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How does GPS determine heading in 2017?

nickmarotta 0 Points
in GPS Discussions
My question is how do GPS systems today determine what direction you are facing, also known as heading. The only two options that immediately come to mind are either with an electronic compass, or by looking at the previous "bread crumbs" coordinates and determining what direction you are going by looking at where you have been. I know most cell phones have compasses built in to them, but is that what is used? What about regular car mounted gps? Thanks!

Comments

  • alanb 532 Points
    edited June 2017
    Some handheld devices have a magnetic compass that kicks in when the speed falls below a certain threshold (2 or 3 MPH). When moving faster than this it uses the incremental track points (breadcrumbs as you say) to determine heading.

    Most (maybe all) Garmin automotive devices just use motion and don't have a magnetic compass. Under certain conditions, it can actually cause the heading to change when stopped (because of drift or false readings). Sometimes in 3D or track up navigation mode it will cause the map display to rotate. In North Up mode your vehicle icon will rotate.
  • nickmarotta 0 Points
    alanb said:

    Some handheld devices have a magnetic compass that kicks in when the speed falls below a certain threshold (2 or 3 MPH). When moving faster than this it uses the incremental track points (breadcrumbs as you say) to determine heading.

    Most (maybe all) Garmin automotive devices just use motion and don't have a magnetic compass. Under certain conditions, it can actually cause the heading to change when stopped (because of drift or false readings). Sometimes in 3D or track up navigation mode it will cause the map display to rotate. In 2D mode your vehicle icon will rotate.

    Interesting. If you're following the GPS on a trip, how is being falsely rerouted prevented? Are the incremental trackpoints accurate enough to not falsely reroute you ?
  • Boyd 1965 Points
    edited June 2017
    alanb said:

    Most (maybe all) Garmin automotive devices just use motion and don't have a magnetic compass.

    I'm not so sure about that Alan. IIRC, Garmin started putting triaxial magnetic compasses in the Nuvi series back in 2010 or 2011. I believe this is how it automatically switches between portrait and landscape view, so my *guess* is that all the Nuvis that automatically sense screen orientation have this feature.

    We discussed this here at the time, I recall a thread where someone claimed you could see it in action if you drove around a parking lot and swerved from left to right. This person felt the vehicle orientation responded much faster than it could have using a satellite fix. I remember trying this with my own 3790 and not feeling like it was conclusive.

    So I think the compass is there, but not clear under what circumstances it is actually used. A quick Google search found this reference to the compass on the Nuvi 2360. But IIRC, Garmin specifically mentioned the compass in the original press release when the 3790 was introduced.

    gpstracklog.com/2011/02/garmin-nuvi-2360lmt-review.html

    __________________

    "A couple of features unique to the 2360LMT (at least as far as 2xxx models go) are a screen that can rotate to portrait view and a tri-axial electronic compass. That latter feature may prove interesting for geocachers or folks planning to use it as a pedestrian navigator."
  • alanb 532 Points
    edited June 2017
    Wow ... I sure don't recall that discussion, but thanks for posting about it Boyd. I could swear I have seen my 3597 swing around on the map view when standing still but I will now start paying more attention.

    And as far as using it for geocaching ... pretty much worthless except for getting you to the nearest parking spot ... then I would switch to the Oregon to hike to the actual cache. That said, I will have to admit that I haven't been geocaching much since I replaced my 855 with the 3597, so maybe I should give it another try.
  • Tim 1474 Points
    I thought they were using Accelerometer/gyro, no? (Or is that what you mean by "motion"?)
  • Boyd 1965 Points
    edited June 2017
    I can't find any other references to it with a quick search, but I specifically recall that a triaxial compass was mentioned. I remember that surprised me since the iPhone of that generation used an accelerometer. I also recall reading that Garmin was using the compass to sense screen orientation on the Montana 600 and wondered if that was the reason is was rather sluggish to respond when you rotated it.
  • Boyd 1965 Points
    edited June 2017
    Here you go:

    gpstracklog.com/2012/03/the-best-garmin-nuvis-for-pedestrian-navigation.html
    ___________

    Here are all the nuvi models with a triaxial compass:

    Garmin nuvi 2360LMT
    Garmin nuvi 2360LT
    Garmin nuvi 3450
    Garmin nuvi 3450LM
    Garmin nuvi 3490LMT
    Garmin nuvi 3550LM
    Garmin nuvi 3590LMT
    __________

    But there is still some ambiguity, see this thread: http://forums.gpsreview.net/discussion/25306/auto-gps-for-trail-riding
    ddabcd277 said:

    3400 series have accelerometer. It is different from 3axis compass. Only 2360 have it AFAIK from the automotive gps.

  • t923347 425 Points
    alanb said:

    Wow ... I sure don't recall that discussion, but thanks for posting about it Boyd. I could swear I have seen my 3597 swing around on the map view when standing still but I will now start paying more attention.

    I leave my 3597 plugged in at home on the bean bag mount all the time and your right Alan it does swing around on the map view fairly often. That's in 3D mode which may make a difference though.
  • alanb 532 Points
    Knowing Garmin they probably removed the compass on the 3597 :-S
  • alanb 532 Points
    edited June 2017
    In thinking about this, Garmin removed the special pedestrian mode after the 34x0/35x0 models. I know my 3597 doesn't have it. Garmin also had the special (extra cost) city maps for the pedestrian mode that had public transportation and some other special features. These maps are now also discontinued.

    So I bet the nuvi triaxial compass went away with the demise of the pedestrian mode.
  • Boyd 1965 Points
    alanb said:

    In thinking about this, Garmin removed the special pedestrian mode after the 34x0/35x0 models. I know my 3597 doesn't have it. Garmin also had the special (extra cost) city maps for the pedestrian mode that had public transportation and some other special features.

    This feature lives on in the Garmin StreetPilot app for iOS. It is a separate in-app purchase called "urban guidance", but it requires a data connection to fetch the public transit schedules as opposed to embedding them in the map. https://www.garmin.com/en-US/blog/automotive/garmin-updates-iphone-navigation-apps-with-public-transportation-features-and-apple-maps-integration/
    ___________

    With Urban Guidance users are able to integrate public transportation into their
    route, complete with detailed itineraries of transit stops. The
    new feature considers trains, trams, busses and water taxis when calculating
    pedestrian routes. Users will be guided to a transit stop by foot and be able
    to look up detailed information on what line to take and where to get off.
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