NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Level of observation accuracy in medium seas
From: Jared Sherman
Date: 2004 Jul 23, 11:38 -0500
From: Jared Sherman
Date: 2004 Jul 23, 11:38 -0500
Sorry to say, no. Only that I did re-read it someplace this or last year and say to myself "Ahah!" and making a pointed mental note of it, with the link that last time I went out in "4-6 waves" and they were very much 8-10 to everyone on board, that explained the difference. > > From: David Weilacher> Date: 2004/07/23 Fri AM 06:42:03 CDT > To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM > Subject: Re: Level of observation accuracy in medium seas > > 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 >