Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet
This paper compares four continental ice sheet radar altimeter retracking algorithms using airborne radar and laser altimeter data taken over the Greenland ice sheet in 1991. The refurbished Advanced Application Flight Experiment (AAFE) airborne radar altimeter has a large range window and stores th...
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ftnasantrs:oai:casi.ntrs.nasa.gov:19980017788 2023-05-15T16:26:54+02:00 Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet Ferraro, Ellen J. Swift, Calvin T. Unclassified, Unlimited, Publicly available May 1995 application/pdf http://hdl.handle.net/2060/19980017788 unknown Document ID: 19980017788 http://hdl.handle.net/2060/19980017788 Copyright, Distribution as joint owner in the copyright CASI Earth Resources and Remote Sensing NASA/CR-95-207160 NAS 1.26:207160 IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 33; 3; 700-707 1995 ftnasantrs 2019-08-31T23:06:14Z This paper compares four continental ice sheet radar altimeter retracking algorithms using airborne radar and laser altimeter data taken over the Greenland ice sheet in 1991. The refurbished Advanced Application Flight Experiment (AAFE) airborne radar altimeter has a large range window and stores the entire return waveform during flight. Once the return waveforms are retracked, or post-processed to obtain the most accurate altitude measurement possible, they are compared with the high-precision Airborne Oceanographic Lidar (AOL) altimeter measurements. The AAFE waveforms show evidence of varying degrees of both surface and volume scattering from different regions of the Greenland ice sheet. The AOL laser altimeter, however, obtains a return only from the surface of the ice sheet. Retracking altimeter waveforms with a surface scattering model results in a good correlation with the laser measurements in the wet and dry-snow zones, but in the percolation region of the ice sheet, the deviation between the two data sets is large due to the effects of subsurface and volume scattering. The Martin et al model results in a lower bias than the surface scattering model, but still shows an increase in the noise level in the percolation zone. Using an Offset Center of Gravity algorithm to retrack altimeter waveforms results in measurements that are only slightly affected by subsurface and volume scattering and, despite a higher bias, this algorithm works well in all regions of the ice sheet. A cubic spline provides retracked altitudes that agree with AOL measurements over all regions of Greenland. This method is not sensitive to changes in the scattering mechanisms of the ice sheet and it has the lowest noise level and bias of all the retracking methods presented. Other/Unknown Material Greenland Ice Sheet NASA Technical Reports Server (NTRS) Greenland |
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NASA Technical Reports Server (NTRS) |
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topic |
Earth Resources and Remote Sensing |
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Earth Resources and Remote Sensing Ferraro, Ellen J. Swift, Calvin T. Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
topic_facet |
Earth Resources and Remote Sensing |
description |
This paper compares four continental ice sheet radar altimeter retracking algorithms using airborne radar and laser altimeter data taken over the Greenland ice sheet in 1991. The refurbished Advanced Application Flight Experiment (AAFE) airborne radar altimeter has a large range window and stores the entire return waveform during flight. Once the return waveforms are retracked, or post-processed to obtain the most accurate altitude measurement possible, they are compared with the high-precision Airborne Oceanographic Lidar (AOL) altimeter measurements. The AAFE waveforms show evidence of varying degrees of both surface and volume scattering from different regions of the Greenland ice sheet. The AOL laser altimeter, however, obtains a return only from the surface of the ice sheet. Retracking altimeter waveforms with a surface scattering model results in a good correlation with the laser measurements in the wet and dry-snow zones, but in the percolation region of the ice sheet, the deviation between the two data sets is large due to the effects of subsurface and volume scattering. The Martin et al model results in a lower bias than the surface scattering model, but still shows an increase in the noise level in the percolation zone. Using an Offset Center of Gravity algorithm to retrack altimeter waveforms results in measurements that are only slightly affected by subsurface and volume scattering and, despite a higher bias, this algorithm works well in all regions of the ice sheet. A cubic spline provides retracked altitudes that agree with AOL measurements over all regions of Greenland. This method is not sensitive to changes in the scattering mechanisms of the ice sheet and it has the lowest noise level and bias of all the retracking methods presented. |
format |
Other/Unknown Material |
author |
Ferraro, Ellen J. Swift, Calvin T. |
author_facet |
Ferraro, Ellen J. Swift, Calvin T. |
author_sort |
Ferraro, Ellen J. |
title |
Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
title_short |
Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
title_full |
Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
title_fullStr |
Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
title_full_unstemmed |
Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet |
title_sort |
comparison of retracking algorithms using airborne radar and laser altimeter measurements of the greenland ice sheet |
publishDate |
1995 |
url |
http://hdl.handle.net/2060/19980017788 |
op_coverage |
Unclassified, Unlimited, Publicly available |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
CASI |
op_relation |
Document ID: 19980017788 http://hdl.handle.net/2060/19980017788 |
op_rights |
Copyright, Distribution as joint owner in the copyright |
_version_ |
1766015926082207744 |