WMS:Mapping Tables

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A mapping table or map table is used by WMS to link values within a project. There are multiple ways this can be accomplished:

  • For distributed models, WMS assign model parameter values to grid cells by linking parameter values to index maps. See File Formats for the different mapping parameters. The GSSHA Wiki also discusses this.
  • For lumped parameter models, a lumped average (or area-weighted average) is created based on the percentages of land use values or soil types within a basin. A mapping table must be imported prior to computing the composite curve numbers. For a land use or soil type coverage, the mapping table may be set up interactively by selecting each polygon and assigning the appropriate parameters. The Compute GIS Attributes dialog then uses the mapping tables created using those coverages, or manually via a text file.

Composite CN Table

A composite CN table is a mapping table containing composite curve numbers (CN), which are a type of lumped parameter. Land use tables with corresponding CNs vary from text to text and agency to agency. WMS supports a user definable method for relating land use to CNs. This is done through a simple table file that is imported prior to computing the composite CN.

For example, the tables in the Handbook of Hydrology can be used to create a TBL file for use in WMS. See Land Use Files to view the format of the table.

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