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RADAR Altimeter Aiding (RALT Aiding) is an augmentation method to GPS to improve the standard GPS position solution accuracy, integrity, and continuity through the inclusion of an additional range measurement into the GPS measurement equation. This additional range measurement is derived through the combination of a radar altimeter and terrain elevation database. This paper extends on work previously competed by the authors and provides an in-depth introduction to the RALT Aiding method, description of work completed in the past, and outlook for the future of the concept.

The global digital elevation model (DEM) is important for various scientific applications. With the recently released TanDEM-X 90-m DEM and AW3D30 version 2.2, the open global or near-global coverage DEM datasets have been further expanded. However, the quality of these DEMs has not yet been fully characterized, especially in the application for regional scale studies. In this study, we assess the quality of five freely available global DEM datasets (SRTM-1 DEM, SRTM-3 DEM, ASTER GDEM2, AW3D30 DEM and TanDEM-X 90-m DEM) and one 30-m resampled TanDEM-X DEM (hereafter called TDX30) over the south-central Chinese province of Hunan. Then, the newly-released high precision ICESat-2 (Ice, Cloud, and land Elevation Satellite-2) altimetry points are introduced to evaluate the accuracy of these DEMs. Results show that the SRTM1 DEM offers the best quality with a Root Mean Square Error (RMSE) of 8.0 m, and ASTER GDEM2 has the worst quality with the RMSE of 10.1 m. We also compared the vertical accuracies of these DEMs with respect to different terrain morphological characteristics (e.g., elevation, slope and aspect) and land cover types. It reveals that the DEM accuracy decreases when the terrain elevation and slope value increase, whereas no relationship was found between DEM error and terrain aspect. Furthermore, the results show that the accuracy increases as the land cover type changes from vegetated to non-vegetated. Overall, the SRTM1 DEM, with high spatial resolution and high vertical accuracy, is currently the most promising dataset among these DEMs and it could, therefore, be utilized for the studies and applications requiring accurate DEMs.

According to the problem that the elevation data does not reflect the slope and surface roughness of target topography, the preprocessing of topographic elevation data and extraction algorithm of topographic feature are proposed, and the corresponding extraction of topographic feature is done. A terrain risk assessment method is presented based on terrain roughness and slope information fusion, aiming at the problem that terrain roughness and gradient cannot be directly reflected from the terrain elevation data, in this paper. The innovation is that it is the first time that the bilinear interpolation algorithm is applied in preprocess of elevation data and extraction of topographic feature, as well as the terrain roughness and gradient information fusion algorithm are applied to terrain feature extraction and risk assessment for the first time. By simulation and checking calculation of a certain digital topography example, it is proved that the extraction method of topographic information based on elevation data is feasible and reliable. It will provide a new research approach for target information recognition and topography risk assessment accurately.

This paper is devoted to the method for a three-dimensional radar image restoration of terrain elevations using airborne two antenna interferometric frequency-domain radar. A method’s main feature is the parallel obtaining of two-dimensional frequencydomain spectra both of radar terrain echo and its derivative for next synthesizing. The architecture of such interferometric radar is proposed, and math equations for one’s performance calculation are presented. The numerical algorithm for the terrain elevations calculation over an arbitrary horizontal plane is developed.

Topography is a key driver of tropical forest structure and composition, as it constrains local nutrient and hydraulic conditions within which trees grow. Yet, we do not fully understand how changes in forest physiognomy driven by topography impact other emergent properties of forests, such as their aboveground carbon density (ACD). Working in Borneo – at a site where 70‐m‐tall forests in alluvial valleys rapidly transition to stunted heath forests on nutrient‐depleted dip slopes – we combined field data with airborne laser scanning and hyperspectral imaging to characterise how topography shapes the vertical structure, wood density, diversity and ACD of nearly 15 km2 of old‐growth forest. We found that subtle differences in elevation – which control soil chemistry and hydrology – profoundly influenced the structure, composition and diversity of the canopy. Capturing these processes was critical to explaining landscape‐scale heterogeneity in ACD, highlighting how emerging remote sensing technologies can provide new insights into long‐standing ecological questions.

Digital elevation models (DEMs) are essential to provide continuous terrain elevation for water surface elevation (WSE) with a variety of horizontal and vertical accuracies in flood inundation modelling. The WSE forecasting depends on the appropriateness of the DEM data used. The comparative methodology is applied to various DEM sources: LiDAR and IFSAR DEM based on different types of land use at each of the cross-sectional lines. The accuracy of the IFSAR DEMs was assessed with LiDAR data, which is a high-precision DEM and was applied in hydraulic modelling to simulate the WSE in Padang Terap, Kedah, Malaysia. Furthermore, Bjerklie’s model is used as predicted discharge to support the analysis. The relationship of the DEMs is established by natural logarithm (ln). Then, the equation is interpolated on the original and resampled IFSAR DEMs to improve the medium-resolution data for WSE delineation. Next, the WSE was validated with observed WSE obtained along the upstream (Kuala Nerang) to the downstream parts (Kampung Kubu) Kedah using R2, mean absolute error (MAE), and root-mean-square error (RMSE). By applying this method, the WSE can be improved by considering uncertainties and lead to produce a better flood hazard map using medium-high-resolution images.

