(Track: 268, Frame: 783). Two different approaches were 
applied to construct the differential interferogram: three-pass 
method using 3 SAR images for ERS data and two-pass method 
using two ASAR images plus an external DEM for Envisat 
data. 
Figure 1 The TM image of Tangshan test site 
Mission 
Orbit 
Date 
Perp. 
baseline/m 
Temporal 
Baseline/d 
ERSI 
32728 
19971018 
-303 
-1 
ERS2 
13055 
19971019 
0 
0 
ERS2 
16061 
19980517 
413 
211 
Table 1 ERS 1/2 
SLC SAR data of frame 
2799 
Mission 
Orbit 
Date 
Perp. 
baseline/m 
Temporal 
Baseline/d 
Envisat 
9841 
20040117 
130 
-241 
Envisat 
13348 
20040918 
0 
0 
Table2 Envisat SLC ASAR data of frame 783 
4. PROCESSING SOFTWARE AND 
INTERPRETATION OF INSAR RESULTS WITH THE 
AID OF GIS 
After reviewing the available software for InSAR processing it 
was decided that DORIS InSAR Processor developed by the 
Delft Institute for Earth-Oriented Space Research (DEOS), 
DORIS is free software (for non-commercial scientific purpose) 
that runs on UNIX/Linux platforms. [Kampes, B., 1999].It can 
generate interferometric products and end-products from Single 
Look Complex radar data provided by ESA. Scenes generated 
by ERSI, ERS2 and Envisat satellites can be processed. 
Interferogram unwrapping was performed using the SNAPHU 
software developed by Curtis W. Chen [Curtis W. Chen ,2002] 
and integrated as module with DORIS. 
4.1 ERS1/2 
The topo-pair of ERS SLC satellite radar images from 18/19 
October 1997 with a base of 303 m were used to generate the 
reference interferogram that includes topographical effects only. 
It is assumed that it has not included any effects of 
deformations as the underground mining had just started. The 
coherence map is presented in figure 2. 
Figure 2 Coherence map over the study region 
The 211 day repeat interferogram was generated using the 
defo-pair from 19-October-1997 and 17-May-1998; this 
interferogram contains both the topography and surface 
motions. And then the topographic phases of the topo-pair are 
subtracted from the defo-pair. 
The differential InSAR results were exported to and 
post-processed in the GIS. The mine subsidence regions can 
now be seen clearly and the color coding indicates the 
magnitude of subsidence, as shown in Figure 3. A further 
advantage of using the GIS is that ground deformation can be 
analyzed and visualized in various ways. For example, profiles 
can be generated along any lines across the subsidence area, as 
shown in Figure 4.