Science.gov

Sample records for 1-degree digital elevation

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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...

  17. 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.

  18. 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.

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

    USGS Publications Warehouse

    Oimoen, M.J.

    2004-01-01

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

  20. 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.

  1. 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).

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

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

    USGS Publications Warehouse

    Haugerud, Ralph A.

    1999-01-01

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

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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)

  17. 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.

  18. 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.

  19. 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

  20. 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.

  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. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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).

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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).

  16. 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

  17. 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

  18. 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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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).

  6. 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.

  7. 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. 

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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.

  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. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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).

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Geologic map of the Dillon 1 degree by 2 degrees Quadrangle, Idaho and Montana

    USGS Publications Warehouse

    Ruppel, E.T.; Lopez, D.A.; O'Neill, J. M.

    1993-01-01

    The digital ARC/INFO databases included in this website provide a GIS database for the geologic map of the Dillon 1 degree by 2 degree quadrangle of southwest Montana and east-central Idaho. The geologic map was originally published as U.S. Geological Survey Miscellaneous Investigations Series Map I-1803-H. This website directory contains ARC/INFO format files that can be used to query or display the geology of USGS Map I-1803-H with GIS software.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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%.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  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.

    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

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  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. 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

  14. 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

  15. A 1-degree FOV 30-meter telescope concept revisited

    NASA Astrophysics Data System (ADS)

    Barden, Samuel C.; McGrath, Andrew J.; Gillingham, Peter R.; Harmer, Charles F.

    2004-10-01

    The science case for wide fields on ELTs is well developed and justifies the implementation of 20 arc-minute and larger fields-of-view with seeing-limited performance on a 20 to 30-meter telescope. However, the practical implementation of a wide field can prove to be challenging with classical telescope design when low-thermal emissivity performance is also being optimized. Segmented mirrors assemblies need not be full aperture, axially symmetric structures. Space for secondary, tertiary, and quaternary mirror support structures that do not cross the optical path can be achieved with off-axis mirror assemblies. Barden, Harmer, Claver, and Dey described a 4-mirror, 1-degree FOV 30-meter telescope. We take that concept further with an off-axis approach. Three conic mirrors are required to produce excellent image quality in the 1-degree FOV (diffraction limited across the central few arc-minutes, better than 0.3" imaging performance at the edge of the field). A flat quaternary mirror is utilized both as a beam steering mirror to different instrument ports on the lower side of the telescope and as an adaptive mirror for wind-buffeting and possible ground layer AO correction. The final f/2.2 focal ratio allows the use of an echidna-style fiber positioner for very dense target field acquisition. Extreme AO and Ground Layer AO ports can both be implemented as well. Diffraction characteristics may possibly be improved given the lack of a spider mount for the secondary mirror but will be elliptical rather than circular.

  16. THE DEVELOPMENT OF A 1990 GLOBAL INVENTORY FOR SO(X) AND NO(X) ON A 1(DEGREE) X 1(DEGREE) LATITUDE-LONGITUDE GRID.

    SciTech Connect

    VAN HEYST,B.J.

    1999-10-01

    Sulfur and nitrogen oxides emitted to the atmosphere have been linked to the acidification of water bodies and soils and perturbations in the earth's radiation balance. In order to model the global transport and transformation of SO{sub x} and NO{sub x}, detailed spatial and temporal emission inventories are required. Benkovitz et al. (1996) published the development of an inventory of 1985 global emissions of SO{sub x} and NO{sub x} from anthropogenic sources. The inventory was gridded to a 1{degree} x 1{degree} latitude-longitude grid and has served as input to several global modeling studies. There is now a need to provide modelers with an update of this inventory to a more recent year, with a split of the emissions into elevated and low level sources. This paper describes the development of a 1990 update of the SO{sub x} and NO{sub x} global inventories that also includes a breakdown of sources into 17 sector groups. The inventory development starts with a gridded global default EDGAR inventory (Olivier et al, 1996). In countries where more detailed national inventories are available, these are used to replace the emissions for those countries in the global default. The gridded emissions are distributed into two height levels (0-100m and >100m) based on the final plume heights that are estimated to be typical for the various sectors considered. The sources of data as well as some of the methodologies employed to compile and develop the 1990 global inventory for SO{sub x} and NO{sub x} are discussed. The results reported should be considered to be interim since the work is still in progress and additional data sets are expected to become available.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

  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. 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.

  8. 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

  9. 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.

  10. 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.