The Kompsat-3 Advanced Earth Imaging Sensor System (AEISS) camera contains two PAN CCD lines for a larger swath width. Merge of sub-images from individual CCD lines requires precise camera calibration before launch as well as in-flight calibration with a number of ground control points to determine the geometric relations between the CCD lines. Even with accurately determined sensor alignment parameters, there can still be exterior effects such as those associated with the ephemeris and terrain elevation. We generated a grid of tie points over the sub-images based on the physical sensor modelling and then evaluated the impacts of sensor alignment, ephemeris effects, and terrain elevation on the coordinate differences between the tie points. This enabled us to develop a procedure to precisely merge the sub-images into a single image. An experiment with three Kompsat-3 images produced successful results and displayed negligible image discrepancy in the overlap area.

A new propagation prediction algorithm based on DTED (Digital Terrain Elevation Data) digital map is presented for the prediction of Radar propagation through large scale irregular complex terrain. The computational accuracy has been greatly improved compared with conventional radio propagation models. The calculated results are compared with Longley-Rice model and Lee model.

The Shuttle Radar Topography Mission (SRTM) successfully acquired terrain elevation data for 80 percent of the Earth’s landmass in February 2000. The radar system and data collection scheme designed by NASA’s Jet Propulsion Laboratory (JPL) met the global requirements of the U.S. Department of Defense for Level 2 Digital Terrain Elevation Data (DTED ® ). JPL processed the raw data into unfinished DTED ® 2 and other products that were delivered to two contractors of the National Geospatial-Intelligence Agency. The contractors edited the unfinished DTED ® 2, updated the associated products, and generated finished products for distribution. Automated processes were developed by each contractor to identify, delineate and set heights for lakes, rivers, and ocean coastlines in conformance with an extensive set of editing rules created to maintain consistency and uniformity in the final products. The finished DTED ® is significantly better than the 16 m vertical accuracy required by the original specification.

A new remote sensing technique using polarimetric synthetic aperture radar (SAR) data has been developed which can measure terrain slopes in the azimuthal, or along-track, direction. Terrain elevation maps can then be generated by integrating these slopes. The processing of both single-pass, and orthogonal two-pass, datasets is investigated. When single-pass SAR data is used elevation groundtruth must be available for at least one point of each profile formed in the azimuthal direction. When orthogonal two-pass slope data is employed, the elevation surface may be generated as an iterative solution of the Poisson equation and only a single elevation tie-point is required. The results of two studies are presented. In the first study slopes have been measured using single-pass P-band data for a forested area in northern California. The elevation surface generated with this data has been compared with a Digital Elevation Model (DEM) produced by a C-band interferometric SAR. The second study uses orthogonal tw...

The distribution of lightning flash density over large areas depends on many factors. In this paper, we analyze one of them, namely the terrain elevation. Some previous studies suggest that the lightning flash density decreases above a certain altitude. We show that this conclusion could be affected by the used method of analysis and we suggest two improved methods. The lightning flash density distribution over Switzerland and Austria was used as an example to test the proposed methods. The results of the application of both methods suggest that the lightning flash density grows over the whole altitude range.

The work applies a methodology of processing and integration of aerogeophysics data coming from the Project Shield of Rio Grande do Sul (CPRM, 2010), together with data from ASTER GDEM of orthometric height (METI / NASA 2009), to verify the effectiveness of techniques FFT (Fast Fourier Transform) applied to the anomalous magnetic field and the analysis of distribution of radionuclides for geologic mapping in northeastern sheet Arroyo Santa Barbara - RS. As end graphics products were made a digital model of terrain elevation (DEM), maps of Anomalous Magnetic Field, Analytical Signal Amplitude, Horizontal and Vertical Derived, maps of the distribution of %K, eU, eTh, Factor F and Ternary Composition (RGB).

This paper describes the use of oct-trees to represent digitised terrain elevation data (DTED) in terrain reference navigation (TRN) systems. Oct-trees provide a regular method to represent digitised terrain data where the level of detail of the terrain is encoded in the tree structure. The use of oct-trees also provides a basis for a significant reduction in the on-line storage requirement for DT-EDs. A method of encoding using Morton ordering is introduced which allows DTEDs to be accessed as oct-trees and quad-trees where the tree structures are represented as pointerless structures. Algorithms to construct and access terrain oct-trees are presented which form a set of access primitives for tree operations required in TRN applications. The paper concludes with examples to illustrate the efficiency of the methods described in the paper for two DTEDs, in terms of performance of the tree access operations and reductions in storage.

