Catchment extraction

Dialog box

The Catchment extraction operation constructs catchments; a catchment will be calculated for each stream found in the output map of the Drainage network ordering operation.

The operation delivers an output raster map, an output polygon map and an output attribute table.

In the attribute table, you will find information on each catchment, such as:

area and perimeter of the catchment,
total upstream area, i.e. the area of all catchments that drain into this catchment, etc.

Dialog box options:

Drainage network ordering map:
	Select an input raster map that is the output of a previous Drainage network ordering operation.
Flow direction map:	Select a raster map that is the output of a previous Flow direction operation.
Output raster map:	Type a name for the output raster map and the output polygon map that will contain the uniquely numbered catchments. The name will also be used for the output attribute table.
Description:	Optionally, type a description for the output map. The description will appear in the status bar of the Main window when moving the mouse pointer over the map in a Catalog, and in the title bar of a map window when the output map is displayed. If no description is supplied, the output map will use its own definition as description.

When you click the Show button, the dependent output map will be defined, calculated and shown. When you click the Define button, the dependent output map will only be defined; if necessary the map will be calculated later, for instance when the map is opened to be displayed.

The output maps and the attribute table will all use the ID domain of the input drainage network ordering map.