[GRASS-user] r.watershed: Interpreting Visual Output Map

[Rich Shepard]

On Tue, 23 Feb 2010, Markus Metz wrote:

> Almost right. ...with surface flow accumulation between 0 and the threshold 
> value.

Markus,

   Now I understand, yet still miss the difference between the accumulation
map and the visual map.

> All flow accumulation values larger than the threshold value are set to the 
> threshold value.

   Got that from the man page.

> Number of cells draining through a given cell. Converted to squared map
> units by multiplying with nsres * ewres, of the flow accumulation map of
> course, and first setting the computational region to match the flow
> accumulation map with g.region -p rast=<my_flow_acc>. -p to check that
> everything is all right.

   I assume that the above calculation is left for me to do; that the
module does not do the math before displaying the results. Am I correct in
my assumption?

   One last point: why no color in the legend? There is color on the visual
map but not on the accompanying legend. Strange and I don't know how to fix
this.

Many thanks,

Rich