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: Dave Weilacher
Date: 2004 Jul 23, 06:42 -0500
From: Dave Weilacher
Date: 2004 Jul 23, 06:42 -0500
Hi Jarad; Can you point me to your source for Noaa wave height definition? Dave W -----Original Message----- From: Jared ShermanSent: 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