5.B.iv. Comparison of GLOBE with Other Available DEMs

GLOBE has considerably higher resolution than earlier predecessors ETOPO5 and TerrainBase. Although TerrainBase was originally considered a candidate for filling GLOBE with areas lacking higher-resolution data, GLOBE ultimately found 30" data from other sources for all areas but Antarctica and Greenland. (The converted SCAR data base, and several other candidates for supplementing GLOBE coverage of Antarctica, are considered better than ETOPO5/TerrainBase; the Greenland GEOSAT-based DEM was converted to 30" by JPL.) GLOBE is a likely source for updating the next version of TerrainBase, which will be regularly updated until user interest indicates that it should be discontinued.

The TerrainBase management philosophy of soliciting contributions, and proactively offering to participate in the design and development of unrestricted regional DEMs for the global compilation, will be continued in the GLOBE project. TerrainBase and GLOBE served as prototypes for each other during TerrainBase's design and development. TerrainBase’s efforts at data compilation led to the SGN DEM for Italy which has since been adapted to GLOBE.

JPL's DEM at 30" was developed for internal support of NASA's Multiangle Imaging Spectro-Radiometer (MISR) mission. The project had permission to reprocess DTED Level 1 data to 30" gridding, but not to share those data with the general public. In addition, JPL used contour-to-grid techniques to convert DCW to 30" DEMs in many areas; but not to the level of effort of USGS's effort with GTOPO30. JPL's effort was largely crafted to meet its mission. Nevertheless, J.-P. Muller's comparison of GTOPO30 and the MISR DEM favored the MISR version for Greenland. As that data set was largely unrestricted, the GLOBE project has incorporated unrestricted coverage for the Greenland Ice Sheet into GLOBE.

The USGS/GTOPO30 effort was also developed partially for NASA, for more general support of NASA's Earth Observing System science community. It worked extensively to develop DCW contour-to-grid procedures. It also acquired and processed several gridded DEMs, and worked cooperatively with GSI to adapt several printed topographic maps to DEMs. Much of its data were incorporated into GLOBE.

The GLOBE project added several data sets, including the first public release from DTED, the AUSLIG/NGDC DEM, and DEMs from GSI and SGN. GLOBE uses the DTED Level 0 discrete values where available between 50^o North and South latitudes, where GTOPO30 uses several inconsistent sampling methods for different areas. The GLOBE project also added the public peer review site, enhanced documentation, and enhanced features on its Web site. Periodic enhancements to data and documentation are anticipated.