Bug report #19437
WGS84 geometry.area() returns -1.0
| Status: | Closed | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Geometry | ||
| Affected QGIS version: | 2.18.21 | Regression?: | No |
| Operating System: | Windows 10 | Easy fix?: | No |
| Pull Request or Patch supplied: | No | Resolution: | end of life |
| Crashes QGIS or corrupts data: | No | Copied to github as #: | 27265 |
Description
Steps to reproduce¶
1. Create or load a vector layer with polygon type, add some polygons. The CRS needs to be WGS84 (EPSG: 4326).
2. Select one or more features.
3. Type the following code in the console.
iface.activeLayer().selectedFeatures()[0].geometry().area()
Observed behaviour¶
"-1.0" is printed to the console.
Expected behaviour¶
A positive numer is printed to the console. This number should be the area of the selected polygon in square meters.
Further remarks¶
I'm regularly experiencing crashes when working with these APIs (in combination with that CRS). I guess that this may have common causes.
Best regards,
Georg
History
#1
Updated by Georg Wicke over 6 years ago
Actually, I am experiencing crashes when accessing "area()" when copying the geometry first.
I.e.: Type the following code in your QGIS console instead to get a crash:
QgsGeometry(iface.activeLayer().selectedFeatures()[0].geometry()).area()
#2
Updated by Georg Wicke over 6 years ago
Another small correction: It works for newly created scratch layers, but it definitely fails when saving the layer and then reloading it in a new instance of QGIS. I.e.:
1. Create a new scratch layer (vector, polygon)
2. Draw a feature
3. Finish editing
4. Save the scratch layer to file (e.g. ESRI shapefile or GeoJSON)
5. Close QGIS
6. Re-open QGIS
7. Open your saved layer
8. Select some feature
9. Type one of the lines that I mentioned previously into the console
#3
Updated by Nyall Dawson over 6 years ago
- Status changed from Open to Feedback
Please test by first storing a reference to the feature:
f=iface.activeLayer().selectedFeatures()[0]
area=f.geometry().area()#4
Updated by Georg Wicke over 6 years ago
- Status changed from Feedback to Open
Yes, that is a workaround. Is it documented somewhere? Storing a reference to the geometry doesn't seem to be enough.
#5
Updated by Jürgen Fischer almost 6 years ago
- Status changed from Open to Feedback
Please test with QGIS 3.4 - QGIS 2.18 reached it's end of life.
#6
Updated by Giovanni Manghi over 5 years ago
- Resolution set to end of life
- Status changed from Feedback to Closed
End of life notice: QGIS 2.18 LTR
Source:
http://blog.qgis.org/2019/03/09/end-of-life-notice-qgis-2-18-ltr/
QGIS 3.4 has recently become our new Long Term Release (LTR) version. This is a major step in our history – a long term release version based on the massive updates, library upgrades and improvements that we carried out in the course of the 2.x to 3x upgrade cycle.
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