Deviation Card / Table?

[Ex-Calif]

Thanks Gord! In summary:

True course plus/minus magnetic variation equals magnetic course plus/minus drift correction angle equals magnetic heading plus/minus compass deviation equals compass heading.

(Thus the mnemonic "True Virgins Do Make Dull Company.")

[jackdale]

Originally Posted by Ex-Calif

Thanks Gord! In summary:

True course plus/minus magnetic variation equals magnetic course plus/minus drift correction angle equals magnetic heading plus/minus compass deviation equals compass heading.

(Thus the mnemonic "True Virgins Do Make Dull Company.")

If you add the phrase "At Weddings" it reminds you to add westerly corrections and subtract easterly one.

The correcting formula can be remembered with:
"Can Dead Men Vote Twice at Elections."

Jack

[Microship]

I use a Maretron SSC200 rate gyro compass on my steel boat, and it is located in the pod above the companionway. A hand-bearing hockey puck swings through 35 degrees when moving through that gap, so I was more than a little skeptical... but the process worked perfectly (taking the boat through three full 360 degree turns at a fixed rate while running a utility on the display). It now agrees precisely with the professionally-tweaked binnacle compass, and I like it a lot better than flux gates.

I was running my GPS datalogger during the calibration, by the way, and didn't realize there was a current running on the mirror-smooth waters in south Puget Sound... made an amusing image.

Steve

[Ex-Calif]

Originally Posted by Microship

I use a Maretron SSC200 rate gyro compass on my steel boat, and it is located in the pod above the companionway. A hand-bearing hockey puck swings through 35 degrees when moving through that gap, so I was more than a little skeptical... but the process worked perfectly (taking the boat through three full 360 degree turns at a fixed rate while running a utility on the display). It now agrees precisely with the professionally-tweaked binnacle compass, and I like it a lot better than flux gates.

I was running my GPS datalogger during the calibration, by the way, and didn't realize there was a current running on the mirror-smooth waters in south Puget Sound... made an amusing image.

Steve

That image is why I don't swing a compass with a gps.