[GRASS-dev] v.breach and v.line.center GRASS addons

[Dylan Beaudette]

Great work Maciej!

On Tuesday 13 March 2007 13:06, Maciej Sieczka wrote:
> Hi
>
> I have submitted 2 new scripts for GRASS 6.x to GRASS WIKI
> http://grass.gdf-hannover.de/wiki/GRASS_AddOns:
>
> 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.
>
> Maciek
>

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,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341