[Talk-ca] Telenav mapping turn restrictions

[James Mast]

Martijn, with your example you gave back 3/30 [1], are you 100% sure that it still might be legal to right turn at the main intersection?  It might be if you haven't been there, even with the slip lane being there.

Case in point, if you were to have one of your mappers modify this intersection [2] with a 'no right turn' relation, you would be adding false information to the OSM database.  While there is a 'slip' lane for right turns, there is overhead signage past that slip lane leaving US-19 saying that you are allowed to make a right hand turn at the intersection.  So, [3] would be completely legal and would be prevented if a false relation were to be added here.

This is just something you can't be 100% sure of without visiting it in person, or have imagery from something like Mapillary to see it.  So, I can see why Andrew was upset about this.

-James

[1] https://www.openstreetmap.org/directions?engine=osrm_car&route=40.66610,-111.86760;40.66386,-111.86464#map=18/40.66520/-111.86552
[2] https://www.openstreetmap.org/directions?engine=osrm_car&route=40.58570%2C-80.04423%3B40.58680%2C-80.04410#map=19/40.58625/-80.04431
[3] https://www.openstreetmap.org/directions?engine=osrm_car&route=40.58614%2C-80.04461%3B40.58680%2C-80.04410#map=19/40.58648/-80.04457


________________________________
From: Stewart C. Russell <scruss at gmail.com>
Sent: Friday, March 31, 2017 7:26:12 PM
To: talk-ca at openstreetmap.org
Subject: Re: [Talk-ca] Telenav mapping turn restrictions

On 2017-03-31 04:29 PM, Martijn van Exel wrote:
> … the engine
> may decide, lacking an explicit restriction, to take the non _link turn
> because it's faster even if that is an illegal turn. That is why we need
> these restrictions to be explicit in the data.

but … but — that's Tagging For The Map, or worse, Tagging To Fix
Software Stupidity. It's explicitly mapping something that's *not*
there, and so is contrary to what we're supposed to map.

I don't have a problem with it being in Telenav's data, but it doesn't
belong in OSM.

 Stewart


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