[OSM-dev] New OSM binary fileformat implementation.

Frederik Ramm frederik at remote.org
Sun May 2 10:58:48 BST 2010


Hi,

Scott Crosby wrote:
> But there may be problems in geographic queries. Things like 
> cross-continental airways if they are in the OSM planet file would cause 
> huge problems; their bounding box would cover the whole continent, 
> intersecting virtually any geographic lookup. Those geographic lookups 
> would then need to find the nodes in those long ways which would require 
> loading virtually every block containing nodes.  I have considered 
> solutions for this issue, but I do not know if problematic ways like 
> this exist. Does OSM have ways like this.

We do not recommend having ways that long (anyway, ways are limited to 
2000 nodes so you'd have to place your nodes very far apart to achieve 
this).

It is however very well possible to have relations that span the globe 
so you will have to think about that. Even today you will find a 
relation describing, say, a whole country boundary, and most people 
asking for geographic queries actually mean something like:

"give me all nodes in my bbox, plus all ways and relations using any of 
these nodes; and after that I am very likely to ask you for (a) all 
other objects which are also part of one of the ways or relations 
returned and (b) any relations that use any of the objects collected"

I belive Matt has just amended the API "map" call CGI to reflect user 
demands and if you're interested in an algorithmic description of what 
people usually want when they ask for an area it would not hurt to look 
at that.

Bye
Frederik





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