SArea does not match F_Area?

[BobChristensen]

Greetings,

I am using 3D analyst to calculate the volume of a reservoir using the Polygon Volume tool.

As part of the process the polygon volume tool calculates a surface area for the polygon. I am confused as to why the surface area calculated by 3D Analyst is different from the surface area calculated by the spatial statistics tool. I would like to have a fairly high degree of confidence in the volume calculation and the different surface volume calculations have got me wondering...

See attached.

Thanks,

b

[TimBarnes]

Is it because 3D analyst is measuring the 3D surface area (i.e. taking into account undulations/slope etc) whereas the spatial statistics tool is just measuring 2D/planar area?

Alternatively, if you have been editing shapefile polygons in between calculating the values, then the area calculations will need to be re-run to incorporate the edits.