[OSM-talk] OSM map renderer - update

Lars Aronsson lars at aronsson.se
Thu Apr 20 05:26:33 BST 2006

Richard Fairhurst wrote:

> http://maps.google.co.uk/maps?f=q&hl=en&q=OX7+3RD&om=1
> If you zoom out a couple of times, you'll see that a junction is 
> implied between Nine Acres Close and Banbury Hill. But as the 
> larger scale maps show, there's no junction there. This is 
> because the round line cap is 'extending' the road beyond its 
> true length.

This is not caused by the round caps per se.  It's just a 
consequence of a buggy generalization.  The same bug could cause 
two parallel city streets to run into each other.  The correct 
generalization is to either remove minor objects as you zoom out, 
or to move them so that the separation between them is maintained.

On road maps, motorways are typically drawn far broader than the 
scale of the map would indicate.  A motorway 50 metres wide in 
real life, would be 0.2 mm wide on a map in scale 1:250,000, but 
can be drawn 2 mm wide, which is an exaggeration by ten times. 
Objects near the motorway must be pushed to the sides accordingly.

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

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