Quality assessment of InSAR digital elevation models (original) (raw)
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DIGITAL ELEVATION MODEL (DEM) GENERATION FROM SAR INTERFEROMETRY
SAR Interferometry (InSAR) provides data that contain information relating to the phase and coherence components of the backscattered radar signals. Phase information is used to derive Digital Elevation Models (DEM). This paper presents the results of an analysis of the accuracy of InSAR DEM derived from ESAR L-band airborne repeat-pass fully polarimetric InSAR data, which were acquired over Thetford Forest, in the east of England. An area with no tree cover of about 300m by 300m in size was chosen as a test site. Then InSAR DEMs for L-band HH, HV and VV polarisations were generated. The accuracy of the InSAR-derived DEMs was deduced by comparison with reference DEMs, which were generated from field data acquired from both Global Positioning System (GPS) & spot height survey and a Lidar DEM. The Lidar DEM was acquired by the UK Environment Agency. The poster reports the results of these comparisons and some concluding remarks about the relationship between the accuracy of the InSAR DEMs, polarization mode, and the nature of the ground surface cover are highlighted.
International Journal of Computing, Communication and Instrumentation Engineering
A Digital Elevation Model (DEM) is a digital representation of ground surface topography. DEMs are used for various applications including flood modeling. The objective of this paper is to evaluate the vertical accuracy of the DEMs acquired from different sources. The study area covered several districts in Kedah, Malaysia. To determine the accuracies of DEMs acquired from NEXTMap Interferometric Synthetic Aperture Radar (IFSAR), ASTER Global Digital Elevation Model (GDEM) and SRTM Void Fill, height points are compared with the Global Positioning System (GPS) height observations. A total of 100 height points extracted from ASTER GDEM and SRTM is also compared with IFSAR Digital Surface Model (DSM). Four (4) different elevation profiles are generated and the heights are compared. The results obtained have shown that the Root Mean Squares Errors (RMSEs) of IFSAR DTM, IFSAR DSM, ASTER GDEM and SRTM over a relatively flat area are ±0.497 m, ±1.529 m, ±5.848 m and ±4.268 m respectively. Over an undulating area, the accuracies of IFSAR DTM, IFSAR DSM, ASTER GDEM and SRTM are ±0.841 m, ±2.092 m, ±3.278 m and ± 5.300 m respectively. Although there are variations between heights generated from these DEMs in some areas along cross-section, the pattern of height profiles is still quite similar. Future work will concentrate on the techniques of converting DEM acquired from ASTER GDEM and SRTM into DSM and the effects of using different DEMs on the accuracy flood inundation mapping.
INVESTIGATION OF ELEVATION BIAS OF THE SRTM C- AND X-BAND DIGITAL ELEVATION MODELS
The paper presents results of a comparative study of the vegetation-caused elevation bias of the space shuttle topographic mission data product, both C-and X-band (SRTM.C/X). The SRTM.C/X bands data were compared against a high-resolution digital terrain model. Pixel-based differences in SRTM.X minus SRTM.C were correlated with land cover ('agriculture', 'house', 'tree', 'water'). Findings of the investigations include that the SRTM.X does not represent a canopy top of vegetation and that the X-band penetrates deeper vegetation cover than the C-band. As a test site, an area of about 159 km 2 on the Gold Coast, Queensland, Australia, was selected. The area of interest is about 57% covered by vegetation varying from grassland and shrubs to forest. The study method allowed the development of a statistical model relating the elevation bias to the percentage of the vegetation cover of a given land parcel. This model, once verified on varieties of vegetation types, could be utilised to estimate and eliminate the elevation bias from the InSAR elevation model. This model could also be utilised for estimating biomass quantities and their variations. It is hoped that the results will also stimulate investigations towards developing a multi-frequency InSAR system for collecting both terrain elevation data and attributes of biomass.
ipcbee.com
Digital Elevation Models (DEMs) are used in many applications in the context of earth sciences such as in topographic mapping, environmental modeling, rainfall-runoff studies, landslide hazard zonation, seismic source modeling, etc. During the last years multitude of scientific applications of Synthetic Aperture Radar Interferometry (InSAR) techniques have evolved. It has been shown that InSAR is an established technique of generating high quality DEMs from space borne and airborne data, and that it has advantages over other methods for the generation of large area DEM. However, the processing of InSAR data is still a challenging task. This paper describes InSAR operational steps and processing chain for DEM generation from Single Look Complex (SLC) SAR data and compare a satellite SAR estimate of surface elevation with a digital elevation model (DEM) from topography map.
