), ice surface elevation was increasing even though the Hetian station summer temperature at the 500 hPa level showed an obvious decrease of 0.78°C compared to 2003. In the upper part of the glacier-covered region, firn compaction and surface density should be taken into account. The glacier surges and bedrock movement may also lead to an underestimate of the volume loss due to the reduced mass conversion.

  5. High-accuracy 2D digital image correlation measurements using low-cost imaging lenses: implementation of a generalized compensation method

    NASA Astrophysics Data System (ADS)

    Pan, Bing; Yu, Liping; Wu, Dafang

    2014-02-01

    The ideal pinhole imaging model commonly assumed for an ordinary two-dimensional digital image correlation (2D-DIC) system is neither perfect nor stable because of the existence of small out-of-plane motion of the test sample surface that occurred after loading, small out-of-plane motion of the sensor target due to temperature variation of a camera and unavoidable geometric distortion of an imaging lens. In certain cases, these disadvantages can lead to significant errors in the measured displacements and strains. Although a high-quality bilateral telecentric lens has been strongly recommended to be used in the 2D-DIC system as an essential optical component to achieve high-accuracy measurement, it is not generally applicable due to its fixed field of view, limited depth of focus and high cost. To minimize the errors associated with the imperfectness and instability of a common 2D-DIC system using a low-cost imaging lens, a generalized compensation method using a non-deformable reference sample is proposed in this work. With the proposed method, the displacement of the reference sample rigidly attached behind the test sample is first measured using 2D-DIC, and then it is fitted using a parametric model. The fitted parametric model is then used to correct the displacements of the deformed sample to remove the influences of these unfavorable factors. The validity of the proposed compensation method is first verified using out-of-plane translation, out-of-plane rotation, in-plane translation tests and their combinations. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively examine the strain accuracy of the proposed compensation method. Experiments show that the proposed compensation method is an easy-to-implement yet effective technique for achieving high-accuracy deformation measurement using an ordinary 2D-DIC system.

  6. State of Florida 1:24,000- and 1:100,000-scale Quadrangle Index Map - Highlighting Low-Lying Areas Derived from USGS Digital Elevation Models

    USGS Publications Warehouse

    Kosovich, John J.

    2008-01-01

    In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts 1:24,000- and 1:100,000-scale quadrangle footprints over a color shaded relief representation of the State of Florida. The first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands, which highlight low-elevation areas at a coarse spatial resolution. Standard USGS National Elevation Dataset (NED) 1 arc-second (nominally 30-meter) digital elevation model (DEM) data are the basis for the map, which is designed to be used at a broad scale and for informational purposes only. The NED source data for this map consists of a mixture of 30-meter- and 10-meter-resolution DEMs. The NED data were derived from the original 1:24,000-scale USGS topographic map bare-earth contours, which were converted into gridded quadrangle-based DEM tiles at a constant post spacing (grid cell size) of either 30 meters (data before the mid-1990s) or 10 meters (mid-1990s and later data). These individual-quadrangle DEMs were then converted to spherical coordinates (latitude/longitude decimal degrees) and edge-matched to ensure seamlessness. Figure 1 shows a similar representation for the entire U.S. Gulf Coast, using coarsened 30-meter NED data. Areas below sea level typically are surrounded by levees or some other type of flood-control structures. State and county boundary, hydrography, city, and road layers were modified from USGS National Atlas data downloaded in 2003. Quadrangle names, dated April, 2006, were obtained from the Federal Geographic Names Information System. The NED data were downloaded in 2004.

  7. Exploring the relationship between hydrologic parameters and nutrient loads using digital elevation model and GIS - a case study from Sugarcreek headwaters, Ohio, U.S.A.

    PubMed

    Prasad, V Krishna; Ortiz, Ariel; Stinner, Ben; McCartney, David; Parker, Jason; Hudgins, Deana; Hoy, Casey; Moore, Richard

    2005-11-01

    Ohio is typical among the Midwestern and Eastern United States with high levels of water pollutants, the main sources being from agriculture. In this study, we used a digital elevation model in conjunction with hydrological indices to determine the role of landscape complexity affecting the spatial and temporal variation in pollutant levels, in one of the most impaired headwater streams in Ohio. More than eighty five percent of the study area is dominated by agriculture. Spatial distribution of slope (S), altitude and wetness index along with other watershed parameters such as flow direction, flow accumulation, stream networks, flow stream orders and erosion index were used within a Geographic Information Systems framework to quantify variation in nitrate and phosphate loads to headwater streams. Stream monitoring data for nutrient loads were used to correlate the observed spatial and temporal patterns with hydrological parameters using multiple linear regressions. Results from the wetness index calculated from a digital elevation model suggested a range of 0.10-16.39, with more than 35% having values less than 4.0. A Revised Universal Soil Loss Equation (RUSLE) predicted soil loss in the range of 0.01-4.0 t/ha/yr. Nitrate nitrogen levels in the study area paralleled precipitation patterns over time, with higher nitrate levels corresponding to high precipitation. Atmospheric deposition through precipitation could explain approximately 35% of total nitrate levels observed in streams. Among the different topographic variables and hydrological indices, results from the step-wise multiple regression suggested the following best predictors, (1) elevation range and upstream flow length for nitrate, (2) flow direction and upstream flow length for ammonia-nitrogen and slope, and (3) elevation range for phosphate levels. Differences in the landscape models observed for nitrate, phosphate and ammonia-nitrogen in the surface waters were attributed partly to differences in the

  8. Slope adjustment of runoff curve number (CN) using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) for Kuantan River Basin

    NASA Astrophysics Data System (ADS)

    Akbari, Abolghasem

    2015-10-01

    The Natural Resources Conservation Service Curve Number (NRCS-CN) method is widely used for predicting direct runoff from rainfall. It employs the hydrologic soil groups and landuse information along with period soil moisture conditions to derive NRCS-CN. This method has been well documented and available in popular rainfall-runoff models such as HEC-HMS, SWAT, SWMM and many more. The Sharply-Williams and Hank methods was used to adjust CN values provided in standard table of TR-55. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) is used to derive slope map with spatial resolution of 30 m for Kuantan River Basin (KRB). The two investigated method stretches the conventional CN domain to the lower values. The study shows a successful application of remote sensing data and GIS tools in hydrological studies. The result of this work can be used for rainfall-runoff simulation and flood modeling in KRB.

  9. Dose reduction and its influence on diagnostic accuracy and radiation risk in digital mammography: an observer performance study using an anthropomorphic breast phantom

    PubMed Central

    Svahn, Tony; Hemdal, Bengt; Ruschin, Mark; Chakraborty, Dev P; Andersson, Ingvar; Tingberg, Anders; Mattsson, Sören

    2008-01-01

    This study aimed to investigate the effect of dose reduction on diagnostic accuracy and radiation risk in digital mammography. Simulated masses and microcalcifications were positioned in an anthropomorphic breast phantom. Thirty digital images, 14 with lesions, 16 without, were acquired of the phantom using a Mammomat Novation (Siemens, Erlangen, Germany) at each of three dose levels. These corresponded to 100%, 50% and 30% of the normally used average glandular dose (AGD; 1.3 mGy for a standard breast). Eight observers interpreted the 90 unprocessed images in a free-response study and the data was analyzed with the jackknife free-response receiver operating characteristic (JAFROC) method. Observer performance was assessed using the JAFROC figure of merit (FOM). The benefit of radiation risk reduction was estimated based on several risk models. There was no statistically significant difference in performance, as described by the FOM, between the 100% and the 50% dose levels. However, the FOMs for both the 100% and the 50% dose were significantly different from the corresponding quantity for the 30% dose level (F-statistic = 4.95, p-value = 0.01). A dose reduction of 50% would result in 3-9 fewer breast cancer fatalities per 100,000 women undergoing annual screening from the age of 40 to 49 years. The results of the study indicate a possibility of reducing the dose to the breast to half of the dose level currently used. This has to be confirmed in clinical studies and possible differences depending on lesion type should be further examined. PMID:17704316

  10. Comparison of transform coding methods with an optimal predictor for the data compression of digital elevation models

    NASA Technical Reports Server (NTRS)

    Lewis, Michael

    1994-01-01

    Statistical encoding techniques enable the reduction of the number of bits required to encode a set of symbols, and are derived from their probabilities. Huffman encoding is an example of statistical encoding that has been used for error-free data compression. The degree of compression given by Huffman encoding in this application can be improved by the use of prediction methods. These replace the set of elevations by a set of corrections that have a more advantageous probability distribution. In particular, the method of Lagrange Multipliers for minimization of the mean square error has been applied to local geometrical predictors. Using this technique, an 8-point predictor achieved about a 7 percent improvement over an existing simple triangular predictor.

  11. Evaluating the Impact of Sea Level Rise and Coastal Flooding on NASA Centers and Facilities by Implementing Terrestrial Laser Scanning Surveys to Improve Coastal Digital Elevation and Inundation Models

    NASA Astrophysics Data System (ADS)

    Bell, L. J.; Nerem, R. S.; Williams, K.; Meertens, C.; Lestak, L.; Masters, D.

    2014-12-01

    Sea level is rising in response to climate change. Currently the global mean rate is a little over 3 mm/year, but it is expected to accelerate significantly over this century. This will have a profound impact on coastal populations and infrastructure, including NASA centers and facilities. A detailed study proposed by the University of Colorado's Center for Astrodynamics Research on the impact of sea level rise on several of NASA's most vulnerable facilities was recently funded by NASA. Individual surveys at several high-risk NASA centers were conducted and used as case studies for a broader investigation that needs to be done for coastal infrastructure around the country. The first two years of this study included implementing and conducting a terrestrial laser scanning (TLS) and GPS survey at Kennedy Space Center, Cape Canaveral, Florida, Wallops Flight Facility, Wallops Island, Virginia, Langley Research Center, Hampton, Virginia, and Ames Research Center, Moffett Field, California. We are currently using airborne LiDAR (Light Detection and Ranging) data and TLS (Terrestrial Laser Scanning) data to construct detailed digital elevation models (DEMs) of the facilities that we have assessed. The TLS data acquired at each center provides a very dense point cloud that is being used to improve the detail and accuracy of the digital elevation models currently available. We are also using GPS data we acquired at each center to assess the rate of vertical land movement at the facilities and to tie the DEM to tide gauges and other reference points. With completed, detailed DEMs of the topography and facilities at each center, a series of simple inundation models will then be applied to each area. We will use satellite altimeter data from TOPEX, Jason-1, and Jason-2 to assess the sea level changes observed near these NASA facilities over the last 20 years along with sea level projections from global climate models (GCMs) and semi-empirical projections to make detailed maps

  12. Use of the ER-2 and IFSAR for digital terrain matrix, difference digital terrain matrix, and vector difference digital terrain matrix collection

    SciTech Connect

    Malliot, H.A.

    1996-10-01

    A national digital terrain matrix (DTM) archive with sub-meter elevation precision and three meter or less post spacing will have numerous commercial government and research uses. The Lockheed Martin Missiles and Space Digital Terrain Elevation Mapping System (DTEMS) will be used to collect a DTM archive with average relative one {sigma} elevation precision of 0.3 meter, average absolute one U elevation precision less than 0.6 meter, and one to three meter post spacing (posting). DTEMS data will satisfy National Map Accuracy Standards (NMAS) contour intervals of one to two meters. DTEMS will also archive orth-rectified digital polarimetric synthetic aperture radar (SAR) imagery with one to three meter resolution. A difference digital terrain matrix (DDTM) is defined as a digital data file containing elevation changes in a DTM. A DDTM archive will be useful for detection and measurement of natural or man made changes in terrain elevation. Using DTEMS to make periodic repeat DTM collections and coherent elevation change detection (CECD) to sense small elevation changes, DTEMS will be capable of resolving elevation changes of a few centimeters. A vector difference digital terrain matrix (VDDTM) is defined as a digital data file containing the X, Y and Z displacements of the ground. Using CECD with a sub-pixel digital image correlation (SPDIC) technique on pairs of DTM`s and radar images collected by DTEMS, it will be possible to measure X and Y ground displacements with resolutions of ten centimeters at posts with spacing of ten meters and measure the elevation (Z) displacement with a resolution of a few centimeters. 8 refs., 6 figs.

  13. eEF1A Controls ascospore differentiation through elevated accuracy, but controls longevity and fruiting body formation through another mechanism in Podospora anserina.

    PubMed Central

    Silar, P; Lalucque, H; Haedens, V; Zickler, D; Picard, M

    2001-01-01

    Antisuppressor mutations in the eEF1A gene of Podospora anserina were previously shown to impair ascospore formation, to drastically increase life span, and to permit the development of the Crippled Growth degenerative process. Here, we show that eEF1A controls ascospore formation through accuracy level maintenance. Examination of antisuppressor mutant perithecia reveals two main cytological defects, mislocalization of spindle and nuclei and nuclear death. Antisuppression levels are shown to be highly dependent upon both the mutation site and the suppressor used, precluding any correlation between antisuppression efficiency and severity of the sporulation impairment. Nevertheless, severity of ascospore differentiation defect is correlated with resistance to paromomycin. We also show that eEF1A controls fruiting body formation and longevity through a mechanism(s) different from accuracy control. In vivo, GFP tagging of the protein in a way that partly retains its function confirmed earlier cytological observation; i.e., this factor is mainly diffuse within the cytosol, but may transiently accumulate within nuclei or in defined regions of the cytoplasm. These data emphasize the fact that the translation apparatus exerts a global regulatory control over cell physiology and that eEF1A is one of the key factors involved in this monitoring. PMID:11514440

  14. Elevating your elevator talk

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An important and often overlooked item that every early career researcher needs to do is compose an elevator talk. The elevator talk, named because the talk should not last longer than an average elevator ride (30 to 60 seconds), is an effective method to present your research and yourself in a clea...

