[GRASS-user] v.net tools with polygons

[Moritz Lennert]

On 02/03/15 21:39, Daniel Victoria wrote:
> Hi list,
>
> I'm beginning to learn and use the v.net <http://v.net> tools in Grass
> in order to evaluate the distance from several crop fields to a
> processing plant.
>
> I've successfully build the road network with the end nodes but now I'm
> in doubt. My starting points in the analysis are crop fields, which are
> polygons. So what is the best (or most common) practice?
>
> 1) Use the field centroids as starting nodes?
> 2) Add field polygon boundaries to the network and run v.net.distance
> backwards (from mill to fields)?
> 3) Some other option?


I don't think that there is a best practice for this. It all depends on 
your application and the desired outcome. Do you want average 
time/distance from anywhere in the field to the plant ? Then probably 
the centroid is ok. Or do you want distance from the point of the field 
that is closest to the network ? Then you could get the coordinates of 
that point through v.distance (with upload=to_x,to_y) and use these 
points as nodes.



> Also, if I'm to add the field boundaries to the network, how would I go
> about it? Should I first v.patch the field with the roads layer and then
> run v.net <http://v.net>?

Adding field boundaries still does not answer the question of where to 
put the start/stop point of your paths...

If you want to add them to the network then yes, patching would be the 
best option, AFAIK.

Moritz

>
> Thanks
> Daniel
>
>
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