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Splitting a raster (.img) to make it smaller

June 10 2009 | 0 comments
Categories: ArcGIS Methods

When I use the tool to convert raster to polygon in Spatial Analyst, the process is often canceled because my output shapefile is too large (over 2G).

Can I split my rasters (.img) down the middle to make them smaller? Is there another way I can make the output smaller?

Mapping Center Answer:

We don't know of a tool to do this (tile your raster). 

I've taken a couple of approaches when confronted with this issue.  First, is to make sure my Geoprocessing Environment settings for "Current" and "Scratch" workspaces are set to a file geodatabase.  Prior to ArcGIS 9.3.1,that did not always help.  Your output polygons should also be written to a file geodatabase--there is no 2GB limit there. 

But if that doesn't work you can produce tiles using the Geoprocessing Environment's Extent setting. The idea is to use the Copy Raster tool and to set the extent of the output using the Geoprocessing Environment's Extent setting.  It is a good idea to write the values down ahead of time, starting with the extent of your raster.

There is also a sample on the ArcScripts page called Tile v0.32 that purports to being able to tile  a raster.  It's a Geoprocessing Script tool (written in Python).  The author says some work may be needed to modernize and deal with bugs--so knowing something about Python for ArcGIS Geoprocessing is very likely required.

 

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