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

[Moritz Lennert]

On 30/01/13 14:18, Johannes Radinger wrote:
> Hi,
>
> I have a network (proper GRASS network) and two point vectors.
> One is representing sampling stations the second contains locations
> of migration barriers with a certain value for its permeability (0-1).
> Both point vectors are located on the network (snapped via v.distance
> and v.in.db).

Note that v.net allows you to easily connect points to the network. And 
in Grass7, it allows you to snap the points onto the network.

> Now I'd like to get all the migration barriers that
> are between any pairwise combination of the sampling stations. In other
> words, I want to get all sampling stations that are located between one
> sampling station and another one (all possible combinations). Moreover
> I'd like to get the sum and product of the permeability values of all
> barriers inbetween. Is there such a tool in GRASS GIS?
>
> What I thought about the solution: 1) Getting paths (vectors) connecting
> all pairwise sampling stations (but how)

v.net.allpairs, if you set the cost of all arcs to 0 and only assign the 
permeability values as costs to the barrier nodes, then I guess the cost 
value in the resulting attribute table should give you the sum of 
permeability values (but I'm not sure, you'll have to test).

> and 2) extracting the barriers
> that are located on each connecting line?

I guess a simple v.distance between the v.net.allpairs vector lines and 
the barriers plus some SQL should give you that info.

Moritz