  15. Improving Approaches for Determining Ice Volume Change on the Greenland Ice Sheet Margin using ASTER and SPOT Digital Elevation Models and Spectral Masking

    NASA Astrophysics Data System (ADS)

    Johnson, K. N.; Rhodes, T.; Tulaczyk, S. M.; Finfrock, A.; Lajoie, L.

    2009-12-01

    The Greenland Ice Sheet (GIS) is the largest ice sheet in the Northern Hemisphere and understanding trends in its mass balance has important implications for predicting global sea level rise. High relief topography along the margin of the GIS makes it difficult to use low-resolution remote sensing to resolve ice elevations. These marginal regions however, tend to be more dynamic than the interior of the ice sheet and may show signs of ice volume loss earlier than the interior. In this study we difference georeferenced ASTER digital elevation models (DEMs) from 2000-01 (30 meter resolution) with SPOT DEMs from 2008-09 (40 meter resolution) made available through the SPIRIT IPY program. ASTER DEMs from 2006-07 are used where SPOT data is not available. The change in these DEMs is divided by the time elapsed between scenes giving change in km3 per year. The method used for DEM production is not accurate over low contrast surfaces such as water, and snow. High relief bedrock can also have more error than areas of glacial ice due to slope. Masking snow, water, and rock from scenes minimizes total error. Most methods of spectral masking available in the literature rely on establishing thresholds for a scene which separate snow from ice from water. In order to apply these methods to multiple scenes taken at different latitudes, seasons, and sun altitudes, a new set of thresholds need to be developed for each scene which proves to be a very time intensive process. When covering large areas with a mosaic of scenes, these methods have not proven applicable. We have developed a method of nesting masks which allows for faster and less subjective trial-and-error threshold setting. This method can be applied to a range of scenes with little to no individual manipulation giving a repeatable result. The first mask eliminates most bedrock with a negative NDSI and fjord water and sea ice with an elevation of about 0. A principal components analysis (PCA) is done under this mask for

  16. Accuracy of DSM based on digital aerial image matching. (Polish Title: Dokładność NMPT tworzonego metodą automatycznego dopasowania cyfrowych zdjęć lotniczych)

    NASA Astrophysics Data System (ADS)

    Kubalska, J. L.; Preuss, R.

    2013-12-01

    Digital Surface Models (DSM) are used in GIS data bases as single product more often. They are also necessary to create other products such as3D city models, true-ortho and object-oriented classification. This article presents results of DSM generation for classification of vegetation in urban areas. Source data allowed producing DSM with using of image matching method and ALS data. The creation of DSM from digital images, obtained by Ultra Cam-D digital Vexcel camera, was carried out in Match-T by INPHO. This program optimizes the configuration of images matching process, which ensures high accuracy and minimize gap areas. The analysis of the accuracy of this process was made by comparison of DSM generated in Match-T with DSM generated from ALS data. Because of further purpose of generated DSM it was decided to create model in GRID structure with cell size of 1 m. With this parameter differential model from both DSMs was also built that allowed determining the relative accuracy of the compared models. The analysis indicates that the generation of DSM with multi-image matching method is competitive for the same surface model creation from ALS data. Thus, when digital images with high overlap are available, the additional registration of ALS data seems to be unnecessary.

  17. Diagnostic yield and accuracy of CT angiography, MR angiography, and digital subtraction angiography for detection of macrovascular causes of intracerebral haemorrhage: prospective, multicentre cohort study

    PubMed Central

    Velthuis, Birgitta K; Rinkel, Gabriël J E; Algra, Ale; de Kort, Gérard A P; Witkamp, Theo D; de Ridder, Johanna C M; van Nieuwenhuizen, Koen M; de Leeuw, Frank-Erik; Schonewille, Wouter J; de Kort, Paul L M; Dippel, Diederik W; Raaymakers, Theodora W M; Hofmeijer, Jeannette; Wermer, Marieke J H; Kerkhoff, Henk; Jellema, Korné; Bronner, Irene M; Remmers, Michel J M; Bienfait, Henri Paul; Witjes, Ron J G M; Greving, Jacoba P; Klijn, Catharina J M

    2015-01-01

    Study question What are the diagnostic yield and accuracy of early computed tomography (CT) angiography followed by magnetic resonance imaging/angiography (MRI/MRA) and digital subtraction angiography (DSA) in patients with non-traumatic intracerebral haemorrhage? Methods This prospective diagnostic study enrolled 298 adults (18-70 years) treated in 22 hospitals in the Netherlands over six years. CT angiography was performed within seven days of haemorrhage. If the result was negative, MRI/MRA was performed four to eight weeks later. DSA was performed when the CT angiography or MRI/MRA results were inconclusive or negative. The main outcome was a macrovascular cause, including arteriovenous malformation, aneurysm, dural arteriovenous fistula, and cavernoma. Three blinded neuroradiologists independently evaluated the images for macrovascular causes of haemorrhage. The reference standard was the best available evidence from all findings during one year’s follow-up. Study answer and limitations A macrovascular cause was identified in 69 patients (23%). 291 patients (98%) underwent CT angiography; 214 with a negative result underwent additional MRI/MRA and 97 with a negative result for both CT angiography and MRI/MRA underwent DSA. Early CT angiography detected 51 macrovascular causes (yield 17%, 95% confidence interval 13% to 22%). CT angiography with MRI/MRA identified two additional macrovascular causes (18%, 14% to 23%) and these modalities combined with DSA another 15 (23%, 18% to 28%). This last extensive strategy failed to detect a cavernoma, which was identified on MRI during follow-up (reference strategy). The positive predictive value of CT angiography was 72% (60% to 82%), of additional MRI/MRA was 35% (14% to 62%), and of additional DSA was 100% (75% to 100%). None of the patients experienced complications with CT angiography or MRI/MRA; 0.6% of patients who underwent DSA experienced permanent sequelae. Not all patients with negative CT angiography and

  18. Digital Elevation Models of the Pre-Eruption 2000 Crater and 2004-07 Dome-Building Eruption at Mount St. Helens, Washington, USA

    USGS Publications Warehouse

    Messerich, J.A.; Schilling, S.P.; Thompson, R.A.

    2008-01-01

    Presented in this report are 27 digital elevation model (DEM) datasets for the crater area of Mount St. Helens. These datasets include pre-eruption baseline data collected in 2000, incremental model subsets collected during the 2004-07 dome building eruption, and associated shaded-relief image datasets. Each dataset was collected photogrammetrically with digital softcopy methods employing a combination of manual collection and iterative compilation of x,y,z coordinate triplets utilizing autocorrelation techniques. DEM data points collected using autocorrelation methods were rigorously edited in stereo and manually corrected to ensure conformity with the ground surface. Data were first collected as a triangulated irregular network (TIN) then interpolated to a grid format. DEM data are based on aerotriangulated photogrammetric solutions for aerial photograph strips flown at a nominal scale of 1:12,000 using a combination of surveyed ground control and photograph-identified control points. The 2000 DEM is based on aerotriangulation of four strips totaling 31 photographs. Subsequent DEMs collected during the course of the eruption are based on aerotriangulation of single aerial photograph strips consisting of between three and seven 1:12,000-scale photographs (two to six stereo pairs). Most datasets were based on three or four stereo pairs. Photogrammetric errors associated with each dataset are presented along with ground control used in the photogrammetric aerotriangulation. The temporal increase in area of deformation in the crater as a result of dome growth, deformation, and translation of glacial ice resulted in continual adoption of new ground control points and abandonment of others during the course of the eruption. Additionally, seasonal snow cover precluded the consistent use of some ground control points.

  19. Accuracy of Cone Beam Computed Tomography, Photostimulable Phosphor Plate Digital Radiography and Conventional Radiography for Detection of Artificial Cancellous Bone Defects

    PubMed Central

    Bardal, Roghieh; Jahanihashemi, Hassan; Mostafavi, Maryam; Kalhor, Esmaeil; Tofangchiha, Maryam; Dehghani, Mahdieh

    2015-01-01

    Objectives: The optimal goal of radiography is to provide high-quality diagnostic images with the least patient radiation dose. The aim of this study was to evaluate the accuracy of cone-beam computed tomography (CBCT) and intraoral photostimulable phosphor plate (PSP) digital and film-based conventional radiography for detection of artificial cancellous bone defects. Materials and Methods: Five dry human mandibles were used in this study. The mandibles were placed inside a water bath made of plexiglass plates; then PSP and CBCT scans were obtained. The mandibles were cut by a coping saw in buccolingual dimension and oval defects measuring 6.1×6.1 mm, 3×6.1 mm and 4×4 mm were created by a milling machine in the spongy bone. After fixing the two parts together (buccal and lingual), radiographs were repeated. Presence or absence of defects on images was evaluated and recorded by the two observers. Using SPSS 16, compatibility level, sensitivity, specificity and receiver operating curve (ROC) analysis were determined for each observer. Results: The intraobserver agreement in all three imaging modalities was low to moderate (kappa≤0.613). The inter-observer agreement in all the three imaging modalities was moderate (kappa=0.406). The area under the curve (AUC) of the imaging modalities in each observation was not significantly different. The area under the curve based on defect size for the two observers was not significantly different either. Conclusion: Defects confined to spongy bone can be identified on film and PSP radiographs and CBCT scans. However, interpretation of PSP images and CBCT scans needs greater expertise and skills. PMID:27507990

  20. The location of Airy-0, the Mars prime meridian reference, from stereo photogrammetric processing of THEMIS IR imaging and digital elevation data

    NASA Astrophysics Data System (ADS)

    Duxbury, T. C.; Christensen, P.; Smith, D. E.; Neumann, G. A.; Kirk, R. L.; Caplinger, M. A.; Albee, A. A.; Seregina, N. V.; Neukum, G.; Archinal, B. A.

    2014-12-01

    The small crater Airy-0 was selected from Mariner 9 images to be the reference for the Mars prime meridian. Initial analyses in the year 2000 tied Viking Orbiter and Mars Orbiter Camera images of Airy-0 to the evolving Mars Orbiter Laser Altimeter global digital terrain model to update the location of Airy-0. Based upon this tie and radiometric tracking of landers/rovers from Earth, new expressions for the Mars spin axis direction, spin rate, and prime meridian epoch value were produced to define the orientation of the Martian surface in inertial space over time. Since the Mars Global Surveyor mission and Mars Orbiter Laser Altimeter global digital terrain model were completed some time ago, a more exhaustive study has been performed to determine the accuracy of the Airy-0 location and orientation of Mars at the standard epoch. Thermal Emission Imaging System (THEMIS) IR image cubes of the Airy and Gale crater regions were tied to the global terrain grid using precision stereo photogrammetric image processing techniques. The Airy-0 location was determined to be about 0.001° east of its predicted location using the currently defined International Astronomical Union (IAU) prime meridian location. Information on this new location and how it was derived will be provided to the NASA Mars Exploration Program Geodesy and Cartography Working Group for their assessment. This NASA group will make a recommendation to the IAU Working Group on Cartographic Coordinates and Rotational Elements to update the expression for the Mars spin axis direction, spin rate, and prime meridian location.

  1. NATIONAL ELEVATION DATASET

    EPA Science Inventory

    The USGS National Elevation Dataset (NED) has been developed by merging the highest-resolution, best-quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital ...

  2. NATIONAL ELEVATION DATASET HILLSHADE

    EPA Science Inventory

    The USGS National Elevation Dataset (NED) has been developed bymerging the highest-resolution, best-quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital E...

  3. High-resolution digital elevation model from tri-stereo Pleiades-1 satellite imagery for lava flow volume estimates at Fogo Volcano

    NASA Astrophysics Data System (ADS)

    Bagnardi, Marco; González, Pablo J.; Hooper, Andrew

    2016-06-01

    Resolving changes in topography through time using accurate high-resolution digital elevation models (DEMs) is key to understanding active volcanic processes. For the first time in a volcanic environment, we utilize very high-resolution tri-stereo optical imagery acquired by the Pleiades-1 satellite constellation and generate a 1 m resolution DEM of Fogo Volcano, Cape Verde -- the most active volcano in the Eastern Atlantic region. Point cloud density is increased by a factor of 6.5 compared to conventional stereo imagery, and the number of 1 m2 pixels with no height measurements is reduced by 43%. We use the DEM to quantify topographic changes associated with the 2014-2015 eruption at Fogo. Height differences between the posteruptive Pleiades-1 DEM and the preeruptive topography from TanDEM-X give a lava flow volume of 45.83 ± 0.02 × 106 m3, emplaced over an area of 4.8 km2 at a mean rate of 6.8 m3 s-1.

  4. Adjustment of Measurements with Multiplicative Errors: Error Analysis, Estimates of the Variance of Unit Weight, and Effect on Volume Estimation from LiDAR-Type Digital Elevation Models

    PubMed Central

    Shi, Yun; Xu, Peiliang; Peng, Junhuan; Shi, Chuang; Liu, Jingnan

    2014-01-01

    Modern observation technology has verified that measurement errors can be proportional to the true values of measurements such as GPS, VLBI baselines and LiDAR. Observational models of this type are called multiplicative error models. This paper is to extend the work of Xu and Shimada published in 2000 on multiplicative error models to analytical error analysis of quantities of practical interest and estimates of the variance of unit weight. We analytically derive the variance-covariance matrices of the three least squares (LS) adjustments, the adjusted measurements and the corrections of measurements in multiplicative error models. For quality evaluation, we construct five estimators for the variance of unit weight in association of the three LS adjustment methods. Although LiDAR measurements are contaminated with multiplicative random errors, LiDAR-based digital elevation models (DEM) have been constructed as if they were of additive random errors. We will simulate a model landslide, which is assumed to be surveyed with LiDAR, and investigate the effect of LiDAR-type multiplicative error measurements on DEM construction and its effect on the estimate of landslide mass volume from the constructed DEM. PMID:24434880

  5. Adjustment of measurements with multiplicative errors: error analysis, estimates of the variance of unit weight, and effect on volume estimation from LiDAR-type digital elevation models.

