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NOTE: Reverb will be decommissioned in the coming months and replaced with Earthdata Search. All links to Reverb will be removed at that time.
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Data Set ID:
GLA01

GLAS/ICESat L1A Global Altimetry Data, Version 33

The Geoscience Laser Altimeter System (GLAS) instrument on the Ice, Cloud, and Land Elevation Satellite (ICESat) provides global measurements of polar ice sheet elevation to discern changes in ice volume (mass balance) over time. Secondary objectives of GLAS are to measure sea ice roughness and thickness, cloud and atmospheric properties, land topography, vegetation canopy heights, ocean surface topography, and surface reflectivity.

GLAS has a 1064 nm laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel for the vertical distribution of clouds and aerosols.

Level-1A altimetry data (GLA01) include the transmitted and received waveform from the altimeter.

Each data granule has an associated browse product that users can quickly view to determine the general quality of the data in the granule. Browse products consist of image plots of key parameters and statistics. Data are in scaled integer binary format, big-endian (Unix) byte order, and are available via FTP.

Version Summary:

For information about Version 33, see the NSIDC ICESat Description of Data Releases page.

Geographic Coverage

Spatial Coverage:
  • N: 86, S: -86, E: 180, W: -180

Spatial Resolution:
  • 60 m to 70 m x 60 m to 70 m
Temporal Coverage:
  • 20 February 2003 to 11 October 2009
Temporal Resolution: 23 minute
Parameter(s):
  • Infrared Wavelengths > Sensor Counts > Waveform
Platform(s) ICESAT
Sensor(s): ALTIMETERS, GLAS
Data Format(s):
  • Binary
Version: V33
Data Contributor(s): H. Zwally, Robert Schutz, Charles Bentley, Jack Bufton, Thomas Herring, Jean-Bernard Minster, James Spinhirne, Robert Thomas

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Zwally, H. J., R. Schutz, C. Bentley, J. Bufton, T. Herring, J. Minster, J. Spinhirne, and R. Thomas. 2011. GLAS/ICESat L1A Global Altimetry Data, Version 33. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/ICESAT/GLAS/DATA121. [Date Accessed].
In GLA01 and GLAH01 waveform plots, what does the "relative time" axis mean?

The relative time axis represents two-way travel time. Two adjacent returns separated by a relative time difference (delta_t) in nanoseconds correspond to a height difference of delta_h in centimeters such that:
delta_h = c / 2 * delta_t
where:
c is... read more

In preliminary data from laser #1, why does the "i_surfType" record indicate surface classifications that are simultaneously land, sea ice, ocean, and ice sheet?

This is not an error. The masks for these surfaces purposely overlap in order to not miss any data; the masks are used to determine which data goes in GLA12-15 (the regional products). Most of the ice sheets are considered both ice sheet and land.

Why is spatial searching not enabled for GLA01 (GLAH01) to GLA04 (GLAH04)?

The orbit for GLA01 (GLAH01) and GLA02 (GLAH02) is a predicted orbit and does not show any target-of-opportunity pointing. The GLAS science team decided not to enable spatial searching for these two products in... read more

How to convert GLAS Binary elevation data to WGS-84

The data tool NGAT provides the option of including a new variable (i_deltaEllip) whose
value is Surface Elevation (T/P ellipsoid) minus Surface Elevation (WGS84 ellipsoid).

This product variable will be added to the end of your output record if you set
"... read more