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I know this is suppose to be simple and I've found similar questions. However when I try to do the same (data management tools > projections and transformations > raster > project) inserting input (GCS_WGS84) and output (WGS84_UTM_Zone23S_SouthAmerica) coordinate systems, ArcMap still requires the choice of a geographic transformation. It shouldn't be this way. How can I transform this lat/long raster to UTM?

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  • I see no 'METHOD', only resampling technique - options should be Nearest, Bilinear, Cubic... you must decide on a resampling technique as the raster must be resampled: cells need to be rectangular, changing the coordinate system will create trapezoidal cells, to make them rectangular again the raster needs to be resampled. Then Geographic Transformation which shouldn't apply as both are on WGS84 datum. – Michael Stimson May 12 '15 at 1:46
  • I just added a screenshot of it. It all seems fine but there is that "Geographic Transformation" field. It says optional but when I hit OK I get the message "Undefined grographic transformation". Can anybody help? – Rodrigues May 12 '15 at 12:41
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Either the WGS 1984 in the original raster, or in the target UTM doesn't match Esri's definition of WGS 1984. It's probably one of the names.

If it's the original raster, try using the Define Projection tool to reset it to Esri's WGS 1984 definition.

If it's the output coordinate system, try using Esri's version instead.

  • Just tried that. The project tool finally worked, but the result is not quite pleasing. There was absolutely no distortion or change in the position of the raster from going to GCS WGS84 to PCS SAD69. That means something is wrong, right? Or perhaps the "on the fly" projection by Arcmap was already doing the projection automaticlly, and hence I saw no difference? – Rodrigues May 20 '15 at 11:11
  • Did the Project Raster tool ask for a transformation? If it didn't, it's a weird, non-reproducible bug that keeps popping up. Instead, try reprojecting in ArcMap, set a transformation, then export the raster via data, export data (using the data frame's coordinate system). – mkennedy May 20 '15 at 13:28

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