topic Re: Define Projection crack-down in ArcGIS Pro Questions

Define Projection crack-down

AustinStreetman — Wed, 28 May 2025 18:09:13 GMT

With ArcPro 3.5, ESRI has cracked down on letting us define the projection on a feature class that has a projection. We have been importing an existing schema from an XML and then using Define Projection in a model to redefine the projection for the new project. In 3.5, this no longer works. We tried it in arcPy as well.

This seems like an unfortunate level of hand-holding. ESRI should trust users to know when it is appropriate to redefine a projection.

Re: Define Projection crack-down

Nick_Creedon — Wed, 28 May 2025 18:22:06 GMT

@AustinStreetman I am not in Version 3.5 yet, this doesn't seem like this is intentional. I would reach out to support about your issue. As long as the tool is in ArcGIS Pro you should still have the capability to change the projection.

Re: Define Projection crack-down

RyanUthoff — Wed, 28 May 2025 18:47:49 GMT

I am not able to replicate this behavior in 3.5. Per the 3.5 documentation, it states: "when a dataset with a known coordinate system is input to this tool, the tool will issue a warning message but will run successfully."

I don't think Esri intentionally took away that functionality. I suspect it's just a bug. You'll probably have to reach out to support and see if they can reproduce the issue on their end.

Re: Define Projection crack-down

DanPatterson — Wed, 28 May 2025 19:12:05 GMT

If you compare the 3.5 to previous versions at

Define Projection (Data Management)—ArcGIS Pro | Documentation

you will notice that there are new restrictions. I can't tell from your code and the files whether this is what you are running up against. Have a look and compare to your previous version using the "Other versions" toggle

Re: Define Projection crack-down

DavidPike — Wed, 28 May 2025 19:44:21 GMT

Certainly run the test in Pro GUI or get and print print the actual error. This could be many different things from switching versions.

Re: Define Projection crack-down

DavidSolari — Wed, 28 May 2025 19:45:50 GMT

Comparing 3.5 to 3.4 in detail, I don't see any new restrictions, there's just more clarifications for why you can't run the tool on EGDB or Feature Dataset classes (as well as workarounds).

@AustinStreetman if you try to define projections for some troublesome data using just the tool interface (no arcpy) do you get a better error message?

Re: Define Projection crack-down

ChristalHigdon_USFS — Tue, 10 Jun 2025 00:04:26 GMT

We use the DefineProjection tool extensively in arcpy for a scripted process that we re-run during development and migration into ArcGIS Parcel Fabric. In prior versions (3.4 and earlier) there were no issues. We have Pro 3.5.0 and all of a sudden I am getting an error ("ERROR 000146: Cannot alter the spatial reference"), in both arcpy and Pro/UI Toolbox for Define Projection. I am trying to open an Esri case because this seems like a bug. I think it should still run with warning as it always has if there is already a projection defined. There is no way to set Unknown spatial reference, so what if you make a mistake, or are conveniently using it to set up a new gdb that does not have any data in it yet?

Re: Define Projection crack-down

MollyJackson — Thu, 12 Jun 2025 23:00:21 GMT

I didn't see this thread when I started my own thread on the topic. My thread I am running into the same issue with the upgrade to 3.5. At first I thought it was because I was trying to use Define Projection on an undefined dataset. With further testing today, I am unable to use Define Projection on any dataset or feature class with a previously defined coordinate system either. If you read my thread, you'll see ESRI's response when I submitted a case. They told me I'm out of luck--it's a known error, and they don't plan on changing it.

I also just got off a chat with a support analyst, and here is the response I was given: "Geodatabase feature datasets and feature classes are not designed to have their coordinate systems changed after creation. The ability to update the coordinate system on feature dataset was an oversight and should not have been allowed. At ArcGIS Pro 3.5, that loophole was blocked. The change was on purpose. The new workflow is to make sure that a feature dataset or feature class has the correct coordinate system upon creation."

The ArcGIS Pro documentation states that the Define Projection tool: "Overwrites the coordinate system information (map projection and datum) stored with a dataset. This tool is intended for datasets that have an unknown or incorrect coordinate system defined."

But it apparently doesn't anymore. There are a number of caveats in the documentation.

Re: Define Projection crack-down

Nick_Creedon — Fri, 13 Jun 2025 11:23:57 GMT

Thank you for this update. This is good to know. The "Project" tool is probably the better way to go, especially when the data is already projected one way. It will add the proper transformations to the data, but it does create a new layer that you now have to work with.

Project Tool: https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/project.htm

Re: Define Projection crack-down

ChristalHigdon_USFS — Fri, 13 Jun 2025 15:45:49 GMT

It is not the better way to go in 3.5, as it loses a bunch of our data structure in the parcel fabric dataset:
Before Project:

After Project:

Even some of the out-of-the-box relationships Esri creates automatically in the Parcel Fabric get lost using the Project Tool. Really kills our workflow and productivity to make this change to the Define Projection tool, with no mention in the release notes, and no working alternative for our use.

Re: Define Projection crack-down

DavidPike — Fri, 13 Jun 2025 20:08:42 GMT

Seems like the opposite of an enhancement. Cui Bono?

Re: Define Projection crack-down

MollyJackson — Thu, 26 Jun 2025 17:40:19 GMT

After two cases with support services regarding this issue, I've basically been told there's nothing they can do, and I should submit my request to ArcGIS Ideas. So here it is. The more kudos an idea gets, the more visible it is to developers:

https://community.esri.com/t5/arcgis-pro-ideas/allow-define-projection-to-work-like-it-used-to/idi-p/1627343

Re: Define Projection crack-down

javalos — Mon, 11 Aug 2025 15:29:03 GMT

I'm having the same issue! Hate that I have to uninstall and go back to 3.4 just to use an out-of-the-box Solution ESRI created themselves for user ease.

Re: Define Projection crack-down

DarylHochhalter — Thu, 11 Dec 2025 13:56:41 GMT

Yes, but also states it won't work on a DS with an existing feature class.

Re: Define Projection crack-down

DarylHochhalter — Thu, 11 Dec 2025 13:59:49 GMT

I jumped from 3.1 to 3.5, it worked in 3.1 for sure. The new 3.5 version greatly reduces the usefulness of the tool. I had to run the same script on a machine that still has Arcmap in order to get it to work on existing data. Nothing short of a ridiculous change!

Re: Define Projection crack-down

DarylHochhalter — Thu, 11 Dec 2025 14:00:59 GMT

Unfortunately it's not a bug, but an intentional change like the original post indicates!

Re: Define Projection crack-down

DarylHochhalter — Thu, 11 Dec 2025 14:02:11 GMT

Project is something you are trying to avoid if you are using the define tool!