Measurement of a Small-scale Subsidence in a Reclaimed Land Using Radarsat-1 Sar

Subsidence rate in a reclaimed coastal land of Noksan industrial complex, Korea, was measured by C-band SAR differential interferometry (DInSAR). Surface conditions of the reclaimed land are very rough without vegetation with respect to C-band, which makes strong radar returns. However, artificially loaded top soil is subject to change within a short period so that it is difficult to obtain coherent interferometric pairs by using C-band in a reclaimed land. Seven RADARSAT-1 data sets of fine beam mode (F4) had been obtained between September 2002 and October 2003, and 4 coherent interferograms were generated from them. A large incidence angle (about 41 degree) of RADARSAT-1 F4 fine-beam mode is not favorable for observing flat areas. To obtain coherent interferograms, we used pairs of short temporal and perpendicular baselines. AIRSAR C-band DEM and a DEM constructed from an ERS tandem pair were used to eliminate topographic phase from the interferograms. Estimated interferometrybased subsidence was evaluated by using in-situ data that had been obtained by magnetic probe extensometers with an accuracy of a few millimeters. Compaction process of the newly filled soil is considered as a main cause of the subsidence. The results prove that DInSAR technique using RADARSAT-1 fine-beam mode SAR is a useful tool in the field of geotechnical engineering.