[GRASS-user] river and dams in netwok analysis

[Johannes Radinger]

Hi Etienne,

Maybe you could use v.net.allpairs with negative/positve costs for up- and downstream direction and then select the smallest positive and negative distance for each dam to get the two neighbours.

Here what I found in the manual of v.net.distance which might also be useful for your purpose: 

"In order to find nearest neighbors within a group of nodes, you can either loop through each node as to and all other nodes as from or create a complete distance matrix with v.net.allpairs and select the lowest non-zero distance for each node."

https://grass.osgeo.org/grass70/manuals/v.net.distance.html

Maybe a start...

/Johannes



<div>-------- Original message --------</div><div>From: Etienne DELAY <etienne.delay at etu.unilim.fr> </div><div>Date:26/10/2015  15:15  (GMT+01:00) </div><div>To: Markus Neteler <neteler at osgeo.org> </div><div>Cc: GRASS user list <grass-user at lists.osgeo.org> </div><div>Subject: Re: [GRASS-user] river and dams in netwok analysis </div><div>
</div>Dear all dear Markus,
Above all great job GRASS dev team ! Grass 7 is so nice and powerful. 
I'm always in the dark with my dams problem.

I would like to export dams points as node and for each node in the 
attribute table 2 new column : dam before | dam after. I'm looking for 
network analysis but it may be a wrong way ?

There is a way to do that in Grass?


Cordialement

Etienne DELAY (Skype : etienne.delay.tic)
Chaire: Capital environnemental et gestion durable des cours d'eau
laboratoire GEOLAB UMR 6042 CNRS
Université de Limoges, FLSH
39E rue Camille Guérin 87036 Limoges
blog : http://elcep.legtux.org

Le 18/10/2015 17:30, Markus Neteler a écrit :
> On Sat, Oct 17, 2015 at 11:17 AM, Etienne DELAY
> <etienne.delay at etu.unilim.fr <mailto:etienne.delay at etu.unilim.fr>> wrote:
>  > Re,
>  > I have read carefully the v.out.ogr as will said for tring to export the
>  > network layer but I've got an error :
>  >
>  > v.out.ogr --overwrite input=network at PERMANENT type=point dsn=~/ layer=2
>  > format=ESRI_Shapefile
>  >
>  > WARNING: 111738 line(s) found, but not requested to be exported. Verify
>  >          'type' parameter.
> ...
>
> (I guess that you need to set "type=line" and not "type=point")
>
> ... this is why you may consider to upgrade to the current 7.0.x stable
> version. Note the differences:
>
> https://grass.osgeo.org/grass64/manuals/v.out.ogr.html
> type=string[,string,...] Feature type(s).
>    Combinations not supported by all output formats. Default: first type
> found in input.
>    Options: point,line,boundary,centroid,area,face,kernel,auto
>    Default: line,boundary
>
> https://grass.osgeo.org/grass70/manuals/v.out.ogr.html
> type=string[,string,...] Feature type(s)
>    Combination of types is not supported by all output formats.
>    Default is to use first type found in input vector map.
>    Options: point, line, boundary, centroid, area, face, kernel, auto
>    Default: auto  <<==
>
> Less to think about, much faster vector data processing, improved
> network analysis along with new graphical frontend:
> https://grasswiki.osgeo.org/wiki/Vector_network_analysis#Screenshots
>
> Best
> Markus
_______________________________________________
grass-user mailing list
grass-user at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20151026/52767743/attachment.html>