[postgis-users] Get only the main river. Smoothline???

[toni hernández]

Thanks Remi,

I thought that but I have no starting/ending points. St_StartPoint and 
St_EndPoint are not working with MultiLinestrings
I'll give it some more intense thought. :)

Cheers.

*Toni Hernández Vallès*
Servei de Sistemes d'Informació Geogràfica i Teledetecció
-
Universitat de Girona
*SIGTE*
-
Pl. Ferrater Mora 1
17071 Girona
Tel +34 972 418 039 (7026 intern)
toni at sigte.udg.edu <mailto:toni at sigte.udg.edu>

http://www.sigte.udg.edu
Twitter http://twitter.com/SIGTE_UDG

On 08/06/2015 17:45, Rémi Cura wrote:
> if you have start and end point of geom B,
> you can get the river path with a shortest path method (one liner 
> using python, can be done in few hours using plpgsql).
>
> The idea is that you cut your geom into segments(pairs of points)
> , the length of the segment is the weight of this edge
> , and you know which segment is connected to which segment (adjacency 
> graph).
> Then you use Networkx 
> <http://networkx.lanl.gov/reference/generated/networkx.algorithms.shortest_paths.generic.shortest_path.html#networkx.algorithms.shortest_paths.generic.shortest_path>shortest 
> path distance.
>
> Else,
> you are up to use some nasty workaround I suppose (playing with 
> buffers on your original river surface, testing which segment 
> intersects etc. ).
> I tried that but it ends up being more work (and more corner cases) 
> than doing the things properly (in my experience).
>
> Cheers,
> Rémi-C
>
> 2015-06-08 16:42 GMT+02:00 toni hernández <toni at sigte.udg.edu 
> <mailto:toni at sigte.udg.edu>>:
>
>     Hi everyone,
>
>     I have a multilinestring with a river and all its afluents as you
>     can see in this image
>     http://sigserver4.udg.edu/apps/geometries.png
>
>     I got geometry A using St_StraithSkeleton.
>
>     Is there a way to go from geometry A to geometry B??
>     Maybe something similar to SmoothLine???
>
>
>     -- 
>     *Toni Hernández Vallès*
>     Servei de Sistemes d'Informació Geogràfica i Teledetecció
>     -
>     Universitat de Girona
>     *SIGTE*
>     -
>     Pl. Ferrater Mora 1
>     17071 Girona
>     Tel +34 972 418 039 (7026 intern)
>     toni at sigte.udg.edu <mailto:toni at sigte.udg.edu>
>
>     http://www.sigte.udg.edu
>     Twitter http://twitter.com/SIGTE_UDG
>
>
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