[GRASS-dev] Re: topology model resume (and some proposals)

G. Allegri giohappy at gmail.com
Thu Dec 1 12:32:29 EST 2011

Ops, wrong post. I wanted to send it to the users maling list.
I'll post it there.


2011/12/1 G. Allegri <giohappy at gmail.com>

> I resume (first as a repeat to myself) what I've learned from the various
> email on the topic
> Vectors can be:
> LEVEL 1:
>  - no topology -> very limited use
> LEVEL 2:
>  - unclean topology -> limited use
>  - clean topology -> full support
> I previously thought that LEVEL 2 was only possible for clean topologies,
> and I was wrong...
> At the moment there isn't a tool to list the the uncorrect geometries from
> a topological point of view. v.build only checks some constraints, not all.
> The proposal is to extend it to check against all the rules that are
> required to consider a geometry topologically correct (an extended flag to
> v defaul.build maybe).
> v.in.ogr builds and cleans (by default). It would be useful to have the
> "clean" phase available to be launched independently. I mean, something
> like an "automatic" flag for v.clean, that would operate the same cleaning
> as during the import of a vector.
> Conclusions: the topological correctness isn't a constraint for the vector
> topology data structure. GRASS haven't all the topology rules hard-coded
> (... or yes?). Most of thems (all?) are defined inside the code of v.build
> and v.clean, but I suppose that there isn't an autonomous
> library/functionality that provide the semantics of a "correct topology".
> Am I wrong?
> Thanks everyone for the support ;)
> giovanni
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