Bug report #17467
|Affected QGIS version:||2.18.9||Regression?:||No|
|Operating System:||Easy fix?:||No|
|Pull Request or Patch supplied:||No||Resolution:||invalid|
|Crashes QGIS or corrupts data:||No||Copied to github as #:||25364|
The function $area (field calculator) does not deliver reliable values in every case.
I have attached two example projects using the same shapefile. Both projects and the shapefile use the same projection (EPSG:25833).
The field "area_1" has been calculated by "export/add geometry columns", which delivers correct values in every case.
Field "t_$area2" was calculated using "$area" in project "01.qgs". The field "diff2" = abs("area_1"-"t_$area2") indicates that $area calculates correctly.
Field "t_$area3" was calculated using "$area" in project "02.qgs". The field "diff3" = abs("area_1"-"t_$area3") indicates that $area calculates not correctly.
Project 01 is a new created project.
Project 02 is a project deriving from a different project with much more layers (vector, raster, wms) which I have deleted for this test.
The Problem exists in older QGIS versions as well.
#1 Updated by Giovanni Manghi about 5 years ago
- Resolution set to invalid
- Operating System deleted (
- Status changed from Open to Closed
- Category changed from Expressions to Field calculator
The point is that in project 2 you have OTFR enabled and set an ellipsoid (wgs84) for measurements (in project properties), in project 1 you don't have OTFR enabled so it use the plane for measurements. If in project2 you set the ellipsoid to "none/planimetric" you get the same values.