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Dead reckoning with CarPlay vs native Toyota nav

Discussion in 'Gen 5 Prius Main Forum' started by tmorrowus, Oct 2, 2023.

  1. tmorrowus

    tmorrowus Member

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    Back when OEM navigation systems were first coming out, they worked better than portable devices like the garmins, because the OEM systems integrated inertial sensors to allow dead reckoning when satellite (or cell) signals were spotty.

    I wonder if there is still some advantage to the OEM navigation systems in this area. Using CarPlay to display the navigation from an iphone in the charging pocket obviously works okay, and I wouldn’t be surprised if the phones have better inertial gyros than cars these days. But the phone is not securely mounted to the car, and could vibrate and jostle in that pocket, producing noisy gyro data.

    Also, perhaps more importantly, the car knows the exact current speed even without satellites.

    How this entered my mind was noticing that the gyros get completely confused when I navigate with an iphone attached to my bicycle handlebars; I assume all the road vibration and imperfectly stiff mount are the cause.

    So I am looking to mount my phone as securely to the car as I can. Ideally the CarPlay system would connect the car’s gyros and speedometer to the phone, but I don’t think it works that way.
     
    #1 tmorrowus, Oct 2, 2023
    Last edited: Oct 2, 2023
  2. roleohibachi

    roleohibachi New Member

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    Location:
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    Vehicle:
    2023 Prius
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    XLE AWD-e
    Besides deep tunnels, you won't encounter areas where a modern GPS receiver can't maintain a hot fix. Receiver sensitivity has improved vastly in the last 20 years. There are no coverage gaps in the constellation. On the other hand, inertial navigation with any accuracy requires greater precision than modern device sensors can offer. I'm not saying you're wrong - just that you're optimizing for a very unlikely corner case.

    At low speeds, modern devices use the internal magnetometer to inform heading. Bearing, on the other hand, is always measured as a difference of previous positions. At regular travel speeds, devices reduce noise by assuming the heading is the bearing. The sensors aren't measured.

    Cell service still has gaps. This is solved using "offline maps" on your device. The method varies by app.
     
    #2 roleohibachi, Oct 3, 2023
  3. tmorrowus

    tmorrowus Member

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    I still have occasional issues getting a GPS fix in downtown areas with tall buildings, heavily wooded areas, off road, and of course parking garages with my iphone 11 pro max. It isn't a huge issue, but my 20 year old dvd navigation with inertial gyros and speedometer integration in my 2004 prius handled these cases a bit better.
     
    #3 tmorrowus, Oct 3, 2023
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