[GRASSLIST:6146] resampling to

[Jan Hartmann]

Probably a dumb question, but I really can't see how to do it. I am 
working with the LandScan 2001 worldwide population database 
(www.ornl.gov/gist), a 30 second population map for the whole world. In 
its original form this consists of a raster of 43200 by 21600 cells with 
estimated population counts. I want to resample to rasters with grid 
sizes of 1, 2 4 and 8 minutes (21600*10800, 10800*5400 etc). Each grid 
cell of a new maps should contain the sum of the four cells of the 
underlying higher resolution map. How do I do this? r.resample uses the 
nearest neighbour to compute the value of the new raster map; 
r.neighbours only works for regions with uneven size, and r.mapcalc 
resamples the input map (with nearest neighbour) *before* actually 
applying its operators. I just want to compute a new map based on data 
from a map with a different resolution.

What am I overlooking?

Jan Hartmann