How about an equal-area map projection? http://en.wikipedia.org/wiki/Map_projection#Equal-area
Cheers, Dylan On Sun, Feb 7, 2010 at 1:37 PM, Matthew Vavrek <matt...@matthewvavrek.com> wrote: > Hello, > I have a question that I have yet to find a definitive answer for on this > mailing list (or elsewhere as of yet) about a method of calculating the area > of a spherical polygon (ie an area on the surface of the earth). I know of > the areapl() function in the splancs package, although as I understand it > can only calculate the area of a planar polygon, not a spherical one. The > polygons I'm trying to calculate are generally simple and convex; is there > any way of doing this in R? > > Also, I would like to get some feedback on a function that I wrote myself > that does this (although not perfectly). The function is called earth.poly() > and can be found in the fossil package on CRAN. Right now, it can only deal > with areas less than one hemisphere in size, and I haven't stress tested it > too much yet. Also, it treats the earth as a sphere rather than a true > ellipsoid for simplicity, which can mean up to a 0.2% error in actual area > (although it is generally much less). Basically though, if anyone knows of > something better out there already, I would gladly use that instead, rather > than spending far too much time doing it myself. > > Cheers > Matthew > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
