I'm working with GRASS 7.0.3 on Ubuntu Linux and attempting to create and
partition a longest flow path in a catchment comprised of 25km2 basin, the
original DEM is a 5 m resolution.
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%
========================
First I use r.watershed like this to create the various raster maps,
r.watershed elevation=topmod_demfill threshold=20000 drainage=topmod_drain \
stream=topmod_streams basin=topmod_basin convergence=5 --overwrite
Next I use r.stream.order to get the strahler numbers and then find the outlet
coordinates
Next I use r.water.outlet as such to get the basin,
r.water.outlet input=topmod_drain output=topmod_basin \
coordinates=$E_outflow,$N_outflow --overwrite
And find the longest flow path, in raster format as such
r.lfp input=topmod_drain output=topmod_lfp \
coordinates=$E_outflow,$N_outflow --overwrite
All seems to work well up to this point. I've found two ways to convert the
raster map of the longest flow path to a vector map. The first is using v.lfp
but it truncates the lfp map, almost in half, only shows the last half in the
new vector lfp. Any ideas why it might do this?
v.lfp input=topmod_lfp output=topmod_lfpv coordinates=$E_outflow,$N_outflow \
--verbose --overwrite
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:
1. Any suggestions as to why v.lfp is not doing the conversion correctly but
r.to.vect appears to do it correctly?
2. Any suggestions as to why v.segment is not working correctly and creating
the 9 segments correctly?
Thanks,
Dr. Jim Maas
University of East Anglia
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