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Old 11-09-2012
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Re: Now Blow (how to adjust compass) Me Down

You have a substantial boat so why not invest in the services of a professional compass adjuster? Do only after all your electrical and electronic changes are complete, at least for the forseeable future. Using a GPS to adjust or compute deviation is a little risky. It only works with no wind or current. GPS shows Course Over Ground(COG) not Heading(HDG). You can use GPS by setting a visible landmark as a waypoint and pointing the bow at it. The difference between course to waypoint and compass is then deviation. As to the adjusting, we cannot get the paint to stick out on the water for a compass rose. We use shore references or a gyro to establish the actual magnetic heading of the vessel. One colleague of mine likes to use Sun azimuths.
Bill
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