Quantitative Subsidence Monitoring: The Integrated InSAR, GPS and GIS Approach

Errors in radar satellite orbit determination are common problems in radar interferometry (InSAR). For example, when trying to locate a radar test site with known geographic coordinates using the geocoding information in SAR image (the latitude and longitude of the four image corners), the location may be well away from the true position. Another example is when there is indeed a significant signal in the differential InSAR result, there is uncertainty as to whether it is due to ground deformation or atmospheric heterogeneity. As a consequence, InSAR is considered mostly as a qualitative tool for subsidence monitoring. Even after these are all corrected, it is necessary to export the InSAR results to a GIS so that they can be overlaid as layers over orthophotos and plans, in order to interpret the results. To aid InSAR applications it is therefore necessary to use both GPS and GIS. Results are presented with an application to monitoring subsidence due to underground mining in Appin, southwest of Sydney, Australia.