[OSM-talk] How do I tag this road in OSM

Lars Aronsson lars at aronsson.se
Wed Aug 2 08:02:20 BST 2006


SteveC wrote:

> When OSM started a few people said 'rah rah WSF-T rah rah'.

Say again, what's WSF-T?

> figured that I'd just do anything practical to get things going.
> This meant nodes and segments.

Yes, a very good decision at the time.  But we're beginning to see 
different scalability problems now, exactly because you 
successfully did get things going.  Maybe it's time now or 
sometime soon to light the second stage of this rocket.

I suspect, even though I haven't studied this in detail, that 
polylines (ways without line segments) is the secret why the 
combination of "shapefiles" and MapServer in many applications can 
be so fast.  Polylines with bounding boxes is a very efficient 
grouping of a large number of nodes, that can scale very nicely.  
On a nationwide map, you only have to study a handful of bounding 
boxes rather than millions of individual line segments.

On top of polylines, there still needs to be larger objects.  
Each polyline by definition only runs between junctions (or street 
corners).  "King Street" or "national road 47" needs to be a group 
of many polylines.


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se




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