Programming Turn-by-turn Navigation

Discussion in 'iPhone/iPad Programming' started by dejo, Jan 21, 2013.

  1. Moderator

    dejo

    Staff Member

    Joined:
    Sep 2, 2004
    Location:
    The Centennial State
    #1
    I'd like to look into programming some turn-by-turn navigation, or as I like to call it: navigation tracking. That is, you have a route, how do you detect that the user stays on that route. Does anybody know of any good resources that go into algorithms and such for this? Is rolling-your-own completely nuts? Thoughts? Suggestions?
     
  2. macrumors demi-god

    KoolStar

    Joined:
    Oct 16, 2006
    Location:
    Kentucky
    #2
    I might look into some of the open source mapping items such as open maps or some other providers. Some have build libraries that you could look at to get an idea.
     
  3. macrumors 6502a

    Joined:
    Mar 30, 2012
    #3
    You took a turn that does not end at the next node expected in the route that
    was found and stored with the recursive algorithm that found the shortest route
    (before one way streets, and tolls etc. enters into it).

    I don't know what liberty you have with Apple maps, but if it's your own GPS
    program, the difficulty is in the auto routing, and maybe lock to road depending on the platform,
    not checking the user is on the route.
     
  4. thread starter Moderator

    dejo

    Staff Member

    Joined:
    Sep 2, 2004
    Location:
    The Centennial State
    #4
    I've found solutions for routing; it's for the tracking that I don't find a lot of information readily available.
     
  5. macrumors 6502a

    Joined:
    Mar 30, 2012
    #5
    So as you're following your route, your program is checking off each node
    as it is passed at every intersection where a turn is required.
    Ignore points in a polyline that only represent bends in the road and not intersections.

    At least for Garmin maps (and I suspect every other data map), roads that
    intersect or join always have exactly the same coordinates where they meet,
    so your node list can be a structure containing the coordinate pairs for intersections of the route.

    http://computer.howstuffworks.com/routing-algorithm3.htm

    In the above example, the preferred route is A,B,D,E.
    If you took the wrong turn at node D, and headed back toward node C,
    it is easy to determine you are on a line (road) that does not connect node E.
    Your GPS doesn't check that you took a left turn at node D,
    it checks that you are still connected to the path that ends in the next node.

    I think a commercial GPS gives a little bit of time to reroute to allow for GPS
    error which is ok because you weren't going to do a 180 on the road and head
    back in most cases. you need to reroute from node C.
     

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