[GRASS-user] Regions and Mapsets

[Hamish]

Rich wrote:
> The PERMANENT mapset holds the base data with
> maximum regions for each map. The project mapset has a smaller region,
> so when I'm working within that mapset on copies of the maps stored in
> PERMANENT, all actions are within the smaller region.

While it is correct that each mapset maintains its own region settings/
bounds, for the record these do not necessarily have to lie exactly
within PERMANENT's region/bounds. It is just a handy way to think about
what the default region might be.

Your grass session will not write outside of the currently loaded mapset.
So anything you do in $MAPSET will not have an effect on PERMANENT. Some-
times it just refuses to go on (like g.setproj) other times it works
around it (eg r.colors keeps a colr2/ color table local override for
maps from other mapsets). The exception is i.rectify which exports X,Y
images to new georeferenced maps in other mapsets.


> With raster maps, too, like the DEM, all calculations are on the visible
> portion only.

right. An extra complication is that a MASK map (if it exists) is filtered
in the same way, but only applies to the reading of existing map data from
the disk.

> So, when I'm finished, the original bounds for each map in
> PERMANENT remain unchanged.

yup. thus multi-user or multi-session (but-different-mapsets) can share
the common mapset (in this case PERMANENT) while being protected from
clobbering each other unawares.


Hamish