[talk-au] Mini Roundabouts.

Simon Biber simonbiber at yahoo.com.au
Fri Apr 30 03:31:47 BST 2010

From: Steve Bennett <stevagewp at gmail.com>

> 1) They're clearly mini roundabouts. I go straight over them on my bike.

You're not supposed to go over a roundabout, unless your vehicle's lack of turning ability necessitates it! :-)

> 2) The roads you've mapped out don't even follow the aerial photos - they cut across people's front lawns.

The roads in that area look OK to me with reference to NearMap photos.

> 3) Why an octagon shape? Ugh. At least use the "tidy" function in JOSM or Potlatch to make them circles.

I mostly use octagons to map roundabouts in my local area too. The OSM Editing Standards and Conventions document says "you should add enough points to make each curve look like a curve". On the other hand, the documentation for junction=roundabout suggests "A standard size roundabout with up to four exits can be drawn simply using four nodes in a diamond shape." 

As the editing conventions say, curves made of lines "always look like a series of lines when zoomed in past a certain 
point". The degree to which this is an issue depends on the zoom level. I particularly dislike the way that a diamond shape renders on (the current maximum) zoom 18 - it looks nothing like a circle. However an octagon looks quite close to a circle. If we had renderers that went to zoom 19 then I would perhaps go beyond the octagon and use a dodecagon (12 sides).



More information about the Talk-au mailing list