[GRASS-user] create a slope vector map

[Hamish]

Luca Penasa wrote:
> - every vector should point to the max slope line, with an arrow 
> representig the flow direction
> - the lenght should rapresent the slope value in degrees, and the
> vector line should start from the center of the square
> - i want to have a vector for every 10x10m square, with an average
> slope value rapresented by the vector lenght
> 
> I know how to create the slope map, with 10x10m resolution... but..
> how can i create the vector map with all the features i said???


d.rast.arrow won't create a vector map, but it will draw your arrows.


to make vector arrows I think you will need to first use a raster
resampling module to get your 10x10 grid (if not already), then use
r.slope.aspect to get slope and aspect maps, then some r.out.xyz or
r.to.vect + unix tool magic (paste + awk & some trig) to create a vector
ascii file suitable for 'v.in.ascii format=standard'. You can copy the
needed trigonometry for the arrow head, etc., out of the d.rast.arrow
source code if needed.


Hamish