Considerations and recommendations for working towards global and automated tropospheric corrections in InSAR
Abstract
The rapid expansion of available SAR data and advancements in InSAR processing methods has enabled the formation of high-quality ground displacement time series for many parts of the world. In particular, the free and open data access from the Sentinel-1a/b satellites, part of ESA's Copernicus program, as well as the prospect of data from upcoming missions such as the NASA-ISRO SAR (NISAR), are encouraging the global community to move towards automated, cloud-based processing that can accommodate these rapidly growing data volumes. A key challenge remaining for the InSAR community is related to the atmospheric path delays introduced when the radar signal propagates through the ionosphere and troposphere. Properly characterizing this noise, particularly in areas of low topographic relief, remains a challenge for wide-spread general and automated InSAR time series users. Tropospheric corrections using phase-based methods and auxiliary data from weather models, GPS, and spectrometers have been included in open-source packages such as TRAIN, PyAPS and GACOS, and community users have reported variable degrees of success using these methods in a range of areas around the world. However, the various statistical metrics used to evaluate the reliability of each correction method are not consistent and often have different implications depending on the area and the spatial scale they are evaluated across. Furthermore, in areas characterized by low topographic relief and strong tropospheric turbulence, conventional metrics derived directly from the InSAR data itself, such as phase-topography correlation, do not provide significant insights. We present a summary of correction techniques, review different statistical methods for assessing their quality, and test each method and statistical metric over a large area in the central US - a region of limited topographic relief that experiences very strong gradients in tropospheric water vapor content. As the SAR community moves towards reliance on global and automated InSAR processing platforms that incorporate tropospheric corrections, approaches such as those examined here can aid researchers in their efforts to evaluate such corrections and include their uncertainties in derived products such as surface displacement time series and coseismic offsets.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G41B0698M
- Keywords:
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- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITYDE: 1241 Satellite geodesy: technical issues;
- GEODESY AND GRAVITYDE: 1908 Cyberinfrastructure;
- INFORMATICSDE: 1932 High-performance computing;
- INFORMATICS