    PubMed

    Shi, Yun; Xu, Peiliang; Peng, Junhuan; Shi, Chuang; Liu, Jingnan

    2013-01-01

    Modern observation technology has verified that measurement errors can be proportional to the true values of measurements such as GPS, VLBI baselines and LiDAR. Observational models of this type are called multiplicative error models. This paper is to extend the work of Xu and Shimada published in 2000 on multiplicative error models to analytical error analysis of quantities of practical interest and estimates of the variance of unit weight. We analytically derive the variance-covariance matrices of the three least squares (LS) adjustments, the adjusted measurements and the corrections of measurements in multiplicative error models. For quality evaluation, we construct five estimators for the variance of unit weight in association of the three LS adjustment methods. Although LiDAR measurements are contaminated with multiplicative random errors, LiDAR-based digital elevation models (DEM) have been constructed as if they were of additive random errors. We will simulate a model landslide, which is assumed to be surveyed with LiDAR, and investigate the effect of LiDAR-type multiplicative error measurements on DEM construction and its effect on the estimate of landslide mass volume from the constructed DEM. PMID:24434880

  6. Validating NASA's Airborne Multikilohertz Microlaser Altimeter (Microaltimeter) by Direct Comparison of Data Taken Over Ocean City, Maryland Against an Existing Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Abel, Peter

    2003-01-01

    NASA's Airborne Multikilohertz Microlaser Altimeter (Microaltimeter) is a scanning, photon-counting laser altimeter, which uses a low energy (less than 10 microJuoles), high repetition rate (approximately 10 kHz) laser, transmitting at 532 nm. A 14 cm diameter telescope images the ground return onto a segmented anode photomultiplier, which provides up to 16 range returns for each fire. Multiple engineering flights were made during 2001 and 2002 over the Maryland and Virginia coastal area, all during daylight hours. Post-processing of the data to geolocate the laser footprint and determine the terrain height requires post- detection Poisson filtering techniques to extract the actual ground returns from the noise. Validation of the instrument's ability to produce accurate terrain heights will be accomplished by direct comparison of data taken over Ocean City, Maryland with a Digital Elevation Model (DEM) of the region produced at Ohio State University (OSU) from other laser altimeter and photographic sources. The techniques employed to produce terrain heights from the Microaltimeter ranges will be shown, along with some preliminary comparisons with the OSU DEM.

  7. Use of Digital Elevation Models to understand and map glacial landforms — The case of the Canigou Massif (Eastern Pyrenees, France)

    NASA Astrophysics Data System (ADS)

    Frankl, Amaury; Nyssen, Jan; Calvet, Marc; Heyse, Irenée

    2010-02-01

    This paper presents an improved geomorphological methodology that uses remotely-sensed data, a Geographical Information System and a brief field campaign to allow rapid, yet, precise mapping as well as interpretation and analysis of glacial earth surface morphology in high mountain areas. The study area consists of the Quaternary-glaciated part of the Coumelade valley (Canigou massif, eastern Pyrenees, France), which ranges between 1450 and 2731 m a.s.l. A topographical-map-derived Digital Elevation Model was used for analyzing glacial landforms by extracting the slope gradient, valley profiles and the slope aspect. The results were gradually refined from the interpretations of aerial photograph and the field investigation. Glacial landforms are present above 1500 m a.s.l. and include glacial and nivation cirques, cirque and latero-frontal moraines (7.7 × 10 6 m³) and micro-scale landforms such as chattermarks, crescent grooves and polished surfaces. The geomorphological investigation reveals that the Quaternary glaciation of the Coumelade valley remained limited, resulting in a low denudation rate of 0.011 mm yr - 1 over the last glacial cycle.

  8. Multi-component mapping of karst features with remote sensing, digital elevation data and GIS: a case study from Central Crete

    NASA Astrophysics Data System (ADS)

    Siart, C.; Bubenzer, O.; Eitel, B.

    2009-04-01

    The application of remote sensing (RS) and GIS techniques based on high resolution satellite imagery in combination with digital elevation models (DEMs) can provide detailed information for geomorphologic purposes such as karst feature mapping. Moreover, area wide surveying is significantly improved and supported, as computer applications allow a very cost and time effective proceeding. The exemplary focus of the project at hand is on the Ida-Ori in Central Crete, a high mountain range predominantly consisting of Palaeozoic to Mesozoic limestones and dolomites. Subdivided into several vast high plateaus, its main geomorphologic characteristics are dry valleys of Miocene age and an intense karstification reaching from the base up to the highest peak at 2456 m a.s.l. Nearly all types of karst forms appear in immediate adjacency, while dolines, uvalas and poljes are the most frequent objects. Such depressions provide sediment traps for eroded soils or aeolian deposits and, thus, can be significantly filled with colluvial materials. Since the area wide karstification of Mount Ida has not been fully explored so far, the prime objective is to evaluate the potential and suitability of satellite data and DEMs (SRTM 90m, ASTER 15m) for the precise mapping of those structures. Furthermore, the dominant influencing variables of karst processes are investigated. To acquire spatially comprehensive information, Quickbird MS tiles (0.6 m resolution) were used for land surface classifications with RS-techniques. Subsequent to image correction and enhancement, a hybrid parallelepiped maximum likelihood classification approach was carried out. Postprocessing and conversion of raster data into vector format finally allowed spatial analyses in a GIS environment. Derivatives of DEMs (slope, aspect, contours, curvature, hydrologic drainage pattern) were generated in order to assess their suitability for karst mapping and to specify the remote sensing outcomes, particularly by conducting

  9. Satellite Remote Sensing of Landscape Freeze/Thaw State Dynamics for Complex Topography and Fire Disturbance Areas Using Multi-Sensor Radar and SRTM Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Podest, E.; McDonald, K.; Kimball, J.; Randerson, J. T.

    2003-12-01

    The annual freeze/thaw cycle drives the length of the growing season in the boreal forest, and is a major factor determining annual productivity and associated exchange of CO2 with the atmosphere. Variations in freeze/thaw processes are spatially and temporally complex in boreal environments, particularly in areas of complex topography and in fire disturbance regimes. We investigate the spatial and temporal characteristics of seasonal freeze/thaw dynamics in complex boreal landscapes, as derived from radar backscatter measured with ERS (C-band, VV polarization, 200m resolution) and JERS-1 (L-band, HH polarization, 100m resolution) Synthetic Aperture Radars (SARs), and with the SeaWinds scatterometer (Ku-band, 25km resolution). C- and L-band backscatter are applied to characterize freeze/thaw transitions for a chronosequence of recovering burn sites near Delta Junction, Alaska, and for a region of complex topography on the Kenai Peninsula, Alaska. We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freeze/thaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields. A temporal change discriminator is applied to classify time series radar imagery to classify the landscape freeze-thaw state. We apply a 30m-resolution digital elevation model (DEM) derived from Shuttle Radar Topography Mission (SRTM) data to orthorectify the time

  10. Investigation of knickpoint propagation in tributaries to the South Fork Eel River, northern California, using 10-m and LiDAR-derived digital elevation models

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Kelsey, H. M.

    2009-12-01

    Base-level lowering is expressed in the long-profile of the South Fork Eel River, northern California by a knickpoint/knickzone ~135 km upstream from its mouth. Numerous knickpoints and knickzones in tributaries of the South Fork Eel River indicate that knickpoint propagation may be the dominant process of Quaternary base-level lowering throughout the basin. We study two tributary basins downstream from the mainstem South Fork Eel River knickzone, Bear Pen and Standley Creeks, for evidence of base-level lowering via knickpoint propagation. Results from the 10-m digital elevation models (DEM) indicate that these two tributaries, and their sub-tributaries, deviate from a typical concave-up long profile, and display a convexity in profile shape toward the stream mouths. When scaled against drainage area, tributary basins within the study area are steeper in the lower reaches of the basins. Steepness indices (ksn) normalized to a reference concavity (θ) of 0.45, are ~40-60 toward the mouth of the tributary basins, whereas in the upper watersheds ksn values are typically 10-40. Knickzones are identified along several of the sub-tributaries using the 10 m DEM data base. In addition, many field-identified knickpoints are not detected on 10m DEMs. Under the auspices of the National Center for Airborne Laser Mapping high-resolution LiDAR data recently (Sept. 2009) have been collected for the study area. We anticipate additional knickpoints and more subtle knickzones will be identified with high-quality LiDAR data. If knickpoint propagation has occurred in these two tributaries, we expect not only a steepening in lower reaches of these watersheds, but an increase in valley wall slopes. LiDAR data will allow precise measurement of valley walls and channel morphometrics, and more subtle indications of knickpoint propagation may be detected.

  11. Precision agriculture in dry land: spatial variability of crop yield and roles of soil surveys, aerial photos, and digital elevation models

    NASA Astrophysics Data System (ADS)

    Nachabe, Mahmood; Ahuja, Laj; Shaffer, Mary Lou; Ascough, J.; Flynn, Brian; Cipra, J.

    1998-12-01

    In dryland, yield of crop varies substantially in space, often changing by an order of magnitude within few meters. Precision agriculture aims at exploiting this variability by changing agriculture management practices in space according to site specific conditions. Thus instead of managing a field (typical area 50 to 100 hectares) as a single unit using average conditions, the field is partitioned into small pieces of land known as management units. The size of management units can be in the order of 100 to 1,000 m2 to capture the patterns of variation of yield in the field. Agricultural practices like seeding rate, type of crop, and tillage and fertilizers are applied at the scale of the management unit to suit local agronomic conditions in unit. If successfully practiced, precision agriculture has the potential of increasing income and minimizing environmental impacts by reducing over application of crop production inputs. In the 90s, the implementation of precision agriculture was facilitated tremendously due to the wide availability and use of three technologies: (1) the Global Positioning System (GPS), (2) the Geographic Information System (GIS), and (3) remote sensing. The introduction of the GPS allowed the farmer to determine his coordinate location as equipments are moved in the field. Thus, any piece of equipment can be easily programmed to vary agricultural practices according to coordinate location over the field. The GIS allowed the storage and manipulation of large sets of data and the production of yield maps. Yield maps can be correlated with soil attributes from soil survey, and/or topographical attributes from a Digital Elevation Model (DEM). This helps predicting variation of potential yield over the landscape based on the spatial distribution of soil and topographical attributes. Soil attributes may include soil PH, Organic Matter, porosity, and hydraulic conductivity, whereas topographical attributes involve the estimations of elevation, slope

  12. Digital map of the elevation of the base of the High Plains Aquifer in the Republican River Basin upstream of Hardy, Nebraska, in parts of Nebraska, Kansas, and Colorado

    USGS Publications Warehouse

    Johnson, Michaela R.; Cornwall, James F.; Landon, Matthew K.

    2002-01-01

    This digital spatial data set consists of the aquifer base elevation contours (50-foot contour interval) for part of the High Plains aquifer in the central United States. This subset of the High Plains aquifer covers the Republican River Basin in Nebraska, Kansas, and Colorado upstream from the streamflow station on the Republican River near Hardy, Nebraska, near the Kansas/Nebraska border. In Nebraska, the digitized contours extend to the South Platte, Platte, and Little Blue Rivers. In Colorado and Kansas, the digital contours extend to the edge of the High Plains aquifer. These boundaries were chosen to simplify boundary conditions for a computer simulation model being used for a hydrologic study of the Republican River Basin. The data are not intended for use at scales larger than 1:500,000.

  13. Development of alternative data analysis techniques for improving the accuracy and specificity of natural resource inventories made with digital remote sensing data

    NASA Technical Reports Server (NTRS)

    Lillesand, T. M.; Meisner, D. E. (Principal Investigator)

    1980-01-01

    An investigation was conducted into ways to improve the involvement of state and local user personnel in the digital image analysis process by isolating those elements of the analysis process which require extensive involvement by field personnel and providing means for performing those activities apart from a computer facility. In this way, the analysis procedure can be converted from a centralized activity focused on a computer facility to a distributed activity in which users can interact with the data at the field office level or in the field itself. A general image processing software was developed on the University of Minnesota computer system (Control Data Cyber models 172 and 74). The use of color hardcopy image data as a primary medium in supervised training procedures was investigated and digital display equipment and a coordinate digitizer were procured.

  14. Releasing the digital elevation model for the whole Italian territory: a case study reporting two years of core-data dissemination for Earth Sciences communities and other stakeholders

    NASA Astrophysics Data System (ADS)

    Tarquini, Simone; Nannipieri, Luca

    2014-05-01

    EPOS (European Plate Observing System) is the European initiative for the implementation and integration of European Research Infrastructures in the field of Solid Earth Sciences. In particular, EPOS is aimed at creating a common environment for data exchange for both the scientific community and relevant stakeholders interested in Earth Sciences. In such a context, a service providing access to the complete topography of one of the countries participating in EPOS represents a step forward towards the realization of the EPOS mission. Here we report about two years of activity of a data dissemination service which released (for free) a digital elevation model (DEM) of the whole Italian territory at 10 m-resolution named TINTALY/01. The new TINITALY/01 DEM for the whole Italian territory was completed and presented by INGV in 2007. This DEM was the final result of a project funded by the Italian Ministry of the Environment. TINITALY/01 was completed in two phases: in a first phase, independent elevation models for single regions were derived, and in a second phase, all the regional models were merged into a single, seamless model covering the whole territory of Italy. In early 2012, a web portal was published (http://tinitaly.pi.ingv.it/) through which the above DEM is open for a full web-GIS navigation (3-D navigation in anaglyph mode or standard 2-D hillshade), and where internet navigators can ask for the download of the DEM dataset (in grid format, 10 m-resolution) through the compilation of an online form (http://tinitaly.pi.ingv.it/account_request_form.html). Submission of the form implies stating the destination of use for the data, and acceptance of the policy of use (i.e. no-profit use). After nearly two years from the opening of the portal, the DEM is still browsed by up to 10-20 users per day (about 3000 visits throughout 2013). As of 31 December 2013, about 220 users affiliated to nearly 150 different institutions or associations (i.e. universities

  15. Map accuracy requirements: The cartographic potential of satellite image data

    NASA Technical Reports Server (NTRS)

    Welch, R.

