GLIMS definition issues

[Frank Rau]

Hello all,

I want to add a few comments to the ongoing discussion from our point of 
view, which is focussed on the Antarctic Peninsula. For us, ice shelves are 
important parts of the entire glaciological systems and, as such, they are 
among the most prominent glacial features of our study area. The 
spectacular disintegrations of the Antarctic Peninsula's ice shelves 
(Wordie, Larsen, etc.) since the early 1980ies have drawn public and 
scientific attention to them. They are consequently a major objective for 
glaciological and climatological research and especially for monitoring 
purposes it seems to essential that they are included in the GLIMS 
database. Furthermore, as remote sensing techniques offer the only 
possibility to monitor their spatial and temporal evolution on a regional 
scale, it would be a failure to exclude them. Therefore, I highly 
appreciate their integration and their treatment as unitary glaciers in the 
database as proposed by Jeff and Bruce. This facilitates direct access to 
the information on the grounded and the floating parts of the glacial 
systems. Hereby, it evidently would be essential to link the ice shelves 
with their nourishing glaciers and vice versa.

For regions with large glaciers and ice sheets (and ice shelves), analysis 
of mosaicked satellite imagery is the most appropriate way to derive the 
glacier parameters. This should be done by using consistently corrected and 
projected image data. In such a case, a simple L/S system based on the 
geometry of a single scene is not implementable. Additionally, on large ice 
sheets or ice shelves with absent nunataks or permanent coast lines, it 
might be difficult to identify a good reference point on the ground and 
therefore, a local N/E system is also difficult to implement. We therefore 
already outlined our needs for a geodetic system such as Lat/Long, ECEF or 
UTM (always with the respective information on the applied datum). Thus, 
the final storage of the coordinates in either N/E or L/L with additional 
information on accuracy and precision seems to be a good solution for all 
users, while image/mosaic processing can be performed by using a local 
coordinate system. Concerning the datum and projection which will be 
applied for individual image/mosaic processing on the Antarctic Peninsula, 
we will follow the recommendations of the SCAR Working Group on Geodesy and 
Geographic Information (Lambert Conformal Conic or Polar Stereographic, 
WGS84 - probably we can establish a common standard among all Antarctic RCs?).

Best regards

Frank



------------------------------------------------------------------
Frank Rau

Department of Physical Geography
University of Freiburg
Werderring 4
D-79085 Freiburg - Germany

phone:	++49 (0)761 203 3550
fax:		++49 (0)761 203 3596
e-mail:	frank.rau at ipg.uni-freiburg.de

http://www.ipg.uni-freiburg.de
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