[GRASS-user] problems with v.segment of longest flow path

[Moritz Lennert]

On 08/05/16 23:15, James Maas (MED) wrote:
> Most of the process appears to work well until I attempt to create
> segments of the vector map of the longest flow path this segment rules file.
>
> ====================
>
> P 1 1 -10%
> P 2 1 -20%
> P 3 1 -30%
> P 4 1 -40%
> P 5 1 -50%
> P 6 1 -60%
> P 7 1 -70%
> P 8 1 -80%
> P 9 1 -90%
> ========================
>

[...]

> The other way is to use r.to.vect, which appears to work well, now the
> new vector lfp map (jamrlfp) is the same shape and length as the
> original raster lfp map.  However the next job is to do the segmentation
> using the above rules file like this,
>
> v.segment input=jamrlfp output=outlets rules=$segment_rules \
>   --overwrite --verbose
>
> And for some reason it only creates the very first outlet (segment).
>
> Sorry for the long missive, but I end up with two questions:
>

[...]

>  2. Any suggestions as to why v.segment is not working correctly and
>     creating the 9 segments correctly?

Just guessing here, but the v.segment man page says "A segment is only 
created for the first line found of the specified category." Are you 
sure that line 1 is one single line or is it many lines all with the 
same category. Maybe you need to run v.polyline before v.segment ?

Moritz