    1982-01-01

    Cartographic products fall into a variety of classes: topographic maps that are concerned with planimetric information and elevations or heights; thematic maps, which might be used for geology, vegetation, water, or to display these subjects; digital elevation maps that would be produced from digital terrain data; and finally image maps. In terms of satellite applications, thematic maps and image maps are emphasized. The objectives are to consider, first, if resolution will be adequate for the identification of control and for the compilation of map products. Then, second, to define map accuracy standards and to determine the potential for meeting these standards with image data from the film camera, scanner and linear array systems of the 1980s.

  16. High-resolution digital elevation dataset for Crater Lake National Park and vicinity, Oregon, based on LiDAR survey of August-September 2010 and bathymetric survey of July 2000

    USGS Publications Warehouse

    Robinson, Joel E.

    2012-01-01

    Crater Lake partially fills the caldera that formed approximately 7,700 years ago during the eruption of a 12,000-foot volcano known as Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama devastated the surrounding landscape, left a thick deposit of pumice and ash in adjacent valleys, and spread a blanket of volcanic ash as far away as southern Canada. Because the Crater Lake region is potentially volcanically active, knowledge of past events is important to understanding hazards from future eruptions. Similarly, because the area is seismically active, documenting and evaluating geologic faults is critical to assessing hazards from earthquakes. As part of the American Recovery and Reinvestment Act (ARRA) of 2009, the U.S. Geological Survey was awarded funding for high-precision airborne LiDAR (Light Detection And Ranging) data collection at several volcanoes in the Cascade Range through the Oregon LiDAR Consortium, administered by the Oregon Department of Geology and Mineral Industries (DOGAMI). The Oregon LiDAR Consortium contracted with Watershed Sciences, Inc., to conduct the data collection surveys. Collaborating agencies participating with the Oregon LiDAR Consortium for data collection in the Crater Lake region include Crater Lake National Park (National Park Service) and the Federal Highway Administration. In the immediate vicinity of Crater Lake National Park, 798 square kilometers of LiDAR data were collected, providing a digital elevation dataset of the ground surface beneath forest cover with an average resolution of 1.6 laser returns/m2 and both vertical and horizontal accuracies of ±5 cm. The LiDAR data were mosaicked in this report with bathymetry of the lake floor of Crater Lake, collected in 2000 using high-resolution multibeam sonar in a collaborative effort between the U.S. Geological Survey, Crater Lake National Park, and the Center for Coastal and Ocean Mapping at the University of New Hampshire. The bathymetric survey

  17. Children's accuracy of portion size estimation using digital food images: effects of interface design and size of image on computer screen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to test the effect of image size and presence of size cues on the accuracy of portion size estimation by children. Children were randomly assigned to seeing images with or without food size cues (utensils and checked tablecloth) and were presented with sixteen food models (foods co...

  18. Digital caliper

    USGS Publications Warehouse

    Cable, Louella E.

    1967-01-01

    The large number of measurements needed to describe fully the characteristics of biological specimens and other objects has always been tedious and time consuming. The work can be done much more rapidly and with greater accuracy with a digital caliper recently developed by us. The digital caliper is a new electronic instrument built to measure objects precisely throughout the range of 0.1 mm to 1.0 m. Calipers of several different discrete sizes make it possible to select the most convenient unit for the particular range of length and degree of accuracy desired.

  19. Combining digital elevation data (SRTM/ASTER), high resolution satellite imagery (Quickbird) and GIS for geomorphological mapping: A multi-component case study on Mediterranean karst in Central Crete

    NASA Astrophysics Data System (ADS)

    Siart, Christoph; Bubenzer, Olaf; Eitel, Bernhard

    2009-11-01

    Remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials. In this context, this paper examines the application and quality of digital elevation models (SRTM and ASTER DEMs), high resolution satellite imagery (Quickbird) and GIS techniques for the detection and mapping of karst landforms (mainly enclosed depressions) at different scales in the Ida Mountains of Central Crete. Besides discussing methodological issues and evaluating suitability potentials, we conducted an exemplary case study based on spatial analysis of the regional karst morphology. Different input datasets and processing methods are applied (GIS-based analysis, land cover classification, raster calculations, etc.) in order to carry out an area-wide surveying and mapping of karst depressions. The findings are supported and validated by auxiliary field studies. Due to the level of detail and occasional data errors, an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently. Our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest, existing environmental conditions and data quality. A semi-automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and DEM analysis yields the best results, especially when indirect karst-indicating variables like iron oxide-rich sediments are included as detection criteria. The multi-component application presented in this paper provides a time-saving and effective tool for meso- to macro-scale object detection and extensive study areas. However, the potential of fully automated karst feature mapping still needs to be explored in future work. Concerning the spatial dimension of karstification in Central Crete, the GIS-based results allow differentiating

  20. Mars elevation distribution

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington-Kraus, Annie E.; Ablin, Karyn K.

    1991-01-01

    A Digital Terrain Model (DTM) of Mars was derived with both Mercator and Sinusoidal Equal-Area projections from the global topographic map of Mars (scale 1:15 million, contour interval 1 km). Elevations on the map are referred to Mars' topographic datum that is defined by the gravity field at a 6.1-millibar pressure surface with respect to the center of mass of Mars. The DTM has a resolution at the equator of 1/59.226 degrees (exactly 1 km) per pixel. By using the DTM, the volumetric distribution of Mars topography above and below the datum has previously been calculated. Three types of elevation distributions of Mars' topography were calculated from the same DTM: (1) the frequency distribution of elevations at the pixel resolution; (2) average elevations in increments of 6 degrees in both longitude and latitude; and (3) average elevations in 36 separate blocks, each covering 30 degrees of latitude and 60 degrees of longitude.

  1. Countrywide digital elevation models for the Islamic Republic of Mauritania—SRTM and ASTER (phase V, deliverable 65): Chapter F in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Lee, Gregory K.

    2015-01-01

    A digital elevation model (DEM) of the entire country of the Islamic Republic of Mauritania was produced using Shuttle Radar Topography Mission (SRTM) data as required for deliverable 65 of the contract. In addition, because of significant recent advancements of availability, seamlessness, and validity of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) global elevation data, the U.S. Geological Survey (USGS) extended its efforts to include a higher resolution countrywide ASTER DEM as value added to the required Deliverable 63, which was limited to five areas within the country. Both SRTM and ASTER countrywide DEMs have been provided in ERDAS Imagine (.img) format that is also directly compatible with ESRI ArcMap, ArcGIS Explorer, and other GIS applications.

  2. Digital Sensor Technology

    SciTech Connect

    Ted Quinn; Jerry Mauck; Richard Bockhorst; Ken Thomas

    2013-07-01

    The nuclear industry has been slow to incorporate digital sensor technology into nuclear plant designs due to concerns with digital qualification issues. However, the benefits of digital sensor technology for nuclear plant instrumentation are substantial in terms of accuracy, reliability, availability, and maintainability. This report demonstrates these benefits in direct comparisons of digital and analog sensor applications. It also addresses the qualification issues that must be addressed in the application of digital sensor technology.

  3. Accuracy of 3d Reconstruction in AN Illumination Dome

    NASA Astrophysics Data System (ADS)

    MacDonald, Lindsay; Toschi, Isabella; Nocerino, Erica; Hess, Mona; Remondino, Fabio; Robson, Stuart

    2016-06-01

    The accuracy of 3D surface reconstruction was compared from image sets of a Metric Test Object taken in an illumination dome by two methods: photometric stereo and improved structure-from-motion (SfM), using point cloud data from a 3D colour laser scanner as the reference. Metrics included pointwise height differences over the digital elevation model (DEM), and 3D Euclidean differences between corresponding points. The enhancement of spatial detail was investigated by blending high frequency detail from photometric normals, after a Poisson surface reconstruction, with low frequency detail from a DEM derived from SfM.

  4. Computer Programs to Display and Modify Data in Geographic Coordinates and Methods to Transfer Positions to and from Maps, with Applications to Gravity Data Processing, Global Positioning Systems, and 30-Meter Digital Elevation Models

    USGS Publications Warehouse

    Plouff, Donald

    1998-01-01

    Computer programs were written in the Fortran language to process and display gravity data with locations expressed in geographic coordinates. The programs and associated processes have been tested for gravity data in an area of about 125,000 square kilometers in northwest Nevada, southeast Oregon, and northeast California. This report discusses the geographic aspects of data processing. Utilization of the programs begins with application of a template (printed in PostScript format) to transfer locations obtained with Global Positioning Systems to and from field maps and includes a 5-digit geographic-based map naming convention for field maps. Computer programs, with source codes that can be copied, are used to display data values (printed in PostScript format) and data coverage, insert data into files, extract data from files, shift locations, test for redundancy, and organize data by map quadrangles. It is suggested that 30-meter Digital Elevation Models needed for gravity terrain corrections and other applications should be accessed in a file search by using the USGS 7.5-minute map name as a file name, for example, file '40117_B8.DEM' contains elevation data for the map with a southeast corner at lat 40? 07' 30' N. and lon 117? 52' 30' W.

  5. Contemporary Accuracy of Digital Abdominal X-Ray for Follow-Up of Pure Calcium Urolithiasis: Is There Still a Role?

    PubMed

    O'Kane, Dermot; Papa, Nathan; Manning, Todd; Quinn, Jonathan; Hawes, Alice; Smith, Neil; McClintock, Scott; Lawrentschuk, Nathan; Bolton, Damien M

    2016-08-01

    Radiological imaging remains the cornerstone of follow-up of patients with urolithiasis. Plain abdominal X-ray (XRKUB) of these patients is largely becoming obsolete in favor of noncontrast computed tomography of the abdomen and pelvis (CTKUB), which offers superior sensitivity and specificity. Contentiousness exists, however, related to the radiation doses associated with CT. Calcium oxalate remains the most common stone composition across most populations. These calculi are radiopaque and thus follow-up with XRKUB may be appropriate in some settings, avoiding the higher radiation doses associated with standard protocol CT. With the emergence of low-dose CT, however, and the modest accuracy of XRKUB, the ongoing role for XRKUB in the management of urolithiasis is debatable. In this study, we assessed the proportion of pure calcium urolithiasis visible on XRKUB to assess the utility of XRKUB for follow-up of pure calcium urolithiasis. Hospital laboratory databases were analysed to identify patients who had undergone urological intervention and extraction of urolithiasis composed of pure calcium salts, who had undergone CTKUB and XRKUB during the same episode for diagnosis of the calculus. One hundred five calculi were included and the imaging for each patient analyzed. 79/105 calculi (75%) identified on CT were visible on XRKUB. The median calculus visible on XRKUB was 7.0 mm (interquartile range [IQR] 5.0-10.0 mm), the median calculus not seen was 4.25 mm (IQR 3.5-7.0 mm) as measured on CT (p < 0.01). XRKUB accuracy varied according to calculus position within the renal tract. Calculi were most often visible in the renal pelvis and proximal ureter (86%), 50% of mid-ureteral and 72% of distal ureteral calculi were visible (p = 0.01). Until low-dose CT protocols become widely adopted, XRKUB still has a limited role in the management of pure calcium urolithiasis in selected patients. Due to its modest accuracy in many settings, this role is limited

  6. Improving forest cover classification accuracy from Landsat by incorporating topographic information

    NASA Technical Reports Server (NTRS)

    Strahler, A. H.; Logan, T. L.; Bryant, N. A.

    1978-01-01

    The paper shows that accuracies of computer classification of species-specific forest cover types from Landsat imagery can be improved by 27% or more through the incorporation of topographic information from digital terrain tapes registered to multidate Landsat imagery. The topographic information improves classification accuracies because many common forest tree species have preferred elevation ranges and slope aspects. These preferences allow the separation of forest cover types which have similar spectral signatures but different species compositions. It is noted that the development of a classification system which uses prior probabilities and sets of prior probabilities conditioned by one or two external variables represents a significant increase in classification power.

  7. Field Accuracy Test of Rpas Photogrammetry

    NASA Astrophysics Data System (ADS)

    Barry, P.; Coakley, R.

    2013-08-01

    Baseline Surveys Ltd is a company which specialises in the supply of accurate geospatial data, such as cadastral, topographic and engineering survey data to commercial and government bodies. Baseline Surveys Ltd invested in aerial drone photogrammetric technology and had a requirement to establish the spatial accuracy of the geographic data derived from our unmanned aerial vehicle (UAV) photogrammetry before marketing our new aerial mapping service. Having supplied the construction industry with survey data for over 20 years, we felt that is was crucial for our clients to clearly understand the accuracy of our photogrammetry so they can safely make informed spatial decisions, within the known accuracy limitations of our data. This information would also inform us on how and where UAV photogrammetry can be utilised. What we wanted to find out was the actual accuracy that can be reliably achieved using a UAV to collect data under field conditions throughout a 2 Ha site. We flew a UAV over the test area in a "lawnmower track" pattern with an 80% front and 80% side overlap; we placed 45 ground markers as check points and surveyed them in using network Real Time Kinematic Global Positioning System (RTK GPS). We specifically designed the ground markers to meet our accuracy needs. We established 10 separate ground markers as control points and inputted these into our photo modelling software, Agisoft PhotoScan. The remaining GPS coordinated check point data were added later in ArcMap to the completed orthomosaic and digital elevation model so we could accurately compare the UAV photogrammetry XYZ data with the RTK GPS XYZ data at highly reliable common points. The accuracy we achieved throughout the 45 check points was 95% reliably within 41 mm horizontally and 68 mm vertically and with an 11.7 mm ground sample distance taken from a flight altitude above ground level of 90 m.The area covered by one image was 70.2 m × 46.4 m, which equals 0.325 Ha. This finding has shown

  8. ELEVATING MECHANISM

    DOEpatents

    Frederick, H.S.; Kinsella, M.A.

