With regards to solution 1) I have never noticed a sliproad onto a
roundabout tagged as junction=roundabout (UK East Midlands). Where is
this common practice? If this is not too widely used then it might be
worth retagging, but I don't know how easy it would be to automatically
detect these.
Jonathan
On 08/09/2011 19:48, Thomas Davie wrote:
Hi,
Today I experimented with using OSM maps on my Garmin sat-nav. The
one thing that I noticed was that roundabouts do not work well. The
problem seems to be the slip roads entering the roundabout. The
sat-nav recognises them as a roundabout in themself, and because of
that gives some fairly poor directions, for example:
• Drive 10 miles then enter roundabout.
(Drive 10 miles)
• Enter roundabout.
(Enter the slip road to the roundabout)
• Enter roundabout and take the third exit.
As you can see, because of the slip road's existence the GPS does not
announce which exit you're expecting to take until the last minute.
This means that you can't get in the right lane early enough.
Proposed solutions (all of which are horrible):
1) Don't tag sliproads onto roundabouts as junction=roundabout,
instead use some other tagging scheme. Not greatly desirable because
it involves a *whole* lot of retagging.
2) Ask garmin to fix it (doesn't sound likely).
3) Write some fancy heuristics in the conversion from OSM to routable
garmin maps that figure out when you're looking at slip roads and when
it's an actual roundabout (sounds unreliable).
Can anyone thing of a better solution to this?
Bob
if (*ra4 != 0xffc78948) { return false; }
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