At 10.7.1, here's the first part of a model I am creating. Please note that I have parameterized the input and output:

enter image description here

My problem is within the Project tool: I want it to always use the same datum transformation, but I am unable to get that transformation to appear. When editing the model, I can drop-down the tool's transformation list, but I cannot make the selected transformation "stick" in the transformation box; the box remains blank. Weird, because I can select the desired Output Coordinate System just above.

I think that the problem has to do with the parameterized input, because if I hard-code an input shapefile, the transformation sticks.

enter image description here

How do I "force" the desired transformation to appear in the model while still allowing parameterized input?


For this tool, the input data will always be NAD83 (specifically: NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet

and the output data will always be NAD83 HARN (specifically: NAD_1983_HARN_StatePlane_Washington_South_FIPS_4602_Feet / VCS:NAVD_1988)

When I Project these two manually, Arc offers a variety of transformations. I always select:


This is the transformation that I want to force my tool to use.

  • 1
    A GeogTran is only necessary if the source GCS is not based on NAD83, at which point, the UI will offer all the potential transformations.
    – Vince
    Mar 5, 2020 at 17:58
  • @Vince good point! That's probably the issue.
    – Hornbydd
    Mar 5, 2020 at 18:33
  • Both good comments, thanks. But in my case I need a transformation. Please see my edited post.
    – Stu Smith
    Mar 5, 2020 at 22:42
  • Stu you could try creating a model variable and set it to the required transformation and link it to the tool parameter, pretty much as I show in my answer?
    – Hornbydd
    Mar 6, 2020 at 9:22

1 Answer 1


I'm using ArcMap 10.6. My test scenario is projecting from BNG to WGS84.

I set up the following model and when I set the output coordinate system in the Project tool it auto-selected the transformation for me. I then exposed it as a parameter


So everything worked for me. The only thing I can think of is does your input dataset have a coordinate system? It would need one for project to even work.

  • Your kind efforts really helped. Although parameterizing the GT works, it unfortunately forces the user to drop-down and select the desired transformation every time the model run - and that transformation value will be the same every time. That's why I'm searching for a way to hard-code that transformation into the model.
    – Stu Smith
    Mar 6, 2020 at 15:17
  • @StuSmith I suspect the Projection tool is doing some sort of internal validation which is causing the drop down to reset and not stay as transformation you have set.
    – Hornbydd
    Mar 6, 2020 at 15:57

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