    1959-02-24

    An elevator is described, which is arranged for movement both in a horizontal and in a vertical direction so that the elevating mechanism may be employed for servicing equipment at separated points in a plant. In accordance with the present invention, the main elevator chassis is suspended from a monorail. The chassis, in turn supports a vertically moveable carriage, a sub- carriage vertically moveable on the carriage, and a turntable carried by the sub- carriage and moveable through an arc of 90 with the equipment attached thereto. In addition, the chassis supports all the means required to elevate or rotate the equipment.

  9. Accuracy of aimed arm movements in changed gravity.

    PubMed

    Bock, O; Howard, I P; Money, K E; Arnold, K E

    1992-11-01

    We studied the accuracy of aimed arm movements in normal gravity, and during the hypergravity (hyper-G) and microgravity (micro-G) episodes of KC-135 parabolic flights. Subjects pointed at mirror-viewed targets without sight of their arm, and final pointing position was measured by a digitizing pad. Compared with the normal gravity (normal-G) baseline, subjects pointed consistently higher in hyper-G, and still higher in micro-G. Results were not different if subjects viewed targets only during normal-G and pointed at their memorized position under changed gravity (changed-G); this suggests that the "elevator illusion" played a minor role in our study. The observed impairments were attributed to degraded proprioceptive feedback and/or inappropriate motor programs in changed-G. Pointing accuracy improved movement-to-movement but not parabola-to-parabola, indicating that prolonged exposure is needed for sustained adaptation. PMID:1445164

  10. Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models

    NASA Technical Reports Server (NTRS)

    Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

    2003-01-01

    We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.

  11. 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.

  12. Accuracy Comparison of Vhr Systematic-Ortho Satellite Imageries against Vhr Orthorectified Imageries Using Gcp

    NASA Astrophysics Data System (ADS)

    Widyaningrum, E.; Fajari, M.; Octariady, J.

    2016-06-01

    The Very High Resolution (VHR) satellite imageries such us Pleiades, WorldView-2, GeoEye-1 used for precise mapping purpose must be corrected from any distortion to achieve the expected accuracy. Orthorectification is performed to eliminate geometric errors of the VHR satellite imageries. Orthorectification requires main input data such as Digital Elevation Model (DEM) and Ground Control Point (GCP). The VHR systematic-ortho imageries were generated using SRTM 30m DEM without using any GCP data. The accuracy value differences of VHR systematic-ortho imageries and VHR orthorectified imageries using GCP currently is not exactly defined. This study aimed to identified the accuracy comparison of VHR systematic-ortho imageries against orthorectified imageries using GCP. Orthorectified imageries using GCP created by using Rigorous model. Accuracy evaluation is calculated by using several independent check points.

  13. 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

  14. 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

  15. Understanding of altered N-glycosylation-related gene expression in recombinant Chinese hamster ovary cells subjected to elevated ammonium concentration by digital mRNA counting.

    PubMed

    Ha, Tae Kwang; Kim, Yeon-Gu; Lee, Gyun Min

    2015-08-01

    To understand the effects of ammonium on N-glycosylation, recombinant Chinese hamster ovary (rCHO) cells that produce the Fc-fusion protein were cultivated in serum-free suspension cultures with 10 mM ammonium addition. The addition of ammonium to the cultures reduced the relative proportion of acidic isoforms and sialic acid content of an Fc-fusion protein. Fifty two N-glycosylation-related gene expressions were assessed by the NanoString nCounter system, which provides a digital readout using custom-designed color-coded probes. Among these queried genes, thirteen genes (gale, nans, gpi, man2a1, b4galt5, b4galt7, st3gal2, st3gal5, glb1, hexa, hexb, neu1, and neu3) were up-regulated over 1.5 times in the culture with ammonium addition after 5 days of culture; however, none of the 54 genes were significantly different after 3 days of culture. In particular, the expression level of neu1 (sialidase-1) and neu3 (sialidase-3), which play a role in reduction of sialylation, increased over 2 times. Likewise, the protein expression levels of sialidase-1 and sialidase-3 determined by Western blot analysis were also increased significantly in the culture with ammonium addition. Transient transfection of neu-1 or neu3-targeted siRNAs significantly improved the sialic acid content of the Fc-fusion protein in the culture with ammonium addition, indicating that the decreased sialic acid content was in part due to the increased expression level of sialidase. Taken together, the results obtained in this study provide a better understanding of the detrimental effect of ammonium on N-glycosylation, especially sialylation, in rCHO cells. PMID:25728222

  16. A Statistical Analysis of the Accuracy of the Digitized Magnitudes of Photometric Plates on the Timescale of Decades with an Application to the Century-Long Light Curve of KIC 8462852

    NASA Technical Reports Server (NTRS)

    Hippke, Michael; Angerhausen, Daniel; Lund, Michael B.; Pepper, Joshua; Stassun, Keivan G.

    2016-01-01

    We present a statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the timescale of decades. In our examination of archival Johnson B photometry from the Harvard DASCH archive, we find a median rt mean square scatter of light curves of the order of 0.15 magnitude over the range B approximately equal to 9-17 for all calibrations. Slight underlying systematics (trends or flux discontinuities) are on a level of less than or equal to 0.2 magnitudes per century (1889–1990) for the majority of constant stars. These historic data can be unambiguously used for processes that happen on scales of magnitudes, and need to be carefully examined in cases approaching the noise floor. The characterization of these limits in photometric stability may guide future studies in their use of plate archives. We explain these limitations for the example case of KIC 8462852, which has been claimed to dim by 0.16 magnitudes per century, and show that this trend cannot be considered as significant.

  17. A Statistical Analysis of the Accuracy of the Digitized Magnitudes of Photometric Plates on the Timescale of Decades with an Application to the Century-long Light Curve of KIC 8462852

    NASA Astrophysics Data System (ADS)

    Hippke, Michael; Angerhausen, Daniel; Lund, Michael B.; Pepper, Joshua; Stassun, Keivan G.

    2016-07-01

    We present a statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the timescale of decades. In our examination of archival Johnson B photometry from the Harvard DASCH archive, we find a median rms scatter of light curves of the order of 0.15 mag over the range B ∼ 9–17 for all calibrations. Slight underlying systematics (trends or flux discontinuities) are on a level of ≲0.2 mag per century (1889–1990) for the majority of constant stars. These historic data can be unambiguously used for processes that happen on scales of magnitudes, and need to be carefully examined in cases approaching the noise floor. The characterization of these limits in photometric stability may guide future studies in their use of plate archives. We explain these limitations for the example case of KIC 8462852, which has been claimed to dim by 0.16 mag per century, and show that this trend cannot be considered as significant.

  18. Monocular Elevation Deficiency - Double Elevator Palsy

    MedlinePlus

    ... Español Condiciones Chinese Conditions Monocular Elevation Deficiency/ Double Elevator Palsy En Español Read in Chinese What is monocular elevation deficiency (Double Elevator Palsy)? Monocular Elevation Deficiency, also known by the ...

  19. 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.

  20. Elevation Derivatives for National Applications

    USGS Publications Warehouse

    U.S. Geological Survey

    2005-01-01

    The Elevation Derivatives for National Applications (EDNA) project is a multi-agency effort to develop standard topographically derived layers for use in hydrologic and environmental modeling. The EDNA takes advantage of the seamless and filtered characteristics for the National Elevation Dataset (NED) to create a hydrologically conditioned Digital Elevation Model (DEM) useful for modeling applications. The goals of the project are to create a hydrologically conditioned DEM and systematically extract a set of standard derivatives that can be used to facilitate data integration with other U.S. Geological Survey (USGS) framework data sets such as the National Hydrography Dataset (NHD) and the Watershed Boundaries Dataset (WBD).

  1. A Digital Solar Aspect Sensor

    NASA Technical Reports Server (NTRS)

    Albus, James S.

    1961-01-01

    The solar aspect sensor described herein performs the analog-to-digital conversion of data optically. To accomplish this, it uses a binary "Gray code" light mask to produce a digital indication, in vehicle-fixed coordinates, of the elevation and azimuth angles of incident light from the sun. This digital solar aspect sensor system, in Explorer X, provided measurements of both elevation and azimuth angles to +/- 2 degrees at a distance of over 140,000 statute miles.

  2. Flood delineation from synthetic aperture radar data with the help of a priori knowledge from historical acquisitions and digital elevation models in support of near-real-time flood mapping

    NASA Astrophysics Data System (ADS)

    Schlaffer, Stefan; Hollaus, Markus; Wagner, Wolfgang; Matgen, Patrick

    2012-10-01

    The monitoring of flood events with synthetic aperture radar (SAR) sensors has attracted a considerable amount of attention during the last decade, owing to the growing interest in using spaceborne data in near-real time flood management. Most existing methods for classifying flood extent from SAR data rely on pure image processing techniques. In this paper, we propose a method involving a priori knowledge about an area taken from a multitemporal time series and a digital elevation model. A time series consisting of ENVISAT ASAR acquisitions was geocoded and coregistered. Then, a harmonic model was fitted to each pixel time series. The standardised residuals of the model were classified as flooded when exceeding a certain threshold value. Additionally, the classified flood extent was limited to flood-prone areas which were derived from a freely available DEM using the height above nearest drainage (HAND) index. Comparison with two different reference datasets for two different flood events showed that the approach yielded realistic results but underestimated the inundation extent. Among the possible reasons for this are the rather coarse resolution of 150 m and the sparse data coverage for a substantial part of the time series. Nevertheless, the study shows the potential for production of rapid overviews in near-real time in support of early response to flood crises.

  3. Accuracy of tablet splitting.

    PubMed

    McDevitt, J T; Gurst, A H; Chen, Y

    1998-01-01

    We attempted to determine the accuracy of manually splitting hydrochlorothiazide tablets. Ninety-four healthy volunteers each split ten 25-mg hydrochlorothiazide tablets, which were then weighed using an analytical balance. Demographics, grip and pinch strength, digit circumference, and tablet-splitting experience were documented. Subjects were also surveyed regarding their willingness to pay a premium for commercially available, lower-dose tablets. Of 1752 manually split tablet portions, 41.3% deviated from ideal weight by more than 10% and 12.4% deviated by more than 20%. Gender, age, education, and tablet-splitting experience were not predictive of variability. Most subjects (96.8%) stated a preference for commercially produced, lower-dose tablets, and 77.2% were willing to pay more for them. For drugs with steep dose-response curves or narrow therapeutic windows, the differences we recorded could be clinically relevant. PMID:9469693

  4. The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets

    NASA Astrophysics Data System (ADS)

    Howat, I. M.; Negrete, A.; Smith, B. E.

    2014-08-01

    As part of the Greenland Ice Mapping Project (GIMP) we have produced three geospatial data sets for the entire ice sheet and periphery. These are (1) a complete, 15 m resolution image mosaic, (2) ice-covered and ice-free terrain classification masks, also posted to 15 m resolution, and (3) a complete, altimeter-registered digital elevation model posted at 30 m. The image mosaic was created from a combination of Landsat-7 and RADARSAT-1 imagery acquired between 1999 and 2002. Each pixel in the image is stamped with the acquisition date and geo-registration error to facilitate change detection. This mosaic was then used to manually produce complete ice-covered and ice-free land classification masks. Finally, we used satellite altimetry and stereo-photogrammetric digital elevation models (DEMs) to enhance an existing DEM for Greenland, substantially improving resolution and accuracy over the ice margin and periphery.

  5. National Guidelines for Digital Camera Systems Certification

    NASA Astrophysics Data System (ADS)

    Yaron, Yaron; Keinan, Eran; Benhamu, Moshe; Regev, Ronen; Zalmanzon, Garry

    2016-06-01

    Digital camera systems are a key component in the production of reliable, geometrically accurate, high-resolution geospatial products. These systems have replaced film imaging in photogrammetric data capturing. Today, we see a proliferation of imaging sensors collecting photographs in different ground resolutions, spectral bands, swath sizes, radiometric characteristics, accuracies and carried on different mobile platforms. In addition, these imaging sensors are combined with navigational tools (such as GPS and IMU), active sensors such as laser scanning and powerful processing tools to obtain high quality geospatial products. The quality (accuracy, completeness, consistency, etc.) of these geospatial products is based on the use of calibrated, high-quality digital camera systems. The new survey regulations of the state of Israel specify the quality requirements for each geospatial product including: maps at different scales and for different purposes, elevation models, orthophotographs, three-dimensional models at different levels of details (LOD) and more. In addition, the regulations require that digital camera systems used for mapping purposes should be certified using a rigorous mapping systems certification and validation process which is specified in the Director General Instructions. The Director General Instructions for digital camera systems certification specify a two-step process as follows: 1. Theoretical analysis of system components that includes: study of the accuracy of each component and an integrative error propagation evaluation, examination of the radiometric and spectral response curves for the imaging sensors, the calibration requirements, and the working procedures. 2. Empirical study of the digital mapping system that examines a typical project (product scale, flight height, number and configuration of ground control points and process). The study examine all the aspects of the final product including; its accuracy, the product pixels size

  6. Monocular Elevation Deficiency - Double Elevator Palsy

    MedlinePlus

    ... Eye Terms Conditions Frequently Asked Questions Español Condiciones Chinese Conditions Monocular Elevation Deficiency/ Double Elevator Palsy En Español Read in Chinese What is monocular elevation deficiency (Double Elevator Palsy)? ...

  7. Lunar Pole Illumination and Communications Maps Computed from GSSR Elevation Data

    NASA Technical Reports Server (NTRS)

    Bryant, Scott

    2009-01-01

    A Digital Elevation Model of the lunar south pole was produced using Goldstone Solar System RADAR (GSSR) data obtained in 2006.12 This model has 40-meter horizontal resolution and about 5-meter relative vertical accuracy. This Digital Elevation Model was used to compute average solar illumination and Earth visibility with 100 kilometers of the lunar south pole. The elevation data were converted into local terrain horizon masks, then converted into lunar-centric latitude and longitude coordinates. The horizon masks were compared to latitude, longitude regions bounding the maximum Sun and Earth motions relative to the moon. Estimates of Earth visibility were computed by integrating the area of the region bounding the Earth's motion that was below the horizon mask. Solar illumination and other metrics were computed similarly. Proposed lunar south pole base sites were examined in detail, with the best site showing yearly solar power availability of 92 percent and Direct-To-Earth (DTE) communication availability of about 50 percent. Similar analysis of the lunar south pole used an older GSSR Digital Elevation Model with 600-meter horizontal resolution. The paper also explores using a heliostat to reduce the photovoltaic power system mass and complexity.

