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    Re: Bowditch tables 12 and 13
    From: Jeremy C
    Date: 2012 Aug 14, 07:18 -0700

    Notice that both formulae are exactly the same. If you look at the radar navigation manual (pg 12-13), it gives a formula and diagrams for radar waves (much longer wavelength than light) which is different. The visible light (optical horizon) is 1.17 verses 1.22 for radar (SHF radio).

    The distance derived from these formulae is actually a great circle path, so curved. If it was straight line (geometric horizon) the contant is 1.06.

    This is how I understand it. This stuff is why the radar picks up ships well before I can see it from the bridge, even with 50+ nm visibility.


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