An error is returned using the Raster Calculator when a shapefile mask is set

Error Message

This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.If a shapefile is used as a mask for an analysis operation, an error, "The cell size value is either invalid or not defined", is returned when using the Raster Calculator.

Cause

This is a known issue with ArcGIS 8.1.

Solution or Workaround

1. Click the ArcGIS Spatial Analyst dropdown arrow and click Options.
2. Click the Cell Size tab and specify a cell size for the analysis results.
3. Perform the analysis using the Raster Calculator.