Misleading turn instructions when route is almost straight at a crossing

[GoogleCodeExporter]

Concerning routes that go straight at a crossing where the continuing way is 
offset by a few meters, like in the center of that place 
http://www.openstreetmap.org/?lat=48.832805&lon=9.095043&zoom=18&layers=M
coming on that track from the west, continuing to the east. 

The written and spoken turn instructions say 'turn left, then after a few 
meters turn right', but when you're actually there, the continuing road 
continues almost straight, so turning left would be wrong.

What version of the product are you using? On what operating system?

branch permaroute commit 603:b11221294165 on maemo 5

Original issue reported on code.google.com by robert.v...@gmx.de on 7 Apr 2012 at 1:59

[GoogleCodeExporter]

Wouldn't this be more of a data issue than a bug in MoNav?

If OpenStreetMap does not reflect reality, you should correct the data.

Original comment by veaac.fd...@gmail.com on 10 Apr 2012 at 8:17

[GoogleCodeExporter]

Sorry, this wasn't a very good expample. The offset there is hard to quantify, 
and it's probably bigger in the map data than in reality.

Let me give a better expample. In the center of

http://www.openstreetmap.org/?lat=48.888545&lon=9.159595&zoom=18&layers=M

coming along Göppinger Str, crossing Leinfeldener Str. The offset in the map 
data is about 3 m, which is close to reality. It's about half the width of the 
road. The situation can be seen in the aerial photo:

http://maps.google.de/maps?q=Ludwigsburg&hl=de&ie=UTF8&ll=48.888552,9.159409&spn
=0.001688,0.00342&sll=51.151786,10.415039&sspn=26.485995,56.030273&oq=ludw&hnear
=Ludwigsburg,+Stuttgart,+Baden-W%C3%BCrttemberg&t=h&z=19

I think most people would prefer to be guided 'straight' here. I imagine there 
are crossings where the offset is smaller than there, and if the data and the 
mapper are accurate, they do not put in a crossing at one point.

Original comment by robert.v...@gmx.de on 10 Apr 2012 at 7:29

[GoogleCodeExporter]

Ok, I can see your point. Should be relatively easy to fix by merging junctions 
less than X meters apart. The only question is what would be the best distance 
for this.

Since you seem to have looked at several examples, at what distance would you 
determine it to be a real turn?

Original comment by veaac.fd...@gmail.com on 11 Apr 2012 at 7:20

• Changed state: Accepted

[GoogleCodeExporter]

The distance depends on the width of the roads, but a single average value may 
also work for most cases. I'd say 7 m.

Original comment by robert.v...@gmx.de on 12 Apr 2012 at 6:48