All:
I have a collection of points that represent the centerline of a river. I need to output them in upstream to downstream order (or the reverse). A simple v.out.ascii does not do this because of the channel meanders. It’s critical to get the x,y locations of these points in the correct order.
Any help is appreciated!
Regards,
Tom
–
Hello
You can create a map of these points contining the elevation as attribute. Once you output this map you could sort points using the elevation values.
you can do this for instance using v.to.rast to convert the points to raster, them combine this map with elevation using r.mapcalc (assigning elevation to the points), and them output the map using r.out.xyz.
To sort the points you can use any sort program or a spreadsheet.
Best regards
Juan Carlos Torres
El 15/04/14 04:52, Thomas Adams escribió:
All:
I have a collection of points that represent the centerline of a river. I need to output them in upstream to downstream order (or the reverse). A simple v.out.ascii does not do this because of the channel meanders. It's critical to get the x,y locations of these points in the correct order.
Any help is appreciated!
Regards,
Tom--
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Thomas Adams escribió:
I have a collection of points that represent the centerline of a river. I need to output them in upstream to downstream order (or the reverse). A simple v.out.ascii does not do this because of the channel meanders. It's critical to get the x,y locations of these points in the correct order.
jctorres wrote:
Hello
You can create a map of these points contining the elevation as
attribute. Once you output this map you could sort points using the
elevation values.
you can do this for instance using v.to.rast to convert the points to
raster, them combine this map with elevation using r.mapcalc
(assigning elevation to the points), and them output the map using
r.out.xyz.
To sort the points you can use any sort program or a spreadsheet.
Who will believe (me) that I was about to send this same idea?
Thanks, Nikos
Hi,
don't know how many points you have to handle along the stream, so the
next solution may not be acceptable :
the idea is to digitize a polyline along your point set in a new map,
respecting the stream direction. Vertices are digitized to "roughly"
meet the existing background points, then v.edit would do the rest like
this (according to e.g. a 6 units snapping threshold) :
v.edit map=streamline type=line tool=move move=0,0 thres=-1,6,0
where="cat>0" bgmap=streampoints snap=vertex
finally v.out.ascii on map streamline.
Yours,
Vincent
Le mardi 15 avril 2014 à 08:13 +0200, jctorres a écrit :
Hello
You can create a map of these points contining the elevation as
attribute. Once you output this map you could sort points using the
elevation values.you can do this for instance using v.to.rast to convert the points to
raster, them combine this map with elevation using r.mapcalc
(assigning elevation to the points), and them output the map using
r.out.xyz.
To sort the points you can use any sort program or a spreadsheet.Best regards
Juan Carlos Torres
El 15/04/14 04:52, Thomas Adams escribió:
> All:
>
>
> I have a collection of points that represent the centerline of a
> river. I need to output them in upstream to downstream order (or the
> reverse). A simple v.out.ascii does not do this because of the
> channel meanders. It's critical to get the x,y locations of these
> points in the correct order.
>
>
> Any help is appreciated!
>
>
> Regards,
> Tom
>
>
> --
>
>
>
>
> _______________________________________________
> grass-user mailing list
> grass-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user--
=======================================================================
Juan Carlos Torres | http://lsi.ugr.es/~jctorres
Laboratorio de Realidad Virtual | Tlf.: (+34) 645 885 167
Dpto. Lenguajes y Sistemas Informaticos | (+34) 958 249 307
ETS. Ing. Informatica | interno ugr 71 260
Univ. de Granada | FAX: (+34) 958 243 179_______________________________________________
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On 15/04/14 08:13, jctorres wrote:
Hello
You can create a map of these points contining the elevation as
attribute. Once you output this map you could sort points using the
elevation values.you can do this for instance using v.to.rast to convert the points to
raster, them combine this map with elevation using r.mapcalc (assigning
elevation to the points), and them output the map using r.out.xyz.
To sort the points you can use any sort program or a spreadsheet.
