Planar calculations not available in ArcGIS Pro when data stored in GCS.

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09-19-2021 07:26 PM
jvenables
New Contributor II

Can someone please confirm if Esri have in fact removed the capability of calculating planar areas when a feature class is stored geographic coordinates? This was a really useful function in ArcMap (when map is projected) but appears to not be available in ArcPro. You used to be able to chose the map projected coord system OR or the data source coord system.

If not available, is it in development, or have they just removed it?

jvenables_0-1632104712473.png

 

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DrewFlater
Esri Contributor

Thanks for bringing up this equivalency problem @jvenables 
In Pro 2.9 this problem has been solved. You will find the planar AREA and LENGTH options (not Geodesic) in the Property choicelist you pictured above, even if your data has a geographic coordinate system, as long as you specify a projected coordinate system in the Coordinate System parameter (you can choose the Current Map option in the Coordinate System choicelist if your map is projected).

Here is the planar Length property being selected for data in WGS 84, with a North American Equidistant Conic projected Coordinate System:

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DanPatterson
MVP Esteemed Contributor

Add Geometry Attributes (Data Management)—ArcGIS Pro | Documentation

you can specify the desired coordinate system for outputs


... sort of retired...
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jvenables
New Contributor II

You can specify the coordinates, but the Property field doesn't allow for planar area calcs. Even if you specify the Coord System in the box, it still calculates the geodesic area. So not actually sure what the purpose of the Coord system box is?

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DanPatterson
MVP Esteemed Contributor

Geodesic versus planar distance—ArcGIS Pro | Documentation

If memory serves since I last used the tool, the units returned are planar but the calculation is done with a shape preserving methodology when forming the perimeter of the polygon prior to area calculations.  Did you get values returned that contradict this?

Calculate Field Python examples—ArcGIS Pro | Documentation

you could always try a field calculation expression like in the above link

!shape.geodesicArea@acres!


... sort of retired...
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jvenables
New Contributor II

When I use the measure tool and select 'Planar', I get 28,400.30ha as my result, which is the result I want to add to my attribute table. When I run the area calculation tool, regardless of which coord system I select, it always returns the geodesic area of 28,391.997ha. The data is stored in GCS, so this makes sense, but I'm looking for a function that will calculate the planar area based on the current projected coordinate system of the map. ArcMap can do this with no issue, but it appears ArcGIS Pro is lacking this functionality. What I'm after is essentially a !shape.planarArea@hectares! expression, but that doesn't seem to work.

 

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DanPatterson
MVP Esteemed Contributor

I wouldn't count on the measure tool, particularly if your projection is Web Mercator which is notoriously bad for measures for distance or area.  Rely on the calculations


... sort of retired...
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DrewFlater
Esri Contributor

Thanks for bringing up this equivalency problem @jvenables 
In Pro 2.9 this problem has been solved. You will find the planar AREA and LENGTH options (not Geodesic) in the Property choicelist you pictured above, even if your data has a geographic coordinate system, as long as you specify a projected coordinate system in the Coordinate System parameter (you can choose the Current Map option in the Coordinate System choicelist if your map is projected).

Here is the planar Length property being selected for data in WGS 84, with a North American Equidistant Conic projected Coordinate System:

DrewFlater_0-1632264110741.png

 

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jvenables
New Contributor II

Thanks @DrewFlater , just wanted to know it hadn't been left off the list; last remaining function I'm still using in ArcMap. Will just have to wait for 2.9 release now :mantelpiece_clock:

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