INTRODUCTION 
The seasonal variation of the snow 
accumulation and melting process in its 
regional or global context has its tremendeous 
economical and ecological impacts. It not only 
affects the run-off pattern and the water balance 
but as well changes the albedo, which again 
feedbacks on the radiation budget of the earth 
and ultimately on the climate. Hence, the 
significance of the snowcover and its changes 
are manifold. 
Adequate remote sensing methods have been 
developed to carefully assess and monitor the 
spatial dynamics of the snowcover from TM, 
SPOT and NOAA data (KELLER, 1987; 
S0GAARD, 1983; ITTEN, 1980). Likewise 
their applications for operational purposes, in 
particular of run-off forecasting for hydroelec 
trical power production (BAUMGARTNER, 
1987; SEIDEL et al., 1989; 0STREM, 1974; 
RAMAMOORTHI, 1983) have been demon 
strated repeatedly. An overview is given by 
HAEFNER (1989). 
Whilst these extended applications are well 
established, detailed studies of particular 
processes and of local features are needed 
today, which ask for its own proper methodo- 
logy. 
Of specific interest are the conditions of the 
snowcover on the surface of glaciers in 
mountainous regions. Here the accumulation 
and melting pattern of the snow strongly 
influences the energy and mass balance of the 
glaciers and consequently its run-off regime. 
Alterations of the weather conditions have a 
direct impact on this process. Or in reverse, by 
monitoring the melting process it becomes 
possible to deduce changes of weather, and in 
the long run of the climate. So far very limited 
attention has been given to these phenomena. 
Some preliminary methodological studies have 
been carried out (LAAGER, 1987; HALL et 
al., 1987; DELLA VENTURA et al., 1987; 
HAEFNER & LAAGER, 1988; MNICH, 
1989). But no practical applications or 
longterm surveying projects resulted from 
these activities. 
Nevertheless ongoing international programs 
such as Global Change (RASOOL & OJIMA, 
1989), World Glacier Monitoring Service 
(MÜLLER, 1988) or World Climate Research 
Programme should consider and include these 
aspects and make use of the monitoring 
capabilities of the various earth observation 
satellite systems. 
Quite a many boundaries and/or ice zones, as 
well as deduced indices have to be taken into 
consideration when dealing withglaciers. We 
refer to PATERSON (1981) for the glaciolo- 
gical aspects and terminology. Only a 
thourough understanding of these various 
types of boundaries, zones and parameters 
allows to appropriately employ remote sensing 
technologies. 
The most important boundary is the 
equilibrium line, which separates the accumula 
tion from the ablation zone. It is the objective 
of our research activities to develop an 
adequate method based on high-resolution 
satellite data for an accurate determination of 
the position of the equilibrium line altitude 
(ELA), and to establish a longterm project to 
monitor its changes on various glaciers of the 
Swiss Alps. 
The assessment of the ELA is a prerequisite to 
determine the accumulation area ratio (AAR), a 
most important index to give evidence on the 
mass balance situation of the glacier and 
consequently on climatic changes. In addition a 
continuous parametrization of the total surface 
of the glacier is needed for the determination of 
the AAR. 
A definition of the most important glaciological 
terms is given in Tab. 1. The various methods 
to derive the necessary parameters from remote 
sensing data are discussed in the chapter on the 
methodology. The corresponding results from 
case studies are presented in the following