I have been watching the discussion with interest. My perspective on mapping is getting the topology absolutely correct. All routing is driven by the topology of the underlying data (and the routing engine of the specific manufacturer). What I say below is said without criticism of the original mapper.<br>
<br>The intersection shown in the links below is an interesting case. As it is currently mapped in OSM, the mapper is showing the turning posibilities at the intersection (and to a lesser extent that the turning lanes have their own separate traffic light sequences). To my mind this is over mapping. While the intersection is displayed neatly at smaller scales, at the largest scale it is not pleasant (not saying it is wrong!). I am wondering if anyone has routed through this intersection with a garmin - what happens? Is it correct? I suspect in the scenario where you were travelling south and wished to turn right (west) into Christine Avenue you would be told to "turn right into 'to Christine Avenue', continue along Christine Avenue" which isn't correct. The intent of the mapper (as far as I can ascertain) was to indicate "move into right lane, turn right into Christine Avenue".<br>
<br>I have also been questioning what to do in a few circumstances, not unlike the above. I have taken the simple approach and introduced relations for any turn restrictions that may exist and just leaving the intersection as two separated ways joining to separated ways (ie no explicit turning lanes) which, I believe, is the currently stated way of doing it on the wiki - happy to be corrected otherwise.<br>
<br>While OSM is essentially a wiki and people can contribute as they see fit, we have to be consistent.<br><br>Craig<br><br>
> 2009/12/18 Ross Scanlon <<a href="mailto:info@4x4falcon.com" target="_blank">info@4x4falcon.com</a>>:<br>
> > Wrong, on everyone of these you have to enter the roundabout and then take the next exit, it is not a graceful sweep.<br>
><br>
> We really shouldn't have to map, if they are an exit they're an exit!<br>
> It shouldn't really matter if they are attached to an adjoining entry<br>
> or not. Until this thread came up I wasn't aware this was even an<br>
> issue and have tagged roundabouts this way myself.<br>
><br>
> We might be able to do something if it is the pre-processor that is to<br>
> blame for that bad routing information, although if it's a problem<br>
> with garmin software we can't do anything about this other than to<br>
> inform people about the issue and hope they will be understanding that<br>
> even though we shouldn't have to go out of our way to tag a roundabout<br>
> in a special kind of way we do for those that have garmin gear.<br>
<br>
Were not tagging it in a special kind of way it's as per the wiki and as per how it is on the ground.<br>
<br>
It's also aparent in intersections like this:<br>
<br>
<a href="http://www.nearmap.com/?ll=-28.085727,153.425859&z=19&t=k" target="_blank">http://www.nearmap.com/?ll=-28.085727,153.425859&z=19&t=k</a><br>
<a href="http://www.openstreetmap.org/?lat=-28.085727&lon=153.425859&zoom=18&layers=B000FTF" target="_blank">http://www.openstreetmap.org/?lat=-28.085727&lon=153.425859&zoom=18&layers=B000FTF</a><br>
<br>
What's currently entered into osm is not whats on the ground. There are
not separate ways going through the center of the intersection but
someone has entered them there for the turning lanes.<br>
<br>
Josm's validator and turnright throw so many warnings for this intersection it's not funny.