The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part BI. Beijing 2008 
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Figure 5 Subsidence 1998.5-2000.5. ETM (1999, band: 321) 
image is shown in the background, and overlapped with the 
mine area map. The largest displacement is 8cm in Tangshan 
mine area, in Gangyao mine and Majiagou mine, it has 
averagely 1 cm displacement, and in west of Tangshan mine 
area, and it has averagely 3 cm displacement due to the Kast 
collapse. 
Figure 6 Subsidence 17 Jan-18 Sep 2004. Tangshan is stable 
except in Tangshan Mine, It forbidden to excavating in cantonal 
Tangshan, and the South-lake Park was built in the south. 
5. ERROR ANALYSE 
4 n B L 
<jA(p = £7 h ,for ERS, A is 5.66cm,R is 850km, 
/1 /?sin/ 
Yis23° , if B ± is 100m, the error of phase due to error of 
height can reach to 3.8° ,that means 0.3mm displacement in 
line of sight. According to the formula, the sensitivity of 
difference of phase to error of height is proportionate increase 
to baseline, which means small baseline is good for eliminating 
topography. For our study, the longest perpendicular baseline is 
413m that means 2.4cm displacement in line of sight, the 
shortest perpendicular baseline is 8m that means 0.48mm 
displacement in line of sight, So, error due to DEM is small 
when perpendicular baseline is small, it is why this research 
can gain good result. noise is difficult to quantize the error for 
interferograms, in general, it is considered not important and 
ignored it. 
rKKffl 
Valueva* 
Figure 7 Subsidence 18 Sep 2004-25 Feb 2006. The largest 
displacement is 8cm in north of Tangshan, which due to 
construction of Tangshan. In Tangshan Mine, it has averagely 
3cm displacement. 
6. CONCLUSION 
In city zone, even have 2 years spanned, it still has good 
coherence because of the low vegetation cover of the ground 
surface. With the aid of GIS tools, mine subsidence regions and 
the magnitude of subsidence has been extracted. 
SAR interferometry plays very important role as the 
independent tool which allows effectively mapping the recent 
subsidence and studying its dynamics, and the presented results 
confirm the applicability of the subsidence monitoring method 
based on time serials of interferograms. 
As showed in formula(l),the phase is composed of these parts 
after unwrapping: 4> disp , <i> topo , 4> delay , 4> noise . 
$ disp is what we want to gain, the others are errors. de iay is 
difficult to gain without the surface subsidence, in our study 
area, atmospheric influence is not obvious, because the change 
trend of interferograms are not abnormity. According to 
From the results, we know that Tangshan suffers serious 
subsidence in 1990’s, especially in 1997.10-1998.5, the largest 
displacement in Tangshan reaches to 18cm.Since 
1998,Tangshan has been in the list of state’s test sites of repair 
subsidence due to mine excavate, the subsidence has been 
controlled.