The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
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earth observation methods is low cost, accessibility for large
area deformation mapping.
(D) TimefYearl
Fig. 4: LOS displacement time series for the point A, B, C, D
5. CONCLUSIONS
This paper is focused on the investigation of the surface
deformation of the city Nanjing, the over all analysis is based
on the exploration of the SBAS-DInSAR approach with a prior
deformation knowledge applied to a SAR data set acquired by
the ERS-2 sensor during 1996-2000 time interval.
This study demonstrates the capability of the SBAS-DInSAR
procedure to investigate the space-time characteristics of the
deformation affecting the overall area. Moreover, we assume a
cubic behaviour for the time variation of the deformation phase
signal as a prior knowledge for the investigated area, and solve
the equation in an optimal LS method directly, which simplify
the SBAS-DInSAR algorithm. In particular, 13 interferograms
in two subsets were generated using 8 ERS-2 SAR images
acquired from August 1996 to April 2000 in Nanjing area,
based on the cubic behaviour for the time variation of the
deformation phase signal as prior knowledge, deformation map
and displacement time series were generated using these 13
interferograms and the implemented SBAS-DInSAR algorithm.
Moreover, we find that the main deformation area is along the
Yangtze River and to the west of the Qinhuai River, the
maximum subsidence is around 12.0cm. finally, although the
SAR images used in this study is relatively few, the
deformation trend in the whole city has a good agreement with
the conventional Leveling measurement, but more SAR images
should be used to get temporal behaviour of the deformation
maps of the area, more sophisticate algorithm for detecting
local deformations on a small spatial scale should be developed.
As an additional remark, the No. 1 north-south subway in
Nanjing began in operation since September 2005. With a
length of 21.72 km and 16 stations, Construction of the east-
west No.2 subway with a length of 25.15 km is also in progress,
developing new algorithm of InSAR technique to detect
deformation along the subways is meaningful and challenge for
the future.
ACKNOWLEDGEMENTS
The work is supported by Nature Science Foundation of China
(No. 50579013).The precise ERS-2 satellite orbit state vectors
have been provided by the Technical University of Delft. We
thank the European Space Agency (ESA) which provides the
ERS SAR data relevant to the city Nanjing. The authors would
also like to express a special thank to Dr. Luo Haibin and Dr.
He min for helps.
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