Have QuadTiles solved the "enclosed area"/"segment outside tile" problems?
The problems: % If you request a tile that's completely enclosed by an area, you won't "see" that area, since all of its nodes lie outside the requested tile. % If a way goes through a tile, but has no nodes in that tile, you won't see that "way" for the same reason as above. The wiki page (http://wiki.openstreetmap.org/index.php/QuadTiles) seems to suggest storing all the tiles a way/area goes through or encloses (including tiles where the way/area has no nodes), but this seems inefficient. Another approach is to store the "bounding box" for each way/area: the smallest QuadTile that completely encloses the way/area. Then, when you're looking for ways/area that intersect a given tile, start with the largest tiles and work your way down. Example: I want the ways/areas intersecting ACBDCBADC. I start by looking at the ways/areas whose bounding box is 'A' (probably aren't any, since that's 1/4 of the world). I then look at the ways/areas whose bounding box is 'AC', 'ACB', 'ACBD', etc. Of course, it's possible that a way has 'ACBD' as its bounding box, but still doesn't intersect ACBDCBADC, so this process only gives me candidates-- I still have to post-process to confirm the ways/areas actually intersect my tile. The process can be extended once for ways/areas entirely within the tile. For example, I can look for ways/areas with bounding box 'ACBDCBADC?' (where '?' is exactly one character), then for ways/areas with bounding box 'ACBDCBADC??', and so on. If I'm limiting myself to the 1000 (for example) biggest ways/areas, I can stop when I've found enough -- I don't have to look for ways/areas with bounding boxes matching "ACBDCBADC????????????????" for example. Of course, recent versions of MySQL support polygons/etc, and that might be another approach. -- We're just a Bunch Of Regular Guys, a collective group that's trying to understand and assimilate technology. We feel that resistance to new ideas and technology is unwise and ultimately futile. _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/newbies
