Full text: Mapping without the sun

ZHANG Ji-chao 1 ’ *, SONG Wei-dong 1 , ZHANG Ji-xian 2 , SHI Jin-feng 1 
1 School of Geomatics, Liaoning Technical University, Fuxin 123000, P.R.China - zmouse@21cn.com 
2 Chinese Academy of Surveying & Mapping, Beijing 100039, P.R.China 
KEY WORDS: InSAR, GPS, data fusion, mining subsidence monitoring 
Mining subsidence monitoring is very important for mining and sustainable development. For monitoring mining subsidence, 
Interferometric synthetic aperture radar (InSAR) and GPS technology are very strong complementary. The integration of InSAR and 
GPS improves the ability of mining subsidence monitoring both in temporal and spatial domain, and it had become a research focus 
in monitoring surface subsidence during resent years. The paper first summarized the current situation of research and application 
for InSAR/GPS used in surface subsidence monitoring, then mainly analysed mining subsidence monitoring with InSAR/GPS data 
fusion. Finally, some corresponding countermeasures are given in the paper, which shall provide technical support for realizing real 
time dynamic monitoring of coal mining-induced subsidence. 
1.1 The necessity of surface subsidence monitoring in 
mining area 
Mining-induced surface subsidence is an inevitable problem. It 
has much impact on coalmine production safety, environmental 
destruction and building distortion. To enforce real-time and 
effective monitoring on it, disciplinarian and tendency of the 
surface subsidence can be discovered in time, so that it can 
provide effective early warnings to district security and 
environmental destruction, and instruct the control and 
comprehensive management of mining subsidence. Thus, 
carrying on the surface deformation monitoring of mining area 
plays an extremely important roles in the national economy and 
the society development. 
1.2 Surface deformation of mining area measurements 
At present, there are many kinds of measurements for surface 
deformation surveying in mining area (Diao, J., 2005), mainly 
including conventional geodetic survey, close-range photo- 
grammetry, GPS network, Synthetic Aperture Radar Interfero 
metry (InSAR) technique and so on. 
Conventional geodetic survey method can exert the advantage 
of existing instruments and equipments, and it can meet the 
required precision of subsidence monitoring. However, this 
method needs the surveyors regularly do the work outdoors and 
the field operation workload is burdensome. Besides, the 
expense is high, and can only do incontinuous surveying. 
Close-range photogrammetry method takes advantages of high 
efficiency and reliable precision, and it may observe the earth’s 
surface continuously. It is adapt to monitor the surface 
deformation for small mining area. But compared with the 
conventional geodetic survey method, this method is more 
complicated and the photographic apparatus is also more 
expensive. * 3 
GPS network method has the virtue of having no use for 
intervisibility among survey stations, the high positioning 
accuracy, the short observation period, the simple operation 
process, the all-weather work and so on. But the stability of 
leveling points and the density of network settings restrict this 
method. Beside, it can only extract the value of surface 
subsidence through data interpolation, the approximate 
subsidence area must be estimated before surveying. 
InSAR technique is a new method used for monitoring the 
surface deformation of mining area and gets gradually 
development. In this technique, the three dimensional informa 
tion of the surface can be extracted by using the phase 
information of radar echo signals. The precision of the earth 
crust vertical deformation measurements can be increased to 
millimeter level through differential InSAR (D-InSAR) 
technology. However, in many cases the problem of temporal 
decorrelation hampers measurements over longer time intervals 
1.3 GPS/InSAR fusion technique 
By comparison, InSAR and GPS technology are very strong 
complementary (Chen, J., 2004). Firstly, GPS belongs to point 
positioning, and the length of base line is usually tens to 
hundreds of kilometres. Such lower point density cannot meet 
the demand for high spatial resolution monitoring of the surface 
deformation. InSAR data can apply continuous information of 
the entire region surface. The spatial resolution can reach to 20 
meters. Secondly, InSAR (spatially differential InSAR) is 
sensitive to elevation information of the earth surface owing to 
the radar incidence angle effect (Xu, C., 2003), while GPS is 
unsubstantial in elevation precision. Thirdly, GPS has high 
temporal resolution (highest can be up to 1 Hz), while InSAR 
data has a lower temporal resolution (more than 20days 
generally, highest only can be 1 day) because of the longer 
revisiting period. Fourthly, C & Continuous GPS networks 
(CGPS) can provide aerosphere delay effect and satellite orbit 
* Corresponding author. ZHANG Ji-chao (1975-), male, lecturer, Ph.D student of Liaoning Technical University, research direction: 
3S technology theory and its application. Tel: +86-418-3352501; Fax: +86-418-3351790.

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