[GRASS-user] Count points in a network between two locations

[Moritz Lennert]

On 01/02/13 11:44, Johannes Radinger wrote:
> Thank you, that might work. I just realized that my permeabilities are
> given as probability and they are added up by a multiplication rule. Thus
> I don't need the sum but rather the product or at least a list of all barries
> between to sampling stations....

At this stage costs can only be summed AFAIK.

> thats what I tried now, v.distance to get from barriers to nearest
> vector lines from v.net.allpairs,
>   but the problem is that the v.net.allpairs lines are partly
> overlapping (sharing parts). So there
> are several barriers on partly overlapping lines, but I want to select
> all barriers per line category.


IIUC v.net.allpairs actually creates several duplicate segments which 
seems contrary to GRASS topology rules. Shouldn't these rather be 
represented by single segments with multiple category values (like 
v.buffer in grass7) ?

> So, a solution could be to loop over the all lines (categories) and
> use v.select as
> v.select does not have any option for stratified selection (e.g. per
> category)...
> I'll try that now, but any other recommendations are mostly welcome...

How about v.distance -a to get a complete distance matrix between nodes 
and paths and then select those elements where distance = 0 (supposing 
that you snapped the nodes onto the network) ?

Moritz