Difference in area between the Area Measurement tool and the Volume Measurement tool?

[AndrewSanford]

Is there anyone who can explain why I might be getting two different area measurements when using the Area vs. the Volume tool? I've noticed this issue before and have attempted to find an answer, but have had no luck. The main issue is when I was measuring this stockpile with the area tool, I was getting a total area of around 2000 sq. ft., however, when I measure the exact same shape with the volume tool, I was getting an area of around 900 sq. ft. I pulled my orthomosaic into ArcPro to confirm that the area presented using the volume measurement tool is more accurate.

I thought that maybe the issue had to do with the base surface option with the volume tool, but I tried changing it to interpolate, minimum, and maximum, and was getting the same area result from each. No matter what I tried with the area tool, I was getting values over twice what the true values should be. 

What is causing this discrepancy in measured values?

[CodyBenkelman]

Hi Andrew - apologies for the long delay on this, and for the confusion.  We need to make a change in the software as well as documentation to address this.  Both measurements should be correct, but we need to clarify what is being measured.  

As you've observed, the VOLUME tool also reports the area of the polygon you've entered.  In this case, it is reporting the the planimetric (2D) area of the polygon projected onto a flat map.

The AREA tool actually calculates the surface area inside your polygon.  So, if you think about measuring a gravel stockpile, the surface area tells you how many square feet of paint would be required to cover it.  If you test a flat area, the numbers should be close, but otherwise the AREA tool is always going to report a larger value. 

We're working to clarify this in the documentation, and my hope is to update the software to define and report both area measurements, no matter which tool you use.  I feel both have value, but we need to be explicit about what is being reported.

Cody B.