Suretta Sud Glacier - Servizio Glaciologico Lombardo

Suretta Sud Glacier (Spluga-Lei Sector) 1
Mass balance evaluation by geodetic method
Since 2002, the net mass balance of the Suretta
Sud Glacier is calculated by comparing the
surface DEMs (Digital Elevation Models) acquired
by direct field surveys using the differential
GPS technique (Tamburini et al., 2003).
1 For the methodology see www.sgl.cluster.it
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The initial reading was taken in September,
2001; the successive measurements were
repeated at the end of each ablation season.
Figs. 1 e 2: The Suretta Sud Glacier, 2 photos taken respectively on September 5, 2004 and on August
28, 2001. The effect of the torrid 2002 and 2003 summers on the glacial mass is clearly visible.
Survey equipment and methodology
The surveys of the glacier have been conducted
by using 2 GPS receivers operating in
a differential mode; the first one (rover) is carried
on the operator’s shoulders, the second
one (reference), is installed on the reference
point established during the 1st measurement,
in order to have the possibility to overlap
the surveys executed in different years,
hence, making possible a direct comparison.
2 GPS TRIMBLE 4000SSE receivers with
a geodetic antenna and dual frequency (or
equivalents) were used for the purpose; these
tools are able to record the phase on which the
GPS signal is modulated, allowing the determination
of the coordinates of the route covered
with centimetric accuracy (typically + 1 cm hor-
izontally and + 2 cm vertically). With this equipment
it is possible to operate in RTK (real time
kinematic) mode whenever there is a direct
radio or GSM link between the two stations,
or else, if a continuous link between the stations
is not possible, in post processing mode.
Considering the characteristics of the area and
the logistic conditions, the latter method was
selected. The need to move along paths able to
produce a detailed model of the surface while,
at the same time, retracing the tracks of the previous
surveys, have prompted the operators to
visualize their movements over the glacial surface
with a Mobile GIS Station constituted by:
• Handheld Compaq PC,
equipped with a Bluetooth door;
mass balance