Georeferencing > Unable to add control points after changing Coordinate or Projected Systems

[SaraJL]

Hello everyone!

I'm running into an issue in ArcGIS Pro (latest version) - I'm trying to georeference an image, and I'm able to add control points until I change the Coordinate/Projected System. For example:

• Add an image
• Add some control points - save the Image
• Close out the Georeference window
• Switch to a different Coordinate or Projected System (any one)
• If you reopen the Georeference panel for the image - most of the Georeference panel is grayed out

Any thoughts? I've been finding the only way to reactivate the buttons is to completely delete the image and start from scratch again. I know in the past I was able to re-add control points multiple times, so it's a little odd.

Thank you!

[RTPL_AU]

Hi @SaraJL 

I think it is made that way in order to not get unexpected behaviour or have images woosh off to the never-never.

Technically it isn't big deal (don't let surveyors see this)  if you mix some datums of the same basic projection- for us skipping between WGS84 UTM & GDA2020 MGA is ~2m difference and for an image scanned off a paper map that hung in a geologist's cupboard for 50 years it really doesn't matter. 
Processing the real transformation takes a few cpu ticks but overall it is just a translate/rotate to get pretty close or dead on.

The same cannot be said for mixing your Lamberts & geographics, etc. While numerically/mathematically possible for Pro to figure out what's going on and keep track of it all behind the scenes during the process, I feel it is a good thing to just not allow it. I don't see how they can make it performant and allow any combination of projections out there in the wild.  

There are some transformations that introduce a level of error - I don't know how that would  be managed in a georeferencing process where the introduced error could be larger than the image accuracy (e.g. high res image with visible surveyed monuments, etc). 

[SaraJL]

@RTPL_AU I think the main challenge was the image that is being used for referencing - there wasn't a projection or coordinate system that was noted for that particular image. So I had to do some guess work a bit - but it ended up not quite working, so I needed to switch it to something else.

In the past - I didn't run into the issue where the panel would completely lock out. For example - I had to create some post-WW2 boundaries of Germany and France for a client's book project once, and that also required a little bit of guesswork because the historical map image didn't quite fit with the typical Mercator projection. So I could close the georeferencing panel, try a different projection, and then when I reopened the georeferencing I would usually have to redo the control points, but the entire panel wouldn't be grayed out. 

In this case, the only way I could reactivate anything was to completely delete the image and re-add a new one from scratch. I couldn't even switch back to the previous projection to reactivate the panel, which was a little odd. It was almost like it was caching information in some weird way.

[DEAF_PROBERT_68]

Hi,  I am trying to remember that I had the same issue but in a different way ... your steps is kind of confuse to me but I guess maybe you have a different workflow.....

So I googled and found this and see if you have not tried this until I post this .

https://support.esri.com/en-us/knowledge-base/problem-georeferencing-tools-are-disabled-in-arcgis-pr...