[OSM-dev] tiles cut corners

[SteveC]

* @ 26/02/06 11:54:07 AM ben at somethingmodern.com wrote:
> On Sat, Feb 25, 2006 at 08:32:17PM +0100, Lars Aronsson wrote:
> > This code is hard to read as it is, and it doesn't get better from 
> > the fact that lat2 < lat1 even though lon1 < lon2.  The call is 
> > dao.getnodes(trlat, bllon, bllat, trlon), whereas the argument 
> > order in the CGI interface is bbox=bllon,bllat,trlon,trlat.  I 
> > must admit I don't fully understand what this deeply nested SQL 
> > statement does.  For example, where do "b" and "c" go?  Does this 
> > statement select any node outside of the current tile?  Isn't it 
> > in fact equivalent to the following?
> > 
> >   select id, latitude, longitude
> >   from nodes
> >   where latitude > minlat
> >     and latitude < maxlat
> >     and longitude > minlon
> >     and longitude < maxlon
> >     and visible = true
> 
> No, you need the subselect (or its equialent) to get the newest elements
> in the bounding box. (It's a wiki, right?)

yes.. to expand: you get the nodes in a bounding box, then you get the
latest versions of those nodes, then you have to retest that the latest
version is still within the bounding box. 

> 
> 		Ben
> 
> 
> 
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have fun,

SteveC steve at asklater.com http://www.asklater.com/steve/