[Qgis-developer] [Qgis-user] Please test length/area measurement in master

[Nyall Dawson]

On 16 February 2016 at 09:34, Blumentrath, Stefan
<Stefan.Blumentrath at nina.no> wrote:
> Hi Nyall,
>
> Thanks for your work on this issue(s) and esp. the unit tests.

Thanks Stefan - it's much appreciated!

>
> I did a swift test with a 100km vector grid using master version 5d989ab (which probably does not contain all your changes?).

Yes, that version is missing some of the changes (specifically the
area related changes).


> Area measurements are consistent across field calculator and identify tool. However, the field calculator (using an 8 digits numeric field) shows some minor and probably neglectable imprecisions (e.g. compared to GRASS). GRASS reports exacly 10000000000.00000000 m2, while the field calculator gives something like 10000000000 +/- 0.0005 (OTF off).

That sounds reasonable to me.

>
> With OTF on measurements differ significantly compared to GRASS and OTF off, due to ellipsoidal metric used with OTF on I guess. Personally, I find this difference confusing, but I trust the difference in behavior btw. OTF on and off is a deliberate choice of the more accurate area measure?!
>
> Choosing no measurement ellipsoid in the project settings gives the same behavior as OTF off.

It *is* a little confusing here, but I'm reluctant to change this
behaviour so close to a release. For 2.16 I'll break the link between
OTF and ellipsoid, so that regardless of the OTF status you can set a
specific ellipsoid or force planar calculations.

Nyall


>
> Kind regards,
> Stefan
>
>
>
>
>
> -----Original Message-----
> From: Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of Nyall Dawson
> Sent: 15. februar 2016 21:49
> To: qgis-developer <qgis-developer at lists.osgeo.org>; qgis-user <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Please test length/area measurement in master
>
> Hi all,
>
> Just putting out a call for extensive testing of length and area measurements in the current master version. Over the past week I've done a bunch of work trying to simplify the situation regarding length/area calculation and unit handling, with the intention of closing http://hub.qgis.org/issues/13209 and the other outstanding area calculation issues (plus locking all this down with unit tests!).
>
> I'd really appreciate thorough testing being done by users to ensure that this bug is now indeed fixed prior to the 2.14 release.
>
> Things to check:
>
> - measured length/area is consistent across the identify tool results, field calculator, and measure tool. (note that there's still an open bug regarding virtual fields - there's a PR open to fix this but it's not merged yet). Testing with different combinations of geographic/non geographic CRS, OTF projection on/off and various ellipsoid/planimetric calculations would be perfect.
> - test the new project properties settings for project distance/area units and coordinate formats
> - test the reworked options for QGIS angle units and measurement of angles using the measure tool
>
> Thanks in advance!
>
> Nyall
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