The paper describes algorithm development for tree height retrieval in the boreal forest zone from TanDEM-X interferometric imagery. A set of 8 TanDEM-X pairs was acquired during summer and autumn 2011 over southern Finland in order to evaluate the potential tree height retrieval performance for this space-borne instrument. Another focus of the study was evaluation of seasonal dependence of interferometric signature of boreal forest. The obtained results are compared to our previous studies on tree height retrieval with the airborne DLR E-SAR instrument in the same area. The obtained results show good potential of TanDEM-X in forest mapping when external terrain elevation model is available, though accuracy seems to be somewhat lower compared to airborne instruments due to increased noise.

In the application of remote sensing at optical wavelengths to vegetated land surfaces from satellite-borne high-resolution instruments, such as those scheduled for the Earth Observing System, an understanding of the various physical mechanisms that contribute to the measured signal is important. In this context, numerical radiative transfer in three-dimensional coupled medium of atmosphere and vegetation has several applications, as in the development of correction routines for atmospheric perturbations, target information retrieval techniques, study of terrain elevation and adjacency effects, etc. A numerical method for solving the radiative transfer equation in three spatial dimensions was recently developed and analyzed for its numerical behavior. In this article, continued development of the method is reported, including an efficient acceleration algorithm. The reliability of coding and accuracy of the algorithm are evaluated by benchmarking. Parameterization of the method and results of a simulation are presented to document the utility of the code for applications in optical remote sensing studies of vegetated land surfaces. A simple model of the hot spot effect and sample calculations are presented. Finally, the radiative transfer method is tested with experimental data of vegetation canopy reflectance factors at two wavelengths.

This paper analyzed the advantage and disadvantage of TERCOM, probabilistic data association filtering(PDAF) and iterative closest contour point (ICCP) at first. Then it introduced the correction factor of tide and self-adaptive correction factor to improve the performance of seabed terrain elevation matching algorithm based on PDAF (STEMPDAF). By using STEMPDAF to make initial matching for ICCP, a combinational seabed terrain elevation matching algorithm was proposed. Mobile navigation is allowed during the matching period in the combinational algorithm. Theoretical analysis and simulation results both show that the performance of combinational algorithm is satisfactory.

Atmospheric effect is one of the most intractable problems in InSAR. Approaches such as stacking SAR interferograms, permanent scatter techniques and calibration with external data sources have been suggested in the past to mitigate the effects. In this paper, an elevation-dependent calibratory method is proposed to model and correct the atmospheric effects in InSAR. Test results with data from a meteorological station and 14 continuous GPS stations over Mount Etna, Sicily show that an improvement of about 27.2% is achieved after the model is applied.

40.61" 1 Abstract The Canada Centre for Remote Sensing (CCRS) C/X airborne SAR system has been upgraded with the addition of a C-band interferometric mode which may be used as a tool to derive terrain elevation, and thereby remove terrain elevation induced distortions from SAR imagery. The CCRS InSAR system is described and some preliminary results and evaluation given. A second, receive only C(H) antennal has been mounted on the right-hand side of the Convair 580 to form the interferometer. This system was flown for the first time on 26 July 1991 over a low relief test site south of Ottawa, Ontario and on 7 Feb. 1992 over Kananaskis region in the Canadian Rockies. The derivation of relative terrain elevation from the phase difference of imagery from the two receive antennas, along with motion compensation parameters, will be explained and illustrated. Estimates of the potentid accuracy for height estimation for the CCRS C-band system will also be given, based on a comparison with an accurate digital elevation model2 for the Ottawa test site. Preliminary analysis shows that height noise, due to phase noise, is in the range 1.5 to 5 m rms and height bias errors, at least for relatively flat terrain, are less than 5 m.

A digital terrain matrix (DTM) with sub-meter precision and at least three meter posting is needed to support a variety environmental, geophysical, economic and resource management tasks. Repeated measurements of DTM changes with five centimeters to one meter vertical resolutions and at least ten meter posting are needed for detection and measurement of a variety of geophysical processes. The Lockheed Martin Missiles and Space Digital Terrain Elevation Mapping System (DTEMS) which will be capable of providing data to satisfy these needs. DTEMS will use a NASA/Lockheed ER-2 aircraft with an X-band interferometric synthetic aperture radar (IFSAR) for collection, processing and archive of DTM with thirty centimeter average precision and one to three meter posting. DTEMS is expected to become operational by April 1997.

