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".
The "column=" parameter needs to have the same number of columns as
the "upload=" parameter. So if you want to upload the to_x, to_y and
to_attr values you need to specify in which three columns to put
those values. Your columns parameter will look something like:
columns=x_coord,y_coord,lat
I also did not get any field to specify the column
parameter to "outlet_x,outlet_y". I am running qgis on Linux.
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:
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.
