[GRASS-user] Help needed for ascii point export

Moritz Lennert mlennert at club.worldonline.be
Tue Apr 15 04:50:06 PDT 2014

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.


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