Land Subsidence Monitoring with Differential SAR Interferome

Land Subsidence Monitoring with Differential SAR Interferometry Tazlo Strozzi, Urs Wegmiiller, Luigl Tosl, Gabrlele Bitelli, and Volker Spreckels
The potential of differential SAR interferometry for land subsidence monitoring is reported on. The principle of the technique and the approach to be used on a specific case are first presented. Then significant results using SAR data from the ERS satellites for various sites in Germany, Mexico, and Italy, representing fast (mlyear) to slow (mmlyear) deformation velocities, are discussed. The SAR interferometric dis~lacement maps are'validated with available leveling data. he accuracy of the subsidence maps produced, the huge SAR data archive starting in 1991, the expected continued availability of SAR data, and the maturity of the required processing techniques lead to the conclusion that differential SAR interferometry is suitable for operational monitoring of land subsidence. Land subsidence (land surface sinking) occurs in many parts of the world, particularly in densely populated regions on deltas (Poland, 1984;Barends et al., 1995). Subsidence is the result of the natural compaction of sediments; of extraction of ground water, geothermal fluids, oil, gas, coal, and other solids through mining; and of underground construction. Most of the major subsidence areas around the world have developed in the past half-century at accelerated rates due to the rapidly increasing use of ground water, oil, and gas. Even if the hazards associated with subsidence are different from those caused by sudden and catastrophic natural events like floods and earthquakes, because surface sinking is a slow event, expansive damage can occur. In particular, many areas of known subsidence are along coasts where the phenomenon becomes obvious when the ocean or lake waters start coming further up on the shore. In addition, spatially heterogeneous subsidence produces damage in buildings and in other man-made structures such as bridges, highways, electric power lines, railroads, and underground pipes. Spatially heterogeneous subsidence is also the cause of changes in the drainage patterns, with canals that no longer carry their original design flows. For all these reasons, there is an increasing demand for accurate monitoring of land subsidence in order to improve the understanding of the phenomena and to give recommendations for a sustainable use of the underground resources.
Abstract
Introduction
T. Strozzi and Urs Wegmiiller are with Gamma Remote Sensing, Thunstrasse 130, 3074 Muri BE, Switzerland (strozzi8 gamma-rs.ch). L. Tosi is with ISDGM, CNR, S. Polo 1364, 30124 Venezia, Italy. G. Bitelli is with DISTART, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy. V. Spreckels is with the Institute for Photogrammetry and Engineering Surveys, University of Hannover, c/o Deutsche Steinkohle AG (DSK),DG, Gleiwitzer Platz 3, 46236 Bottrop, Germany. PHOTOGRAMMmRIC ENGINEERING & REMOTE SENSING
The problems of land

subsidence are a known environmental aspect in many cites and were among those included in Internathe list of research projects recommended-~~o's tional Hydrological Decade, which began in 1965, and the International Hydrological Program, a continuing UNESCOprogram beginning in 1975 (Barends et al., 1995). Traditionally, land subsidence is determined with precision leveling surveys. Wide networks of benchmarks were set up in most of the subsiding cities, and measurements are periodically repeated (FigueroaVega, 1976;Poland, 1984;Balestra and Villani, 1991; Brighenti, 1991;Capra et al., 1991; Bertoni et al., 1995; Carbognin et al., 1995; Gottardi et al., 1995).Leveling allows the monitoring of land subsidence in selected locations with high precision but is, for large areas, time consuming and expensive. Recently, GPS stations were implemented in few significant points of large subsiding areas in order to have a fast, cheap, and global measurement of subsidence (Bitelli et al., 2000). In the context of traditional surveying techniques, differential SAR interferometry has the potential to provide very important subsidence information over urban areas because of its two-dimensional spatial coverage, its high vertical accuracy, the SAR data availability, and its competitive cost. The potential of differential synthetic aperture radar (SAR) interferometry to map coherent displacements at centimeter to millimeter resolutions resulted in recent years in spectacular new results for the geophysical sciences. Earthquake displacement (Massonetet al., 1993),volcano deformation (Massonetet al., 1995),glacier dynamics (Goldstein et al., 1993;Joughin, 1996, Mohr et al., 1998),and land subsidence (Strozzi and Wegmiiller, 1999; Strozzi et al., 1999;Fruneau et al., 1999; Ferretti et al., 1999; Strozzi et al., 2000b) were mapped. In the SARinterferometric approach, two SAR images are combined to exploit the phase difference of the signals. The interferometric phase is sensitive to both surface topography and coherent displacement along the look vector occurring between the acquisitions of the interferometric image pair. The basic idea of differential SAR interferometry is to subtract the topography related phase from the interferogram to derive a displacement map. For a specific case, different approaches can be applied depending on the availability of a digital elevation model (DEM), on the characteristics of the SAR data with respect to spatial baseline, on acquisition time difference and coherence, on the displacement rates and shapes, on the land cover, and on the topography. In this contribution we review the principles of the differential interferometric SAR technique for subsidence monitoring, discuss how the approach is adapted to a specific case, and present significant results for sites in Germany, Mexico, and
Photogrammetric Engineering & Remote Sensing Vol. 67, No. 11, November 2001, pp. 1261-1270. 0099-1112/01/ …… 此处隐藏：13079字，全部文档内容请下载后查看。喜欢就下载吧 ……