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7.A.ii. Data from Cartographic Sources

Topographic contour lines in maps at 1:1,000,000 scale used for DCW and source/lineage categories 15 - 17) can be stylized so as to be 30" (one GLOBE grid cell) off. The SCAR data base (source/lineage category 18) could be mislocated by a greater amount, owing to the pioneering status of current mapping of Antarctica. However, errors can exceed such figures locally. For example, the ONC for northern Greenland contains notices such as: "CAUTION: Arctic Institute of North America Project Nord (Control Data Corp.) indicates position discrepancies in excess of 11 nautical miles (Nov. 68)."

In addition, surface generation algorithms might impose horizontal errors at least 30" off in areas without much control by contour lines. This is because interpolated surfaces may be misguided by patterns in point or contour data sources, especially where such data are stylized or scarce.

Similarly, the AUSLIG/NGDC data (source/lineage category 8) may be shifted horizontally by the interpolation process, in areas with relatively low density of source data. Due to the high density of source data points, this problem should be unusual. Stylization of source maps should have little effect on horizontal accuracy in GLOBE, as these have relatively high resolution.


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