ArcGIS Spatial Analyst

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Map Algebra

ArcGIS Spatial Analyst includes advanced map algebra functions for combining multiple maps, performing suitability analyses, assigning weights, and identifying relationships.

Map algebra provides an easy-to-use and powerful way to define geographic analyses as algebraic expressions. This allows users to take their real-world data and apply algebraic functions to derive new results.

For example, a single expression can be constructed to find the combined value of two datasets:

>[(Raster1) + (Raster2)]

These algebraic expressions can be simple arithmetic expressions or can consist of complex spatial and algebraic functions.

You can 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. Such an expression might look like the following:

>=Elev_meters = Elev_feet * 3.2808=
Rain_total = Rain_April + Rain_May + Rain_June
Outgrid = (Con (elevation > 1000, Slope (elevation * 3.2808))) =
Spatial Math Add

This graphic illustrates how mathematical operators and functions can be used to combine data on a cell-by-cell basis to derive new information.