[OSM-dev] [Mapnik-users] How does Mapnik know which nodes are "important"?

[Jon Burgess]

On 27/12/2007, Gabriel Ebner <ge at gabrielebner.at> wrote:
> On Thu, Dec 27, 2007 at 02:06:48AM +0000, Jon Burgess wrote:
> > > By using QuadTiles, you only have to look at 120,000 nodes (10,000
> > > nodes each for the QuadTile and all of its parents) to determine what to
> > > map. Of course, you could use this in conjunction with spatial
> > > indexing to make things even faster.
> >
> > We do not directly deal with this level of detail in Mapnik. The
> > PostgreSQL Postgis extensions deal with efficiently performing spatial
> > queries on the data in the tables. It uses an radix-index scheme which
> > I believe is a more generalised form of quad-tiling.
>
> AFAIK postgis uses R-trees for indexing, i.e. no sort of tiling whatsoever.

I was thinking that the prefix / trie structure of the r-tree is quite
similar to the quad tiling scheme. The further you go down the tree
the smaller spatial area is covered by the objects deeper in the tree.

-- 
    Jon