[OSM-dev] spatial index - B-Tree over z-order curves vs R-Tree over GIST

Frederik Ramm frederik at remote.org
Thu Apr 9 11:30:33 BST 2009


Hi,

pablo platt wrote:
> Is the tiles resolution predetermined 

Yes, it is 32 bits.

We take lat and lon and scale them to a 16 bit value each (this means we 
get 0.0055° precision in the East-West direction and 0.0027° precision 
in the Norh-South direction). Then we use first bit of the 16-bit 
longitude value, then the first bit of the 16-bit longitude value, then 
the second of each, and so on, to build a 32-bit tile value.

Bye
Frederik





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