[GRASS-user] Re: correcting a series of images for wrong bounding box (extend)

[Micha Silver]

Hamish wrote:
> Micha wrote:
>   
>> So r.region actually does a kind of affine transformation? I don't
>> remember seeing this documented anywhere (the manual says
>> "...manage the boundaries...") , and I must say it's confusing and
>> unexpected that a module called r.region (similar to g.region)
>> shifts/changes the data, rather than just defining the region
>> and resolution. 
>>     
>
> it does not touch the data array. It only modifies where that array is
> thought to be in space. i.e. it just edits the $MAPSET/cellhd/$MAPNAME
> file.
>
> if you put new bounds which don't exactly match the array size it will
> adjust your resolution so that it does.
>
>
> Hamish
>
>
>
>   
I guess my misunderstanding is just semantic. If the module were named 
r.shift or r.translate I'd have no problem. 
If I do something silly like: starting with a raster with an extent of 
N=560000 and S=360000 and I run:
r.region map n=480000 s= 440000
then the raster gets "squashed" into the smaller region.

By comparison, there's no v.region which shifts where the vector 
features are in space. But if I choose to shift a vector map, I use the 
"move" tool in v.edit. That makes perfect sense, but r.region doing such 
a shift caught me by surprise.  So r.region seems closer to gdalwarp 
that to any region settings.

Micha