[gdal-dev] format for topology?

[Even Rouault]

Michael,

you won't find much support for that in GDAL itself. You'd better have a 
look at Spatialite topology, PostGIS topology or GRASS topology. The 
process is basically: import your geometries as a topology,  do 
reprojection or other work in the topology domain, and go back to the 
geometry domain.

QGIS has a plugin to work with PostGIS topology: 
https://plugins.qgis.org/plugins/pgtopoeditor/

(I was involved in discussions yeaaars ago about having GDAL offering a 
generic API and translation between all those topology formats but that 
never materialized)

Even

Le 09/10/2023 à 21:55, Michael Sumner via gdal-dev a écrit :
> Are there any formats that record "coverage" topology? What I'm 
> worried about is when shapes are encoded as blob geometry with 
> initially identical  coordinates at shared vertices, is there any 
> process that can validate or record that particular coords should have 
> the same values even after reprojection or decomposition/rebuild?
>
> I know how to do this in custom ways, I'm hoping to find some 
> off-the-shelf process to at least refer to (I'm a bit pressed for time 
> so I'm asking without doing the extra homework that's needed).  I 
> would build an indexer of the unique coordinates and how they relate 
> to the blob geometries before and after and do checks there, but I 
> don't know of an existing process that guarantees this.
>
> I understand that precision-setting is used to prevent numeric loss, 
> but is there any formalization about that loss? (i.e.  different 
> instances of a vertex really do stay unique). I guess the result is 
> going to be pretty good if you choose the precision appropriately and 
> modifications aren't extreme?
>
> Thanks for consideration!
>
> Cheers, Mike
>
>
>
>
>
>
> --
> Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> Hobart, Australia
> e-mail: mdsumner at gmail.com
>
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