Knowledge Base - Technical Articles

Technical Article   HowTo:  Merge rasters using ArcGIS Spatial Analyst

Article ID: 20988
Software:  ArcGIS - ArcEditor 8.1, 8.1.2 ArcGIS - ArcInfo 8.1, 8.1.2 ArcGIS - ArcView 8.1, 8.1.2
Platforms: N/A


Instructions provided describe how to merge rasters using ArcGIS Spatial Analyst's Raster Calculator. This method allows the combination of up to 23 rasters at a time.


Follow the steps below.

  1. Start ArcMap.
  2. Add all of the rasters to combine into the current document.
  3. Select Options from the Spatial Analyst dropdown menu.
  4. Switch to the Extent tab.
  5. Set the Analysis Extent dropdown list to 'Union of Inputs' and click OK.
  6. Select Raster Calculator from the Spatial Analyst dropdown list.
  7. Type 'MERGE(' in the expression box. Do not include the quotation marks.
  8. Double-click one of the rasters in the Layers list and add a comma after the raster's name in the expression box.
  9. Double-click the next raster in the Layers list and add a comma. Repeat until all rasters have been added.
  10. End the expression with a close parenthesis ')'.

    Merge([Raster1], [Raster2], [Raster3], [Raster 4])

     Do not press return after entering the last parenthesis. The cursor must be to the right of it. Failure to do so causes the following error:

    "Failed to evaluate the calculator equation"

  11. Click Evaluate.

    The resulting raster appears with the name 'Calculation' in ArcMap. To make it a permanent dataset, right-click 'Calculation' and select 'Make Permanent'.

Created: 11/21/2001
Last Modified: 12/14/2004

Article Rating: (9)
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By Anonymous - 07/29/2010 2:57 PM

I’d like to suggest some keywords to help find this article.

The process worked except that the whole merged grid layer was shifted by about 10m. This is not very good if masking accuracy is needed for the resulting layer.


By Anonymous - 12/11/2004 8:39 PM

I was in a fix and this really helped me out. All the methods I tried (in raster calculator and with toolbox (e.g. combine) only give me the intersection of the two rasters. THANKS!


By Anonymous - 05/08/2003 5:53 AM


By Anonymous - 03/11/2003 12:43 PM

Just the job, but one wonders why you should have to go all around the houses just to join a few rasters together in the first place.


By Anonymous - 03/10/2003 11:11 AM


By Anonymous - 02/17/2003 4:39 AM


By Anonymous - 02/17/2003 3:29 AM

It would be great to add this to the ArcMap help file.


By Anonymous - 01/28/2003 4:21 AM

Thanks a lot for this article, it's been 3 days that i tried to fix this problem.


By Anonymous - 01/14/2003 5:33 AM

why wasnt' i able to find this technique in the help section of arcmap?