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Map algebra is the analysis language for Spatial Analyst. It is a simple syntax similar to traditional algebra. The input can be as simple as a single raster or feature data set. The manipulation can be multiplying each of the location's values by a conversion factor, or there can be a series of input raster or feature data sets to which the manipulation is applied such as when adding three raster data sets or layers together.
Map algebra also allows you to build complex expressions and process them as a single command. For example, you can use a single expression to find all the cells within a specific elevation range, apply a unit conversion such as feet to meters, and calculate the slope at each of those cells.
The examples above would be written in map algebra as:
Elev_meters = Elev_feet * 3.2808
Rain_total = Rain_April + Rain_May + Rain_June
Outgrid = (Con (elevation > 1000, Slope (elevation * 3.2808))
All ArcGIS Spatial Analyst functions can be used with the map algebra syntax. Some of the more traditional mathematical operators and functions available are:
- Abs
- Divide
- Exp
- Exp10
- Exp2
- Float
- Int
- Ln
- Log10
- Log2
- Minus
- Mod
- Negate
- Plus
- Power
- Round Down
- Round Up
- Square
- Square Root
- Times
- ACos
- ACosH
- ASin
- ATan
- ATan2
- ATanH
- Cos
- CosH
- Sin
- SinH
- Tan
- TanH
- Boolean And
- Boolean Not
- Boolean Or
- Boolean Xor
- Combinatorial And
- Combinatorial Or
- Combinatorial XOr
- Equal To
- Greater Than
- Greater Than or Equal
- Is Null
- Less Than
- Less Than or Equal
- Not Equal
- Test
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