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| Titel |
Operational use of airborne laserscanning for glacier monitoring in Switzerland |
| VerfasserIn |
Philip Claudio Joerg, Felix Morsdorf, Michael Zemp |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032165
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| Zusammenfassung |
| Glacier mass balance is widely accepted as a key parameter in hydrological and climate
change research. Traditionally, the mass balance of a glacier is measured in-situ, at an annual
or seasonal basis, using ablation stakes and snow pits and compared with decadal volume
changes derived from photogrammetric analysis of aerial photographs. A major drawback in
glacier photogrammetry is the lack of contrast in shady and snow covered (accumulation)
areas. Since the 1990s, pilot studies have repeatedly shown that laserscanning has the
potential to overcome these problems and can provide accurate elevation changes at an even
higher spatial resolution.
In this study, we show the operational use of airborne laserscanning for the
calibration of the glaciological mass balance measurements at Findelgletscher in
the Valaisan Alps, Switzerland. So far, two flight campaigns were carried out in
June/October 2005 and in October 2009. The area of interest covers 27 km2 with a
mean point density of more than two laser echoes per square meter. Besides the
geometrical data, the Optech ALTM 3100 laserscanning system provides as well
intensity data with 12bit resolution for every return. Using terrestrial survey data of
roof tops, the positional and vertical accuracy of the corrected point cloud was
estimated to be better than 50 cm and 15 cm, respectively. The point cloud was
subsequently converted into a gridded digital surface model with one meter spatial
resolution.
Preliminary results show that between 2005 and 2009 the ice thickness reduced over the
entire Findelgletscher. In the region of the glacier tongue maximum thickness losses of 25 m
to 30 m occurred. On average, the glacier, having an area of about 14 km2, lost 3.4 m of ice.
Assuming a density of 900 kg m-3, this results in a mean annual mass balance of -0.8 m a-1
and indicates that the corresponding in-situ measurement might have a systematic positive
bias.
Next steps in the project are detailed analyses of the uncertainties of both the volume
changes as estimated by remote sensing and the in-situ mass balances. Furthermore, we aim
at using calibrated laser intensity values for estimating the spectral albedo distribution on
the glacier. A next flight campaign is planned for spring 2010 and shall provide
high-resolution information on the spatial distribution of the winter accumulation. |
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