project on the fly warning symbol in Edit group of Contents Pane

[MariahBlackhorse1]

I am encountering an interesting issue with the project on the fly warning showing up in ArcPro editing group even though the layers are projected to the same spatial reference.

I have tracked it down to the difference between NAD 1983 UTM Zone 11N and NAD_1983_UTM_Zone_11N (spaces vs underscores in the name of the projected spatial reference).

The map uses the version with spaces and all layers using THAT version do not show the warning, all layers using the underscore version do.

There isn't actually any difference between the two projections is there?

[DavidPike]

Is the data from an enterprise GDB?  Some databases can have very slight differences (usually legacy before EPSG standardisation I guess) in definitions of ellipsoid/datum/degree precision etc.  

I'd have a look at the parameters for both and look for any differences.

[MariahBlackhorse1]

I did more extensive testing this morning and using the same input dataset I chose the projected coordinate system with Spaces or Underscores (two tests).

Using the same input feature class I PROJECTed the output to NAD 1983 UTM Zone 11N choosing either the 'spaces' version or the 'underscore' version.  The resulting output differs in SPHEROID and some subsequent parameters (Details attached). 

Output Coordinate System PROJCS["NAD_1983_UTM_Zone_11N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-117.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]

Output Coordinate System PROJCS["NAD_1983_UTM_Zone_11N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["Geodetic_Reference_System_of_1980",6378137.0,298.2572221008916]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["false_easting",1640416.66666667],PARAMETER["false_northing",0.0],PARAMETER["central_meridian",-117.0],PARAMETER["scale_factor",0.9996],PARAMETER["latitude_of_origin",0.0],UNIT["Foot_US",0.3048006096012192]]

[DavidPike]

The custom one is also in feet.  I'd have a strong suspicion that this is either a user-created system or more-likely a system used by a spatial database like Oracle etc. which has then been exported as a feature class.  The underscores in the name also likely come from the geometry metadata from that database - rather than being an Esri thing.  If it was an Esri system it should have an Esri WKID rather than 'custom'.

[MariahBlackhorse1]

I noticed that as well, the UNIT Foot, but I have zero idea where that might be coming from.  I just choose from the projected coord system options during the PROJECT operation and go on my merry way.  Where do these options come from in the menu then?

[MelitaKennedy · Accepted solution]

What is confusing the issue is because the coordinate system properties pages in ArcGIS Pro show the coordinate system names without underscores, but if you look at the actual definitions, the underscores are there. Internally, when we compare two coordinate systems, we usually ignore underscores/spaces so if everything else is the same, that type of difference in the names won't matter. 

We've also changed the UI so that doing a save as/defining a custom coordinate system usually won't allow you to use the same name as an existing coordinate system but that was a relatively late change. 

The well-known ID, 26911, is the ID for the meter version of UTM zone 11N. The closest we come to a US survey feet version for NAD 1983 zone 11N, is the "BLM" zones. EPSG:4431 is the equivalent, but the name differs: 

NAD_1983_BLM_Zone_11N

In the coordinate system picker, if you're seeing all layers that use both definitions (meter-based and US foot-based) under the same coordinate system name under "Layers", then that could be a bug. We're probably sorting the layers into different "folders" based on their coordinate system's name. With both definitions using the same name, that would make it tricky to differentiate them. 

The software can easily reproject between the two definitions. You would likely only notice if you check attributes for the lengths or areas or did some analysis where the output values were in the layer's units and it wasn't what you expected. 

In the coordinate system picker, if you look under "projected coordinate systems", UTM, NAD 1983, and check its parameters, you'll see its unit of measure is meter. 

Melita

[MariahBlackhorse1]

Thank you.

I did another test session this morning with a new project and now I understand what you mean about the 'layers' that show up where I select the coordinate system.  With a fresh map and only one added layer (which came in with just a geographic coord system) I projected that and only had the 'spaces' option of the NAD 1983  UTM Zone11N available to choose.  So that other 'underscore' version must have come from some other layer in that other project I was working in.

I will be on the lookout for it now.