The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
A — it represents the centre urban of Shanghai where the 
severe subsidence has occurred. As shown in figure. 13, the 
pumpage of ground water is smaller than 5 million nr / yr, and 
the recharge of a large amount of ground water is undertaken to 
control subsidence. With the rapid development of centre urban 
in recent years, the urban land use ratio has reach 100% 
(figure. 14). Comparing the subsidence results of two periods 
(figure. 15), the average subsidence velocity is slowing down. 
Hence we can deduce that subsidence due to exploitation of 
underground has been mitigated to under the control, while 
subsidence due to urban land use has become the predominant 
cause. 
B — it represents one new town of Baoshan in Shanghai. 
Severer subsidence occurred in the East of Baoshan. As shown 
in figure. 13, the huge pumpage of ground water is larger than 
20 million m 3 / yr, and as an important industrial base of 
metallurgy, the land use ratio of the town exceeds 50% 
(figure. 14). Comparing the results of two periods (figure. 15), 
the magnitude of subsidence is increasing. Hence we can 
deduce that exploitation of under ground water is the main 
cause of subsidence and tendency of subsidence is speeding up. 
C — it represents a developing new town of Jiading in 
Shanghai. As shown in figure. 13, the pumpage of ground water 
is approximately 5 million m 3 / yr, and as a new developing 
town, the urban land use ratio of the town is only 40% 
(figure. 14). The study area of C region is very small in the new 
town, but it takes up a large proportion of subsidence area. 
Average subsidence velocities in two periods are basically the 
same (figure. 15). We can deduce that exploitation of under 
ground water leads to a majority of subsidence in C region. 
D — it represents a high and new technology industrial 
development town of Pudong in Shanghai. As shown in 
figure. 13, the huge pumpage of ground water is approximately 
30 million m 3 / yr, and some measures of recharge is taken to 
relieve the over-pumping. As the most developed industrial 
zone, the urban land use ratio of the town is 54% (figure. 14), 
and the developed lands mainly consists of large plants and 
municipal engineering constructions. Average subsidence 
velocity is becoming faster (figure. 15). We can deduce that 
exploitation of under ground is the main cause of subsidence 
and the land use accelerate the process. 
E — it represents three agricultural towns of Minghang, 
Nanhui and Qingpu in Shanghai. The study area of E region 
includes a part of three towns. As shown in figure. 13, the 
pumpage of ground water of each of three towns is 
approximately 5 million m 3 / yr. Being agricultural towns, urban 
land use ratio of each town is not more than 51% (figure. 14). 
Average subsidence velocity accelerates due to pumping of 
ground water in the new aquifer, e.g. the exploitation in the 
fourth aquifer in Nanhui town. We can deduce that exploitation 
of under ground water is the main cause of subsidence and 
tendency of subsidence is speeding up. 
The above analysis gives us an impression that subsidence 
disaster in Shanghai urban is mainly caused by joint action of 
exploitation of ground water and urban land use. Exploitation of 
ground water is still the main cause leading to subsidence and 
the urban land use accelerates the process. The measure of 
recharge has been taken to control subsidence so that the 
subsidence of some regions has mitigated. But with the rapid 
development of urban area, urban land use has become a new 
cause leading to subsidence and shown extending tendency in 
some regions. 
Owing to lack of a great deal of detailed ground truth data, the 
quantitative analysis concerning the relations among the 
subsidence, pumpage of ground water and land use status has 
not been made in the paper, and more in-depth studies will be 
conducted in the future. 
7. CONCLUSIONS 
In this paper, the two PS-InSAR techniques are applied in long 
term and short-term subsidence measurements are proved to be 
effective in Shanghai urban, and it suffices to meet different 
needs of survey tasks. On the other hand, the cause of 
subsidence and subsidence variation of two periods are 
qualitatively analyzed to provide a guidance to detect and 
control subsidence disaster for decision-making department. 
REFERENCES 
Best M. Kampers, 2006. RADAR INTERFEROMETRY 
Persistent Scatterer Technique. Springer, Germany, pp.43-66. 
Ferretti, A., Prati, C., Rocca, F., 2001.Persistent scatterers in 
SAR interferometry. IEEE Transactions on Geoscience and 
Remote Sensing, 39(1), pp. 8 - 20. 
Ferretti, A., Prati, C., Rocca, F., 2000. Analysis of Permanent 
Scatters in SAR Interferometry. Geoscience and Remote 
Sensing Symposium. Proceedings[C]. IGARSS 2000, 2 pp.761- 
763. 
Li D R, Liao M S, Wang Y, 2004. Progress of Permanent 
Scatterer Interferometry. Geomatics and Information Science of 
Wuhan University. 29(8), pp.664-668. 
Lijun Lu, Mingsheng Liao, Changcheng Wang, etc, 2008. A 
New Method of Identification of Stable Pointwise Target in 
Small SAR Dataset. Proceedings of the 2008 Dragon 
Symposium - Dragon Programme Final Results Results (in 
press). 
ACKNOWLEDGEMENTS 
The work in the paper was supported by the National Key Basic 
Research and Development Program of China (Contract No. 
2007CB714405) and 863 High Technology Program (Contract 
No. 2006AA12Z123). The authors thank ESA for providing the 
SAR data through ESA-NRSCC Cooperational Dragon 
Programme (id: 2567). And the author would also thank the 
Shanghai Institute of Geological Survey for providing the 
ground validation data. 
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