WMS:Mapping Tables: Difference between revisions

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The mapping table is different depending on whether composite curve numbers or runoff coefficients are being computed. A mapping table must be imported using the '''Import''' button prior to computing the composite curve numbers. The radio group above the mapping window specifies whether the land use or soil type mapping table is displayed. 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. Such files can then be exported and later imported. For grid attributes, define a land use or soil type table by defining a land use or soil type coverage and then using the '''Attributes''' command from the ''Feature Objects'' menu (in the Map module) to define individual polygon attributes that constitute the table. See [[WMS:Land Use|Land Use coverages]] and [[WMS:Soil|Soil Type coverages]] for information on assigning parameters to land use and soil type polygon coverages. See [[WMS:WMS Supported File Formats|File Formats]] for the different mapping parameters.
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 [[WMS:WMS Supported File Formats|File Formats]] for the different mapping parameters. The [https://gsshawiki.com/Mapping:Mapping_tables 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 [[WMS:Land Use|land use]] or [[WMS:Soil Type Coverage|soil type coverage]], the mapping table may be set up interactively by selecting each polygon and assigning the appropriate parameters. The [[WMS:Compute GIS Attributes|''Compute GIS Attributes'' dialog]] then uses the mapping tables created using those coverages, or manually via a text file.  


==Composite CN Table==
==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.


Because 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. The file scsland.tbl is an example of such a file and was created from a table given in the [[WMS:References|Handbook of Hydrology]]. This file can be edited to supply user defined values or a new table with the same format can be created. See [[WMS:Land Use Files|Land Use Files]] to view the format of the table.
For example, the tables in the [[WMS:References#Handbook of Hydrology|''Handbook of Hydrology'']] can be used to create a TBL file for use in WMS. See [[WMS:Land Use Files|Land Use Files]] to view the format of the table.
 
==Runoff Coefficient Table==
 
The [[WMS:Runoff Coefficient Table|runoff coefficient table]] must be defined to relate soil type IDs to runoff coefficient values. A very simplified file named soiltype.tbl is provided with the distribution of WMS.  This file can be edited to supply user defined values or a new table with the same format can be created. See [[WMS:Soil Type Runoff Coefficient Files|Soil Type Runoff Coefficient Files]] to view the format of the table.


==Related Topics==
==Related Topics==
* [[WMS:Compute GIS Attributes|Compute GIS Attributes]]
* [[WMS:Land Use|Land Use]]
* [[WMS:Land Use|Land Use]]
* [[WMS:Soil Type|Soil Type]]
* [[WMS:Soil Type|Soil Type]]
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[[Category:WMS Map|T]]
[[Category:WMS Map|T]]
[[Category:External Links]]

Latest revision as of 00:27, 21 December 2019

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.

Related Topics


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