[OSM-talk] OSM map renderer - update

Richard Fairhurst richard at systemeD.net
Thu Apr 20 10:00:39 BST 2006


Quoting Lars Aronsson <lars at aronsson.se>:

> [misleading road junctions]
> 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.

Sure. It just happens that the buggy generalisation is a result of the round
caps 'extending' the road beyond its natural length. If Google (or an SVG
renderer, or whatever) shortened the path before putting the round cap 
on, then
this wouldn't occur... but they don't.

> 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.

Absolutely, and this is even more true of minor roads (which might only be 5m
wide but would perhaps be 0.15 mm on the map). The most-quoted example of
generalisation in Britain is the valleys of South Wales, where the physical
geography often has to be reordered to accommodate several roads, a railway or
two, a canal, a river and several settlements all running up the same narrow
valley.

Richard





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