[Qgis-user] Problems with profile from line altitude values + r.water.outlet command

[Jaime Palalane]

Regarding the explanation marked below in red, I tried several times to run
the following command v.distance but always getting the error message "Not
enough column names".

 v.distance from=Pxy at Lisboa from_layer=1 to=Proximo at Lisboa to_type=line
to_layer=1 upload=to_x,to_y,to_attr to_column=label column=lat output=Res3
dmax=-1 dmin=-1

I also did not get any field to specify the column parameter to
"outlet_x,outlet_y". I am running qgis on Linux.

Jaime



2012/7/13 Micha Silver <micha at arava.co.il>

>  On 07/13/2012 04:02 PM, Jaime Palalane wrote:
>
> Dear qgis users,
>
> I am trying to use qGIS to characterize a hydrographic basin but I am
> facing problems with the profile from line tool as it is giving an unique
> altitude value for my rivers and lengths in grades. I would like to have
> them in SI units. I would appreciate some tips in how to solve this problem.
>
>
> The units should be the units of the coordinate system. I think that if
> you want altitudes and lengths in meters, you'll have to project both the
> raster and the line features to a projected CRS with meters as units.
>
>
> I am also trying to use the r.water.outlet command to define a basin
> draining to a specific point of a stream in raster format but without
> success as it gives me back only one cell as the basin and not a
> combination of cells which could form a real basin. Any tutorial or video
> in how to use this command?
>
>
> Perhaps the problem is that the outlet point must fall exactly on a
> stream.  There's a trick using v.distance to find a drainage point exactly
> on the stream, described here:
>
> http://www.surfaces.co.il/?p=241
>
> First add two columns to the streams layer: outlet_x, outlet_y. Now use
> v.distance with your outlet point as the "from" parameter, and the stream
> as the "to" parameter. Set the upload parameter to "to_x,to_y" and the
> column parameter to "outlet_x,outlet_y". Now after you run, you should get
> the X,Y coordinates of a point *on the stream* nearest to your planned
> outlet point. Use those coordinates in your r.water.outlet command, and you
> should get the full drainage area.
>
> HTH,
> Micha
>
>
> Saudaçoes!
>
> Jaime
>
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>
>
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>
>
>
>
> --
> Micha Silver
> GIS Consultant, Arava Development Co.http://www.surfaces.co.il
>
>


-- 
Jaime Palalane
+258 82 70 56 990
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