[GRASS-user] Interactive editing (was: Memory issues)

[Rich Shepard]

On Tue, 17 Jul 2018, Micha Silver wrote:

> I don't think there's any need for manual editing. What I do is change the
> regions settings to the area of interest. Then almost all raster
> calculations work only inside that region. So:

Micha,

   I did not think of changing the region, only of creating a mask, based on
the thread I started on regions vs. masks.

> # First save the current settings for restoring later
> g.region save=FULL_REGION

   I have this saved as the default region.

> # Now reduce the region (leave the resolution as is)
> g.region -ap n=<max y> s=<min y> e=<max x> w=<min x>

   I do this by moving the cursor from side to side and recording the
displayed coordinates. And, I can save as many named regions as needed and
apply them for the entire area or specific sub-areas. I like this and it
avoids the constraints of trying to interactively create boundaries over a
displayed raster map.

> # Do your stuff
> r.contour input=<your DEM> output=contours
> # If you really need a vector rectangle bounding the small analysis area region then
> v.in.region output=analysis_area
> # In future you get back to this smaller region with g.region -ap vect=analysis_area
> 
> # Now, if necessary, return to the full region with
> g.region -ap region=FULL_REGION

   Sometimes we get stuck in a rut and cannot see over the rim to other
solutions. Thanks very much for the detailed lesson.

Toda raba,

Rich