Maybe directly using v.what.rast might be easier...
And, Thomas, have you checked the category values of the points ? If the points were created in stream order than the cat values should give the correct order.
Moritz
Best regards
Juan Carlos Torres
El 15/04/14 04:52, Thomas Adams escribió:
All:
I have a collection of points that represent the centerline of a
river. I need to output them in upstream to downstream order (or the
reverse). A simple v.out.ascii does not do this because of the channel
meanders. It's critical to get the x,y locations of these points in
the correct order.Any help is appreciated!
Regards,
Tom--
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user--
=======================================================================
Juan Carlos Torres |http://lsi.ugr.es/~jctorres
Laboratorio de Realidad Virtual | Tlf.: (+34) 645 885 167
Dpto. Lenguajes y Sistemas Informaticos | (+34) 958 249 307
ETS. Ing. Informatica | interno ugr 71 260
Univ. de Granada | FAX: (+34) 958 243 179_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
Moritz et al,
Thank you for the helpful suggestions. One of the problems I have is that about half of the points are in a tidal estuary where the elevations are all zero (sea level); so utilizing the elevations to sort will not work – I have several thousand points I’m dealing with, which I obtained by doing a vect–>rast conversion and then got the points from the rast (I know this sounds screwy).
I have to explain what I’m doing. I want to use r.inund.fluv to generate a flood inundation map. The problem stems from the fact that I have a USACE HEC-RAS model implementation which was not georeferenced, from which I have modeled water surface elevations from a historic flood. From an ascii output file, I basically have the channel centerline locations (x,y) and water surface elevations and I have calculated the distance to the river mouth at each point. In GRASS I have independently, using a UTM map projection, the channel centerline as a vector. I have also identified the corresponding upstream and downstream end points, which identify the same locations – so I plan I ‘mapping’ the HEC-RAS water-surface elevations (WSEL) at the un-georeferenced channel centerline locations based on scaling the entire river reach length between this data and what I have in GRASS. I can use the scaled distance from the river mouth to spatially interpolate locations where I know the WSEL.
The GRASS addon command r.inund.fluv needs X, Y, WSEL as an ascii file.
Now if I can go directly from the GRASS vector centerline and output verticies of that feature, so I have the x,y locations of the verticies my problem would be solved. I looked at v.distance and other modules but could not see how to generate the verticies and export them – but, in the end, I need an ascii file of centerline point locations in upstream to downstream order. I have/am writing Perl scripts to manipulate the data. I was afraid the order would not be preserved by v.out.ascii, which was confirmed by my script that calculated the distances from the river mouth when I saw them starting to bounce around in odd ways as I looked at the calculated values when I looked at the downstream to upstream distances.
Cheers!
Tom
On Tue, Apr 15, 2014 at 5:21 AM, Moritz Lennert <mlennert@club.worldonline.be> wrote:
On 15/04/14 08:13, jctorres wrote:
Hello
You can create a map of these points contining the elevation as
attribute. Once you output this map you could sort points using the
elevation values.you can do this for instance using v.to.rast to convert the points to
raster, them combine this map with elevation using r.mapcalc (assigning
elevation to the points), and them output the map using r.out.xyz.
To sort the points you can use any sort program or a spreadsheet.Maybe directly using v.what.rast might be easier…
And, Thomas, have you checked the category values of the points ? If the points were created in stream order than the cat values should give the correct order.
Moritz
Best regards
Juan Carlos Torres
El 15/04/14 04:52, Thomas Adams escribió:
All:
I have a collection of points that represent the centerline of a
river. I need to output them in upstream to downstream order (or the
reverse). A simple v.out.ascii does not do this because of the channel
meanders. It’s critical to get the x,y locations of these points in
the correct order.Any help is appreciated!
