Satellite remote sensing can now allow a globally-uniform inventory of land ice. Although some regional inventories now exist, major regions have little or irregular coverage. No substantial Geographic Information System (GIS) inventories exist, even for the best-studied regions, such as Scandinavia and the Alps. Analog maps, even if of high resolution, do not support quantitative assessment of change without intense human labor. A digital geographic database incorporating detailed location of glacier boundaries is required for practical quantitative determination of change among glaciers. Considering the importance of glaciers as an indicator of climate, and the value that a global baseline would have to future studies of climate change, it is imperative that an image-based global GIS of glaciers (e.g., small mountain glaciers, ice fields, ice caps, ice sheets, outlet glaciers from the latter three types) be created as soon as practical, with Digital Terrain models (DTM's) where possible. This can be augmented by historical data of lower resolution or less complete coverage.

Both high-resolution optical (15m) and radar (~25m) imaging will be available in the next few years. Their combined capabilities can be used to map the more difficult situations, including mapping of debris-laden termini. The potential of combining these with precision altimetry surveys will allow remote mapping of ice volume changes.

Global Land Ice Monitoring from Space (GLIMS) is a specific program that has been established to use the EOS ASTER instrument (15m, along-track stereo, plus multiband imaging) to map the areal extent of all land ice and the annual motion of large glaciers. The image data will be archived at EDC, and derived products related to glaciers curated by NSIDC. The data acquisition required for 3 to 5 image attempts each year for the periphery of Greenland and Antarctica, and all other land ice, has been considered in the design of ASTER and in its mission planning and data-processing requirements; the GLIMS data requirements represent less than 1% of the total ASTER capability. The GLIMS concept includes involvement of "Regional Centers" with expertise on the typical weather/climate and specific glacier conditions of each area; the overall activity would be coordinated by the USGS. The GLIMS data base will be cross-indexed to World Glacier Monitoring Service (WGMS), which maintains an archive of scalar data for ~100,000 glaciers.

The GLIMS concept is distinctly different than, and complementary to, detailed observations on a small number of "benchmark" glaciers. It also complements the comprehensive overview of the Earth's glaciers from 1970's Landsat MSS images that are discussed in U.S. Geological Survey Professional Paper 1386 A-K, Satellite Image Atlas of Glaciers of the World. [an error occurred while processing this directive]