On Fri, Sep 30, 2011 at 10:00 AM, Zsombor Szabó <[email protected]> wrote: > Hi, > > studying the OSM database schema over at > http://wiki.openstreetmap.org/wiki/Database_schema I was wondering for > what the 'tile' attribute is used for in the current_nodes, nodes, > gps_points tables. > > If you know then please share.
it's a geometric index using a B-tree of the (truncated) morton code of the lat/lon of those elements. for the gory details, see the sql_for_area function in the source code [1]. there's also some general discussion on the wiki [2], info about the general method on wikipedia [3] and in the mailing list archives [4]. cheers, matt [1] http://git.openstreetmap.org/rails.git/blob/HEAD:/lib/quad_tile.rb#l63 [2] http://wiki.openstreetmap.org/wiki/Quadtile#Indexing_single-point_geo-locations [3] http://en.wikipedia.org/wiki/Z-order_curve [4] http://lists.openstreetmap.org/pipermail/dev/2008-September/011694.html _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
