[GRASS-user] v.net tools with polygons

[Mark Wynter]

Hi Daniel, 

I've done something similar - I call it "off road routing", and uses a regular lattice of nodes and arcs. You can then constrain the off road "network" by closing arcs that cross major watercourses, fence lines or where the terrain or vegetation is non navigatable. For farms, I added paddock boundaries as rings, as well as gate nodes that constrain movement between paddocks. In essence you build a network topology that reflects the off-road aspect of your network.  Relevant to mining as well as agriculture.


> 
> Ok Moritz,
> 
> Thanks for the tips. I'll try to go the centroids way
> 
> Cheers
> Daniel
> 
> On Tue, Mar 3, 2015 at 5:35 AM, Moritz Lennert <mlennert at club.worldonline.be
>> wrote:
> 
>>> 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
>> 
>>  *********