Using GPS to Mitigate Atmospheric Stratification in Corner Reflector InSAR, Examples From 6 Years of Observations
Abstract
Propagation delay caused by tropospheric turbulence and stratification is a severely limiting factor for operational use of InSAR. Changes in the tropospheric propagation delay between two SAR acquisitions used to form an interferogram will lead to an unknown phase component. The total tropospheric delay can be divided into a stratified part, which correlates with the topography, and a turbulent part. For displacement monitoring in mountainous areas, the stratification is often the dominating part, and mitigation is thus critical for analysis. Landslide sites often have poor InSAR coherence due to steep topography, vegetation, and snow cover large parts of the year. We have therefore installed radar corner reflectors at several high-risk rockslide sites in Norway. The 1.8 m trihedral reflectors are covered to prevent snow accumulation, permitting year-round displacement monitoring. At the Åknes rockslide in Storfjorden, western Norway, we have operated four reflectors since 2005, and at the Jettan rockslide in Troms county, northern Norway, we have operated four reflectors since 2009. The reflectors are installed on the moving blocks, as well as on the area above the slides, which is presumed to be stable. In the period 2005-2010, SAR data was regularly acquired with Envisat's ASAR instrument on several tracks. Currently, both sites are covered by RADARSAT-2 Fine and Ultra-fine modes, as well as the TerraSAR-X Stripmap mode. InSAR processing of the reflector data is complicated by the vertical separation between the reflectors which gives rise to an unmodeled tropospheric phase component. In this study, we apply zenith wet delay estimates from dense GPS networks to correct for the stratified phase delay. The corrected InSAR deformation time series will be compared to displacement observed at collocated GPS points.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.G43A0902L
- Keywords:
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- 1240 GEODESY AND GRAVITY / Satellite geodesy: results;
- 1294 GEODESY AND GRAVITY / Instruments and techniques;
- 4337 NATURAL HAZARDS / Remote sensing and disasters