012 
lated 
lic phase 
  
glacier 
\R images 
97, and 2 
nd July 29 
| pair. with 
62 meters. 
pair with 
ows their 
tion about 
ioving the 
coding the 
amplitude 
s acquired 
esult from 
  
;endicular 
seline /m 
  
62 
——M 
   
  
59 
ages used 
  
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
80°D0'E 90 Q0"E 
    
100700'E 
  
40700"N 
À 
  
30°00"N 
i 
  
  
  
     
   
——] 
Qinghai 
T 
30*0'0"N 
  
  
  
Figure 2. 
0 200 400 800 
GC 3 Km 
T 4 T T 
80‘00"E s0"0'0"E 10070'07E 
Location of the study area. The gray block in the middle of the figure was imaged by ERS SAR and ENVISAT ASAR. 
SAR image of this area is shown in Figure 3(a). 
Height /m 
6522 
4958 
(a) (b) 
Figure 3. SAR amplitude image (199708 10) (a) and SRTM 
DEM (b) in Geladandong region 
4. RESULTS 
At first, 2 ERS SAR images acquired in 1997 are used to 
generate interferogram. Figure 4 shows the difference of 
coherence and phase between glacial area (A) and non-glacial 
area (B), from which we can see that in the coherence map 
(Figure 4a), A and B are very similar with low coherence. But 
in the phase map (Figure 4b), the difference between A and B is 
visible, where A is noisy with no phase information while B has 
clear interferometric phase. 
This figure demonstrates that the phase texture in glacial and 
non-glacial area is quite different. Thus it is possible to 
distinguish them using phase texture information. Based on 
GLCM, texture features of interferometric phase are generated, 
including mean, variance, homogeneity, contrast, dissimilarity, 
entropy, second moment, and correlation. Among them, 
variance, contrast and dissimilarity are selected as RGB pseudo- 
colour combination. Finally, maximum likelihood classification 
(MLC) is performed to the pseudo-colour image to extract 
glacier. By post-classification process and geo-coding, glacial 
area is obtained (Figure 5). The GIS statistics shows that glacial 
area of Geladandong in 1997 is 862.32 km”. 
As for the interferometric pair 20070624 ~ 20070729, the same 
strategy as ERS SAR image was applied to extract the glacial 
area of Geladandong in 2007. Figure 6(a) is the interferometric 
phase generated by ENVISAT ASAR images. Figure 6(b) 
shows the glacier extracted from phase, with an area of 839.35 
km’. By comparing the glacial area between 1997 and 2007, we 
can find that severe glacier retreat has taken place during the 10 
years, with a loss of 22.97 km”. 
    
"i cca 
(a) Interferometric coherence — (b) Interferometric phase 
Figure 4. Interferogram generated by ERS SAR images 
(master: 19970810, slave: 19970914)