Ice Sheet Topography, Slopes, and Flow Directions from ERS Altimetry
| H. J. Zwally (1), Anita Brenner (2),John DiMarzio(2), and Mario Giovinetto(3) |
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(1)NASA
Goddard Space Flight Center
Code 971
Greenbelt, MD
(2)Hughes STX
7701 Greenbelt Rd. Suite 400
Greenbelt, MD 20770
(3) University of Calgary
Calgary, Canada
(1)jay@intrepid.gsfc.nasa.gov (2) anita@ice.stx.com
john@ice.stx.com (3)mgiovine@acs.ucalgary.ca
http://crevasse.stx.com |
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Abstract
The surface topographies of the Greenland and Antarctic ice sheets
are mapped from two 168-day cycles of the ERS-1 geodetic mission and
two 35-day cycles from the multi-disciplinary mission. The Waveform
Altimeter Product from the
UK-PAF provides the altimeter waveforms, the ECMWF atmospheric
corrections, solid tides, and the DPAF revision one precision orbits.
Our waveform retracking algorithm (version 4) derives range
corrections by fitting a 9 or 5-parameter function to each waveform
and deletes ranges for which the waveforms are not representative of
surface returns. The 9 or 5-parameter function describes a single or
double surface return and calculates the range correction to the
midpoint of the first return, which represents the average surface
within the first pulse-limited footprint. Elevations are corrected
for the slope-induced error and gridded on a 5-km grid with respect to
a geoid derived from the NASA/GSFC and NIMA EGM96 gravity model.
Grids of surface slopes are derived from the elevation grids and used
to define the ice flow directions and delineate the ice sheet
drainage basins. The grids with interactive plotting software will
be available on a CD-ROM.
Keywords: altimetry,Topography, Cartography, Glaciology
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,
atmospheric chemistry
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