Weighted Overlay function

This function allows you to overlay several rasters using a common measurement scale and weight each according to its importance.

There are three parameters for this function: a table that defines the weights of the rasters, how the cell size is handled, and how the extent is handled.

Weighted Overlay Table

The simplest way to enter a weighted overlay table is to load a preexisting table. A weighted overlay table can be created using the Weighted Overlay geoprocessing tool. To create the table, open the tool, fill in the parameters, and click the Save Table button

• Raster—All input rasters must be integer.
• % Influence—Each input raster is weighted according to its importance, or its influence, as a relative percentage. The sum of the percent influence weights must equal 100, and each weight must be specified by integer values.
• Field—An integer or string field on the input raster to use for weighting.
• Remap—Each value in an input raster is assigned a new value based on the remap. The remap value can be a valid value or a NoData value. The format of the string used to assign the remap is to specify the old value, a space, the new value followed by a semi colon.

  The following table shows both original values and remap values. The remap string representing the information in the table is formatted 1 10;2 9;3 8

  Original value	Remap value
  1	10
  2	9
  3	8

  A table with original values and remap values.

Cell Size

Choose the cell size to use for the output raster. If all the input cell sizes are the same, all the options will yield the same results.

Cell size	Description
First	Use the first cell size of the input rasters. This is the default.
Last	Use the last cell size of the input rasters.
Max	Use the largest cell size of all the input rasters.
Mean	Use the mean cell size of all the input rasters.
Min	Use the smallest cell size of all the input rasters.

Extent

Choose which extent should be used for the output raster.

Extent	Description
First	Use the extent of the first input raster to determine the processing extent. This is the default.
Intersection	Use the extent of the overlapping pixels to determine the processing extent.
Last	Use the extent of the last input raster to determine the processing extent.
Union	Use the extent of all the rasters to determine the processing extent.