The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
70 
It is important to note that the fringes are very clear in the 
heavily vegetated area, and the phase can still be unwrapped 
correctly. A maximum subsidence of approximately 40cm has 
been measured at the Appin Mine site between the period 29 
Jun 2007-14 Aug 2007. It is observed that the phase 
discontinuities and decorrelation problems are much less in the 
case of the ALOS PALSAR interferograms compared to the 
ENVISAT ASAR interferograms, which is mainly due to the 
fact that ALOS PALSAR images have finer spatial resolution 
PALSAR has much higher successful rate for generating 
displacement maps, especially for pairs with difference of only 
1 repeat cycle. With this advantage, six successive subsidence 
maps were able to be generated with eight ALOS PALSAR 
images from both ascending and descending orbit acquisitions. 
The 6 DInSAR results generated from interferograms 2-7 
(Table 1) are post-processed and overlaid on the mine plan in 
Figure 6. The location has been confirmed by comparison with 
the actual mine schedule. 
Interferogram 
Pair 1 
Pair 2 
Oribit Heading 
Period 
(Days) 
Perpendicular 
Baseline (m) 
Date 
Mode 
Date 
Mode 
1 
27 Dec 2006 
FBS 
11 Feb 2007 
FBS 
Ascending 
46 
530 
2 
29 Jun 2007 
FBD 
14 Aug 2007 
FBD 
Ascending 
46 
45 
3 
14 Aug 2007 
FBD 
29 Sep 2007 
FBD 
Ascending 
46 
-501 
4 
29 Sep 2007 
FBD 
14 Nov 2007 
FBS 
Ascending 
46 
-110 
5 
14 Nov 2007 
FBS 
30 Dec 2007 
FBS 
Ascending 
46 
-735 
6 
30 Dec 2007 
FBS 
14 Feb 2008 
FBS 
Ascending 
46 
24 
7 
06 Feb 2008 
FBS 
23 Mar 2008 
FBS 
Descending 
46 
-127 
Table 1. ALOS PALSAR interferogram data used for this study. 
Figure 4. (Left) Mine plan overlaid with high resolution optical 
image. (Right) ENVISAT ASAR differential interferogram 
acquisition during 05 Jul 2007-09 Aug 2007 (35 days) with 
Bperp (perpendicular baseline) = 89.94m, ascending pass, IS1 
on (upper right) Westcliff Mine and (lower right) Appin Mine. 
Figure 5. (Left) Mine plan overlaid with high resolution optical 
image. (Right) ALOS PALSAR differential interferogram 
acquisition during 29 Jun 2007-14 Aug 2007 (46 days) with 
Bperp = 44.75m, ascending pass, on (upper right) Westcliff 
Mine and (lower right) Appin Mine. 
4.3 Validation 
Subsidence (cm) 
■i-M MM-» 
Figure 6. Colour-coded DInSAR-derived subsidence maps from 
ALOS PALSAR data pairs from (a) 29 Jun 2007-14 Aug 2007, 
(b) 14 Aug 2007-29 Sep 2007, (c) 29 Sep 2007-14 Nov 2007, 
(d) 14 Nov 2007-30 Dec 2007, (e) 30 Dec 2007-14 Feb 2008, 
(f) 06 Feb 2008-23 Mar 2008. Positive displacement indicates 
subsidence.