About raster data in the ArcGIS Spatial Analyst extension

When using ArcGIS Spatial Analyst extension for your processing, you will have to use or create raster datasets. A raster is composed of an array of equally sized cells arranged in rows and columns, where each cell contains a value representing information such as elevation, temperature, or land-cover type.

It is important to understand how a raster dataset is represented in ArcGIS and the issues you need to be aware of when using and creating rasters. To get the maximum benefit of the capabilities of Spatial Analyst, you should be familiar with some fundamental aspects of raster data. There is extensive information on raster data available in the Rasters and images section of the Data Management > Managing geographic data documentation.

Some particular concepts to be aware of include:

What the cell size meansWhat raster bands areHow features are represented in a raster formatThe difference between discrete and continuous dataZones and regions in raster dataThe attribute tables of raster data

It would also be helpful to have some knowledge of raster datasets, including the following:

Supported raster dataset file formatsRaster dataset propertiesBuilding and managing a raster database

For more information on cell-based modeling with rasters, see Modeling Our World: The ESRI Guide to Geodatabase Design from Esri Press.

The shape of raster cells

It is important to note that Spatial Analyst performs operations on square cells only. Thus, the size of each cell, known as its resolution, must be the same in each dimension.

If you have input raster data in formats that support non-square cells, before the operation is performed, the raster will first be converted to square cells.