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    Re: Do We Still Need to Use Sextants?
    From: Jeremy C
    Date: 2013 Apr 8, 05:57 -0700

    These solutions seem squarely aimed at military applications. The hardware cost, both initial and upkeep, would be very high.

    To take this on a bit of a tangent, I would like to see sextants integrated into the ECDIS like we can do with RADAR and terrestrial bearings. What would be needed, on the "cheap," would be a sextant that is linked in real time to the ECDIS computer. I would think that a high accuracy digital time movement corrected via GPS (to UTC, not GPS time) and some method of transmitting the angular measurements (Hs and Azimuth) to the computer. I would think this could be accomplished via bluetooth.

    I would think that a flux gate compass could be attached to the sextant for AZ, but am not sure how to design a method to read the arc. I am sure that some electrical engineer could figure that out.

    The method of use would be something like this: the navigator goes to the wing, and when he marks the sight he would hit a button. The button would take input from the arc, compass, and clock and send it the the computer. The computer would take the data and figure out which body it was. Then computer, based on the GPS position at the time of the sight, would reduce the body, and then plot the LOP on the ECDIS. When the full round of sights is taken, the navigator can either take the LOP's as they lie, or tell the computer to advance/retard them to a common time for a MPP using all sorts of statistical mathematics to do so.

    Of course if the GNSS system is down, the computer would use the DR, and time can be entered manually as corrected via the time ticks, and the computer can use that information to make it's calculations.

    I think that it would be good enough for the high seas. Of course as you make landfall you would shift to your RADAR and terrestrial bearing lines to check your GNSS, or navigate totally if the birds are being jammed or otherwise disrupted.

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