[Qgis-psc] Grant progress report: Add vertical CRS handling to QGIS

[Marco Bernasocchi]

9Thanks a lot Nyall, i just noticed I never answered.

That is really great! And indeed I think a clear communication of where
this is used is the most beneficial way. We for sure don't want a GIS team
to mess-up a multi-million projeect somewhere ;)

Thanks again!

Marco


On Thu, 1 Aug 2024, 20:38 Nyall Dawson via QGIS-PSC, <
qgis-psc at lists.osgeo.org> wrote:

>
>
> On Fri, 2 Aug 2024 at 03:23, Régis Haubourg <regis at qgis.org> wrote:
>
>> Wow Nyall. This is huge.
>> Thanks for the very clear explanations and the cautious path you took to
>> avoid regressions.
>>
>
> Thanks for the kind words Régis!
>
> We will have to make some noise in the deodetic and topographic
>> communities that QGIS is now fully z aware.
>
>
> I agree, and it would be fantastic to have eyes on this and more feedback
> from domain experts! One thing on my mind is that we should try to be quite
> cautious about how we describe this functionality and be explicit about
> everywhere in QGIS where vertical datums are respected. (I.e. for vector
> and point cloud layers in elevation profiles, identify results and 3d map
> views). There's still many places in QGIS where we are using z values
> without any handling of vertical transforms, e.g. in all the processing
> tools. And then there's all the plugins which may be doing calculations and
> analysis based on Z without any consideration of this too 😬. So I'd love
> us to take the approach that we always advertise exactly where the
> transform is used, just to reduce the risk of someone getting misleading
> results from a tool which doesn't support these. (I once worked in an
> office where someone messed up a multi-million dollar engineering project
> because they incorrectly handled the vertical datum for a bunch of surveyed
> elevation points. Fun times. I was just glad it was someone from the
> CAD/design team, and not GIS who was responsible! 😅 )
>
> Nyall
>
>
>
>
>
>> Hats off
>> Régis
>>
>> Le jeu. 1 août 2024, 05:26, Nyall Dawson via QGIS-PSC <
>> qgis-psc at lists.osgeo.org> a écrit :
>>
>>> PSC,
>>>
>>> I'm writing to provide an update on the grant for QEP 267 -- Add
>>> vertical CRS handling to QGIS.
>>>
>>> This project has been underway since the grant application, with work
>>> being slowly "drip-fed" into QGIS over the last year's worth of releases.
>>> All work has been done in a step-by-step, atomic approach, to ensure that
>>> every little part of it is thoroughly reviewed and that no regressions have
>>> been introduced before moving to the next step. This approach was taken to
>>> reduce the risk of regressions in our critical transformation code. I've
>>> been carefully monitoring the issue tracker after each part is merged (and
>>> after each stable release during this time) to watch for any regression
>>> reports, and thankfully we've avoided them so far!
>>>
>>> Work which has been completed to date includes:
>>>
>>> - As of QGIS 3.34, QGIS can now create and handle vertical and compound
>>> CRSes. (Prior to this work QGIS was limited to creation and handling of
>>> horizontal CRS only, for various legacy reasons). There are a range of new
>>> PyQGIS API calls which make creation of vertical and compound CRS easy, and
>>> to make it possible to eg query the vertical component of an existing
>>> compound CRS.
>>> - In QGIS 3.36 the coordinate reference selection widgets were updated
>>> to offer choices of 2d only, compound, or vertical only CRSes. We use these
>>> in QGIS itself, but plugins can now also offer users choices of eg "pick a
>>> vertical CRS" where ONLY vertical CRSes are offered.
>>>  - In QGIS 3.34 coordinate transforms were reworked so that they
>>> function correctly with vertical transformation, if both the source and
>>> destination CRS have vertical components. (We delegate the actual
>>> transformation to PROJ, but QGIS itself no longer gets in the way and
>>> forces 2d only transformations!)
>>>   - In version 3.38 we introduced a new setting for QGIS projects, for
>>> their vertical reference system. Users can control this through project
>>> properties, and it's accessible via PyQGIS and via associated expression
>>> variables (eg @project_vertical_crs) for use in print layouts.
>>> - Similarly, in 3.38 we introduced the API support for map layers to
>>> have a vertical CRS. (This was not exposed to users in 3.38 though)
>>> - In QGIS 3.40 so far we have exposed the vertical CRS setting for
>>> vector layers to users (via the layer properties dialog), allowing users to
>>> specify the associated vertical CRS for these layers. The vertical CRS is
>>> respected in elevation profile plots, in Identify tool results, and in 3D
>>> Map views (assuming the 3D map is created with an associated vertical CRS).
>>> - There is an open pull-request for 3.40 to expose the vertical CRS for
>>> point cloud layers in a similar way, with the vertical CRS being respected
>>> in elevation profiles, identify tool results, and 3D map views
>>> - We have open pull requests for 3.40 to show layer vertical CRS
>>> information in the layer properties "information" pages, and add expression
>>> variables at the layer scope (eg @layer_vertical_crs).
>>>
>>> While the work conducted to date satisfies the original target
>>> deliverables of the grant*, we also accounted for follow ups to this work
>>> as user feedback and tickets are submitted. We'll continue to monitor the
>>> QGIS issue tracker and mailing lists for these reports, and (where
>>> appropriate) will address them in future releases.
>>>
>>> Kind regards,
>>> Nyall
>>>
>>> * We've gone a little further than the original deliverables here, and
>>> have implemented some of the functionality originally identified as "out of
>>> scope"! 😁
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>   - QGIS map layers also have individual settings for the vertical
>>> reference system. This isn't YET exposed for user control. Before I expose
>>> this setting I want to ensure that the layer type correctly uses vertical
>>> transforms in the elevation profiles, in 3d views, and in the identify tool
>>> z values. This will definitely be done for vector layers in 3.40, (and
>>> hopefully the other layer types too)
>>> _______________________________________________
>>> QGIS-PSC mailing list
>>> QGIS-PSC at lists.osgeo.org
>>> https://lists.osgeo.org/mailman/listinfo/qgis-psc
>>>
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