COMPARISION OF ELEVATION DERIVED FROM INSAR DATA WITH DEM FROM TOPOGRAPHY MAP
aars.org
Digital Elevation Models (DEMs) are used in many applications in the context of earth sciences such as in topographic mapping, environmental modelling, rainfall-runoff studies, landslide hazard zonation, seismic source modelling, etc. During the last years multitude of scientific applications of Synthetic Aperture Radar Interferometry (InSAR) techniques have evolved. It has been shown that InSAR is an established technique of generating high quality DEMs from spaceborne and airborne data, and that it has advantages over other methods for the generation of large area DEM. However, the processing of InSAR data is still a challenging task. This paper describes InSAR operational steps and processing chain for DEM generation from Single Look Complex (SLC) SAR data and compare a satellite SAR estimate of surface elevation with a digital elevation model (DEM) from Topography map. The operational steps are performed in three major stages: Data Search, Data Processing, and product Validation. The Data processing stage is further divided into five steps of Data Pre-Processing, Co-registration, Interferogram generation, Phase unwrapping, and Geocoding. The Data processing steps have been tested with ERS 1/2 data using Delft Object-oriented Interferometric (DORIS) InSAR processing software. Results of the outcome of the application of the described processing steps to real data set are presented.
Evaluation of Insar Dem from High-Resolution Spaceborne Sar Data
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2012
In recent years a new generation of high-resolution SAR satellites became operational like the Canadian Radarsat-2, the Italian Cosmo/Skymed, and the German TerraSAR-X systems. The spatial resolution of such devices achieves the meter domain or even below. Key products derived from remote sensing imagery are Digital Elevation Models (DEM). Based on SAR data various techniques can be applied for such purpose, for example, Radargrammetry (i.e., SAR Stereo) and SAR Interferometry (InSAR). In the framework of the ISPRS Working Group VII/2 "SAR Interferometry" a long term scientific project is conducted that aims at the validation of DEM derived from data of modern SAR satellite sensors. In this paper, we present DEM results yield for the city of Barcelona which were generated by means of SAR Interferometry.
Comparison of High Resolution InSAR and Optical DEMs
A Digital Elevation Model (DEM) alias Digital Height Model (DHM) is the digital cartographic representation of the elevation of the terrain at regularly spaced intervals in X and Y directions, using Z-values related to a common vertical datum. DEMs are required for several applications and in order to satisfy the need, various DEM generation techniques have been developed up to this time. Remote sensing is one of those techniques and contains two main methods for DEM generation as optical imagery and interferometric synthetic aperture radar (InSAR). These methods have several advantages and disadvantages against each other. For example; object recognition is easier in optical imagery but the images should be cloud-free. In contrast to optical imagery, object recognition is poor in InSAR but data collection is independent from weather conditions, clouds can be penetrated and large coverage up to global can be obtained fast at specific times. In the study, the comparison of high resolution InSAR and optical DEMs was aimed at the same test field to determine the quality of TerraSAR-X (TSX) which is one of the most advanced InSAR satellite. TSX is German made and launched on June 15 th , 2007. It offers high resolution (~1m by Spotlight mode) imagery which could not been achieved from radar technologies up to this time similar to high resolution optical imagery. The data sets provided by TSX newly obtained by scientific community and evaluations are currently being performed. According to the aims of the study, high resolution spotlight (HRS) mode TSX and panchromatic (PAN) IKONOS DEMs were generated with 3m grid spacing in Istanbul, Turkey and evaluated using more accurate reference DEM, generated by photogrammetry. It has 1m grid spacing and 10cm up to 2m accuracy. At the evaluation processes, absolute and relative accuracy, stability, homogeneity and dependency upon various parameters are determined. After the evaluation analysis of the height models, it has been seen that HRS mode TSX model has nearly same visual quality and absolute accuracy with IKONOS model and has better relative accuracy.
Producing Digital Elevation Models with Radar Interferometry
2010
The main objective of this paper is to discuss how satellite radar interferometry (InSAR) can be applied for production of high-resolution digital elevation models (DEMs). DEM is the most important natural environment data layer used in the archaeological landscape analyses. From the high-resolution elevation models numerous essential information layers used in archaeological regional analyses can be derived: slope, aspect, cross sections, and inter-visibility. This data can be flirther on used for modeling of boundaries and territories as well as for optimal paths calculations. In the areas where suitable DEMs do not exist or are not available, interferometry is an effective alternative for their production. In this paper general background and the production of digital elevation model for Slovenia is presented. The results have proved that interferometry can be used for fast, effective and cheap production of accurate DEMs over large areas.
Digital elevation models (DEM) are numerical representation of terrain elevation data that has been used in a wide range of spatial analysis applications. The principles for acquisition, storage, management, update, spatial analysis, visualization as well as integration with other systems are reasonably well known. However, as DEM applications are becoming increasingly more widespread, so does concern about the quality of the available elevation data and the propagation of DEM errors through the analysis. It is now well known by analysts and researchers that the results of many DEM-based quantitative operations are significantly affected by the magnitude and also by the spatial distribution of elevation errors in DEM. However, currently available DEM's frequently report only the average magnitude of errors as the root mean square error (RMSE), which does not provide information on systematic bias nor on the spatial patterns of the DEM errors (Heuvelink, 1998). A very important ...