[GRASS-user] Raster Map subset

[MS]

There is probably a more eloquent way, but I have taken a vector  
watershed boundary, converted to a raster, and set as mask.  Then used  
a r.mapcalc expression like "newMap=oldMap+0".

Mark

On Feb 6, 2010, at 3:23 AM, Micha Silver <micha at arava.co.il> wrote:

> Rich Shepard wrote:
>
>> On Fri, 5 Feb 2010, stephen sefick wrote:
>>
>>> Is there a way to get a subset of a larger raster map.  I have  
>>> zoomed
>>> into an area and would like to make a raster map only containing  
>>> that
>>> area. Can I do this? I am going to use this as input into R for some
>>> topmodel runs.
>>
>> Stephen,
>>
>>  Yes, you can. This subject has come up several times in the past  
>> month or
>> so so the archives have a lot of options for you. One to look at  
>> closely is
>> v.in.region. After zooming to the area you want, run v.in.region  
>> and save
>> that vector map. You can then use it with the g.region command to  
>> limit the
>> displayed bounds of your raster map. You can use r.patch to make a  
>> new
>> raster map that's the size of the newly created vector map.
> I'm not sure this is entirely correct. v.in.region saves the current  
> *computational* region to a vector, not the area zoomed to. Setting  
> the desired region first with g.region, I think, is the correct way  
> to go. Then r.mapcalc can create a new raster, limited to the new  
> smaller region.
>>
>>  Are you aware of r.topmodel within GRASS?
>>
>> Rich
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>
>
> -- 
> Micha Silver
> Arava Development Co. +972-52-3665918
> http://surfaces.co.il
>
>
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