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Mapping without the sun
Zhang, Jixian

YAN Ming-xing, MIAO Fang, WANG Bao-cun, QI Xiao-ying
The Center Of Geological information Chengdu 610059, Sichuan, China
yanmingxing_ 1013@ 163 .com, mf@cdut.edu.cn
KEY WORDS: DInSAR; GIS; mine subsidence; ERS; Envisat; Tangshan
This research used both ERS and Envisat images to investigate the feasibility of differential radar interferometry (DInSAR) for mine
subsidence monitoring in Tang Shan, Hebei Province, China. DInSAR results are analyzed and validated with the aid of Geographic
Information System (GIS) tools. The drawbacks of using interferometric measurements for mine subsidence monitoring are discussed.
The repeat-pass tandem and Envisat DInSAR results are presented.
Interferometric synthetic aperture radar (InSAR) systems
exploit the phase differences between two SAR images
acquired over the same area. Useful topographic information,
such as digital elevation model (DEM), can be derived.
Differential InSAR (DInSAR) has been further used to measure
the deformation of the ground terrain. A number of experiments
have demonstrated that InSAR is very useful in such fields as
earthquake-related deformation, volcanic motion, ice-sheet shift,
urban settlement. [Massonet and Feigl, 1998; Rosen et al.,
Compared with the conventional approaches (such as GPS
monitoring), using of InSAR and D-InSAR in surface
deformation monitoring can cover a large area on the earth, and
the result can be obtained in a relatively short time. The cost of
InSAR is lower and it is very useful for the rural area or the
dangerous places where we can’t easily arrive. Finally, because
the cloud and the light have no effect on the Synthetic Aperture
Radar images, the images can be obtained every times when the
SAR satellites pass the area. The feasibility and capability of
DInSAR for underground mine subsidence monitoring have
been tested in the UK [Wright, P. and R. Stow. 1999], France
[Carnee, C. and C. Delacourt, 2000], Germany [Wegmuller,
2000]. In these studies, the images acquired by the two ERS
satellites are the only data source.
This paper reports the progress of the ongoing ESA CAT-1
project (ID 4527). We used radar images acquired by the ERS
and Envisat satellites to investigate the use of radar
interferometry for mining-induced subsidence monitoring in
Tang Shan, Hebei Province, China. Successful DInSAR results
are exported to the GIS and mine subsidence regions extracted.
The DInSAR results are analyzed and validated against other
spatial information, such as TM images and mine plans.
Repeat-pass space-borne DInSAR has been used to derive
ground displacement maps. Two SAR images acquired from
two slightly different positions, at different revisit times, are
used to measure the phase difference, or so-called interferogram,
between the two acquisitions.
As shown in (l)[Liu Guo-xiang,2006], the phase change in the
interferogram is the composite of systematic phase(also termed
flat-earth trend phases)from the reference surface, 4) flat ,
topographic information, t0 po, surface displacement between
the two acquisitions, 4> disp , atmospheric delay, 4> de i ay , and noise,
4* noise-
4* — 4* flat"^ 4> topo "F 4> d ispF 4> delay F 4> noise (1)
DInSAR requires the removal of phase signatures that are
contributed by the flat-earth and topography, and so isolating
the ground displacement component. The fl at can be
predicted using the satellite state vectors or baseline data and
based on the interferometric geometry, and then subtracted
from the initial interferogram. The top o can be simulated and
eliminated by introducing DEM information. The atmospheric
component, 4> delay , is primarily due to fluctuations of water
content in the atmosphere between the satellite and the ground,
it is difficult to eliminate because the absence of the
weather-information and the limited resolution of the SAR
sensors. We can use filter to enhance the signal-to-noise level.
Tangshan City and Kailuan Mining Area, located in east of
China, are selected as the experimental district.Tangshan city is
the main coal city in China. Since 1970s, underground mining
extended to downtown area. Especially since 1990s,
underground mining has induced large area of land surface
subsidence; many buildings, road and pubic establishment were
damaged. Kailuan Mining Area has been exploited for 123
years, the mining area covers 670 km 2 , and the subsidence area,
affected by underground coal mining, covers 208 km 2 .[Wu
Figure 1 is TM image of Tangshan test site. We select ERS
SAR data (Track: 175, Frame: 2799) and Envisat ASAR data