[GRASS-user] Use v.net.path to generate shortest path MATRIX?

GRASS GRASS user
1

Hello:

Perhaps someone can direct me to the correct GRASS function(s)
for accomplishing the following analysis (Ive read the documentation,
am still unsure which, if any, GRASS tools will do the job):

I have stream network data, in ArcMap line Shape File format, acquired from
the USGS NHP2 dataset. The network data includes distance in Km.
And, I have a point shape file containing the coordinates
of lakes in the same region.

I would like to generate an 'n x n' shortest path matrix between all of the 'n' lakes using the
stream network distances.

It looks like v.net.path is the correct function to use, judging from the manual page.
My actual question: Is there a way to skip the command line input of start/end points
and use the point shape file as the source, so that a shortest path matrix is created?

I suppose I could write a script to do this, but only if necessary.

Thanks for any suggestions!
Rick Reeves

Looks like I have to represent streams and lakes as separate vector layers

2

Hi,

script would be the best. v.net.path can read start and end coordinates
from stdin:

echo "1 startx,starty,endx,endy"|v.net.path in=network out=path

it should be possible, run with v.out.ascii output from your point file

for point in `v.out.ascii in=point`; do
  echo $point |grep|sed|awk|perl|python| v.net.path in=streams out=pathX
done

jachym

Rick Reeves píše v Čt 14. 02. 2008 v 11:52 -0800:

Hello:

Perhaps someone can direct me to the correct GRASS function(s)
for accomplishing the following analysis (Ive read the documentation,
am still unsure which, if any, GRASS tools will do the job):

I have stream network data, in ArcMap line Shape File format, acquired from
the USGS NHP2 dataset. The network data includes distance in Km.
And, I have a point shape file containing the coordinates
of lakes in the same region.

I would like to generate an 'n x n' shortest path matrix between all of
the 'n' lakes using the
stream network distances.

It looks like v.net.path is the correct function to use, judging from
the manual page.
My actual question: Is there a way to skip the command line input of
start/end points
and use the point shape file as the source, so that a shortest path
matrix is created?

I suppose I could write a script to do this, but only if necessary.

Thanks for any suggestions!
Rick Reeves

Looks like I have to represent streams and lakes as separate vector layers
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Jachym Cepicky
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