355
Hotos
upare
with
ely
struc-
aterial
the
aiform
high
npor-
tographs
fast and
ase.
moun-
íistru-
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Drtho-
observation and the precision required. Since the official Swiss data-bank
is based on a square grid of 100 x 100 m, the use of the same size or an
easy divisible fraction of it is advisable (50/25 m). For Grevasalvas a
square grid of 50 x 50 m was selected.
3. RESULTS
So far the inventory and mapping procedure for both test areas could be
carried out for the most important surface features (snow, vegetation, land-
use, phenology etc.). But additional data-sets in particular of the seasonal
and yearly changes as well as ground measurements (climatic elements) are
still needed. The information system for the Grevasalvas test site is estab
lished and fully operational. The necessary software for the data output in
form of computer maps is available. Consequently all necessary preparations
and the basic data-sets for successful ecological studies are completed and
the remote sensing methods for an easy additional data input are tested.
Only very selected examples of this inventory phase may be presented
here, dealing primarily with the interpretation of fast changing surface
features. Since the methodological approach is rather different for the two
test sites, the results will be presented separately.
d ma
is
bion
is
n cor-
a
etc.).
Ltative
rical
. The
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photo
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ting
1er
3.1. Dischma Valley
Fig. 3 shows a generalized map of the snowmelting process in its dyna
mics for a "normal" year (i960), e.g. an year of average snowfall and of no
substantial late snowstorms in spring. The interpretation was carried out on
b&w photographs of an average scale of 1 : 60'000 and the boundaries were
transferred onto a map 1 : 10*000. The snowcover is classified into seven
different categories (100-99» 98-38, 87-63» 62-38, 37-13» 12-2 and 1-0 J />
snowcovered land).
The situation as described was mapped for three different dates.(14.5.60,
31.5.60 and 22.6.60) during the most important melting period. Fig. 3 inclu
des only the boundaries between snowcovered and snowfree areas (87 ^ and more
snowfree area) for the three dates and consequently the zones which got snow-
free in between two dates, providing an excellent picture of the dynamics in
volved.
The combination of the three maps 1 : 10'000 showing the distribution
of the snowcover in great detail allows an extensive further qualitative and
quantitative evaluation of the changes in the snowcover and its correlation
with the relief, exposure and especially the vegetation and phenology (Lit.
10). In addition the comparison of different specific locations (e.g. an
altitudinal belt, slopes of the same gradient and the same exposure etc.)
regarding its relation to snowmelt may be easily evaluated.
For a further study of the correlation between snowcover and plant com
munities the melting process for two extreme winters (one with a minimal