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    Avoiding the symmedian (and other) points
    From: Gary LaPook
    Date: 2018 Nov 5, 13:43 -0800

    I made the sugestion several times in the past that the way to avoid all the discussion and desention about finding the proper point to represent the "fix" in a three-star "cocked hat" was simply to only observe two stars. It appears that this is the method used by the Air Force in its automated star-tracker systems, only using two stars at a time. And it acheives better than a 1,000 foot CEP. This means that 50% of the fixes will be within 1,000 feet, 93,7% will be within 2,000 feet, and only 0.2% will fall outside of 3,000 feet. The automatic star tracker is sugested for surface Navy ships but, for surface navigation, the same old problem of clouds raises its ugly head. At 25,000 feet the probability of a clear line of sight anywhere on earth and at any time is 68% and becomes 100% at higher altitudes. Would it were it this good on the surface! 

     http://www.dtic.mil/dtic/tr/fulltext/u2/a090649.pdf

    https://www.sr-71.org/blackbird/manual/4/4-161.php?fbclid=IwAR0NWtsAhGXlRyghSFgK-8BPpS7oA5Z_pUWjwLSCxlDV4B7sepDLvIfQUoE

    https://www.maritime-executive.com/blog/automated-celestial-navigation-for-the-navy?fbclid=IwAR32JyfjX4GJHYsr8KvQg-AdWaLJEpSK-md8BQr1_N59bhPU39ggetNMar0

    gl

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