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ICESat/GLAS Data at NSIDC

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ICESat/GLAS Surface-Type Mask

The GLAS science team developed a global mask to flag surface types for use in creating standard ICESat/GLAS data products. This mask was originally for science team use only, to ensure proper transition from one surface type to another, with surface types overlapping. NSIDC is now offering this surface-type mask as a standalone product to the public. It should be used strictly as a tool to learn how surface types were flagged for use in creating standard ICESat/GLAS data products. Other publicly available surface-type masks may be more suitable for other applications, depending on the scientific objective. The surface-type mask is available via FTP.

Following is a reduced-resolution image created from the surface-type values.

Surface types

Valid pixel values range from 1 to 15. The surface types are bit-coded, and any combination of surface type is allowed. The bit coding is:

1 = land
2 = sea ice (winter maximum extent)
3 = ocean
4 = ice sheet


Color in above image Binary value Decimal value Surface types Percentage of the mask
Not shown 00000000 0 No type assigned 0
  00000001 1 Land 18.88
Not shown 00000010 2 Sea ice 0
Not shown 00000011 3 Sea ice + land 0.02
  00000100 4 Ocean 43.12
  00000101 5 Ocean + land 5.12
  00000110 6 Ocean + sea ice 17.06
  00000111 7 Ocean + sea ice + land 3.69
Not shown 00001000 8 Ice sheet 0
  00001001 9 Ice sheet + land 9.18
Not shown 00001010 10 Ice sheet + sea ice 0
Not shown 00001011 11 Ice sheet + sea ice + land 0.01
Not shown 00001100 12 Ice sheet + ocean 0
Not shown 00001101 13 Ice sheet + ocean + land 0.02
Not shown 00001110 14 Ice sheet + ocean + sea ice 0
  00001111 15 Ice sheet + ocean + sea ice + land 2.90

Page last updated: 10/03/05