[GRASS-user] flowdirection

[Hamish]

Manuel Seeger wrote:
> 
> another thing. when I use Terraflow with MFD, how are the
> flowdirections expressed in the flowdirection grid? I get values
> between -1 and 255, but I'm  not really shure how to treat them/ what
> they express.

M.D.F.= multi-dimensional flow

MDF directions:
 (based upon the rules in r.terraflow's findDominant() funtion in
direction.cc)

   32 64 128
   16 *   1
   8  4   2

so a value of 255 is flow in all directions, a value of 3 is E and SE, a
value of 65 is E and N, etc. I'm not sure exactly what 0 and -1
represent, hopefully that becomes obvious.

The r.terraflow help page talks about MDF a bit, it should really have
this info too.

see my dominant_dir.m and calc_terraflow_dir.m Matlab scripts in the
wiki add-ons page (raster section) for some simple exploration.


Hamish