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    Re: Magnetic variation changing faster than anticipated
    From: Bill Lionheart
    Date: 2019 Feb 25, 08:03 +0000

    All small boats still use magnetic compasses to steer. Typically this
    is a binacle compass at the steering position and an electronic
    compass to feed the heading to the autopilot. GPS is only accurate to
    a few m so it cannot provide the heading on a time scale required to
    steer, but it can give a very reliable True course that has been
    steered. Accelerometers and inertial navigation can help of course and
    they are used in land and air vehicle navigation systems to
    interpolate GPS fixes. Modern high end boat autopilots also have
    accelerometers, but I dont know they have a system that works without
    a magnetic compass yet.How necessary it is to no the relation between
    magnetic and true however is not so clear given GPS, one only needs to
    go 100m before you have it calibrated! All it needs to be is
    approximately uniform.
    On Mon, 25 Feb 2019 at 04:47, David C  wrote:
    > Is the magnetic compass used today or is it of theoretical/histrorical 
    interest only. I believe that in a moving vehicle GNSS can give the track and 
    surely that is what matters, not heading.
    > View and reply to this message

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