| Calculation on glacier volume variations are still greatly limited by the vertical
accurate of various data sources till now (Stevens et al., 2004). Therefore, one of
the major methodological gaps in the observation of glaciers from space is the
measurement of glacier volume changes (Kääb, 2008). Glacier volume changes
needs an integrated study and correction on generated DEMs from multi-sources
remote sensing data and evaluation of the vertical errors and accuracy. Here, we
produced DEMs over mountain glaciers from ASTER and ALOS/PRISM on the
northern slope of Mt. Qomolangma (hereafter called the Mt. Qomolangma region),
also known as the Mt. Everest, located in the middle Himalayan Mountains, 27Ë
59-28Ë 11´N and 86Ë 44´- 86Ë 59´E. A series of digital images, include Aster
images on 23 Oct 2003, ALOS/AVNIR-2 on 19 Jan 2007, ALOS/AVNIR-2 on 24 Oct
2008, 3 scenes of ALOS/PRISM on 04 Dec 2006, 1:50,000 topographic maps with
contour interval of 20 m produced from aerial photographs acquired in 1974 and
the 1:50,000 DEM (cell size: 25 m) generated from the topographic maps were
used.
The DEM was generated based on the three scenes from ALOS/PRISM images and PCI
Orthoengine module. The process of DEM generation from ASTER images is very similar to
that of ALOS/PRISM. The difference is that: only two images ASTER from nadir and
backward views were used here.
Table 1 The differences between generated DEMs and the 1:50,000 topographic maps in
the non-glacierized area
dem5wdemasterprism12_50mprism13_50mprism14_25mprism15_100mSRTM DEMASTER_GDEM
Maximum 80.0 920.0 218.0 174.0 258.0 168.0 240.0 437.0
Minimum -123.0 -331.0 -297.0 -367.0 -459.0 -393.0 -315.0 -182.0
aveDEV 23.8 84.0 33.9 36.0 31.3 45.9 67.6 57.9
AVERAGE6.9 75.3 11.3 5.9 1.7 17.2 32.3 45.0
StDEV 30.5 128.0 55.7 59.4 60.6 64.4 85.8 77.2
RMSe 31.2 148.3 56.7 59.6 60.5 66.5 91.5 89.2
Compared various kinds of products of the generated DEMs in the non-glacierized area
with the 1:50,000 topographic maps using 215 random points, we found that the mean
difference of PRISM DEM to the topographic maps is 1.7 m. However, the mean difference
of ASTER GDEM (ASTER_GDEM) is 45m, which is released Version 1 of the Advanced
Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation
Model (GDEM) on 29 June, 2009. Our result shows that the quality of ALOS/PRISM DEM
is better than that of ASTER GDEM, and the calibrated ALOS/PRISM DEM based on the
relationship between aspect and DEM difference was more accurate than the original
generated one.
Fig.1 The generated ASTER DEM on 23 Oct 2003 Fig.2 the generated PRISM DEM on
04 Dec 2006 |