Secondly, use high time/frequency GPS data to interpolate the 
original results mentioned above. Then the quasi-GPS time 
series data can be obtained with time domain interpolation. 
Finally, Kalman filtering can be used to estimate and predict the 
quasi-GPS data with both spatial and time domain interpolation 
to get full surface subsidence deformation value of mining area 
with high precision. 
3. MAIN PROBLEMS OF GPS/INSAR DATA FUSION 
The researches of InSAR/GPS data fusion fields already 
acquired important progress, while this technique also needs to 
be improved because of its problems. The main problems are as 
follows: 
1) At present, there isn’t a set of complete InSAR/GPS data 
fusion theory and method. The GPS data correction researches 
focused on a certain InSAR error. 
2) The phase unwrapping algorithm takes great effect on InSAR 
products precision, however, up to now no practical 
unwrapping algorithm was applied. 
3) Only GPS data was used to establish the model of 
atmospheric delay error, whereas the InSAR data itself is 
ignored. Theoretically, GPS data could create high precision 
atmospheric delay model, but it can only apply single point 
information and must use spatial interpolation to realize 
modeling, this will cause the decrease of data precision 
undoubtedly. 
4. CONCLUSIONS 
InSAR/GPS data fusion technique plays an important role in 
monitoring the surface subsidence in mining area. GPS 
technique can take its advantages on InSAR data, such as the 
modeling of atmospheric delay error; the establishment of 
InSAR satellite orbital parameters, the geometric correction of 
InSAR data, and so on. While InSAR data could apply 
furthermore detailed spatial information of the mining area 
surface. 
In monitoring the surface subsidence of mining area, the 
following countermeasures are given as references to improve 
the monitoring precision, the spatial and time resolution, and 
the result reliabilities. Which may provide technical support for 
realizing real-time dynamic monitoring of coal mining-induced 
subsidence. 
1) PS-InSAR technique should be used in InSAR/GPS data 
fusion field widely. This could reduce the impact of spatial and 
time resolution limitation of traditional InSAR greatly, and 
improve the monitoring precision even to sub-centimetre. 
2) Making associated use of permanent scatterer points, grade 
levelling root control points and GPS levelling points 
measurements, and adopting suitable data processing algorithm 
(spatially the phase unwrapping algorithm) could improve the 
calculation precision and reliability. 
With the implement of the world’s GPS network engineering 
and the improving of SAR resolution (including the 
improvement of SAR satellites orbital parameter precision), 
The integration of InSAR and GPS data’s application in 
mining-induced subsidence monitoring will be more extensive. 
InSAR/GPS data fusion technology may become one of the 
most powerful means in monitoring the surface subsidence of 
mining area hopefully. 
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ACKNOWLEDGEMENTS 
This work is supported by the National Natural Science 
Foundation (No.40571104) and the Excellent Youth Research