[GRASS-user] Obtaining unique nodes from a topology

[Achim Kisseler]

Hi Will,

I think it is possible:
building a network from boundaries with
v.net

and then using the report option in v.net
it is not possible to update the table with these infos, but it is 
possible to save the results in a list, import this to your database and 
connect these infos to the table.

Achim

William Temperley schrieb:
> Hi Achim
> 
> Thanks - but what I really want is a list of unique nodes (i.e. where 
> three boundaries meet, there would be one node, with an id) and assign 
> this id to the relevant boundaries. Perhaps that isn't possible. It 
> might be easier to do this in PostGIS.  I need to be able to run 
> recursive queries in PostGIS to pick up connected boundaries.
> 
> Cheers
> 
> Will
> 
> 
> 2010/1/15 Achim Kisseler <ak7 at jupiter.uni-freiburg.de 
> <mailto:ak7 at jupiter.uni-freiburg.de>>
> 
>     Hi Will,
> 
>     for lines you can use
> 
>     v.to.db -p map=... option=start
> 
>     -p to print your result
>     option=start to get start points
>     option=end to get end points
> 
>     the result looks like
>     cat|x|y|z
>     ...
> 
>     without -p you can upload the results to the table with:
>     columns=x,y(,z)
> 
>     Hope it helps,
>     Achim
> 
>     William Temperley schrieb:
> 
>         Hi all
> 
>         I've used Grass to build a topology out of a polygon shapefile,
>         so far so good.
>         I now need to export it as an arc-node topology (i.e. boundaries
>          with startnode_id, endnode_id) which I will then use in PostGIS.
> 
>         Does anyone know of a way to get the nodes from the topology and
>         attach these attributes to the boundaries?
>         I know I can get the start/end coordinates, but I need the
>         unique nodes and their ids.
> 
>         Thanks
> 
>         Will Temperley
>          
> 
> 
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