[GRASSLIST:3578] Re: r.drain

[rgrmill at rt66.com]

Ivan, you wrote:

> the problem is that after a little path the segment created by 
r.drain
> stops. I went to see where it stops, and I saw that there were cells, 
around
> the last cell of the segment created, which had the same integer value 
of
> elevation but bigger decimal values (ie 275.7 against 275.8). The area 
I'm
> studing is large 140 kmq and I use a grid resolution of 5 X 5 meters. 
Do you
> think I have to try to increase the resolution??? or there are some 
other
> problems I don't know....?

This kind of problem is very common with digital terrain models.  
r.fill.dir was written to help cure the problem.  It is used to fill in 
artificial depressions in DTMs (or DEMs).  Use r.fill.dir to create a 
second DTM with filled basins, then use r.drain on the new DTM.


Roger Miller
Lee Wilson and Associates