[GRASS-user] Obtaining unique nodes from a topology

[William Temperley]

Ah this is probably what I'm looking for, thanks Achim

Will

2010/1/15 Achim Kisseler <ak7 at jupiter.uni-freiburg.de>

> 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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