  8. Assessment of Photogrammetric Mapping Accuracy Based on Variation Flying Altitude Using Unmanned Aerial Vehicle

    NASA Astrophysics Data System (ADS)

    Udin, W. S.; Ahmad, A.

    2014-02-01

    Photogrammetry is the earliest technique used to collect data for topographic mapping. The recent development in aerial photogrammetry is the used of large format digital aerial camera for producing topographic map. The aerial photograph can be in the form of metric or non-metric imagery. The cost of mapping using aerial photogrammetry is very expensive. In certain application, there is a need to map small area with limited budget. Due to the development of technology, small format aerial photogrammetry technology has been introduced and offers many advantages. Currently, digital map can be extracted from digital aerial imagery of small format camera mounted on light weight platform such as unmanned aerial vehicle (UAV). This study utilizes UAV system for large scale stream mapping. The first objective of this study is to investigate the use of light weight rotary-wing UAV for stream mapping based on different flying height. Aerial photograph were acquired at 60% forward lap and 30% sidelap specifications. Ground control points and check points were established using Total Station technique. The digital camera attached to the UAV was calibrated and the recovered camera calibration parameters were then used in the digital images processing. The second objective is to determine the accuracy of the photogrammetric output. In this study, the photogrammetric output such as stereomodel in three dimensional (3D), contour lines, digital elevation model (DEM) and orthophoto were produced from a small stream of 200m long and 10m width. The research output is evaluated for planimetry and vertical accuracy using root mean square error (RMSE). Based on the finding, sub-meter accuracy is achieved and the RMSE value decreases as the flying height increases. The difference is relatively small. Finally, this study shows that UAV is very useful platform for obtaining aerial photograph and subsequently used for photogrammetric mapping and other applications.

  9. Digital Sensor Technology

    SciTech Connect

    Thomas, Ken D.; Quinn, Edward L.; Mauck, Jerry L.; Bockhorst, Richard M.

    2015-02-01

    The nuclear industry has been slow to incorporate digital sensor technology into nuclear plant designs due to concerns with digital qualification issues. However, the benefits of digital sensor technology for nuclear plant instrumentation are substantial in terms of accuracy and reliability. This paper, which refers to a final report issued in 2013, demonstrates these benefits in direct comparisons of digital and analog sensor applications. Improved accuracy results from the superior operating characteristics of digital sensors. These include improvements in sensor accuracy and drift and other related parameters which reduce total loop uncertainty and thereby increase safety and operating margins. An example instrument loop uncertainty calculation for a pressure sensor application is presented to illustrate these improvements. This is a side-by-side comparison of the instrument loop uncertainty for both an analog and a digital sensor in the same pressure measurement application. Similarly, improved sensor reliability is illustrated with a sample calculation for determining the probability of failure on demand, an industry standard reliability measure. This looks at equivalent analog and digital temperature sensors to draw the comparison. The results confirm substantial reliability improvement with the digital sensor, due in large part to ability to continuously monitor the health of a digital sensor such that problems can be immediately identified and corrected. This greatly reduces the likelihood of a latent failure condition of the sensor at the time of a design basis event. Notwithstanding the benefits of digital sensors, there are certain qualification issues that are inherent with digital technology and these are described in the report. One major qualification impediment for digital sensor implementation is software common cause failure (SCCF).

  10. Mapping from ASTER stereo image data: DEM validation and accuracy assessment

    NASA Astrophysics Data System (ADS)

    Hirano, Akira; Welch, Roy; Lang, Harold

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on-board the National Aeronautics and Space Administration's (NASA's) Terra spacecraft provides along-track digital stereo image data at 15-m resolution. As part of ASTER digital elevation model (DEM) accuracy evaluation efforts by the US/Japan ASTER Science Team, stereo image data for four study sites around the world have been employed to validate prelaunch estimates of heighting accuracy. Automated stereocorrelation procedures were implemented using the Desktop Mapping System (DMS) software on a personal computer to derive DEMs with 30- to 150-m postings. Results indicate that a root-mean-square error (RMSE) in elevation between ±7 and ±15 m can be achieved with ASTER stereo image data of good quality. An evaluation of an ASTER DEM data product produced at the US Geological Survey (USGS) EROS Data Center (EDC) yielded an RMSE of ±8.6 m. Overall, the ability to extract elevations from ASTER stereopairs using stereocorrelation techniques meets expectations.

  11. Digitization Best Practices

    SciTech Connect

    Xue, Fei; Holtkamp, Irma S.; Knudson, Frances L.

    2012-07-31

    This project involved performing tests and documenting results to determine best practices for digitizing older print documents. The digitization process is complicated, especially when original documents exhibit non-standard fonts and are faded. Tests focused on solutions to improve high quality scanning, increase OCR accuracy, and efficiently use embedded metadata. Results are summarized. From the test results on the right sides, we know that when we plan to digitize documents, we should balance Quantity and Quality based on our expectation, and then make final decision for the digitization process.

  12. Improve the ZY-3 Height Accuracy Using Icesat/glas Laser Altimeter Data

    NASA Astrophysics Data System (ADS)

    Li, Guoyuan; Tang, Xinming; Gao, Xiaoming; Zhang, Chongyang; Li, Tao

    2016-06-01

    ZY-3 is the first civilian high resolution stereo mapping satellite, which has been launched on 9th, Jan, 2012. The aim of ZY-3 satellite is to obtain high resolution stereo images and support the 1:50000 scale national surveying and mapping. Although ZY-3 has very high accuracy for direct geo-locations without GCPs (Ground Control Points), use of some GCPs is still indispensible for high precise stereo mapping. The GLAS (Geo-science Laser Altimetry System) loaded on the ICESat (Ice Cloud and land Elevation Satellite), which is the first laser altimetry satellite for earth observation. GLAS has played an important role in the monitoring of polar ice sheets, the measuring of land topography and vegetation canopy heights after launched in 2003. Although GLAS has ended in 2009, the derived elevation dataset still can be used after selection by some criteria. In this paper, the ICESat/GLAS laser altimeter data is used as height reference data to improve the ZY-3 height accuracy. A selection method is proposed to obtain high precision GLAS elevation data. Two strategies to improve the ZY-3 height accuracy are introduced. One is the conventional bundle adjustment based on RFM and bias-compensated model, in which the GLAS footprint data is viewed as height control. The second is to correct the DSM (Digital Surface Model) straightly by simple block adjustment, and the DSM is derived from the ZY-3 stereo imaging after freedom adjustment and dense image matching. The experimental result demonstrates that the height accuracy of ZY-3 without other GCPs can be improved to 3.0 meter after adding GLAS elevation data. What's more, the comparison of the accuracy and efficiency between the two strategies is implemented for application.

  13. Fault growth and propagation during incipient continental rifting: Insights from a combined aeromagnetic and Shuttle Radar Topography Mission digital elevation model investigation of the Okavango Rift Zone, northwest Botswana

    NASA Astrophysics Data System (ADS)

    Kinabo, B. D.; Hogan, J. P.; Atekwana, E. A.; Abdelsalam, M. G.; Modisi, M. P.

    2008-06-01

    Digital Elevation Models (DEM) extracted from the Shuttle Radar Topography Mission (SRTM) data and high-resolution aeromagnetic data are used to characterize the growth and propagation of faults associated with the early stages of continental extension in the Okavango Rift Zone (ORZ), northwest Botswana. Significant differences in the height of fault scarps and the throws across the faults in the basement indicate extended fault histories accompanied by sediment accumulation within the rift graben. Faults in the center of the rift either lack topographic expressions or are interpreted to have become inactive, or have large throws and small scarp heights indicating waning activity. Faults on the outer margins of the rift exhibit either (1) large throws or significant scarp heights and are considered older and active or (2) throws and scarp heights that are in closer agreement and are considered young and active. Fault linkages between major fault systems through a process of "fault piracy" have combined to establish an immature border fault for the ORZ. Thus, in addition to growing in length (by along-axis linkage of segments), the rift is also growing in width (by transferring motion to younger faults along the outer margins while abandoning older faults in the middle). Finally, utilization of preexisting zones of weakness allowed the development of very long faults (>100 km) at a very early stage of continental rifting, explaining the apparent paradox between the fault length versus throw for this young rift. This study clearly demonstrates that the integration of the SRTM DEM and aeromagnetic data provides a 3-D view of the faults and fault systems, providing new insight into fault growth and propagation during the nascent stages of continental rifting.

  14. Accuracy Validation of Large-scale Block Adjustment without Control of ZY3 Images over China

    NASA Astrophysics Data System (ADS)

    Yang, Bo

    2016-06-01

    Mapping from optical satellite images without ground control is one of the goals of photogrammetry. Using 8802 three linear array stereo images (a total of 26406 images) of ZY3 over China, we propose a large-scale and non-control block adjustment method of optical satellite images based on the RPC model, in which a single image is regarded as an adjustment unit to be organized. To overcome the block distortion caused by unstable adjustment without ground control and the excessive accumulation of errors, we use virtual control points created by the initial RPC model of the images as the weighted observations and add them into the adjustment model to refine the adjustment. We use 8000 uniformly distributed high precision check points to evaluate the geometric accuracy of the DOM (Digital Ortho Model) and DSM (Digital Surface Model) production, for which the standard deviations of plane and elevation are 3.6 m and 4.2 m respectively. The geometric accuracy is consistent across the whole block and the mosaic accuracy of neighboring DOM is within a pixel, thus, the seamless mosaic could take place. This method achieves the goal of an accuracy of mapping without ground control better than 5 m for the whole China from ZY3 satellite images.

  15. Evaluating point cloud accuracy of static three-dimensional laser scanning based on point cloud error ellipsoid model

    NASA Astrophysics Data System (ADS)

    Chen, Xijiang; Hua, Xianghong; Zhang, Guang; Wu, Hao; Xuan, Wei; Li, Moxiao

    2015-01-01

    Evaluation of static three-dimensional (3-D) laser scanning point cloud accuracy has become a topical research issue. Point cloud accuracy is typically estimated by comparing terrestrial laser scanning data related to a finite number of check point coordinates against those obtained by an independent source of higher accuracy. These methods can only estimate the point accuracy but not the point cloud accuracy, which is influenced by the positional error and sampling interval. It is proposed that the point cloud error ellipsoid is favorable for inspecting the point cloud accuracy, which is determined by the individual point error ellipsoid volume. The kernel of this method is the computation of the point cloud error ellipsoid volume and the determination of the functional relationship between the error ellipsoid and accuracy. The proposed point cloud accuracy evaluation method is particularly suited for small sampling intervals when there exists an intersection of two error ellipsoids, and is suited not only for planar but also for nonplanar target surfaces. The performance of the proposed method (PM) is verified using both planar and nonplanar board point clouds. The results demonstrate that the proposed evaluation method significantly outperforms the existing methods when the target surface is nonplanar or there exists an intersection of two error ellipsoids. The PM therefore has the potential for improving the reliability of point cloud digital elevation models and static 3-D laser scanning-based deformation monitoring.

  16. Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2

    NASA Astrophysics Data System (ADS)

    Helm, V.; Humbert, A.; Miller, H.

    2014-03-01

    The ESA satellite CryoSat-2 has been observing Earth's polar regions since April 2010. It carries a sophisticated radar altimeter and aims for the detection of changes in sea ice thickness as well as surface elevation changes of Earth's land and marine ice sheets. This study focuses on the Greenland and Antarctic ice sheets, considering the contemporary elevation of their surfaces. Based on 2 years of CryoSat-2 data acquisition, elevation change maps and mass balance estimates are presented. Additionally, new digital elevation models (DEMs) and the corresponding error maps are derived. Due to the high orbit of CryoSat-2 (88° N/S) and the narrow across-track spacing, more than 99% of Antarctica's surface area is covered. In contrast, previous radar altimeter measurements of ERS1/2 and ENVISAT were limited to latitudes between 81.5° N and 81.5° S and to surface slopes below 1°. The derived DEMs for Greenland and Antarctica have an accuracy which is similar to previous DEMs obtained by satellite-based laser and radar altimetry (Liu et al., 2001; Bamber et al., 2009, 2013; Fretwell et al., 2013; Howat et al., 2014). Comparisons with ICESat data show that 80% of the CryoSat-2 DEMs have an error of less than 3 m ± 30 m. For both ice sheets the surface elevation change rates between 2011 and 2012 are presented at a resolution of 1 km. Negative elevation changes are concentrated at the west and south-east coast of Greenland and in the Amundsen Sea embayment in West Antarctica (e.g. Pine Island and Thwaites glaciers). They agree well with the dynamic mass loss observed by ICESat between 2003 and 2008 (Pritchard et al., 2009). Thickening occurs along the main trunk of Kamb Ice Stream and in Dronning Maud Land. While the former is a consequence of an ice stream stagnated ∼150 years ago (Rose, 1979; Retzlaff and Bentley, 1993), the latter represents a known large-scale accumulation event (Lenaerts et al., 2013). This anomaly partly compensates for the observed

  17. Airborne Topographic Mapper Calibration Procedures and Accuracy Assessment

    NASA Technical Reports Server (NTRS)

    Martin, Chreston F.; Krabill, William B.; Manizade, Serdar S.; Russell, Rob L.; Sonntag, John G.; Swift, Robert N.; Yungel, James K.

    2012-01-01

    Description of NASA Airborn Topographic Mapper (ATM) lidar calibration procedures including analysis of the accuracy and consistancy of various ATM instrument parameters and the resulting influence on topographic elevation measurements. The ATM elevations measurements from a nominal operating altitude 500 to 750 m above the ice surface was found to be: Horizontal Accuracy 74 cm, Horizontal Precision 14 cm, Vertical Accuracy 6.6 cm, Vertical Precision 3 cm.

