depending on the scale and the accurancy you need.... Lambert area is a good way for world wide [non polar] data, like Behrmann and maybe also Peters...to view Areas in the nearly real [scaled] size - but with a bit deformation for the well known shapes... e.g. look at Behrmann http://mapsof.net/map/behrmann-projection#.UlfIJhDGD5w Standard-mercator: http://www.math.ubc.ca/~israel/m103/mercator.png
for worldwide area-calculations it would be a good solution to get some approach formulas to correct the calculations from your data...but for worldwide data I don't beleive that theres a beter way to get results better than several/many square km's....from far away I would suggesting the usage of the spherical area formular - or reproject your data into any cylindric Projection for getting cartesian coordinates, so then you can use the much easier gaussian polygon area formular ....keep in mind that both results will finally differ you should difference between the view of an areaconform projection and the calculation of the area itself...1st thing is madeable using such projection (s.a.) to get a graphical view over size-differences....2nd would be solvable much more easier - resulted accurancy depending primary on the data and then to the used correction formular and of course commonly there's just the 2D projected Area :)....e.g. switzerland would have a bigger 3D area [natural area], then complete denmark [as a flat area] would have... in 2D it is swiched [I'd never never calulated...]... also different projection will cause different deformations.... an calculated area in e.g. WGS84[worldwide] <> UTM-Zone <> Gauss-Krüger [germany] <> Nature.... so also true nescessary for wich application you need the area of any worldwide polygon...and wich accurancie will be needed...the resulting work ranges from a few minutes upo to workload for following generations ... regards rolf gabler-mieck > Hello, > > what I understood so far: > for calculating the area of a polygon, a fitting equal area projection for > the region of the world is required to get good results. > For different areas different projections are required. > So when I plan to cover the whole world (lets say for an online application) > I have to find out which projection is good for this area, which might be a > complex requirement. > > Is this correct? Or is there one standard way which is working for the whole > world ? > > Or - Is there a different approach to calculate the area with geotools, for > example like the geodesic calculation of Open Layers? > > Regards, > Peter -- #-/\-#-/\-#-/\-#-/\-#-/\-#-/\-#-/\-# Dipl. Ing. d. Geomatik Rolf Gabler-Mieck Geographisches Institut der CAU-Kiel LGI Ludewig-Meyn Str. 14 24098 Kiel Tel.: 0431-880 2955 #-/\-#-/\-#-/\-#-/\-#-/\-#-/\-#-/\-# ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134071&iu=/4140/ostg.clktrk _______________________________________________ GeoTools-GT2-Users mailing list GeoTools-GT2-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
