[GRASS-dev] what does zoom= do?

[Glynn Clements]

Michael Barton wrote:

> With -a, g.region will slightly adjust the extents (instead of the  
> resolution) to come up with an integer number or rows and columns as  
> close as possible to the selected extents while exactly maintaining  
> the specified resolution.

It does a bit more than that. It aligns to a grid which is aligned to
the origin of the coordinate system.

IOW, even if the region dimensions are an exact multiple of the
resolution, the bounds may still be shifted.

E.g. if you have an X/Y coordinate system with res=10 and bounds:

	e=15, w=25, s=15, n=25

the -a switch will cause the extents to be changed to:

	e=10, w=30, s=10, n=30

so that they align to a 10-unit grid which is aligned to the origin.

-- 
Glynn Clements <glynn at gclements.plus.com>