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With ArcGIS for Desktop, I tried a datum conversion of Transverse Mercator ED50 Datum to Transverse Mercator WGS84 Datum.

Normally, the difference between two projections is approximately 180 meters but when the conversion is completed with ArcGIS' "Project" tool, the shift of the two features becomes 80 meters, not 180 meters.

On a projected data frame, ArcGIS shows the exact same place for two datums, which is an expected issue, but in fact the WGS84 one is not at the correct location.

After completing this process with a different software I opened two features on the same data frame with an ED50 datum.

Features are not on the exact locations and there is approximately 100 meters visualization error (it means, the datum conversion error of the ArcGIS is 100 meters):

True datums and coordinates (Data Frame is ED50)

A data frame without a projection and datum shows the real difference between the datums, which is approximately 180 m:

enter image description here

Is this a known issue with ArcGIS or is there a solution for converting ED50 to WGS84 with "Project" tool of ArcGIS correctly?

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I was wondering if you have used the correct transformation when you did the projection? I opened up the tool and projected from WGS84 to European 1950 and there was a bewildering list of transformations. I found this document on-line which lists the appropriate area of use, this may help?

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  • I think this is the solution of the problem. ArcGIS chooses transformation parameter automatically while converting a file or personal database to another but while converting shp to shp it does not choose one. I did not realize this while I was converting datum of a shapefile. Now I can fully understand with the list you share. Thank you very much.
    – mkturkeri
    Commented Jun 25, 2014 at 12:40

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