Map Algebra is a way to perform spatial analysis by creating expressions in an algebraic language. With the Calculator function, you can create and run expressions and incorporate those into function chains.
There are four inputs to the Calculator function:
- Raster Variables
- Extent type
- Cell size type
The calculator function requires single-band inputs. If you need to perform expressions on bands in a multispectral image as part of a function chain, you can use the Extract Bands Function before the Calculator function. This function provides access to all existing math functions so you can make calls to them when building your expressions. To assist you, autocomplete is built in to provide access to the operators as well as the math functions.
The operators available to you are listed in the table below.
Greater than or Equal to
Less than or Equal to
Not Equal to
Minimum of two rasters on a per-pixel basis
Maximum of two rasters on a per-pixel basis
Examples of expressions
Simple Conditional Statement
Find elevation values above 4,000 feet. Give these areas a value of 1 and all other areas a value of 0.
Nested Conditional Statement
Find areas where slope is below 10 degrees and NDVI is above 0.5. Give these areas a value of 1. For all other areas, assign a value of 2 if slope is above 10 degrees and elevation is over 2,500 feet. All other areas are assigned a value of 3.