Chapter 29: Gyro-compass Error.

Status: In Progress  |  Genre: Non-Fiction  |  House: Booksie Classic

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Gyro-compass Error.



One does not normally find a gyro-compass on vessels traveling less than 200 miles or so from shore for they are too costly. Simply regard a gyro-compass as a compass run by machinery rather than attracted to the magnetic north pole like a magnetic compass. The gyro can be set to read any heading, thus it is set to read true courses.

You do not have to deal with variation and deviation when moving from the plotting sheet to the gyro, but most navigators do, as all courses in good practice are logged. The point being, gyro error works the same as magnetic compass error.

If the gyro has an error of 1° east (E) and the true course is for instance 076°, all that is required to do is subtract that one degree. That produces a true course of 075° on the gyro. If the gyro has an error of 1° west (W), add that one degree to produce a true course of 077°.

Any westerly error is added to the course line, and any easterly is subtracted. There is nothing difficult about it until having to include leeway, wind push.

On the true course of 075°, a wind is coming out of the south. This wind is trying to push the vessel more northerly, so you need to over steer to your right, or more southerly, (or clockwise on the compass), four degrees more southerly and so you add the four degrees and steer a true course of 079°.

This is a Gyro true course and not a magnetic compass course, and means the "M" of TVMDC, not the "C". It is going from "M" up to "T" for true.

Submitted: September 23, 2022

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