Regards,
Tom–
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user–
=======================================================================
Juan Carlos Torres |http://lsi.ugr.es/~jctorres
Laboratorio de Realidad Virtual | Tlf.: (+34) 645 885 167
Dpto. Lenguajes y Sistemas Informaticos | (+34) 958 249 307
ETS. Ing. Informatica | interno ugr 71 260
Univ. de Granada | FAX: (+34) 958 243 179
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
On 15/04/14 13:03, Thomas Adams wrote:
Moritz et al,
Thank you for the helpful suggestions. One of the problems I have is
that about half of the points are in a tidal estuary where the
elevations are all zero (sea level); so utilizing the elevations to sort
will not work -- I have several thousand points I'm dealing with, which
I obtained by doing a vect-->rast conversion and then got the points
from the rast (I know this sounds screwy).I have to explain what I'm doing. I want to use r.inund.fluv to generate
a flood inundation map. The problem stems from the fact that I have a
USACE HEC-RAS model implementation which was not georeferenced, from
which I have modeled water surface elevations from a historic flood.
From an ascii output file, I basically have the channel centerline
locations (x,y) and water surface elevations and I have calculated the
distance to the river mouth at each point. In GRASS I have
independently, using a UTM map projection, the channel centerline as a
vector. I have also identified the corresponding upstream and downstream
end points, which identify the same locations -- so I plan I 'mapping'
the HEC-RAS water-surface elevations (WSEL) at the un-georeferenced
channel centerline locations based on scaling the entire river reach
length between this data and what I have in GRASS. I can use the scaled
distance from the river mouth to spatially interpolate locations where I
know the WSEL.The GRASS addon command r.inund.fluv needs X, Y, WSEL as an ascii file.
Now if I can go directly from the GRASS vector centerline and output
verticies of that feature, so I have the x,y locations of the verticies
my problem would be solved. I looked at v.distance and other modules but
could not see how to generate the verticies and export them -- but, in
the end, I need an ascii file of centerline point locations in upstream
to downstream order.
v.to.points ? If you only want vertices, use the -v flag.
Moritz
Moritz,
Thank you – v.to.points seems as if it should do what I want – I’m not sure how I missed seeing this. My wife says I have “guy sight” and often miss seeing something plainly in view.
Best,
Tom
On Tue, Apr 15, 2014 at 7:50 AM, Moritz Lennert <mlennert@club.worldonline.be> wrote:
On 15/04/14 13:03, Thomas Adams wrote:
Moritz et al,
Thank you for the helpful suggestions. One of the problems I have is
that about half of the points are in a tidal estuary where the
elevations are all zero (sea level); so utilizing the elevations to sort
will not work – I have several thousand points I’m dealing with, which
I obtained by doing a vect–>rast conversion and then got the points
from the rast (I know this sounds screwy).I have to explain what I’m doing. I want to use r.inund.fluv to generate
a flood inundation map. The problem stems from the fact that I have a
USACE HEC-RAS model implementation which was not georeferenced, from
which I have modeled water surface elevations from a historic flood.
From an ascii output file, I basically have the channel centerline
locations (x,y) and water surface elevations and I have calculated the
distance to the river mouth at each point. In GRASS I have
independently, using a UTM map projection, the channel centerline as a
vector. I have also identified the corresponding upstream and downstream
end points, which identify the same locations – so I plan I ‘mapping’
the HEC-RAS water-surface elevations (WSEL) at the un-georeferenced
channel centerline locations based on scaling the entire river reach
length between this data and what I have in GRASS. I can use the scaled
distance from the river mouth to spatially interpolate locations where I
know the WSEL.The GRASS addon command r.inund.fluv needs X, Y, WSEL as an ascii file.
Now if I can go directly from the GRASS vector centerline and output
verticies of that feature, so I have the x,y locations of the verticies
my problem would be solved. I looked at v.distance and other modules but
could not see how to generate the verticies and export them – but, in
the end, I need an ascii file of centerline point locations in upstream
to downstream order.v.to.points ? If you only want vertices, use the -v flag.
Moritz