[Qgis-user] Different values for $area and 'Add Geometry Attributes'

[Andrea Giudiceandrea]

Hi Jochen,
I forgot to mention that the "Add geometry attributes" processing 
algorithm can calculate length, perimeter and area values either 
planimetric in the layer's CRS (as the "length", "perimeter", and "area" 
functions) or planimetric in the project's CRS or ellipsoidal (as the 
"$length", "$perimeter" and "$area" functions) depending on the 
"Calculate using" (CALC_METHOD) algorithm's parameter setting.

I suppose you have set the "Calculate using" (CALC_METHOD) algorithm's 
parameter to "0 — Layer CRS" (which is the default value) or "1 — 
Project CRS".

Regards.

Andrea

Il 13/03/2025 19:47, Andrea Giudiceandrea ha scritto:
> Hi Jochen,
> as described in the user manual, the "Add geometry attributes" 
> processing algorithm [1] "generates a new vector layer ... containing 
> geometric measurements based on a selected CRS.", i.e. it measures 
> Cartesian planimetric length and area on the CRS's cartographic plane.