[Qgis-user] QGIS-User Digest, Vol 228, Issue 27

[Garth Fletcher]

Is the layer CRS a projected CRS, e.g., with units of feet?
If a geographical CRS, such as WGS84, measured in degrees Lat/Long it 
won't work.

Also, does the layer include at least 1 polygon?  If not then you'll see 
"NULL".
But I've never seen "nan" in that context.

I've used the approach you describe many times.

Garth Fletcher

On 2/14/25 Marc Bordelon <marcbordelon at yahoo.com> wrote
> Subject: [Qgis-user] Calculate acres
>
> I've created a shape file, geometry is polygon, I have the CRS set as
> what the project is set at.I open the field calculator-Create a new
> field "Acres" - set the Output field type to "Decimal number (real) -
> output field length to 5 and precision to 2 - using the Geometry-
> expression: $area to calculate the acres it gives me "nan" for the
> preview. No acres.I've been able to create a new field and calculate
> acres and length (ft) with no problem.?
> I'm running qgis 3.34.7
> MarcBordelonmarcbordelon at yahoo.com