GeoSAR is a program to develop a dual frequency airborne radar interferometric mapping instrument designed to meet the mapping needs of a variety of users in government and private industry. Program participants are the Jet Propulsion Laboratory (JPL), Calgis, Inc., and the California Department of Conservation with funding provided initially by DARPA and currently by the National Imagery and Mapping Agency. Begun to address the critical mapping needs of the California Department of Conservation to map seismic and landslide hazards throughout the state, GeoSAR is currently undergoing tests of the X-band and P-band radars designed to measure the terrain elevation at the top and bottom of the vegetation canopy. Maps created with the GeoSAR data will be used to assess potential geologic/seismic hazard (such as landslides), classify land cover, map farmlands and urbanization, and manage forest harvests. This system is expected to be fully operational in 2002. In this paper we describe an experiment conducted at California's Latour State Demonstration Forest located near the city of Redding. This experiment marks the first operation of the-P-band radar in a vegetated area.

This paper discusses the flight test results of a real-time Digital Elevation Model (DEM) integrity monitor for Civil Aviation applications. Providing pilots with Synthetic Vision (SV) displays containing terrain information has the potential to improve flight safety by improving situational awareness and thereby reducing the likelihood of Controlled Flight Into Terrain (CFIT). Utilization of DEMs, such as the digital terrain elevation data (DTED), requires a DEM integrity check and timely integrity alerts to the pilots when used for flight-critical terrain-displays, otherwise the DEM may provide hazardous misleading terrain information. The discussed integrity monitor checks the consistency between a terrain elevation profile synthesized from sensor information, and the profile given in the DEM. The synthesized profile is derived from DGPS and radar altimeter measurements. DEMs of various spatial resolutions are used to illustrate the dependency of the integrity monitor s performance on the DEMs spatial resolution. The paper will give a description of proposed integrity algorithms, the flight test setup, and the results of a flight test performed at the Ohio University airport and in the vicinity of Asheville, NC.

A new computer program named read_terrain.c is developed to generate the elevation data for the Battlescale Forecast Model (BFM) from the U. S. Geological Survey (USGS) 30 arc-second elevation data (GTOPO3O data set). Since the data set covers the entire globe, terrain data for the BFM can be obtained for any part of the world, except for the areas in high latitudes. This report describes the GTOPO3O data set, which contains the data every 30 arc-second over the entire globe. The data was originally contained in five compact disk read only memory (CDROM)s to increase the portability and ease of use. The data were compressed and stored on a single CDROM. The method of data extraction from the data set is mentioned, which is capable of producing the terrain data for the BFM from a multiple number (up to four) tiles. Several function subprograms are used in this "C" language program, and the role of each subprogram is described. Examples of terrain data produced by this program are shown. The program codes in "C,, language are included in appendix A.

The Digital Terrain Elevation Mapping System (DTEMS) is a system that will combine SAR interferometry with high altitude flight operations in a NASA ER-2 for large area high precision digital terrain matrix (DTM) and polarimetric synthetic aperture radar (SAR) imagery collection. DTEMS will provide a national geocoded DTM with less than one meter error in geo-centered rectangular coordinates and three meter post spacing. Geocoding will obtain the DTM in geo-centered rectangular coordinates referenced to the WGS-84 mean ellipsoid. Coordinate transformations will convert the DTM to geographic or to universal transverse mercator (UTM) coordinates. Earth tide models will provide temporal corrections for diurnal deviations from the mean ellipsoid. The US Air Force Wide Area Differential GPS network (which is called WAGT) will be used to make differential corrections on the GPS data collected during each flight. In post flight processing the data will be transmitted via Internet to the differential correction processor. The corrected data will be transmitted via Internet back to the DTEMS data processing facility.

Airborne laser systems have demonstrated enormous potential for topographic and bathymetric mapping. Both profiling and scanning systems have been evaluated for terrain elevation mapping, stream valley cross-section determination, and nearshore bottom profiling. Performance of the laser systems has been impressive and for some applications matches current operational accuracy requirements. Determining the position of individual laser measurements remains a constraint for most applications. Laser technology constrains some terrain and bathymetric applications, particularly for water penetration and frequency of measurements for high-spatial resolution over large areas.

Ground track location on contour map for given terrain elevation profile, using digital computer

A new radionavigation LORAN C chain has been set up in France in 1985. This chain works with two transmitting stations : a master located in Lessay (Normandy) and a slave located in Soustons (Landes) near the Spanish-French border. Therefore this chain can only provide a range to range fix to an user equiped with an appropriate LORAN receiver and an accurate clock.

The advent of new generation of very high resolution radars for combat aircraft has underscored the importance of data compaction in radar simulation. This paper presents the design of a very efficient compactor to solve this problem. Traditionally, data compaction efforts have focused on terrain elevation alone. A method to compress both terrain elevation and culture data is given in this paper and its superiority to the conventional approach to terrain elevation compaction is also demonstrated.