International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
  
  
The graphs in fact begin from 0.52 pm value; three bars are also 
visible in correspondence of the first three ASTER bands 
(green, red and near infrared), which report the used channel in 
the false colour composition of fig. 2. We decided to stop the 
reflectance values at 3 um because after 2.4 pm the y value is 
constant in both cases (Biotite and Serpentinite). As you can see 
from the graphs, the minerals have two different laboratory 
behaviours. The Serpentinite has high reflectance values at low 
wavelengths. Then reflectance values begin to low after 1.6 um, 
they fall after 2.3 jum and then they remain constant from 2.4 
um. The Biotite instead has low reflectance values at low 
wavelengths, then it has a growing almost linear trend till 2.2 
pm, when it begins to register a constant reflectance value. 
On the basis of the laboratory spectral response behaviours, we 
tried to discriminate GHGr and GHGa rock complexes in the 
outcrops of the study arca. This discrimination has been realized 
on the basis of the presence/absence of the Biotite and the 
Serpentinite minerals. The Biotite presence may point out the 
GHGr rock composite presence in the study area while the 
Serpentinite presence may point out the GHGa rock composite. 
In order to classify the ASTER sensor we applied the 
Constrained Energy Minimization algorithm (CEM). CEM 
algorithm produces a thematic layer with pixel that can assume 
a value from 0 to 1. If the pixel value is close to 1, there is a 
close similarity between laboratory and land spectral response; 
if the pixel value is close to 0, the contrary. We applied CEM 
algorithm twice: one for the Biotite and one for the Serpentinite. 
Fig. 4 shows CEM estimated Biotite concentrations: white 
pixels have high values while dark pixels, low values. In fig. 4a 
you can see the absolute frequencies histogram of fig. 4. Fig. 5 
shows CEM estimated Serpentinite concentrations. Fig. 5a 
shows the absolute frequencies histogram of fig. 5. 
      
aedis 
Figure 4. CEM estimated Biotite concentrations: white pixels 
have high values while dark pixels, low values. 
histogram 
83964” e 
  
  
  
  
à A 
-0.300302 0.357879 
Figure 4a. The figure shows the absolute frequencies histogram 
of fig. 4. 
  
Figure 5. CEM estimated Serpentinite concentrations: white 
pixels have high values while dark pixels, low values. 
histogram 
76214” 2 | 
  
  
  
À A 
0.118323 0.10848 
Figure Sa. The figure shows the absolute frequencies histogram 
of fig. 5. 
We give also the following statistical information about the two 
CEM thematic layers: 
e  Biotite (fig. 4). Min value: -0.3; max. value: 40.357; 
mean: 0.005; st. dev.: 0.041. 
1236 
  
  
Intern 
Obser 
inforn