  18. Characterization of a 16-Bit Digitizer for Lidar Data Acquisition

    NASA Technical Reports Server (NTRS)

    Williamson, Cynthia K.; DeYoung, Russell J.

    2000-01-01

    A 6-MHz 16-bit waveform digitizer was evaluated for use in atmospheric differential absorption lidar (DIAL) measurements of ozone. The digitizer noise characteristics were evaluated, and actual ozone DIAL atmospheric returns were digitized. This digitizer could replace computer-automated measurement and control (CAMAC)-based commercial digitizers and improve voltage accuracy.

  19. Precision Improvement of Photogrammetry by Digital Image Correlation

    NASA Astrophysics Data System (ADS)

    Shih, Ming-Hsiang; Sung, Wen-Pei; Tung, Shih-Heng; Hsiao, Hanwei

    2016-04-01

    The combination of aerial triangulation technology and unmanned aerial vehicle greatly reduces the cost and application threshold of the digital surface model technique. Based on the report in the literatures, the measurement error in the x-y coordinate and in the elevation lies between 8cm~15cm and 10cm~20cm respectively. The measurement accuracy for the geological structure survey already has sufficient value, but for the slope and structures in terms of deformation monitoring is inadequate. The main factors affecting the accuracy of the aerial triangulation are image quality, measurement accuracy of control point and image matching accuracy. In terms of image matching, the commonly used techniques are Harris Corner Detection and Scale Invariant Feature Transform (SIFT). Their pairing error is in scale of pixels, usually lies between 1 to 2 pixels. This study suggests that the error on the pairing is the main factor causing the aerial triangulation errors. Therefore, this study proposes the application of Digital Image Correlation (DIC) method instead of the pairing method mentioned above. DIC method can provide a pairing accuracy of less than 0.01 pixel, indeed can greatly enhance the accuracy of the aerial triangulation, to have sub-centimeter level accuracy. In this study, the effects of image pairing error on the measurement error of the 3-dimensional coordinate of the ground points are explored by numerical simulation method. It was confirmed that when the image matching error is reduced to 0.01 pixels, the ground three-dimensional coordinate measurement error can be controlled in mm level. A combination of DIC technique and the traditional aerial triangulation provides the potential of application on the deformation monitoring of slope and structures, and achieve an early warning of natural disaster.

  20. Exploring the Role of Genetic Algorithms and Artificial Neural Networks for Interpolation of Elevation in Geoinformation Models

    NASA Astrophysics Data System (ADS)

    Bagheri, H.; Sadjadi, S. Y.; Sadeghian, S.

    2013-09-01

    One of the most significant tools to study many engineering projects is three-dimensional modelling of the Earth that has many applications in the Geospatial Information System (GIS), e.g. creating Digital Train Modelling (DTM). DTM has numerous applications in the fields of sciences, engineering, design and various project administrations. One of the most significant events in DTM technique is the interpolation of elevation to create a continuous surface. There are several methods for interpolation, which have shown many results due to the environmental conditions and input data. The usual methods of interpolation used in this study along with Genetic Algorithms (GA) have been optimised and consisting of polynomials and the Inverse Distance Weighting (IDW) method. In this paper, the Artificial Intelligent (AI) techniques such as GA and Neural Networks (NN) are used on the samples to optimise the interpolation methods and production of Digital Elevation Model (DEM). The aim of entire interpolation methods is to evaluate the accuracy of interpolation methods. Universal interpolation occurs in the entire neighbouring regions can be suggested for larger regions, which can be divided into smaller regions. The results obtained from applying GA and ANN individually, will be compared with the typical method of interpolation for creation of elevations. The resulting had performed that AI methods have a high potential in the interpolation of elevations. Using artificial networks algorithms for the interpolation and optimisation based on the IDW method with GA could be estimated the high precise elevations.

  1. Influence of solar elevation in radiometric and geometric performance of multispectral photogrammetry

    NASA Astrophysics Data System (ADS)

    Honkavaara, Eija; Markelin, Lauri; Rosnell, Tomi; Nurminen, Kimmo

    2012-01-01

    Solar elevation is an important factor in passive, airborne data collection. The minimum solar elevation allowed in missions for topographic mapping is typically 30° from the horizon. A general hypothesis is that the new, high dynamic range, digital large-format photogrammetric sensors allow for high data quality, even with lower solar elevations, which would improve the feasibility and cost-efficiency of photogrammetric technology in various applications. Objectives of this study were to investigate theoretically and empirically the impacts of solar elevation in modern photogrammetric processes. Two cutting-edge aspects of novel photogrammetric technology were considered: point cloud creation by automatic image matching and reflectance calibration of image data. For the empirical study, we used image data collected by a large-format photogrammetric camera, Intergraph DMC, with low (25-28°) and medium (44-48°) solar elevations from 2, 3 and 4 km heights. We did not detect negative influences of decreasing solar elevation during our general evaluations: an analysis of image histograms showed that the ranges of digital numbers could be tuned to similar levels with exposure settings, and evaluations of density and the accuracy of point clouds did not show any reduction of quality. We carried out detailed evaluations in forests, roads and fields. Our results did not indicate deterioration of the quality in sun-illuminated areas with decreasing solar elevation. In shadowed areas, we observed that the variation of image signal was reduced in comparison to sun-illuminated areas and emphasized the issue of complication of reflectance calibration. Artefacts appeared in automatically generated point clouds in areas shadowed by trees, which we observed in flat objects as up to 3 times increased random height variation and decreased success in measuring the terrain surface. Our results also showed that the overall performance of point cloud generation was high. Typically

  2. 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.

  3. Photogrammetric Accuracy and Modeling of Rolling Shutter Cameras

    NASA Astrophysics Data System (ADS)

    Ye, W.; Qiao, G.; Kong, F.; Guo, S.; Ma, X.; Tong, X.; Li, R.

    2016-06-01

    Global climate change is one of the major challenges that all nations are commonly facing. Long-term observations of the Antarctic ice sheet have been playing a critical role in quantitatively estimating and predicting effects resulting from the global changes. The film-based ARGON reconnaissance imagery provides a remarkable data source for studying the Antarctic ice-sheet in 1960s, thus greatly extending the time period of Antarctica surface observations. To deal with the low-quality images and the unavailability of camera poses, a systematic photogrammetric approach is proposed to reconstruct the interior and exterior orientation information for further glacial mapping applications, including ice flow velocity mapping and mass balance estimation. Some noteworthy details while performing geometric modelling using the ARGON images were introduced, including methods and results for handling specific effects of film deformation, damaged or missing fiducial marks and calibration report, automatic fiducial mark detection, control point selection through Antarctic shadow and ice surface terrain analysis, and others. Several sites in East Antarctica were tested. As an example, four images in the Byrd glacier region were used to assess the accuracy of the geometric modelling. A digital elevation model (DEM) and an orthophoto map of Byrd glacier were generated. The accuracy of the ground positions estimated by using independent check points is within one nominal pixel of 140 m of ARGON imagery. Furthermore, a number of significant features, such as ice flow velocity and regional change patterns, will be extracted and analysed.

  4. Evaluation of the Global Multi-Resolution Terrain Elevation Data 2010 (GMTED2010) Using ICESat Geodetic Control

    NASA Technical Reports Server (NTRS)

    Carabajal, Claudia C.; Harding, David J.; Boy, Jean-Paul; Danielson, Jeffrey J.; Gesch, Dean B.; Suchdeo, Vijay P.

    2011-01-01

    Supported by NASA's Earth Surface and Interior (ESI) Program, we are producing a global set of Ground Control Points (GCPs) derived from the Ice, Cloud and land Elevation Satellite (ICESat) altimetry data. From February of 2003, to October of 2009, ICESat obtained nearly global measurements of land topography (+/- 86deg latitudes) with unprecedented accuracy, sampling the Earth's surface at discrete approx.50 m diameter laser footprints spaced 170 m along the altimetry profiles. We apply stringent editing to select the highest quality elevations, and use these GCPs to characterize and quantify spatially varying elevation biases in Digital Elevation Models (DEMs). In this paper, we present an evaluation of the soon to be released Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010). Elevation biases and error statistics have been analyzed as a function of land cover and relief. The GMTED2010 products are a large improvement over previous sources of elevation data at comparable resolutions. RMSEs for all products and terrain conditions are below 7 m and typically are about 4 m. The GMTED2010 products are biased upward with respect to the ICESat GCPs on average by approximately 3 m.

  5. Evaluation of the Global Multi-Resolution Terrain Elevation Data 2010 (GMTED2010) using ICESat geodetic control

    USGS Publications Warehouse

    Carabajal, C.C.; Harding, D.J.; Boy, J.-P.; Danielson, J.J.; Gesch, D.B.; Suchdeo, V.P.

    2011-01-01

    Supported by NASA's Earth Surface and Interior (ESI) Program, we are producing a global set of Ground Control Points (GCPs) derived from the Ice, Cloud and land Elevation Satellite (ICESat) altimetry data. From February of 2003, to October of 2009, ICESat obtained nearly global measurements of land topography (?? 86?? latitudes) with unprecedented accuracy, sampling the Earth's surface at discrete ???50 m diameter laser footprints spaced 170 m along the altimetry profiles. We apply stringent editing to select the highest quality elevations, and use these GCPs to characterize and quantify spatially varying elevation biases in Digital Elevation Models (DEMs). In this paper, we present an evaluation of the soon to be released Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010). Elevation biases and error statistics have been analyzed as a function of land cover and relief. The GMTED2010 products are a large improvement over previous sources of elevation data at comparable resolutions. RMSEs for all products and terrain conditions are below 7 m and typically are about 4 m. The GMTED2010 products are biased upward with respect to the ICESat GCPs on average by approximately 3 m. ?? 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

  6. Digital Libraries.

    ERIC Educational Resources Information Center

    Fox, Edward A.; Urs, Shalini R.

    2002-01-01

    Provides an overview of digital libraries research, practice, and literature. Highlights include new technologies; redefining roles; historical background; trends; creating digital content, including conversion; metadata; organizing digital resources; services; access; information retrieval; searching; natural language processing; visualization;…

  7. Regional Elevations in the Southern Hemisphere of Mars From the Mars Orbiter Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Zuber, M. T.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Muhleman, D. O.; Neumann, G. A.; Pettengill, G. H.; Phillips, R. J.; Solomon, S. C.

    1999-01-01

    The Mars Orbiter Laser Altimeter (MOLA) is an instrument on the Mars Global Surveyor (MGS) spacecraft that is currently providing the first high vertical and spatial resolution topographic measurements of surface elevations on Mars. The shot size in the mapping orbit is about 100 m and the shot-to-shot spacing is 330 m. The instrument has a vertical precision of 37.5 cm and a vertical accuracy that depends on the radial accuracy of the MGS orbit that is currently in the range 5-30 km. The initial focus on observations in the nominal mapping mission will be on the southern hemisphere, which was not sampled during the MGS aerobraking hiatus and Science Phasing orbits. During the first several weeks of global mapping there will be emphasis on producing a digital terrain model (DTM) of the Mars '98 landing site.

  8. Relative accuracy evaluation.

    PubMed

    Zhang, Yan; Wang, Hongzhi; Yang, Zhongsheng; Li, Jianzhong

    2014-01-01

    The quality of data plays an important role in business analysis and decision making, and data accuracy is an important aspect in data quality. Thus one necessary task for data quality management is to evaluate the accuracy of the data. And in order to solve the problem that the accuracy of the whole data set is low while a useful part may be high, it is also necessary to evaluate the accuracy of the query results, called relative accuracy. However, as far as we know, neither measure nor effective methods for the accuracy evaluation methods are proposed. Motivated by this, for relative accuracy evaluation, we propose a systematic method. We design a relative accuracy evaluation framework for relational databases based on a new metric to measure the accuracy using statistics. We apply the methods to evaluate the precision and recall of basic queries, which show the result's relative accuracy. We also propose the method to handle data update and to improve accuracy evaluation using functional dependencies. Extensive experimental results show the effectiveness and efficiency of our proposed framework and algorithms. PMID:25133752

  9. Relative Accuracy Evaluation

    PubMed Central

    Zhang, Yan; Wang, Hongzhi; Yang, Zhongsheng; Li, Jianzhong

    2014-01-01

    The quality of data plays an important role in business analysis and decision making, and data accuracy is an important aspect in data quality. Thus one necessary task for data quality management is to evaluate the accuracy of the data. And in order to solve the problem that the accuracy of the whole data set is low while a useful part may be high, it is also necessary to evaluate the accuracy of the query results, called relative accuracy. However, as far as we know, neither measure nor effective methods for the accuracy evaluation methods are proposed. Motivated by this, for relative accuracy evaluation, we propose a systematic method. We design a relative accuracy evaluation framework for relational databases based on a new metric to measure the accuracy using statistics. We apply the methods to evaluate the precision and recall of basic queries, which show the result's relative accuracy. We also propose the method to handle data update and to improve accuracy evaluation using functional dependencies. Extensive experimental results show the effectiveness and efficiency of our proposed framework and algorithms. PMID:25133752

  10. Lunar Pole Illumination and Communications Statistics Computed from GSSR Elevation Data

    NASA Technical Reports Server (NTRS)

    Bryant, Scott

    2010-01-01

    The Goldstone Solar System RADAR (GSSR) group at JPL produced a Digital Elevation Model (DEM) of the lunar south pole using data obtained in 2006. This model has 40-meter horizontal resolution and about 5-meter relative vertical accuracy. This paper uses that Digital Elevation Model to compute average solar illumination and Earth visibility near the lunar south pole. This data quantifies solar power and Earth communications resources at proposed lunar base locations. The elevation data were converted into local terrain horizon masks, then converted into selenographic latitude and longitude coordinates. The horizon masks were compared to latitude, longitude regions bounding the maximum Sun and Earth motions relative to the moon. Proposed lunar south pole base sites were examined in detail, with the best site showing multi-year averages of solar power availability of 92% and Direct-To-Earth (DTE) communication availability of about 50%. Results are compared with a theoretical model, and with actual sun and Earth visibility averaged over the years 2009 to 2028. Results for the lunar North pole were computed using the GSSR DEM of the lunar North pole produced in 1997. The paper also explores using a heliostat to reduce the photovoltaic power system mass and complexity.

