Generation of high precision DEMs of the Wadden Sea with airborne interferometric SAR (original) (raw)
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IEEE Transactions on Geoscience and Remote Sensing, 2018
In this paper, a dual-frequency and dual-baseline (DFDB) processing framework for the extraction of highprecision terrain information from airborne interferometric synthetic aperture radar (SAR) data is presented. Specifically, we propose the use of two single-pass data sets acquired simultaneously in two different frequency bands and two largebaseline repeat-pass data sets also acquired simultaneously in two frequency bands. The configuration profits from the stability of the single-pass derived elevation maps in relation to spatially correlated artifacts as well as from the increased sensitivity associated with large-baseline acquisitions. Moreover, the dualfrequency nature of the data set enables the tackling of the phase unwrapping issue, promoting the retrieval of unambiguous measurements. Several algorithms for the interferometric processing of the DFDB airborne data set are proposed, including the outline of multichannel phase calibration and unwrapping error correction strategies and approaches to remove spatially correlated artifacts and extract the common underlying topography. Elevation models generated from a DFDB data set acquired with the airborne F-SAR sensor over tidal flats in northern Germany are presented, and comparisons with an airborne laser scanner reference show errors with a standard deviation of around 14 cm and a mean absolute deviation of less than 10 cm.
DEM by Ground-Based SAR Interferometry
IEEE Geoscience and Remote Sensing Letters, 2000
In this letter, a ground-based synthetic aperture radar (SAR) interferometer was used to generate digital elevation maps (DEMs) of the illuminated area. With respect to other ground-based data processing techniques, here, the effect of the propagation through the atmosphere is considered. An algorithm similar to multipass satellite SAR techniques was developed in accordance with the phase model used in the ground-based interferometry. Many images taken from different viewing angles were collected and combined to form different interferograms at a test site in Austria. Results from this technique have been compared with an existing geographic model of the test area.
CRUCIAL POINTS OF INTERFEROMETRIC PROCESSING FOR DEM GENERATION USING HIGH RESOLUTION SAR DATA
Data collection for digital elevation model (DEM) generation can be carried out by two main methods in space-borne remote sensing such as stereoscopy using optical or radar satellite imagery (stereophotogrammetry, respectively radargrammetry) and interferometry based on interferometric synthetic aperture radar (InSAR) data. These techniques have advantages and disadvantages in comparison against each other. Especially filling the gaps which arise from the problem of cloud coverage in DEM generation by optical imagery, InSAR became operational in recent years and DEMs became the most demanded interferometric products. Essentially, in comparison, DEM generation from synthetic aperture radar (SAR) images is not a simple manner like generation from optical satellite imagery. Interferometric processing has several complicated steps for the production of a DEM. The quality of the data set and used software package come into prominence for the stability of the generated DEM. In the paper, the interferometric processing steps for DEM generation from InSAR data and the crucial threshold values are tried to be explained. For DEM generation, a part of Istanbul (historical peninsula and near surroundings) was selected as the test field because of data availability. The data sets of two different imaging modes (StripMap ~ 3 m resolution and High Resolution Spotlight ~ 1 m resolution) of TerraSAR-X have been used. At the implementation, besides the determination of crucial points at interferometric processing steps, to define the effect of computer software, DEM production have been performed using two different software packages in parallel and the products have been compared In the result section of the paper, besides the colorful visualizations of final products along with the height scales, accuracy evaluations have been performed for both DEMs with the help of a more accurate reference digital terrain model (DTM). This reference model has been achieved by large scale aerial photos. Normally, it has a 5 m original grid spacing, however it has been resampled at a spacing of 1 m towards the needs of the research.
Quality assessment of interferometric SAR DEMs
2000
A new interferometric SAR (InSAR) procedure for DEM generation was employed to generate different DEMs from ERS SAR image pairs. The procedure was validated comparing the InSAR DEMs with a suited reference DEM. In the first part of the paper the principal features of the procedure are briefly summarised. The second part is focused on the quality assessment of the InSAR DEMs. They cover the same test area and come from one ascending SAR image pair, one descending pair and from the fusion of data coming from ascending and descending images. The analysis includes the influence of the SAR image coherence, the degradation of the DEM quality related to the terrain topography and the artefacts due to atmospheric effects.
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.
Accuracy assessment of DEMs derived from multi-frequency SAR images
Digital elevation model (DEM) is useful for land surface terrain analysis and is an important requirement for topographic correction of SAR backscatter data in hilly region. SAR interferometric (InSAR) techniques are very useful for deriving DEM of a large patch of land area with considerable accuracy in a faster and cost-effective manner. Today, various orbital radars operating in different frequencies and orbital periods are capable of providing data suitable for interferometric analysis. In the present study we have generated DEMs of Jharia coalmine region, India using InSAR techniques from ALOS-PALSAR, Radarsat-2 data and compared them with SRTM (Shuttle Radar Topography Mission) DEM and then, validated the DEMs against DGPS elevations measured as Ground Control Points (GCPs). We have then attempted to use the InSAR generated high resolution DEM for topographic corrections of SAR backscatter data. Index Terms-Digital elevation model (DEM); SAR Interferometry; Multi-frequency SAR; DGPS I.
International Journal of Remote Sensing, 2006
Repeat-pass synthetic aperture radar interferometry (InSAR) appears to be an excellent tool for generating digital elevation models (DEMs) of high spatial and vertical resolution. However, in recent years, it has been noticed that the atmosphere causes errors in the elevation accuracy. The objective of this paper is to try to identify climatic regions in India where InSAR can be used for generating DEMs. A detailed study was carried out to quantify atmospheric effects on the DEMs derived from repeat-pass InSAR. Three test sites were selected for the analysis: one over Mumbai, which is a part of the western ghats region with hilly terrain, lakes and forests; another is the Kolar area with gently undulating terrain with agricultural and forested lands; and the last was Bhuj, an arid plains region which is close to the Rajasthan Thar desert, India. Six interferograms of the Bhuj area derived from two tandem pairs were analysed and it was found that there were varying atmospheric effects of the order of 0.2l to 1l and at specific locations more than l. In the case of the Mumbai and Kolar study areas with two interferograms each, the atmospheric effects were almost negligible. In these cases, it is shown that it was also possible to estimate the height of buildings to an accuracy of 1-2 m. Therefore, it is concluded that one should be cautious when using InSAR techniques for generating DEMs of desert/ arid regions where the climate may be very dynamic and only small amounts of water vapour can cause strong atmospheric artefacts.
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.
Topographic SAR interferometry formulation for high-precision DEM generation
IEEE Transactions on Geoscience and Remote Sensing, 2002
In repeat-pass synthetic aperture radar (SAR) interferometry, the approximations, allowing the phase-to-height conversion, prevent high-resolution mapped relief. In this paper, we present a more general and exact formulation giving a new relationship between the interferogram phase and the target height. It is based on the interferometric SAR geometry and on a better expansion of the path length difference between the sensor and the target. This formulation emphasizes the impact of baseline uncertainties on digital elevation model (DEM) accuracy.