Taking the delineated equilibrium line into 
account also well, the accumulation area can be 
assessed, too. 
DELLA VENTURA et al. (1988, p f 203) 
"identify glacier surfaces by evaluating the 
intensity values of visible images combined 
with clearness conditions related to exposure, 
slope and the surface homogeneity of the 
^glacier. Conditions of clarity, in the absence of 
a digital terrain model, are estimated from the 
number of saturated pixels in the visible bands. 
At a higher level, the near-infrared data is used 
to identify snow and ice surfaces inside the 
glacier boundaries." In a first step the total 
glaciated area is classified, which then is 
subdivided into individual glaciers by 
superimposing a lineary fixed structure mask 
(such as the watershed line). In the final step 
the areal extent of the accumulation areas are 
computed. 
It must be stated that using MSS data, and not 
applying extended geometric corrections nor 
including a DTM, the achievable accuracy for 
the monitoring of the AAR will not be 
sufficient. In addition the exact delineation of 
the actual surface of the glacier and the 
separation of its accumulation area from the 
adjacent snowcover causes servere problems. 
MNICH (1989) in her study on the Aletsch 
Glacier first delineates the surface of the glacier 
by creating a digital mask. Small mountains 
and rocks within the accumulation area were 
not excluded but separated during the 
classification procedure. The results could be 
compared with a ground survey from the same 
year and showed a difference of 0.2 sqkm, 
using geometrically corrected TM data. But 
again the masking of the surface of the glacier 
asks for an experienced interpreter with good 
local knowledge. 
In conclusion the measurement and monitoring 
of the areal extent of the surface of a glacier 
needs a careful geometric correction of the 
satellite data and a precise (digital) masking of 
the boundary of the glacier. The inclusion of a 
DTM is mandatory for this task. Combining 
the procedure with the delineation of the 
equilibrium line the calculation and monitoring 
of the AAR then can be carried out with great 
accuracy. 
But it has to be underlined again that images 
only from the latest state of the melting season 
(October in the Alps) may be used (which e.g. 
has not been oberserved in the work of DELLA 
VENTURA et al., 1987) to achieve exact and 
comparable information. 
CONCEPT OF PROJECT AND FIRST 
RESULTS 
Based on these methodological considerations 
and studies a longterm project has been 
established by the Remote Sensing 
Laboratories, Department of Geography, 
University of Zurich, for the surveying and 
monitoring of the various glaciological 
parameters, in particular the ELA, as indicators 
to climatological variations in the Swiss Alps. 
The project includes the following steps: 
- Monitoring of the highest transient 
snowline and of the firnline on 
different types of glaciers in various 
climatic regions of the Swiss Alps for 
a longer time sequence, and comparative 
studies of the variations 
- Estimation of the exact altitudinal position 
of these boundaries by transference onto 
topographic maps, and assessment of the 
mean altitude 
- Establishment of a relationship between 
these detectable boundaries and the ELA 
- Deduction of the relationship between the 
shift of the ELA and the weather records 
(in particular the temperature) of the nearest 
measuring stations