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Custom Geographic Transformation Logic?

Question asked by lsmh_COWI on Oct 16, 2018
Latest reply on Jan 8, 2019 by MKennedy-esristaff



I need help on understanding the logic in setting up and using custom geographic transformations in ArcGIS Pro. I think I've read everything I was able to find online incl. several issues here on GeoNet. I would like to take advantage of a Custom Geographic Transformation in the "Project"-geoprocessing tool or as an alternative in the "Copy Feature"-tool (Environments-part) in Model Builder. If ESRI were to implement an "Epoch"-parameter when converting between WGS84 and ETRS89 making it possible to specify Year (WGS84 and ETRS89 are getting more and more different (I think it is around 60 centimeters currently) we would not have to set up our own custom transformations but I don't know if there are any plans on implementing this?


I've created a gtf-file using the "Create Custom Geographic Transformation"-tool (Position Vector containing 7 parameters) and the gtf-file gets created and is found in %appdata%\ESRI\ArcGISPro\ArcToolbox\CustomTransformations. I am able to find, apply and take advantage of the custom transformation in Map Properties (please refer to Map_Properties.jpg) and the transformation seems to work but when exporting data I am not able to apply the custom transfromation in order to get a dataset containing transformed coordinates. I noticed that in ArcMap the user is asked whether or not to use the coordinate system definition of the data frame when exporting and in this case the data gets transformed but unfortunately not in ArcGIS Pro.


I am also able to find and specify the transformation in the Project-tool but for some reason it is saying that it is invalid (please refer to Project-error-message.jpg). Does the Project-tool compare type of custom transformations with coordinate systems in such a way that I am only allowed to apply e.g. a Geocentric Translation when converting between ETRS89 and WGS84 and not the Position Vector type of transformation? It seems to accept the "standard" custom transformation supplied with the software (please refer to Project-message.jpg). What is the difference between these two transformations? Is the ETRS_1989_To_WGS_1984 a .gsb-file?


As an alternative I was thinking about specifying it in the Environments-part of the Copy/Copy Feature-tool but in this case the custom transformation for some reason doesn't show up in the drop down box (please refer to Copy_Environments.jpg.). What does it take for my custom transformation to show up in this drop down list? The "standard" ETRS_1989_To_WGS_1984 seems to also be included in this list. Is the ETRS_1989_To_WGS_1984 a .gsb-file and if that is the case how do I create a .gsb-file? I haven't been able to find out how by using google :-)


A lot of questions; I know; In short I would just like to know how to take advantage of a custom transformation (Position Vector) in ArcGIS Pro when transforming data between WGS84 and ETRS89? :-)


Kind regards,