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Ground Subsidence Measurements of Reclaimed Land using Radar Interferometry

Chang-Wook Lee(1), Hyung-Sup Jung(1), Sang-Wan Kim(2) and Joong-Sun Won(1)

(1) Yonsei Univ., 134 Sinchon-Dong, Seodaemun-Gu, 120-749, Seoul, Korea
(2) SeJong Univ., Gunja-dong, Gwangjin-gu, 143-747, Seoul, Korea

Abstract

Noksan industrial complex is a reclaimed coastal land at southern Korea. Subsidence rate in this area had successfully been measured in a previous study by using L-band (JERS-1) Interferometric Syntehetic Aperture Radar from 1996 to 1998. RADARSAT-1 (C-band) data had been used to measure displacements of surface from September 2002 to October 2003 soon after JERS-1 satellite results. C-band data are also efficient at surface conditions of the reclaimed land because of very rough surface without vegetation, which makes strong radar returns. Eight RADARSAT-1 data sets of fine beam mode (F4) had been obtained between September 2002 and October 2003, and 13 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 retrieve a time sequence deformation, we applied to a singular value decomposition and finite difference smoothing methods. In this method, the atmospheric and orbital contributions were reduced by spatial LP and temporal HP filterings in the DInSAR interferogram datasets. AIRSAR C-band DEM and a DEM constructed from an ERS tandem pair were used to eliminate topographic phase from the interferograms. Estimated interferometry-based subsidence was evaluated by using in-situ data that had been obtained by magnetic probe extensometers with an accuracy of a few millimeters. A two-dimensional DInSAR subsidence map derived from the measurements enabled us to map unstable foundation in detail. The results reveal about 10 cm subsidence for a year at the southern area of Noksan industrial complex by continuous interferograms. Compaction process of the newly filled soil is considered as a main cause of the subsidence. This DInSAR application is very useful to determine construction period for industrial buildings. The results prove that DInSAR technique using RADARSAT-1 fine-beam mode SAR is a useful tool in the field of geotechnical engineering.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry