The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part Bl. Beijing 2008 
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amplitude dispersion index of the point targets in a time series 
of SAR images. Image coregistration was generated prior to 
identifying the PS candidate. Each pair of interferogram was 
processed with respect to the master image. Shuttle Radar 
Topography Mission (SRTM) Digital Elevation Model (DEM) 
which has three arc-second resolution was used to remove the 
topographic phase and generate the initial differential 
interferograms. Finally, displacement of PS candidate was 
estimated. It involved phase unwrapping as well as correction 
for linear deformation, DEM error, baseline error and 
atmospheric noise. The PSInSAR results were interpreted and 
compared to investigate with the effect of groundwater over 
extraction to urban deformation. The GIS software is used to 
interpret the PSInSAR result. The combined methods between 
PSInSAR and GIS allow an integration of information from 
various sources and hence improve the efficiency for 
interpreting the data. 
Figure 5. SAR image at test site 
To compare with DInSAR methods, which is normally used to 
ground subsidence monitoring, we were used CRC-DInSAR 
software. Theoretically, differential radar interferometry can 
survey deformation to high level (up to 1cm) of accuracy over 
large spatial extents with high spatial resolution. [Ge et al, 
2007]. However, source of DInSAR has limitation of temporal 
baseline and perpendicular baseline. In our research, test field is 
located in the city area and deformation of ground is small per 
year. So it is too difficult to detect the deformation in the city 
area. Figure 6 is the interferogram of test area using DInSAR. 
Figure 6. Interferogram of test site using DInSAR 
From the interferogram shown in figure 6, it is not able to 
obtain much useful information of land deformation around test 
region. For long term deformation monitoring, PSInSAR 
technique is more powerful, precise and fully operational tool 
than DInSAR method [Kampes 2006]. 
Photogrammetry used two pairs (10/1994, 10/2004) of aerial 
photography for investigation of small area deformations which 
are detected from PSInSAR results. Each projects of aerial 
photo are processed and detected using SOCETSET software. 
Ground Control Point (GCP) was achieved 10mm resolution 
from GPS surveying for external orientation. Building 
extraction of subsidence area was conducted by feature 
extraction method in SCETSET. The ArcGIS software was 
used to interpret the building deformation result. The aerial 
photo information and image are shown in table 2 and figure 7. 
DATE 
ID 
Frames 
Focal Length 
1994/10 
NSW 4224 
161 & 162 
152.76 
2004/10 
NSW 4877 
21&22 
152.76 
Table 2. Information of aerial photo 
Figure 7. Aerial photo of test site 
161 161 161 151 151 161 161 161 
151 161 161 151 151 161 161 151 
Figure 8. Deformation result using PSInSAR