[GRASS-user] Help needed for ascii point export

Thomas Adams tea3rd at gmail.com
Tue Apr 15 05:03:15 PDT 2014


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.


On Tue, Apr 15, 2014 at 7:50 AM, Moritz Lennert <
mlennert at 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
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