[OSM-talk] Tile data server

Nic Roets nroets at gmail.com
Sat May 31 22:47:59 BST 2008


> - 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.

Changing to linestrings throughout OSM is possible conceptually. To do
it properly IMO, we will need a slightly more advanced upload protocol
for the editors : Instead of just modifying linestrings, there will
also be commands like "find all linestrings that visit (lat,lon) and
remove that entry" and "find all linestrings that visit (lat,lon) and
move it to (lat1,lon1)". The editors will still display nodes to the
user but when they are altered the above mentioned commands will be
used.

Of course it will have massive benefits for applications parsing OSM XML.




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