[GRASS-user] Obtaining unique nodes from a topology

William Temperley willtemperley at gmail.com
Fri Jan 15 07:21:35 EST 2010

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.



2010/1/15 Achim Kisseler <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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