[OSM-talk] Topology (was: OSM the mediocre alternative)

Schuyler Erle schuyler at nocat.net
Fri Apr 27 05:49:11 BST 2007


* On 23-Apr-2007 at  5:12AM PDT, Frederik Ramm said:
> 
> And then uploading it to the server as two points which just happen  
> to be at the same location? To me there's a world of difference  
> between two nodes that just happen to be at the same position and two  
> features connecting at the same node because it is (topo)logically  
> the same node.
>
> For example, there's a railway line going over a bridge, and below it  
> is a river.

This reads to me more as an argument for z-index, or even altitude,
than one for topology.

> It is always hard to create something from nothing. If the
> information isn't there, where should the editor get it from? Trying
> to infer topology from simple features, in my eyes, is pure
> guesswork  and I will always be able to provide an example where it
> fails,  blatantly.

Do you have any examples that don't involve a difference in altitude
or z-index? I can't think of one. :-/

SDE





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