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Title
Mapping without the sun
Author
Zhang, Jixian

(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.