Bug report #17467
Function $area
| Status: | Closed | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Field calculator | ||
| 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 |
Description
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.
History
#1
Updated by Giovanni Manghi over 6 years ago
- Resolution set to invalid
- Operating System deleted (
Windows 10) - 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.
#2
Updated by Thomas Nogatz over 6 years ago
Now I understand. Thank you very much!
Best wishes, Thomas