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8.B. Ancillary Data

The GLOBE Task Team originally expressed a desire to include "ancillary" data with the GLOBE DEM. Original discussions centered around a registered, full-resolution source file, ocean mask, slope, aspect, shaded relief, bathymetry, and possibly other data.

ETOPO5 included bathymetry, to make the first integrated global surface relief model. TerrainBase used the bathymetric data from ETOPO5 to do the same. The GLOBE Task Team decided to forego resampling these data and to exclude bathymetric data until better bathymetric data might appear.

8.B.i. Source/Lineage File (with Contained Ocean Mask)

A source/lineage file accompanies GLOBE Version 1.0. It is tiled in the same manner as the DEM. Its file naming convention is "?10S", where "?" is the tile letter ranging from A to P (see diagram in Section 11.A).

The source/lineage file not only identifies the original source data set, but also certain important details of processing used to make the 30" DEM. In some cases, it goes back earlier in the history of a data set than source maps in other compilations (for example, noting that NIMA was the designer of DCW, and that DMA originated certain DEMs distributed by NGDC and USGS). In other cases, it notes subsequent processing that might be important, such as who might have adapted printed maps to digital format, and who might have converted the digital vector lines to 30" raster grids.

The legend for the source/lineage map of GLOBE Version 1.0 is given in Section 11.E.

8.B.ii. Slope and Aspect Data (Why Aren't They Provided?)

Although the GLOBE Task Team originally hoped to have slope and aspect data as ancillary data sets, we currently consider the data at too early a stage of development to justify this. Users may compute their own slope and aspect data, with the caveat that considerable care should go into the derivation of such products. The DEMs still contain significant artifacts. Such artifacts are within individual DEMs from individual sources/lineages. There are also discontinuities or steep gradients at seams between data sources/lineages (caused by or incidental to the mosaicking process). Until additional artifact removal is performed, the GLOBE Task Team believes that users should be fully responsible for the results of their own slope and aspect maps.

Shaded relief and color images from GLOBE are provided on the GLOBE Web site, in the Gallery of GLOBE Images.


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