Tobias Wendorff <[email protected]> writes: > Matthias Julius schrieb: >> This is actually a good example why we might want to use Mercator for >> calculating rectangles. > > Which Mercator are you talking about? > - Spehrical Mercator / Web Mercator (it's using a sphere) > - "real" Mercator (Earth is flattened) > - Transverse Mercator (on sphere or ellipsoid?) > - Universal Transverse Mercator (on sphere or ellipsoid?)
Spherical Mercator. > > If you want to use the "normal" Web Mercator, OSM and Google use, > it would be better to use spherical geometry ... it's more accurate > than calculation into a projection and back to LatLon. The point is that things like the state of Wyoming only look rectangular in spherical Mercator projection or similar. > > Spherical geometry allows you to calculate _directly_ on the sphere > without using a projection ... you simple use LatLon in radian > degrees. True, but it's not really trivial. > > I can do some calculations about accurancy the next week, perhaps > sphere is enough ... but as soon as you work on big objects, you > might run into problems. The question is: What is big? When does the error become more than, say, 0.1 m? Matthias _______________________________________________ josm-dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/josm-dev