  11. Evaluation of Remotely Sensed Vegetation and Elevation Products in a Tropical Forest

    NASA Astrophysics Data System (ADS)

    Leigh, H. W.; Neuenschwander, A. L.; Magruder, L. A.

    2014-12-01

    Space-based methods of remote sensing have enabled the generation of global or near-global elevation and vegetation products that have been applied to a wide spectrum of earth sciences, while airborne remote sensing platforms have enabled the collection of high resolution data products with regional coverage. In order to use small-footprint airborne data together with space-based products in future applications, it is necessary to understand how the data products are related, particularly in regards to accuracy and systematic biases. This work addresses the need for a better understanding of the quality of existing global elevation and vegetation products by validating a radar-derived, void-filled digital elevation model and a lidar-derived global canopy height model against ICESat waveforms and a small-footprint airborne lidar survey over tropical forests in the country of Gabon. The bare-earth digital terrain model and canopy height model obtained from the airborne lidar survey are validated against ICESat waveforms, and are then used to evaluate errors and biases in SRTMv3 and the 1km global canopy height model developed by Simard, et al. across the extent of the survey region near the city of Libreville, Gabon. ICESat waveforms are subsequently used to evaluate SRTMv3 and Simard, et al.'s canopy height model for the entire country of Gabon.

  12. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  13. Mars digital terrain model

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington, Annie-Elpis

    1987-01-01

    The Mars Digital Terrain Model (DTM) is the result of a new project to: (1) digitize the series of 1:2,000,000-scale topographic maps of Mars, which are being derived photogrammetically under a separate project, and (2) reformat the digital contour information into rasters of elevation that can be readily registered with the Digital Image Model (DIM) of Mars. Derivation of DTM's involves interpolation of elevation values into 1/64-degree resolution and transformation of them to a sinusoidal equal-area projection. Digital data are produced in blocks corresponding with the coordinates of the original 1:2,000,000-scale maps, i.e., the dimensions of each block in the equatorial belt are 22.5 deg of longitude and 15 deg of latitude. This DTM is not only compatible with the DIM, but it can also be registered with other data such as geologic units or gravity. It will be the most comprehensive record of topographic information yet compiled for the Martian surface. Once the DTM's are established, any enhancement of Mars topographic information made with updated data, such as data from the planned Mars Observer Mission, will be by mathematical transformation of the DTM's, eliminating the need for recompilation.

  14. Digital Preservation.

    ERIC Educational Resources Information Center

    Yakel, Elizabeth

    2001-01-01

    Reviews research on digital preservation issues, including born-digital and digitally recreated documents. Discusses electronic records research; metadata and other standards; electronic mail; Web-based documents; moving images media; selection of materials for digitization, including primary sources; administrative issues; media stability…

  15. Digital cartography of Mars

    NASA Technical Reports Server (NTRS)

    Batson, R. M.

    1987-01-01

    A medium-resolution Digital Image Model (DIM) of Mars is being compiled. A DIM is a mosaic of radiometrically corrected, photometrically modelled spacecraft images displaying accurate reflectance properties at uniform resolution, and geometrically tied to the best available control. The Mars medium-resolution DIM contains approximately 4700 Viking Orbiter image frames that were used to compile the recently completed 1:2,000,000-scale controlled photomosaic series of Mars. This DIM provides a planimetric control base to which all other Mars maps will be registered. A similar control base of topographic elevations (Digital Terrain Model, or DTM) is also being compiled. These products are scheduled for completion in 1989.

  16. Sensors feel digital pressure

    SciTech Connect

    Ham, J.

    1996-05-01

    Anyone who has connected a field instrument to an analog input card for a DCS, PLC or PC-based data acquisition or control system has faced the issue of analog-to-digital (A/D) conversion. Signal conversion always involves compromises in accuracy and speed. Digital communication with fieldbus eliminates the problem, right? Not exactly; fieldbus may simply move the A/D interface from the control room to the field. The vast majority of measuring instruments have analog sensors with signals that must be converted to strings of bits somewhere, somehow. Instrument manufacturers must embrace digital technology in sensor design, not just in transmitter design. One way to address the issue is to use microsystems technology, such as microelectro-mechanical systems (MEMS). Research at Delft University of Technology in the Netherlands, for example, is aimed at fabricating devices in silicon with all the components of a data-acquisition unit integrated on one chip. These smart sensors would host the sensor itself along with signal conditioning and A/D conversion circuits, and circuits for digital interfacing with a data processor. A/D conversion is still there, but encapsulated within and characterized as part of the sensor. Single-chip integration allows more signal processing within a manageable-sized package. Also, eliminating transmission of the analog signal, even within an instrument, reduces the chance for noise pickup. Less noise means instrument accuracy closer to actual sensor accuracy. 2 figs.

  17. Assessment Of Accuracies Of Remote-Sensing Maps

    NASA Technical Reports Server (NTRS)

    Card, Don H.; Strong, Laurence L.

    1992-01-01

    Report describes study of accuracies of classifications of picture elements in map derived by digital processing of Landsat-multispectral-scanner imagery of coastal plain of Arctic National Wildlife Refuge. Accuracies of portions of map analyzed with help of statistical sampling procedure called "stratified plurality sampling", in which all picture elements in given cluster classified in stratum to which plurality of them belong.

  18. National Digital Orthophoto Program

    USGS Publications Warehouse

    USDA Natural Resources Conservation Service; Farm Service Agency; National States Geographic Information Council; U.S. Forest Service; U.S. Geological Survey

    1996-01-01

    A critical component of the National Spatial Data Infrastructure (NSDI) is Framework. Framework provides a base on which to collect, register, and integrate geospatial information accurately and consistently. The Federal Geographic Data Committee (FGDC) proposed that Framework include geodetic control, orthoimagery, elevation, transportation, hydrography, governmental units, and cadastral data. The Mapping Science Committee of the National Research Council recommends that geodetic control, orthoimagery, and elevation data become the critical foundation of the NSDI. The National Digital Orthophoto Program (NDOP) is a working model on how Federal, State, and local government, as well as private industry, can participate to develop the orthoimagery Framework for the Nation.

  19. a New High-Resolution Elevation Model of Greenland Derived from Tandem-X

    NASA Astrophysics Data System (ADS)

    Wessel, B.; Bertram, A.; Gruber, A.; Bemm, S.; Dech, S.

    2016-06-01

    In this paper we present for the first time the new digital elevation model (DEM) for Greenland produced by the TanDEM-X (TerraSAR add-on for digital elevation measurement) mission. The new, full coverage DEM of Greenland has a resolution of 0.4 arc seconds corresponding to 12 m. It is composed of more than 7.000 interferometric synthetic aperture radar (InSAR) DEM scenes. X-Band SAR penetrates the snow and ice pack by several meters depending on the structures within the snow, the acquisition parameters, and the dielectricity constant of the medium. Hence, the resulting SAR measurements do not represent the surface but the elevation of the mean phase center of the backscattered signal. Special adaptations on the nominal TanDEM-X DEM generation are conducted to maintain these characteristics and not to raise or even deform the DEM to surface reference data. For the block adjustment, only on the outer coastal regions ICESat (Ice, Cloud, and land Elevation Satellite) elevations as ground control points (GCPs) are used where mostly rock and surface scattering predominates. Comparisons with ICESat data and snow facies are performed. In the inner ice and snow pack, the final X-Band InSAR DEM of Greenland lies up to 10 m below the ICESat measurements. At the outer coastal regions it corresponds well with the GCPs. The resulting DEM is outstanding due to its resolution, accuracy and full coverage. It provides a high resolution dataset as basis for research on climate change in the arctic.

  20. Glacier-specific elevation changes in western Alaska

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Le Bris, Raymond

    2013-04-01

    Deriving glacier-specific elevation changes from DEM differencing and digital glacier outlines is rather straight-forward if the required datasets are available. Calculating such changes over large regions and including glaciers selected for mass balance measurements in the field, provides a possibility to determine the representativeness of the changes observed at these glaciers for the entire region. The related comparison of DEM-derived values for these glaciers with the overall mean avoids the rather error-prone conversion of volume to mass changes (e.g. due to unknown densities) and gives unit-less correction factors for upscaling the field measurements to a larger region. However, several issues have to be carefully considered, such as proper co-registration of the two DEMs, date and accuracy of the datasets compared, as well as source data used for DEM creation and potential artefacts (e.g. voids). In this contribution we present an assessment of the representativeness of the two mass balance glaciers Gulkana and Wolverine for the overall changes of nearly 3200 glaciers in western Alaska over a ca. 50-year time period. We use an elevation change dataset from a study by Berthier et al. (2010) that was derived from the USGS DEM of the 1960s (NED) and a more recent DEM derived from SPOT5 data for the SPIRIT project. Additionally, the ASTER GDEM was used as a more recent DEM. Historic glacier outlines were taken from the USGS digital line graph (DLG) dataset, corrected with the digital raster graph (DRG) maps from USGS. Mean glacier specific elevation changes were derived based on drainage divides from a recently created inventory. Land-terminating, lake-calving and tidewater glaciers were marked in the attribute table to determine their changes separately. We also investigated the impact of handling potential DEM artifacts in three different ways and compared elevation changes with altitude. The mean elevation changes of Gulkana and Wolverine glaciers (about -0

  1. Today's CAD/CAM: flexible digital technologies expanding workflow options.

    PubMed

    Ferencz, Jonathan L

    2015-03-01

    CAD/CAM and digital scanning technologies have become essential components of dentistry. Digital impression scanning, restoration design, and manufacturing techniques yield greater treatment predictability, high-level esthetics, and functional accuracy using a variety of materials. PMID:25822749

  2. Interferometer combines laser light source and digital counting system

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Measurement of small linear displacements in digital readouts with extreme accuracy and sensitivity is achieved by an interferometer. The instrument combines a digital electro-optical fringe-counting system and a laser light source.

  3. Nonlinear feedback reduces analog-to-digital converter error

    NASA Technical Reports Server (NTRS)

    Munoz, R. M.

    1965-01-01

    Nonlinear analog-to-digital converter measures the analog input level and continuously adjusts the digital readout scale sensitivity to effectively increase the accuracy. It is able to acquire more accurate low-level data.

  4. INTEGER ELEVATION MODEL GRIDS FOR US EPA REGION 9

    EPA Science Inventory

    Integer Digital Elevation Models in GRID format for the mainland US administrative boundary of the US EPA Region 9 developed from the United States Geological Survey (USGS) National Elevation Dataset (NED). The administrative boundary is represented by the state boundaries of Ca...

  5. Analysis of RDSS positioning accuracy based on RNSS wide area differential technique

    NASA Astrophysics Data System (ADS)

    Xing, Nan; Su, RanRan; Zhou, JianHua; Hu, XiaoGong; Gong, XiuQiang; Liu, Li; He, Feng; Guo, Rui; Ren, Hui; Hu, GuangMing; Zhang, Lei

    2013-10-01

    The BeiDou Navigation Satellite System (BDS) provides Radio Navigation Service System (RNSS) as well as Radio Determination Service System (RDSS). RDSS users can obtain positioning by responding the Master Control Center (MCC) inquiries to signal transmitted via GEO satellite transponder. The positioning result can be calculated with elevation constraint by MCC. The primary error sources affecting the RDSS positioning accuracy are the RDSS signal transceiver delay, atmospheric trans-mission delay and GEO satellite position error. During GEO orbit maneuver, poor orbit forecast accuracy significantly impacts RDSS services. A real-time 3-D orbital correction method based on wide-area differential technique is raised to correct the orbital error. Results from the observation shows that the method can successfully improve positioning precision during orbital maneuver, independent from the RDSS reference station. This improvement can reach 50% in maximum. Accurate calibration of the RDSS signal transceiver delay precision and digital elevation map may have a critical role in high precise RDSS positioning services.

  6. Digital Citizenship

    ERIC Educational Resources Information Center

    Isman, Aytekin; Canan Gungoren, Ozlem

    2014-01-01

    Era in which we live is known and referred as digital age.In this age technology is rapidly changed and developed. In light of these technological advances in 21st century, schools have the responsibility of training "digital citizen" as well as a good citizen. Digital citizens must have extensive skills, knowledge, Internet and …

  7. Mapping soil texture classes and optimization of the result by accuracy assessment

    NASA Astrophysics Data System (ADS)

    Laborczi, Annamária; Takács, Katalin; Bakacsi, Zsófia; Szabó, József; Pásztor, László

    2014-05-01

    There are increasing demands nowadays on spatial soil information in order to support environmental related and land use management decisions. The GlobalSoilMap.net (GSM) project aims to make a new digital soil map of the world using state-of-the-art and emerging technologies for soil mapping and predicting soil properties at fine resolution. Sand, silt and clay are among the mandatory GSM soil properties. Furthermore, soil texture class information is input data of significant agro-meteorological and hydrological models. Our present work aims to compare and evaluate different digital soil mapping methods and variables for producing the most accurate spatial prediction of texture classes in Hungary. In addition to the Hungarian Soil Information and Monitoring System as our basic data, digital elevation model and its derived components, geological database, and physical property maps of the Digital Kreybig Soil Information System have been applied as auxiliary elements. Two approaches have been applied for the mapping process. At first the sand, silt and clay rasters have been computed independently using regression kriging (RK). From these rasters, according to the USDA categories, we have compiled the texture class map. Different combinations of reference and training soil data and auxiliary covariables have resulted several different maps. However, these results consequentially include the uncertainty factor of the three kriged rasters. Therefore we have suited data mining methods as the other approach of digital soil mapping. By working out of classification