[GRASSLIST:8567] Changing scale of raster map

[Bruno GUILLAUME]

Dear GRASS users,

My problem concerns a raster in lat-lon projection, having a given 
resolution of ewres1,nsres1. For every cell, the category value is 
expressed in kilogram.
I need to transform it into  the same grid but with coarser resolution, 
say ewres2=10*ewres1 and nsres2=10*nsres1, BUT the transformation need 
to be mass-conservative (so, I need to get exactly the same amount in 
kilograms with finer and coarser resolution).

Can I do in a simple way with GRASS ?

Thanks in advance,

Bruno Guillaume.