H - À tan 0 -cos € 12
gi f : ! (12)
2B,:cos 0 -cos(0 — €)
By removing the intrferometric phase, which results from SAR
imaging geometry and is called “flat terrain phase”, the glacier
slope € can be determined by the next equation
l ; 2HA ;
€, , = arctan| — — coto t [cot^ 0 + -——— zz lL] (13)
2 BW, cos 0
where JV z W.sing and W is the width of interferometric
fringe directly measured in the interferogram. Positive or
negative values of & imply the direction of slope toward or away
from the sensor, respectively.
The practical application of this algorithm allowed the elevations
of several largest ice caps in FJL to be defined and compared. In
order to diminish the influence of the Earth's curvature and to
reduce the computing times, only small image fragments,
corresponding to separate islands of the FJL archipelago, were
processed. The areas of glacial surface subjected to layover
distortion and affected by shadows were excluded from the
analysis. Several vertical control points taken from available
maps and verified in the field by spirit levelling were used for
the georeferencing of interferograms and radiometric profiles.
[mage processing was carried out using RSG 2.52 and ENVI 2.7
software packages. Figure 9 represents some results of
interferometric processing of complex SAR images obtained in
October 1995 with time interval of 24 hours from ERS-1 and
ERS-2 satellites, which operate in tandem mode.
250 00 —4
| Shore
| line IN
200 00 — 4 |
iv Lal
| |
| Glacier
5000 —4 top
1 %=627 €
9.88 7 T T T T l
0 00 100 00 200 00 300 00
Fig. 9. Results of SAR interferometric data processing:
fragment of amplitude image for Hall Island (a); coherency
image (b); interferogram of Moscow Ice Cap at Hall Island (c);
high-pass filtering of the interferogram (d); radiometric profile
taken across the interferogram (e).
Scrupulous analysis of radioometric profiles in the interferogram
generated from SAR-data of 3-4. September‘ 95 has clearly
shown that Peak Parnas on Wiener Neustadt Island is, at least, 15
m higher than the highest top of the Wullerstorf Mountains on
Wilczek Land. Absolute values of their elevations and main
interferometric parameters determined for the average value of
slope € & 5? are specified in Table 6. Very similar elevation
values were also obtained from the analysis of the interferogram
generated from SAR images taken in October. Slight differences
208 International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
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