[Project: Short_Name='NOAA/NASA PATHFINDER']
Ice Altimetry Data for Greenland and Antarctica from NASA Goddard Space Flight CenterEntry ID: NASA_GSFC_OIB_ICE_ALTIMETRY
Abstract: The Oceans and Ice Branch of NASA's Goddard Space Flight Center has processed
satellite radar altimetry and aircraft laser altimetry over the continental ice
sheets of Greenland and Antarctica and surrounding sea ice to calculate surface
elevations. The radar processing is currently being funded by the NASA Mission
to Planet Earth Pathfinder Program.
The data ... have been obtained from the Seasat, Geosat, ERS-1, ERS-2 and GFO
satellites radar altimeter missions and from the Arctic Ice Mapping (AIM)
mission which utilizes NASA's Airborne Topographic Mapper (ATM) laser
altimeter. Radar Altimetry data from Seasat, Geosat, ERS-1, ERS-2 and GFO
satellites is available for distribution upon request. Data from ENVISAT will
be available in the near future.
The following data products are available:
Level 1: Waveform Data Records
Orbital format waveform data records at the full data rate which contain the
time, location altimeter return waveform, and retracking parameters.
The altimeter waveform return gives a measure of the surface roughness on
scales of sub-meter to tens of kilometers and indicates if surface penetration
and/or volume scattering is present. These results are used to investigate
regional, interdecadal and interannual changes in the ice sheet and sea ice
surface characteristics. The returns are also used to identify sea ice
boundaries and extent.
Level 2: Ice Data Records
Orbital format ice data records at the full data rate which contain the time,
precise location, altimeter height measurement, corrected precise surface
elevation, atmospheric corrections, tidal values, retracking corrections, and
AGC. These data are updated on-line as more precise orbits, corrections, and
tide values become available.
These data are mainly used by scientists who are trying to improve the
algorithms to calculate the corrections or who require knowledge of what effect
the corrections have on the data. Most researchers do not require this much
detail and would be better served by the georeference data bases which contain
the precise surface height after all corrections have been applied at the full
Level 3: Geo-referenced Database
Contain surface height measurements derived from altimetry data, ordered by
geographic areas or "bins". Each data record contains the geodetic position,
revolution number, surface elevation relative to a reference ellipsoid, and
slope correction. This database contains detailed elevation information for the
full-rate along track data.
Level 4: Elevation Grids
Gridded elevations are calculated from the data by a weighted fitting of a
bi-quadratic function (bi-linear where data distribution is poor) on a polar
stereographic projection with a nominal spacing of 5 km (ERS-1) 10 km (GEOSAT)
and 20 km (Seasat).
The dense topographic coverage is crucial for a variety of glaciological
studies, from numerical modeling of the ice dynamics to monitoring of key
glaciological features: ice drainage basins, ice-shelf grounding lines, ice
divides, subglacial lakes, ice shelf fronts, and ice rises.
The crossover data give interpolated elevations for different tracks at the
same location including the corrections also interpolated to the crossover
location. These data are best used for ice sheet change studies.
[This summary was adapted from the GSFC Ice Altimetry WWW pages.]
Data Set Citation
Dataset Originator/Creator: Zwally, H.J,
Dataset Title: Ice Altimetry Data for Greenland and Antarctica from NASA Goddard Space Flight CenterOnline Resource: http://icesat4.gsfc.nasa.gov/
Email: Jay.Zwally at nasa.gov
Laboratory for Hydrospheric Processes NASA/Goddard Space Flight Center Code 614
Province or State: MD
Postal Code: 20771
Davis, C.H. and H.J. Zwally,"Geographic and Seasonal Variations in the Surface
Properties of the Ice Sheets by Satellite Radar Altimetry", Journal of
Glaciology, Vol. 39, 1993
Lingle, C.S., L.-h. Lee, H.J. Zwally and T.C. Seiss, "Recent Elevation Increase
on Lambert Glacier, Antarctica, From Orbit Crossover Analysis of Satellite
Radar Altimetry", Annals of ... Glaciology, 20, 1994
Martin, T.V.,H.J. Zwally,A.C. Brenner, and R.A. Bindschadler "Analysis and
Retracking of Continental Ice Sheet Radar Altimeter Waveforms", J. Geophys.
Res.,88, C3, 1983.
Zwally, H.J, A.C. Brenner, J.A. Major, and R.A. Bindschadler, and J.G. Marsh,
"Growth of Greenland Ice Sheet: Measurement", Science Vol 246, 1989a
Zwally, H.J, "Growth of Greenland Ice Sheet: Interpretation", Science Vol 246,
Zwally, H.J, A.C. Brenner, J.A. Major, and R.A. Bindschadler, "Satellite Radar
Altimetry Over Ice, Vol 1,2, and 4", NASA Ref. Pub. 1233, 1990
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Creation and Review Dates
Last DIF Revision Date: 2011-07-25