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Figure 1. Geologic map (Capponi et al. 1999) of the study area
Prince Albert Mountain, around the Larsen Glacier (the digital
map has been rectified in the Polar Stereographic coordinate
system WGS 84 spheroid).
We imported the 1/11/2000 ASTER sensor scene in the Erdas
Imagine format and we rectified it in the Stereo Polar coordinate
system. We isolated the study area with another subset
procedure. Fig. 2 shows the ASTER scene in false colour
composition (red channel: near infrared; green channel: red:
blue channel: green).
Figure 2. The ASTER scene (1/11/2000 ASTER sensor) in false
colour composition (red channel: near infrared; green channel:
red; blue channel: green); this subset of the study zone has been
rectified in the Stereo Polar coordinate system.
Observing fig. 2 you can see clearly the wide icy cover on the
land: the isolated rock outcrops are in fact concentrated in the
Mount Crummer area (North of the Larsen Glacier). You can
123
sce other rock outcrops in the Stierer and Bellinghansen
Mountains area, at the East of Philippi Cape. Other rock
outcrops are visible on the South part of the image, near Urville
Wall.
Observing again the fig. 1, you can see that in the study there
are two principal kinds of composite rocks. These are: Granite
Harbour Granodiorite and Granite (GHgr); Granite Harbour
Gabbro and Ultramafite (Ghga). GHGr rocks are painted in pink
while GHGa in violet. GHGr areas are very diffuse on the land,
GHGa areas are instaed concentrated in a small area, close to
the North side of Philippi Cape. The two rocks are characterized
by the presence of several particular minerals, we choose among
them the Biotite and the Serpentinite in order to recognize the
type of rock on the basis of the presence of the mineral in it.
The rock outcrops with high biotite concentration (and low
Serpentinite) belong to the granite GHGr complex, while rock
outcrops with high serpentinite concentrations (and low Biotite)
belong to the granite GHGa complex.
In order to discriminate the two granite complexes, we used the
Jet Propulsion Laboratory (JPL) spectral libraries (2). In fig. 3
are drawn the spectral responses of the Serpentinite (light blue)
and the Biotite (yellow) in the different wavelengths recorded
by the ASTER sensor bands. The grain particulate is the bigger
one (125-500 um). We choose this grain size because it is the
one that gave the best results in our analysis.
Figure 3. Spectral responses of the Serpentinite (light blue) and
the Biotite (yellow). It is used the Jet Propulsion Laboratory
(JPL) spectral libraries.
On the horizontal axis is measured the wavelength (um). On the
vertical axis is measured the relative reflectance normalized to
one. If we check table 1, which has some ASTER sensor
information (spectral, spatial, radiometric resolution of each
band in the sensor subsystem: visible — VNIR, middle infrared —
SWIR, termal infrared — TIR), we can realize that the laboratory
measurements are fit in the sensor features.
System | Band Spectral Spatial Radiometric |
Range Resolution | Resolution |
VNIR ] 0.52-0.60 15m 8 bit
2 0.63-0.69
3 0.78-0.86 —
SWIR |4 1.60-1.70 30m 8 bit
5 2.145-2.185
6 2.185-2.225
7 2.235-2.285 |
8 2.295-2.365 |
9 2.360-2.430 |
TIR 10 8.125-8.475 90 m 12 bit
11 8.475-8.825
12 8.925-9.275
13 10.25-10.95
14 10.95-11.65 =
Table 1. Aster main characters. Modified by: “Aster User
Handbook, vers. 2" (Abrams and others, 2003).
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