Jerry Griffith wrote: > Ok, since GRASS does account for differing cell size in lat/long raster > files, what I am after is mapcalc is to do something like: > > croparea = [cellsize] * corn_map (my corn_map has a floating point > value, ex. 0.29 that gives the fraction of the cell that is in corn > cultivation) > > I have tried simply typing in for [cellsize] the functions listed below, > but that doesn't work or my syntax is wrong. > > G_begin_cell_area_calculations() > G_area_of_cell_at_row()
These are C functions; they don't exist in r.mapcalc. > and I haven't found in r.stats or related commands that allows an > intermediate multiplication step. I have tried using r.proj (and with > -n) to reproject to an equal area projection, but my crop maps are > global coverages and the other Locations in lambert equal area are for > the US, so the result is my global crop maps get clipped to the US. If you can't use a global equal-area projection, you could just use the underlying equations within r.mapcalc. Depending upon the required accuracy, multiplying by cos(y()) might be sufficient. Otherwise, see lib/gis/area_ellipse.c for the equations used. -- Glynn Clements <[EMAIL PROTECTED]> _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user