5.B.i.i. DCW vs. Other Cartographic Sources

Several analyses of DCW-generated 30" DEMs were conducted by USGS and UCL (see Muller and others, 1998c), including comparisons with higher-resolution DEMs, and with other DEM candidates for GLOBE. These analyses tended to show that DCW produced a less-than-ideal DEM. This was largely due to the large contour interval in the source Operational Navigational Charts (ONC). The stylization of ONC contours also contributed to artifacts in derived DEMs. Nevertheless, DCW-based DEMs were determined to be generally much more useful at 30" than regridded ETOPO5 or TerrainBase data (whose source data have grid spacings as coarse as 10').

DCW lacks contours for many parts of the world. In some cases other DEMs were contributed to GLOBE or GTOPO30. In other areas, GSI and USGS located cartographic sources that could be used to supplement DCW.

For parts of Indonesia, Brazil and neighboring South American countries, GSI and USGS located maps for GSI adaption to digital contours, and subsequent USGS contour-to-grid conversion to 30" DEMs.

This effort was only done when DCW contours were lacking or troublesome. Thus, for every area where other cartographic sources were used, those other sources were automatically preferred. DCW-based DEMs are unavailable for such areas.