Hi, Chris Browet wrote:
Yo mean the interpretation is up to the implementer? It might be difficult to have consistent maps for a given style this way...
I agree to that, but...
In this case (and in 90% of the non lat/lon-mercator projections) the bbox is not orthogonal/rectangular (have a look at http://en.wikipedia.org/wiki/Map_projection for some exotic ones). The basic assuptions of tiles is that the world representation is rectangular, which is mostly not the case for projections. Which is why TMS only accepts lat/lon (EPSG:4326) and mercator as projections...
... this is a non sequitur. You can use *any* projection with tiles. The tiling happens after the projecting; after projecting, you have the world on a plane and it doesn't matter the slightest bit if it looks like a square or like an egg - the basic ideas "zoom level 0 = world on one tile" and "zoom level n+1 = four times the size of zoom level n" can be implemented just the same. You might have large unused areas on the outside but that doesn't negatively affect tiling.
What you will have is, of course, that the area covered by a tile on a certain zoom level and at a certian lat/lon will be different between projections.
The only generally "recognized" zoom levels are map scales (e.g. 1:5000) which are clear and precise for everyone.
For a raster rendering engine, they are only clear and precise if combined with a resolution. Whoever prepares the raster thatis ultimately sent to paper for the printed map, needs to know not only the map scale but also the resolution. If you do not know the display or print resolution, then there is no way you can accurately create an "1:5000" image.
Bye Frederik _______________________________________________ Mapcss mailing list [email protected] http://lists.openstreetmap.org/listinfo/mapcss
