[GRASS-user] r.composite changing pixel resolution?

José María Michia jose.maria.michia at gmail.com
Fri Feb 13 03:48:25 EST 2009


Hi Tim and all!

2009/2/13 Tim Holland <timothyholland en gmail.com>:
>
> Dear all,
>
> I am new to both Grass and this forum, so apologies in advance for something
> which is likely a simple mistake or oversight on my part (but I have
> searched the forum and can't seem to find an answer).
>
> I am trying to create RGB-composite images from various sets of Landsat
> bands (3,2,1 or 4,5,3).  When I try to do this using r.composite, the
> resulting raster file has a far courser pixel resolution than the original
> images (it looks like it is scaling up by a factor of 12 - so 30m x 30m
> pixels become 360m x 360m).  I can't see anything in the r.composite manual
> that suggests why this would be happening.
>
> If it is relevant, I am also using i.landsat.rgb to balance the colours
> before I am using the r.composite.  Also, I am using Grass 6.3, and running
> it through the plugin on QGIS 0.11.0.

	
When you run a command that produces a new map, usually the new map
has the size and resolution of the active region, not far and the
resolution of input maps.

To check the values of the active region, use the following command:

g.region-p

To set the values of the active region to the same values as their
input maps, use:

RAST g.region P = name_of_raster_map

To check the values of some map, use:

r.info map name_of_raster_map =

I hope this helps!

Saludos
José María


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