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I have a raster dataset that is projected with the "NAD_1983_Albers" projected coordinate system and a shapefile projected with "WGS 1984 Web Mercator (auxiliary sphere)."

I am trying to use the Zonal Histogram tool with these data. When I use Zonal Histogram on the data with their original projections it seems to work correctly. However, when I reproject the raster data to the shapefile projection coordinate system and run the Zonal Histogram tool the output seems incorrect. By incorrect I mean the area reported in the histogram does not match the area of the shapefiles.

Why do these reprojected raster data not match up when using Zonal Histogram? Is the reprojection of the raster data necessary?

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  • Welcome to GIS SE. As a new user, please take the Tour. The area reported by Web Mercator is going to be extremely wrong. You should project the vector to the raster's projection.
    – Vince
    Dec 11, 2023 at 16:24
  • Just checking--did you use the Project Raster tool or the Define Projection tool?
    – mkennedy
    Dec 17, 2023 at 16:12
  • I used Project Raster. I ended up reprojecting the shapefiles to match the raster projection and that worked out fine.
    – Ben M
    Dec 18, 2023 at 20:46

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I would ensure both datasets are in the same coordinate system so projecting one into another was the correct thing to do. There is always some level of distortion when you project data and unless you polygons were derived from the raster you would never expect to see a close match in area. Reading the Usage section of the help file for the tool will also provide further advice on expected tool behaviour.

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