Owner, Green Bay Packers
Join Date: Sep 2006
Location: SW Michigan
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THAT'S IT! We're done now. Here, the Electronic Sailor and I part ways. Big time. Steering your boat by your GPS compass is a bunch of tomfoolery, particularly in coastal waters. You are relying on a device that is subject to update interruptions, like the one in my truck that decided to take last Thursday off, although reported for duty Friday morning with no signs of hangover. The magnetic compass is reliably on duty twentyfour/seven.
Furthermore, Camaraderie's Guide to Automated Sailing continues to ignore, or diminish the importance of, those skills essential to being a competent mariner. If you are relying on your GPS for steering, knowing it is correcting for set and drift, you probably have little or no idea what the set and drift are. You do not know because you are altering course continuously to adjust for them. To the inexperieced, this is bassackwards and risky. In fact, it may come as a surprise to them that there is such a strong current present.
Perhaps the biggest troublesome aspect of this mindless sailing is that all of your decision making is being made by a little black box and how well and accurately the destination Lat/Long was plugged in. One, count 'em, one error in initial programming throws the whole navigational exercise off, ot the window, and maybe on the rocks. Garbage in/Garbage out you know. That grinding sound under the keel you do not.
There is, in fact, no such thing as a GPS bearing. It is a computed course suitable for a DR track. A bearing is an angular measurement taken between two terrestial points. Furthermore, your "GPS bearing" is a Great Circle course, not a rhumb line. If you do not know the difference between those two you may be quite surprised by what your GPS is telling you to do and what the line you drew on the chart is telling you. Anotherwords, the "GPS bearing" you are reading is not the course you will steer the entire way from departure to destination. It is what is called, the "initial course" or departure course. If you assume that this "GPS bearing" is your course to steer, and you hold to it, you will not arrive at your destination. Bowditch articles on catography, specifically mercator charts, Lambert Conformal, and polyconic will be of help, and the meat and potatoes will be found in the sailings where rhumb lines and GC are defined. The polyconic projection will be of interest to Great Lakes sailors as those charts use it, versus the more common coastal use of mercator.
Cam's suggestions provoke in me the same feeling one would get on the Greyhound bus, if the bus driver pushed a button and got up, walked aft to use the head, all at seventy miles an hour. Cam also knows that most sailors are going to have one GPS only, not the two or more he recommends and that his offshore arguments against celestial do not apply inshore against traditional practises of piloting. And the stark reality is, when the fog rolls in, the GPS gets wet, a dumb look is less than what is required when gazing upon your magnetic compass for the first time seriously.
To others reading this, I would encourage you to learn everything you can about your magnetic compass, it's use, it's adjustment, and maintenance. It is the first tool in the navigator's arsenal, regardless of what some "autosailors" may think. Stay alive-learn the practise of navigation.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.