ınternational Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
snow-frec ground and the probability of a pixel coinciding with 
HK% snow-covered ground increased with altitude. There was 
no snow on coniferous tree branches while larchs (Larix 
deviduas) were without their needle-type leaves, But some 
Show was observed to occur on the land below the tree cover. 
About one-quarter of Lake Alleghe, towards the down stream 
side, was covered by a thin laver of melting ice. 
4. TERRITORIAL IMAGE SYNTHESIS SYSTEM 
The elevation, slope and aspect are the most obvious 
components of the landscape. In high mountain areas the snow 
distribution is not homogeneous owing to rapid variation of 
these parameters. In addition. the ruggedness of the terrain 
complicates interpretation of the satellite scene (Seidel et al 
1983). The registration of remote sensing data on the digital 
elevation. model enables correction for varving illumination 
angle and shadowing effect (Haefner. 1980; Dozier. 1984). 
Digital terrain data for the region has been produced by 
digitizing the contour lines for every 200 mewters and. for 
some specific areas, for every 10m from 1:50000 scale of the 
Istituto Geogratico Militared Italia (GMI) using a graphic 
tablet and AUTOCAD software. The resulting vector data were 
manually edited to remove noise introduced in the digitization 
Digital elevation. models have been generated from 
the vector contours using locally developed software known as 
l'erritorial Image Synthesis System (TISS) (Figure 4). 
process. 
  
Figure 4 Black and White representation of false colour 
composite registered and superimposed over DEM using TISS 
1223 
In addition. the slope, aspect and shaded relief maps were also 
developed. The integration of digital satellite data with the 
DEM has been carried out and three dimensional perspective 
views for different illumination angles have been generated to 
study the snow cover distribution in the catchment (Figure 5). 
5. SATELLITE DATA 
The nature of the snow cover must be characterized adequately 
if distributed models are to improve hvdrological modeling 
through improved representation of the sale variables (Beven, 
1989). Knowledge of the areal distribution of the snow cos er 
within and between land limits is required in order to make 
reasonable estimates of the total water available in the snow 
cover of a watershed (Goodison et al 1987) 
Altogether nine sets of digital Landsat Multispectral Scanner 
System (MSS) and Thematic Mapper (IM) Computer 
Compatible Tapes belongs to one hydrological vear have been 
analyzed using digital image processing techniques ( Table 1). 
lable 1 Satellite scenes processed 
The sub-scenes of 350 x 512 pixels (MSS) and 800 x 1024 
pixels (TM) containing the area of investigation haven been 
extracted from the full scenes of cach image (Figure 6). All the 
sub-scenes were geometrically corrected by geo-coding on 10 
the coordinate system of the topographic maps, 
  
Figure 6 Black and while representation of Landsat-MSS 
subscene standard false colour composite on 21 April 1984, 
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