[GRASS-user] r.mask vs g.region

[Rich Shepard]

On Tue, 10 Jul 2018, Huidae Cho wrote:

> g.region creates a rectangular computational region while r.mask can
> create an irregular mask. If you use r.mask, any cells outside the mask
> will be ignored, so you have to make sure that your mask is big enough to
> cover your basin. In terms of computational time, r.mask can be faster
> depending on what modules you need. For example, when you run flow
> accumulation, you may save some time using r.mask because you don't have
> to calculate flow accumulation outside your area of interest. If you use
> g.region that covers your basin, you calculate flow accumulation outside
> the basin within the rectangular region. So in general, I would say r.mask
> is preferred if and only if the mask is correct.

Huidae,

   This is a perfect answer as it covers all the important differences
between the two. Thanks very much for the lesson.

Regards,

Rich