Analytics

What happens with rectangular raster cells in Spatial Analyst?

While it is common knowledge that Spatial Analyst tools are designed to operate on square cells, rasters with rectangular cells are supported as input. Have you ever wondered what happens when rasters with non-square cells are used?

Basic behaviour

When an input raster has rectangular cells, the data will be processed by Spatial Analyst in such a way that the output will have square cells. It is important to understand how the cell size and extent are changed and how the values of the original cells are handled.

In the following graphic, you’ll note that in the output, the third and fourth rows from the top have essentially duplicate values.  This is a result of the center of those cells being closest to the same cell in the input raster.  When resampling with Nearest neighbour, having adjacent rows or columns with identical values is a common occurrence.

Rectangular cells in Spatial Analust

Read on for information on how you can have more control over the operation.

Controlling with the Environment

In order to better control how the rectangular input cells are handled in the processing, you can use the geoprocessing Environments.

Controlling resampling

You cannot control the type of resampling that Spatial Analyst tools will use in their operation; for most of them it will always be Nearest neighbour.  However, if you wish to control how the input values are resampled in the operation, first run the Resample tool on the input rectangular-cell raster.  With this tool you can select other methods of resampling, such as Bilinear interpolation and Cubic convolution, as well as the desired cell size.

Note:
Spatial Analyst tools only support certain of the Raster Storage environment settings.  The Resampling Method is not one of them, and so will not have any effect.

About the author

Juan is a Product Engineer and Documentation Lead on the Spatial Analyst team. He has been working with raster analysis using Esri software since the good old days of ARC/INFO Workstation on UNIX machines.

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