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I am creating an exercise for remote sensing students and would like to take an existing raster and remove the spatial reference from the file so that the students can practice using another image to orthorectify the first. I am using ArcGIS 10.

Any hints?

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    It depends on the file format of your image. Which files do you have (.tif .prj .tfw .aux.xml ...)? – Jens May 29 '13 at 15:44
  • It is a .tif file with an .aux.xml and .ovr. – Chris Strother May 29 '13 at 15:48
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The fastest way to do this is to just delete the files that supply the spatial information related to the raster. If the image is stored as a tiff or you can just open up the folder it's stored in and delete all the files except the actual image. Then give that file to the students.

Looking at the image below, you would delete everything except the highlighted file, then distribute that.

enter image description here

I'm not certain how this would work with other raster formats that encapsulate the spatial information but you could always just export them to a tiff and then use this technique.

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    What about tiffs that store georeferencing information in GeoTiff tags in the actual tiff file, not in an external header file...? – user2856 May 30 '13 at 3:41
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Another way that will completely strip any internal GeoTiff tags is by using the GDAL gdal_translate utility to convert the tif to a baseline tiff.

gdal_translate -co PROFILE=BASELINE in.tif out.tif

I realise you are using ArcGIS, so do I, but I have found GDAL to be another valuable tool in my geospatial software toolbox. Precompiled GDAL binaries can be downloaded from the GISInternals website.

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You can define the coordinate system as unknown by using the Define Projection tool. At the point of selecting the spatial reference, click on the little down arrow as indicated below and select clear.

Define Projection Tool

  • This will remove only the header, but not the coordinates themselves. Thus, you can try to find the correct coordinate system using the search method (brute force). – Mr. Che Jan 22 at 8:43

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