[Qgis-developer] Topology editing in QGis

[Radim Blazek]

On Thu, Oct 31, 2013 at 8:28 AM, Martin Dobias <wonder.sk at gmail.com> wrote:
> Hi Denis & Pierre
>
> On Thu, Oct 31, 2013 at 1:45 PM, Denis Rouzaud <denis.rouzaud at gmail.com> wrote:
>>
>> I put the dev list in copy, since there should be someone arond who's more
>> aware on the topic.
>> I  saw that Martin Dobias was the committer for the topology editing [0].
>> Martin, do you have any suggstion on this?
>
> Let me give some historical context first because I am afraid we are
> mixing two different things :-)
>
> For a long time QGIS has some support for "topology editing". But
> that's not a proper topology editing as one may think - from
> documentation:
> "The option  Enable topological editing is for editing and maintaining
> common boundaries in polygon mosaics. QGIS ‘detects’ a shared boundary
> in a polygon mosaic and you only have to move the vertex once and QGIS
> will take care about updating the other boundary."
>
> Originally there were separate map tools for addition, removal and
> moving of points which were also doing updates to the shared
> boundaries of polygons if the "topological editing" was enabled. The
> old commit Denis is referring to was basically meant to add the same
> functionality also to the newly created node tool that was meant to
> replace the three separate tools.
>
> Now about "real" topology editing of data consisting of nodes and
> edges - as discussed already in issue #3483, there are various
> topology models (PostGIS topo, GRASS, OpenStreetMap, ...?) that would
> need slightly different set of tools and validation methods. I have
> not really investigated if it is possible to have a support to cover
> all of those models - or even it is worth it. Maybe for a start it
> would be enough to pick one and focus just on that (PostGIS topo being
> my personal favorite).

I would prefer something generic from the beginning. We started to
talk about such common editing interface (PostGIS / GRASS) with strk
in Zurich. IIRC we were able to find common editing methods. There
should be some photos of our hand drawn schemas around and strk should
have a paper with the list of methods. Strk, could you publish a scan
of it somewhere on Web?

Radim

> In general I would love to see a new "topology" layer type in QGIS
> (next to vector and raster) that would bring native topology viewing
> and editing capabilities to QGIS. I am not aware of anyone working on
> that - if you can spend some time on that matter, I am sure you will
> make many people happy :-)
>
> Regards
> Martin
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