QGIS : Digitize Detailled geometries for Water Structures (as example)

[ponceta]

With @dsavary we thought that QGIS is not so handy when digitizing alternative geometries for new objects.

Creating a water structure as a tank or eq. with a point geometry is easy.

But then to add the detailled structure, you must change layer, select the newly created line in the attribute table, add a part geometry (and not a new geometry) which is all but clear as water for the user.

With QGEP, @m-kuhn tried another approch using contextual python actions :

http://qgep.github.io/docs/fr/user-guide/digitizing/digitizingdetailedgeometry.html

A better integration of this mechanic on QGIS would be nice.

[m-kuhn]

QGIS 3 will hopefully have better integration of additional geometry columns (QgsReferencedGeometry just got merged yesterday), so we are a step closer to this. Jumping on the train here would be great!

[3nids]

@m-kuhn can you explain how QgsReferencedGeometry helps here? what would be the remaining bits?

[m-kuhn]

So far additional geometry columns were exposed as text only, now they can be exposed as (referenced) geometries.

We need tools to work on these.

Either

• An option to switch the main geometry column at runtime (I don't like that too much)
• Feature actions to work on these columns (all the "adjust geometry", "delete geometry", "add ring" etc tools)
• Multiple "sublayers" in the layer tree
• ...

[3nids]

I see, it's indeed quite promising.

[haubourg]

Is there anything new in QGIS3 concerning the additional geometry handling?

thinking of this, I think that we should keep with something less dependant of the QGIS desktop client.

I would vote for a feature action calling a stored_procedure like "select qgep_api.init_alternative_geometry('myLayer', 'myFeatureId', 'alternative_geometry_field', [object_size]);

that could create a default alternative geometry, with an optionnal default size for polygons. We could create a default octogonal or square object centered on the feature, with a default size of 2m*2m, optionnally bigger or smaller.

Thoughts?