Bug report #21965
Different length measures between QGIS 2.18 and QGIS 3.4
| Status: | Feedback | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Field calculator | ||
| Affected QGIS version: | 3.4.6 | Regression?: | No |
| Operating System: | Easy fix?: | No | |
| Pull Request or Patch supplied: | No | Resolution: | |
| Crashes QGIS or corrupts data: | No | Copied to github as #: | 29780 |
Description
I noticed that the "$length" command returns slightly different values in QGIS 2.18 and QGIS 3.4.6 As the values in QGIS 2.18 conincide with calculation made in ArcMap, I suppose an issue with QGIS 3.4.6
History
#1
Updated by Giovanni Manghi over 5 years ago
- Status changed from Open to Feedback
$ length > "The length calculated by this function respects both the current project's ellipsoid setting and distance unit settings. For example, if an ellipsoid has been set for the project then the calculated length will be ellipsoidal, and if no ellipsoid is set then the calculated length will be planimetric"
are you sure you are using the same project properties regarding the ellipsoid being used?
#2
Updated by Florian Hruby over 5 years ago
I´m pretty sure, but maybe you could check back on your side with both QGIS 3.4 and 2.18? the shape I used can be downloaded here:
https://drive.google.com/file/d/1azK-l4w2hbW1XJicmIQkyHXDl3rnikqx/view?usp=sharing
#3
Updated by Giovanni Manghi over 5 years ago
Florian Hruby wrote:
I´m pretty sure, but maybe you could check back on your side with both QGIS 3.4 and 2.18? the shape I used can be downloaded here:
https://drive.google.com/file/d/1azK-l4w2hbW1XJicmIQkyHXDl3rnikqx/view?usp=sharing
nope, I don't have a 2.18 installation at the moment (not on the pc I'll have at hand in the upcoming days).
#4
Updated by Florian Hruby over 5 years ago
Seems that the $length command gives the planar distance in QGIS 2.18, but the geodesic distance in QGIS 3.4:
https://gis.stackexchange.com/questions/321176/different-length-measures-in-qgis-vs-arcmap
Not sure if this is intentional?
#5
Updated by Giovanni Manghi over 5 years ago
Not sure if this is intentional?
there have been changes, and they were by design.