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    Re: Level of observation accuracy in medium seas
    From: Robert Gainer
    Date: 2004 Jul 23, 12:44 +0000

    Dave
    A 50-foot wave by the Beaufort Scale means that you are in �exceptionally
    high waves. The air is filled with foam and the sea completely white with
    driving spray. Visibility greatly reduced�. The short description is
    �hurricane�. You might want to check out
    http://facs.scripps.edu/surf/luds.html, it has a very good and readable
    description of predicting wind speed and wave height. In practice you will
    not get a shot at anything because the wind and spray make it all but
    imposable to hold the sextant still. I have been in these conditions and
    speak from experience. By the way I think the height of a wave is measured
    from the trough to the crest.
    Robert Gainer
    
    
    >From: David Weilacher 
    >Reply-To: Navigation Mailing List 
    >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    >Subject: Re: Level of observation accuracy in medium seas
    >Date: Fri, 23 Jul 2004 06:42:03 -0500
    >
    >Hi Jarad;
    >
    >Can you point me to your source for Noaa wave height definition?
    >
    >Dave W
    >
    >
    >-----Original Message-----
    >From: Jared Sherman 
    >Sent: Jul 22, 2004 9:34 PM
    >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    >Subject: Re: Level of observation accuracy in medium seas
    >
    >Dave-
    >  <50 foot waves with a mile between peaks.  I take my shot when my boat is
    >at the top of a wave.  This is easy to tell because I can actually see a
    >horizon.  The horizon I see is 8 miles away.>
    >  Seems like short horizon. NOAA says that waves are measured from the sea
    >level, not from the trough to peak, so are you talking about real fifty
    >foot
    >waves, or "real" 50 foot waves, which most sailors would call hundred
    >footers?
    >
    >If the former, you're observing from 25' above sea level, figure ten more
    >for your deck and standing eye height, since you've got a good enough grip
    >to rider those doggies. That's 35' asf now, about your eight miles.
    >(7.9+)
    >
    >Nah, you're only in 25' waves, that's the problem. Wait for rougher
    >weather,
    >you'll get a better horizon.
    >
    >But you could certainly figure the math. A sphere (close enough) 25,000
    >miles in circumference, two points 8 miles apart on that. Change the radius
    >of one by the 25' your far wave is blocking you...run some tangents and
    >angles..."A simple exercise left to the reader."
    >
    >Just remember, you're only in 25' waves.
    >
    >
    >Dave Weilacher
    >.US Coast Guard licensed captain
    >.    #889968
    >.ASA instructor evaluator and celestial
    >.    navigation instructor #990800
    >.IBM AS400 RPG contract programmer
    
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