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post #15 of Old 07-17-2007
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Please do not get caught up in the use of the word declination when describing variation-even though it is technically correct. For instance, Bowditch is known as The American Practical Navigator since we are interested in practical means of navigation. Keep it simple and refer to declination as the difference between Compass North and Magnetic North. Variation is the difference between Magnetic North and True or Polar North.

This is important because, as you've seen, errors tend to be double the number involved, and even Cam can steer within 26 degrees of his course. You'll find many different ways of doing the same thing, one will stick. I'd recommend remembering, for now, the Virgins, thus keeping things in order.

Bowditch explains all of this to whatever level of detail desired and comprehendably.

And while I was joking with Cam, I am entirely serious about the use of charts and navigation. Your instincts are correct. Your wife's attitude, with all due respect, will get you killed. What you are learning now constitutes the basis for all other navigation. Errors in learning or inadequate learning will translate downward to whatever form of navigation you are using. If you intend to sail out sight of land, or in any type of restricted visibility, the concepts you are studying must be had down cold.

Here's a sample question from the USCG exam for Third Mate-Oceans:

While enroute from Montevideo to Walvis Bay a vessel's course is 116 pSC. If the variation for the locality is 25 West and the deviation is 6 west, what is the true course made good if a west wind produces 1 degree leeway?

A 084True
B 086True
C 148True
D 085True note: pSC= per Steering Compass

Here's another. (give you a hint-ignore the Gyro info, it's extraneous)

While proceeding up a channel on course 010 per Gyro Compass you notice a pair of range lights in alignment with the masts of your ship when viewed forward. A check of the chart shows the range to be 009 True and the variation to be 15 West. If the ship's course is 026 pSC, what is the deviation for the present heading?

A. 1 West
B. 2 East
C 2 West
D 1 East

Answers will be found in Off Topic in the AFOC thread.


“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.
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