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    Re: Compass error correction
    From: Joe Schultz
    Date: 2010 Jul 5, 08:15 -0700

    He's back! Yahoo!

    Master Chief, a question for your memory bank. The old pierside or anchorage compass error technique was trial and error, with at least three LOPs. I used tracing paper to do the work, by the way. This trial and error method was mentioned in the book "A Navigation Compendium," which was originally written in the early 1960s. Then, by the 1980s and perhaps before, the method was cookbooked and called "Franklin Trial and Error Method" in the senior quartermaster training manual "Quartermaster 1 & C." How and when did your name get attached to the trial and error method?

    And I laughed when I read your Piloting Technique handout. Toward the bottom it says "The drafting machine can be adjusted by adding the error." I got into trouble for doing just that, on the YP at OCS in Newport - we weren't given your handout. Instructor wanted us to play "Dead Men True Virgin" with the gyro. I thought "why bother" and adjusted the drafting machine all by myself, before he planned to show us the trick. Silly me.

    Your Piloting Technique works quite well for anybody when sitting still. Replotting with correct compass error will give a fix identical to GPS if surveyed objects are shot. And, for the sake of completeness, identical means within the limits of equipment which includes GPS, and providing the "indicator" isn't too close. Determining "what is too close" is the key point of your compass error uncertainty innovation. I proved that last month, using a lensatic compass on land.

    Different story when merchie/yachtie gets underway. They don't have the manpower/equipment to shoot multiple LOPs. The only way I can think of is to steer a range while shooting an athwartship range. The bearing uncertainty will be large, as compared to a sitting vessel, but that's life. He's not going to pay a surveyor to ensure his athwartship marks are exactly correct, and there will always be some set/drift (the steering compass lubber line doesn't point the range because the vessel is crabbing). Is there another way?


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