ArcGIS Pro 3.x: What happened to 'Acres'?

[ZacharyHart]

We've noticed a slight change in the Calculate Geometry Attributes tool. 

Here are the area units in the 2.9.x tool reference:

Here are the area units in the 3.x tool reference:

Questions: 

1. Were 'Acres' before 3.x always US Survey Acres?
2. Does this have anything to do with this Federal Registrar Notice?

It's also curious this geoprocessing appendix does not exist prior to 3.x. 

[curtvprice]

Yes this is new. From the What's New in ArcGIS Pro 3.0 under Analysis and Geoprocessing / General

The majority of geoprocessing tools with linear or areal unit parameters have been updated to include both US Survey Foot-based units and International Foot-based units.

I think it's a safe bet that US Survey Foot acres were the old ones used. They are pretty close but the time has finally come to finally go to international foot when one can. They've only been urging it since 1959. 😀

US Survey Foot FAQ

[ZacharyHart]

That's totally in line with the documentation  as well as the federal registrar link we provided.

However, and I'm waiting for confirmation: geometry calculations for 'Acres’ vs the US Survey Acres seem to yield a slightly different result,but we are testing further.

Can you confirm parity/exact acreage calculation via the same tool and parameters for the data you manage?

[ZacharyHart]

@curtvprice 

A colleague of mine went ahead and actually tested this out using a feature class containing the state of Vermont. I can provide the actual PCS that was used, but it is an equal-area projection.

Current findings:

• We are unable to match acres as previously calculated in ArcMap 10.8.1
• The difference is minimal but it does exist. 
• ArcGIS Pro 'Acres' previous to 3.x appears to match International Acres.
• The closest match to ArcMap 'Acres' is Area(geodesic) International Acres.

[curtvprice]

The PCS truly matters for this test because it includes the linear unit used (foot or international foot) Also the equal area projection will be more or less equal area for the polygon in question depending on how close it is to meridians and parallels used.

Thanks for this test it is useful. At this point I recommend (and ask) for you to file an incident report with Esri and share what you learn from them here in this thread.

[ZacharyHart]

@curtvprice  We've not yet found the time to engage with tech support regarding this yet.

[GB_-_MariahBlackhorse__READ_]

This is interesting.  My understanding was that Arcmap did Planar calculations only while Pro now has the geodesic option so that calcs can be done that account for the curvature of the projection (using the geodesic option). 

It appears there are two different factors then, the planar vs geodesic area for the calc and the International vs US Survey area.