Perski, Zbigniew 
  
  
  
T. ERS SAR COVERAGE 
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AZ Coei mins 
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4 
4. 
Geological extent 
of the Upper Silesian 
Coal Basin 
  
  
  
Figure 1. Location map of the study area with ERS SAR coverage 
In the AO-3 127 project the couples of ERS SAR data acquired from very close orbits, with perpendicular baselines not 
exceeding 100 m have been selected (Perski 1998, Perski, Jura 1999). Such selection practically eliminates the effects 
of the topographic influence, since the height resolution becomes very coarse. These carefully selected pairs have been 
further selected according to weather and season condition on the day of acquisition (Perski 1999). In the second phase 
of this project the selection of SAR images for InSAR processing have been carried out according to larger baselines 
and longer time-bases despite different seasons and variable weather. The different criteria of selection have been 
applied to establish the real extents of capability of InSAR method. 
In the presented work, the methods of two-pass interferometry (Pratti et al. 1996) and four-pass interferometry (Atlantis 
1997) have been applied for generation of interferograms. The topographic phase removal have been carried out using 
the interferometricaly processed DEM from ERS tandem data. The final DEM was obtained based on two InSAR 
DEM s processed from ascending and descending tandem ERS SAR data. The correction of coordinates and height 
values of DEM have been performed based on GCP points digitized from topographic map scale 1:10 000. In the 
future, the correction will be done also based on GPS measurements. The resulted intereferograms have then been 
analyzed together with digital maps of mining activity and geological maps, and with the database of geodetic and 
GPS measurements. For integration and analysis of different data the GIS system ILWIS 2.2 have been used. 
3 THE INTERPRETATION OF INTERFEROGRAMS 
The interpretation of interferometric data shows that the pattern of the interferometric fringes represents the increment 
of subsidence within a period between two data acquisitions - in practice 35 and 70 days. The centre of the fringe - an 
area of maximum surface downwarp - is located exactly in the middle of the active (advancing) slope of the extending 
subsidence trough and thus indicates the zone ofthe highest rate of surface changes (Jura, Perski1999). The comparison 
between the location of the fringe and the position of underground exploitation front allows us to evaluate the rate 
of retardation in subsidence phenomena and its dependence on the mining technology. The results of accurate 
measurements of the rate of subsidence and the location of the fringes performed on interferograms allow calculating 
the increment of inclination and the velocity of subsidence. On the basis of the geological interpretation of ERS SAR 
interferograms, in conjunction with the mining and geological maps, the dependence of the velocity of subsidence 
on the structure of the cap rock and dip of the strata can also be determined. 
  
1138 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 
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