[GRASS-dev] v.breach and v.line.center GRASS addons
dylan.beaudette at gmail.com
Wed Mar 14 02:46:42 CET 2007
Great work Maciej!
On Tuesday 13 March 2007 13:06, Maciej Sieczka wrote:
> I have submitted 2 new scripts for GRASS 6.x to GRASS WIKI
> v.line.center creates a points vector map with each point located in
> the middle of the length of one input vector line.
So this script locates a line's midpoint, and puts a new point there? Does
this point have the same attributes as the line which was used as the input?
> v.breach creates vector maps of lines and points of continously
> lowering elevation down the input watercourses, based on the input
> raster DEM.
> v.line.center is a simple self-explanatory tool.
> v.breach is more complex. It is similar to r.carve -n, with the
> following differences:
> 1. It takes the direction of input vector lines into account; which
> means it is less prone to artifacts in the input DEM but more demanding
> to input watercourses. As a result you can breach DEM even against the
> slope, if that's needed ;).
cool. any examples yet?
> 2. It does not breach the DEM itself, but outputs vector points which
> have the breached elevation attribute stored in the table. These points
> can be used as additional data for interpolating more hydrologicaly
> sound DEM from scratch, or rasterized and burned into the input DEM
> manually (v.to.rast, r.mapcalc).
> 3. It also outputs vector lines, which are the input vector
> watercourses segmented one segment per each DEM cell through which a
> given input watercourse flows. Those segments have the breached
> elevation attribute same as the output vector points. I needed such
> output for my work. Maybe it will be of some use for others.
> 4. It is way slower than r.carve. Shell (I have got rid of bashisms I
> hope) + Awk + standard UNIX tools.
> See the v.breach manual for more details.
Did this approach allow you to use RST in complex terrain with drainage
enforcement- to create a better DEM than was previously possible? I recall
severall discussions pertaining to the creation of DEM from difficult input
points, specifically with the RST interpolator.
Looking forward to trying these new modules soon,
Soils and Biogeochemistry Graduate Group
University of California at Davis
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