NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Da Lurk
From: Fred Hebard
Date: 2003 Feb 9, 13:37 -0500
From: Fred Hebard
Date: 2003 Feb 9, 13:37 -0500
Rodney, How does a GPS unit sense the direction a boat is steering? I have no clue. My impression, 5 years after 5 partial days aboard, is that the unit on the boat I chartered needed to be swung to the boat. My analysis, 5 years ago, was that it was swung incorrectly. I vaguely recall an error of 15 degrees. I don't know whether it was a 15 degree error or a 30 degree error, and definitely do not know the direction. I meant to say in my previous email that it was _not_ a true/magnetic issue, but see that I don't have sufficient data now to resolve that one way or the other. If the unit needed to be swung to the boat, nor do you. I am aware of magnetic/true issues since I usually plot with a triangle and routinely have to convert course and sight bearings from one to the other. I vividly recall a splitting headache of many years ago from figuring out a course for another guy's fishing boat compass that was about 90 degrees out, but varying depending upon the heading, working at night down below over a throbbing engine housing, with too much alcohol on board, not having thought I'd be called upon to plot a course. Fortunately, we had about a mile visibility and some lights for bearings. Fred