[OSM-talk] Tile data server

[Shaun McDonald]

On 31 May 2008, at 22:47, Nic Roets wrote:

>> - still contains node IDs, so you can locate connections (unlike
>> postGIS linestrings)
>
> You can locate connections without node IDs. Just index the
> coordinates according to the concatenation of lat and lon. Where
> lat1=lat2 and lon1=lon2, it most likely refers to the same node
> (>99.9%) and where it does not, there are two cases :
> 1. A meaningless connection like landuse connecting with highway
> 2. Highway connecting with highway which is most likely bad editing
> that the validator / link program should flag.
>
> Gosmore uses this approach and no one has complained.

There is a flaw with this approach, where you have over and under  
passes, or double decker bridges for example.


Shaun