[GRASS-user] r.mapcalc r.mapcalculator question

[Micha Silver]

On 15/06/2010 16:45, Dr. Manfred Redslob wrote:
> Am Dienstag, den 15.06.2010, 06:39 -0700 schrieb varunvarma:
>    
>> Hi, I am a new user to GRASS and have run into a problem while processing
>> rasters
>>
>> I have 2 raster files (TIFFs) which I have loaded with GRASS in QGIS 1.0.2
>> Kore. The rasters contain values of 0 and 1 and represent 2 time steps. What
>> I wanted to do is either a simple addition of the 2 rasters or apply an OR
>> operator between them. For this I used the r.mapcalc and r.mapcalculator
>> tool. However, the cell size of the resulting raster is increased from 250m
>> to 2500m which leads to loss of fine scale information.
>>
>> Does anyone know why this is happening and what I could do to maintain the
>> fine scale information?
>>
>> Thank you
>>      
> Hi however,
>
> please check the actual resolution with g.region -p. Is the result
> res=2500? If so, set region with g.region -ap res=250 or with g.region
> rast=inputrasterfile. You can controll it again with  g.region -p. After
> this settings run r.mapcalc again.
>
> Regards,
>
> Manfred
>
>    
In addition, to do the same thing within QGIS, you can use the "Edit 
current region" button on the GRASS toolbar. Just enter the value you 
need in the N-S resolution and E-W text boxes.

Another note: I might suggest you upgrade to a newer version of QGIS.  
Version 1.4 (and soon to be released 1.5) have many improvements and bug 
fixes.
Regards

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-- 
Micha Silver
http://www.surfaces.co.il/
Arava Development Co.  +972-52-3665918