Le 8 décembre 2016 07:25:46 GMT+01:00, Glynn Clements <gl...@gclements.plus.com> a écrit : > >Moritz Lennert wrote: > >> Yes. Do we have any existing module to calculate area by pixel ? An >> area() function in r.mapcalc would be nice... > >I notice that this has been added, but I'm not sure that it's adequate >for this task. > >For anything other than lat-lon locations, G_area_of_cell_at_row() >assumes that the area of a cell is constant over the region. That's >true for equal-area projections, and not far off for small scales >(where projection would be almost an affine transformation), but it >could be quite far off at larger scales.
Do I understand correctly that you would like the function to return geodesic area in projected locations? That would be a nice feature, but I wouldn't make it the default. I think most people would expect constant pixel area in such location, knowing (at least some) that there is inherent error in the projection. Moritz _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
