topic Area Calculations Not Returning Correct Value in ArcGIS Pro Questions

Area Calculations Not Returning Correct Value

mpboyle — Wed, 14 Dec 2022 19:01:56 GMT

Can someone explain to me how to get consistent area results from a hosted feature layer? Below is an example from one of our polygon hosted feature layers.

If I bring a hosted feature layer into Pro and use the Arcade area function or manually calculate the area (which should be sq meters because the hosted feature layer is using Web Mercator) to acres, I get an incorrect value when the map is in Web Mercator.

If I change the coordinate system of the map to State Plane, which is the coordinate system of the source geometry, the Arcade function returns the expected area value, but the manual conversion is still way off, see screenshots below.

Label expression being used in all screenshots

Arcade function and manual calculation are incorrect when map is in Web Mercator.

If I change the map to State Plane, the Arcade area function is now showing the expected results, while the manual sq meter to acres calculation is still way off.

The problem persists to the Map Viewer in AGO. If I use the Arcade area function, I'm getting an incorrect value because the map viewer is in Web Mercator.

Is there a reason the Arcade area function is not returning the expected area value when the map is in Web Mercator? Is there some sort of conversion that needs to be done prior to performing the area function? Is there a reason the manual sq meter to acres calculation is not correct...?

Re: Area Calculations Not Returning Correct Value

Luke_Pinner — Wed, 14 Dec 2022 20:53:17 GMT

Measuring distances and areas when your map uses the Mercator projection

Re: Area Calculations Not Returning Correct Value

mpboyle — Wed, 14 Dec 2022 20:56:58 GMT

So...when will Arcade have a Geometry function that supports projecting a feature to a different SRID...?

Re: Area Calculations Not Returning Correct Value

Luke_Pinner — Wed, 14 Dec 2022 22:07:04 GMT

Should get a more accurate result with AreaGeodetic https://developers.arcgis.com/arcade/function-reference/geometry_functions/#areageodetic

Re: Area Calculations Not Returning Correct Value

mpboyle — Wed, 14 Dec 2022 22:12:13 GMT

Thank you! These areas are showing expected values.