[GRASS-user] raster area calculations in lat/long

[Jerry Griffith]

Dear List,

I'm a new grass user and have been learning on the command line.  I have 
a raster file of the world in which the cells are floating point values 
of the percentage of a crop type within that cell (ex., 0.01, 0.29, 
0.45).  It's in Lat/Long.  I want to calculate the total area of crop in 
specific regions that are defined in a separate raster file.    I want 
to multiply the value of the cell by the cell area and then sum the cell 
values in each region to get total acreage.  My questions are: 1) Can I 
do this in r.stats, r.report or r.coin, or do I need to use r.mapcalc?, 
and 2) Because my files are in lat/long, the area covered by each cell 
changes based on its latitude.  Can this be accounted for in trying to 
come with total area?

Thanks in advance for any suggestions to a grass newbie,

Jerry Griffith