An overview of the Map Algebra tools

Map Algebra is the analysis language for ArcGIS Spatial Analyst. It is a simple syntax similar to any algebra. Generally, an output raster dataset will result from manipulation of the input. Several different types of input can be used, such as a single raster dataset, raster layer, feature dataset, feature layer, or shapefile.

Manipulation can be done by applying mathematical function on of each location's values, such as the sine or the square root. The manipulation can be applied to a series of inputs as well. An example would be adding the values of three raster datasets or raster layers together.

Map Algebra also allows you to build complex expressions and process them as a single command. For instance, as in the previous example you could calculate the sine of the values in an input raster, and then add those values to two other input rasters, all in one statement. It would look something like:

``	Output = sine (Input1) + Input2 + Input3``

There are four main ways to access Map Algebra. In geoprocessing, Map Algebra is accessed through the Single Output Map Algebra and Multi Output Map Algebra tools. On the ArcGIS Spatial Analyst toolbar, it is accessed through the Raster Calculator. In ArcGrid Workstation, it is accessed through the command line prompt.

Like all languages, Map Algebra is comprised of a series of rules. By understanding the basic rules, you will be able to use ArcGIS Spatial Analyst in new ways.

Learn about tools that implement Map Algebra

Learn about Map Algebra rules for compound expressions

Learn about Map Algebra input types

Learn about Map Algebra precedence for operators

The geoprocessing, Map Algebra tools offer different capabilities on how they can be executed and what types of output can be generated. The Multi Output Map Algebra tool is designed for processing single or multi-line Map Algebra statements and expressions. The Single Output Map Algebra tool processes a Map Algebra expression and provides the capability to link to other data and processes, as well as expose the input and output datasets, in ModelBuilder. The Multi Output Map Algebra tool can create more than one output, while the Single Output Map Algebra tool produces only one.

NOTE: Often you will see these tools referred to as 'MOMA' (Multi Output Map Algebra) and 'SOMA' (Single Output Map Algebra).

The following is a list of tools in the Map Algebra toolset followed by a brief description of each.

Tool Description
Single Output Map Algebra Runs a single expression built with the Map Algebra language.
Multi Output Map Algebra Runs an expression built with the Map Algebra language.