2010/11/18 Andy Allan <[email protected]>: > As far as I'm aware, 900913, 3785 and 3857 are all identical, and > don't have the difference that you are describing above. From > spatialreference.org > From the proj4 project:
> Moreover, you refer to changes made to the generate_image.py file, but > I don't see such a change: > http://trac.openstreetmap.org/browser/applications/rendering/mapnik/generate_image.py#L38 yes, sorry, this was probably part of my own tests (and as I used primarily generate_tiles it didn't harm). > However, the following two entries at EPSG are conflicting with all > the above, and do in fact appear to be different: > http://www.epsg-registry.org/report.htm?type=selection&entity=urn:ogc:def:crs:EPSG::3785&reportDetail=short&style=urn:uuid:report-style:default-with-code&style_name=OGP%20Default%20With%20Code&title=EPSG:3785 > http://www.epsg-registry.org/report.htm?type=selection&entity=urn:ogc:def:crs:EPSG::3857&reportDetail=short&style=urn:uuid:report-style:default-with-code&style_name=OGP%20Default%20With%20Code&title=EPSG:3857 yes, I also found that proj4 treats them equally, but in the end I thought it would be the best to rely on EPSG for issues on EPSG... > Ho hum. Maybe take it up with the proj project? Anyway, we use > Spherical Mercator ie. the one without the +rf=298.25... so I'd find a > different copy of generate_image.py Thanks for clarifying this. I think we should write this in the wiki (basically we shouldn't write that we are using EPSG 3857 but we could stick to 900913) , as you get (obviously) different results with and without the ellipsoid. It is quite confusing indeed, but maybe I was wrong with the 3785 / 3857 idea: I found out that EPSG themselves has 2 versions of EPSG 3857: one is "not valid" (and identical to what before they called 3785) and one is "valid" (according to EPSG) which has the ellipsoid with inverse flattening. cheers, Martin _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
