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    Re: Do We Still Need to Use Sextants?
    From: Yves Robin-Jouan
    Date: 2013 Apr 6, 02:49 -0700

    Frank, you said :

    "May I ask, regarding the "optronic turret" which you mention, how
    does it get its vertical? Do you do this with accelerometers and band
    This is a good question. A number of solutions are being investigated. One of them is a connection to the IMU (Inertial Measurement Unit) used with the hybridization. But even with IMU, there are some limitations.

    You said :
    "A system like this could handle certain kinds of problems with GNSS jamming,
    but celestial is always at the mercy of the weather."
    I agree it's true with a ship, but it is better with an aircraft or an UAV...
    Moreover, we can use IR cameras and image processing to point at the Sun through clouds.

    About jamming, a way to cope with it is to use directive antennas (passive or active devices). It is difficult with MEO satellites like GPS and GNNS ones. But it is easier with GEO satellites like for WAAS or EGNOS augmentation.
    For instance, a basic problem should be to get a fix from two GEO and the Sun (or the Moon, sometimes)!

    I agree wih you, Frank, that it may appear quite unrealistic. But a number of such projects are considered in several countries at this time. We will see the results...
    (Sorry if I come back to previous discussions in NAVLIST: I was not aware of them)
    Best Regards,

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