Rationale for the SLC version 2.2 data structure

Background

For version 2.2, all visible water bodies were moved out of the SLC coverage, and all references to water were removed from the COMPONENT Table. Water is now visible only in the HYDRO coverage, and the area covered by water is found only in the LANDSCAPE table.

Why was this done?

1. to simplify calculations and reduce potential errors in calculations;
2. to eliminate the ambiguity in the representation of water (and thus the calculation of land area) inherent in the former structure;
3. to simplify the SLC coverage and the COMPONENT Table;
4. to simplify future maintenance of the SLCand HYDRO coverages.

No information was lost in the process. It is possible to recreate a Version 2.1 dataset and structure from Version 2.2.

How was this done?

It was assumed that the water identified in the COMPONENT Table as KINDMAT="WA" is in addition to all of the water that is mapped in the HYDRO coverage.