slide 73

The speaker conducted a CAD study using InSAR to measure lens subsidence in central valley caused by groundwater overextraction. They used SAR images from Sentinel-1A and preprocessing software ICE for co-illustration and interferometry. SPS was used for time series analysis. InSAR successfully captured the subsidence pattern, and the results were constrained to the GNSS frame. The RNSD with GNSS results was 23 mm/year, which is somewhat high but acceptable for the half-year data used in this example. Here is the CAD study made by me. The purpose is to show you the real CAD of using InSAR. I used the SAR images from Sentinel-1A to measure the lens subsidence in central valley. There is severe lens subsidence in central valley due to the overextraction of groundwater. A good understanding of how severe it is can let us make a good plan to address it. Because it is just an example, I only used the half-year data. In real cases, more data are recommended for a good solution. I used the preprocessing software ICE to do the co-illustration and form interferometer. And I used SPS to do time series analysis. The star is a reference point at a GNSS station. You can see InSAR is able to capture the pattern of lens subsidence. I constrain the InSAR results to the GNSS frame. The triangle is the GNSS velocity. And the circle is the InSAR's velocity at GNSS stations. RNSD with GNSS results is 23 millimeters per year. Although the RNSD is still a bit high, it is still acceptable for only the half-year data.