How do you do algebra on a map?

The simplest approach is map algebra on a cell-by-cell basis. For example, you have 2 rasters stacked on top of each other. Then, you add each cell one-by-one. If raster cells represent temperature, you can subtract them both at different time periods.

What is Map Algebra in ArcGIS?

Map Algebra is a simple and powerful algebra with which you can execute all Spatial Analyst tools, operators, and functions to perform geographic analysis. Map Algebra is available through the Spatial Analyst module; an extension of the ArcPy Python site package.

How does Map Algebra work?

Map Algebra uses math-like expressions containing operators and functions with raster data. Map Algebra operators, which are relational, Boolean, logical, combinatorial, and bitwise, work with one or more inputs to develop new values.

What is raster algebra?

The raster algebra functions enable the usage of the expressions and support cell value-based conditional queries, mathematical modeling, classify operations, and cell value-based updates or edits over one or many raster layers from one or many GeoRaster objects.

How do you use the raster calculator in ArcGIS?

Procedure

  1. In ArcMap, navigate to ArcToolbox > Spatial Analyst Tools > Map Algebra > Raster Calculator.
  2. In the Raster Calculator window, double-click one of the rasters to be analysed, click the minus sign (-), and double-click the second raster.
  3. Specify the name and location for the output raster.
  4. Click OK.

What is a global function in GIS?

Global functions allow you to perform processing at a specific resolution and extent. By default, global functions process rasters at the source resolution and full extent. This means that applying a global function may take some time, depending on the size of the outputs.

What are zonal statistics?

A zonal statistics operation is one that calculates statistics on cell values of a raster (a value raster) within the zones defined by another dataset. There are two tools that calculate statistics by zones, Zonal Statistics and Zonal Statistics as Table.

How do you use the raster calculator in Arcgis?

What is a raster calculation?

The Raster Calculator is a Spatial Analyst function that provides powerful tools for performing multiple tasks: you can perform mathematical calculations using operators (such as addition and subtraction) and functions, and set up selection queries (similar to “Select by” queries done on vector data).

How do you calculate the area of a raster?

An easy way to find the area is to right click the output raster that you just created, click Properties, click the Symbology tab, and note the Count for the pixels that are displayed. Click the Source tab and note the cell size and linear units.

What is NDVI in ArcGIS?

The normalized difference vegetation index (NDVI) is a standardized index allowing you to generate an image displaying greenness, also known as relative biomass.

What is focal statistics in ArcGIS?

The Focal Statistics tool performs a neighborhood operation that computes an output raster, where the value for each output cell is a function of the values of all the input cells that are in a specified neighborhood around that location.