On 04/18/2011 12:55 PM, Moritz Lennert wrote:
On 18/04/11 08:19, Johannes Radinger wrote:
Am 16.04.2011 um 17:25 schrieb Daniel Victoria:
Not sure how to split and label the rivers but to snap the point to
the closest river you could use v.distance
I also thought about v.distance. There I get the coordinates of the
closest points on the new line (stdout). I just have to create a new
pointfile from the standard output coordinates...or is there any
simpler way?
>
And I also still don't know how to split the lines at these points.
I thought about v.split but here are segemnts created at equidistant
breakpoints and one can only set the distance in metres but
it is not possible to use coordinates as input...anyone knows how
to do that?
v.edit tool=break coords=CoordinatesOfYourPoints
Maybe a few more details might be helpful:
If you want to first get the coordinates of the new points along the
(simplified) river line,
(starting with a line vector 'river' and a set of points 'old_pts'
displaced from the line) you first do:
~>v.db.addtable old_pts col="x double precision, y double precision"
then:
~>v.distance --o to=river from=old_pts out=connectors upload=to_x,to_y
col=x,y
This puts the *new* X-Y coordinates of points exactly on the river, and
at the node of perpendicular 'connectors' from the old points to the
river into the old_pts attribute table.
Now:
~>v.db.select -c old_pts col=x,y >new_pts.txt
~>v.db.select -c old_pts fs=, col=x,y | v.in.ascii out=new_pts
THis gives you both a new point vector of the points along the river,
and a text file of their coordinates. Next, I used Moritz's method to
split the river at these new points, in a loop like:
~>while read coord; do v.edit river tool=break coord=$coord; done <
new_pts.txt
This leaves you with a multi-segment line vector, split at the new points.
v.net option=connect + some cleaning afterwards might be another
possible solution. For each point, it will create a line connecting it
to the river, breaking the river at the intersection.
v.distance should be able to do the labelling for you.
I tried this part, but couldn't get it to work :-( . I used v.what.vect
(and v.distance directly) to get the cat values from the new points into
the river vector line segments, but each time it gave me:
~ > v.distance from=river to=new_pts upload=cat col=pt_cat to_col=cat
100%
100%
1 categories exist in the table
0 records updated
v.distance complete.
But the new_pts vector has 6 cats:
~ > v.category new_pts opt=print
1
2
3
4
5
6
and the river vector has 7 segments:
GRASS 6.4.0 (WGS84):~ > v.info -t river
nodes=8
points=0
lines=7
boundaries=0
centroids=0
areas=0
islands=0
faces=0
kernels=0
primitives=7
map3d=0
So I don't know what to suggest to get the cat values from the new
points into the river segments...
Regards,
Micha
Moritz
cheers
/johannes
Cheers
daniel
http://grass.fbk.eu/grass65/manuals/html65_user/v.distance.html
On Thu, Apr 14, 2011 at 6:36 AM, Johannes Radinger <jradin...@gmx.at>
wrote:
Hello,
I have a line-vector (river) and some points on that line. First I am
straightening that line with v.generalize (method: boyle). Now, there
is the problem that the points are not exactly on the line anymore.
So I want to snap (move) the points to the new generalized line
again. Which tool is able to do that?
After that I want to split the line at these points and want to give
the attribute value to the newly created segments. These segment
values should represent the number/value of the upstream point (which
was used to split). How can this be done in GRASS?
Do you have any ideas to solve these two problems/challenges?
thank you
/johannes
--
GMX DSL Doppel-Flat ab 19,99 Euro/mtl.! Jetzt mit
gratis Handy-Flat! http://portal.gmx.net/de/go/dsl
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
This mail was received via Mail-SeCure System.
--
Micha Silver
Arava Development Co. +972-52-3665918
http://www.surfaces.co.il
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
