Abstract
Abstract. Interferometric Synthetic Aperture Radar (InSAR) has been well developed for several decades and is known for its powerful capability of retrieving three-dimensional ground information from SAR imagery. One of the most important application of InSAR technique is topographic mapping. The technique is limited when confronting certain poor conditions which lead to low coherence. In this research, we aim at investigating the relationship between SAR-based digital elevation models (DEMs) and related factors that contribute to the error budget by conducting a linear regression analysis. The surface deformation in line of sight (LOS) direction and the amount of integral refractivity change over two acquisition events are considered as two related factors. Eight pairs of Sentinel-1 images were selected to conduct InSAR processing over Chaiyi City of Taiwan, and SNAP software was used to generate SAR-based DEMs. The coherence mask was applied during the InSAR workflow in order to alleviate unwrapping error. The result has shown that the coherence thresholds help to improve the accuracy by up to 52.61%. Since some large errors were observed from the resulting InSAR-DEMs, these points were removed based on standard error. In regression analysis, there were 15 set of data, categorized by different coherence threshold and data removal standard, to test the model. As the result has shown, when the coherence threshold is 0.3 and the points were filtered with half standard error, the R2 can achieve 0.85. However, the rest of the dataset did not produce desirable results. In our discussion, we have provided several reasons which might have contributed to this outcome.
Highlights
IntroductionOne of the most important application of Interferometric Synthetic Aperture Radar (InSAR) techniques is topographic mapping, which is essential for various purposes such as three-dimensional visualization, terrain analysis, disaster analysis and navigation
Interferometric Synthetic Aperture Radar (InSAR) has been extensively used for decades to extract 3D information of a surface
If we only look into the relationship between the height error and either factor (Figure 9, take 0.5 standard deviation (SD) as an example) by calculating correlation coefficient (r), we can observe that the relationship between error and surface deformation is much more apparent than integral refractivity
Summary
One of the most important application of InSAR techniques is topographic mapping, which is essential for various purposes such as three-dimensional visualization, terrain analysis, disaster analysis and navigation. A few common issues that have been discussed are geometric decorrelation, temporal decorrelation, and atmospheric disturbance (Hanssen, 2001; Usai, 1997; Zebker and Villasenor, 1992). These obstacles could seriously deteriorate the quality of the final DEM products, depending on the selection of InSAR image pairs and the environmental conditions of the area of interest
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