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SUBSIDENCE MEASUREMENT WITH PS-INSAR TECHNIQUES 
IN SHANGHAI URBAN 
Lijun Lu Mingsheng Liao 
State Key Laboratory for Information Engineering in Survey, Mapping and Remote Sensing,Wuhan University Luoyu 
Road 129, Wuhan,P.R.China,430079,lulijun@lmars.whu.edu.cn 
Commission VII, WG VII/2 
KEY WORDS: DInSAR, PS-InSAR, Subsidence, Measurement, Urban 
ABSTRACT: 
Spacebome SAR Differential interferometry (DInSAR) has been used to monitor some geological disasters such as ground 
subsidence. This paper applies two Permanent Scatterer InSAR(PS-InSAR) techniques to measure long-term and short-term 
subsidence in urban area of Shanghai urban. A great number of archieved ERS data are utilized to measure long-term subsidence 
during 1993-2000 year. A small set of ASAR data are utilized to measure short-term subsidence during 2003-2005 year. The 
subsidence measurement results are examined with simultaneous leveling during the two periods, and comparison result shows a 
good agreement. Furthermore, the causes of subsidence are qualitatively analyzed in the main subsidence regions of Shanghai urban, 
and the variation of subsidence in two different periods can be detected according to the obtained subsidence measurement results. 
1. INTRODUCTION 
The surface deformations monitoring using DInSAR technique 
has shown some good results in the last years of research. As 
the extension of DInSAR technique, PS-InSAR technique has 
been recognized as a powerful tool for large-scale and long 
term monitoring small surface deformations in urban areas (Li, 
Liao et al., 2004). The strategies of PS technique is to find 
point-wise permanent scatters (hereafter called PSs) that exhibit 
phase stability over a long period of time, estimate and remove 
atmospheric phase contribution, DEM error and system/thermal 
noise etc., and finally measure precise displacement on 
permanent scatters. The advantage of PS-InSAR technique lies 
in that it can practically overcome the problems of geometrical 
and temporal decorrelation existing in DInSAR by using a large 
amount of SAR data. 
In this paper, PS-InSAR techniques are applied to the 
subsidence measurement in Shanghai urban as Shanghai urban 
has been suffering the subsidence disaster since 1920s. Aiming 
to the different survey applications, this author utilized the two 
PS-InSAR techniques on two different amount of SAR dataset. 
In the first study, the long-term subsidence can be measured by 
applying traditional PS-InSAR technique—Permanent Scatterer 
(Ferretti et al., 2000; 2001), as an amount of ERS-1/2 archived 
images from 1993 to 2000 in Shanghai urban are available from 
ESA. In the second study, the short-term subsidence from 2003 
to 2005 in Shanghai urban can be measured. As the extension of 
ERS-1/2 satellite, ENVISAT satellite has just in operation for 
several years, only small ASAR dataset are acquired so that it is 
insufficient to make an analysis in long time series. Considering 
limitation in the data availiability, another PS-InSAR technique 
— Spatio-Tempral Unwrapping Network (STUN) (Bert M. 
Kampers, 2006) can be applied. The STUN technique is 
improved in this paper for subsidence measurement in small 
dataset. 
Since Shanghai government has been made continuous leveling 
since 1990s, it provides us a good validation standard for 
precise evaluation of subsidence results by two PS-InSAR 
techniques. The subsidence results are validated by comparing 
the corresponding PSs and Leveling Benchmarks (LBs). On the 
basis of results validation, the causes of subsidence are 
qualitatively analyzed in the main subsidence regions of 
Shanghai urban, and the variation of subsidence in two different 
periods also can be detected according to the achieved 
subsidence results. 
2. DESCRIPTION OF TEST AREA AND DATA SET 
2.1 Test area 
Shanghai is the largest industrial city in China, standing on the 
East China Sea and situated at the front edge of Yangtze Delta, 
as showed in the left pictures of figure. 1. Subsidence due to 
underground water over-pumped has become a major problem 
in the city since 1920s. In the recent decade, with the increasing 
land use for urban development, the subsidence disaster has 
become worse. The severe subsidence generally occurred in the 
urban areas of Shanghai where the sites of underground water 
extraction and major municipal engineering constructions are 
located. Therefore we lay emphasis study on the urban of 
Shanghai, as shown by the right picture in figure. 1. 
Figure. 1 The location of Shanghai city. The left picture shows 
the location of Shanghai city in China, the right picture shows 
the location of test area, i.e. urban of Shanghai, covering an 
area about 1000 km 2 .