Marine Magnetic Compass Calibration and Deviation Card

Introduction

A marine magnetic compass is a vital tool for navigation, but it can be affected by a variety of factors that cause deviation. Deviation is the difference between the direction indicated by the compass and the true direction of travel. It can be caused by the presence of ferromagnetic materials on the vessel, such as steel hulls, machinery, and equipment. Deviation can also be caused by the Earth’s magnetic field, which is not uniform.

To ensure accurate compass readings, it is important to calibrate and adjust the compass on a regular basis. Calibration involves swinging the compass, which means rotating it through 360 degrees while observing its deviation on a compass rose. Adjustment involves adding or removing corrector magnets to the compass binnacle to compensate for the deviation.

Steps for Calibrating and Adjusting a Marine Magnetic Compass

The following steps are involved in calibrating and adjusting a marine magnetic compass:

1. Prepare the vessel. Remove all ferromagnetic materials from the vicinity of the compass, including lifeboats, buoys, and fenders.
2. Set up the compass rose. The compass rose should be located in a clear area on the deck where the compass can be swung freely.
3. Swing the compass. Rotate the compass through 360 degrees while observing its deviation on the compass rose.
4. Record the deviation. Record the deviation for each heading on the compass rose.
5. Add or remove corrector magnets. Add or remove corrector magnets to the compass binnacle to compensate for the deviation.
6. Recheck the deviation. Once the corrector magnets have been added or removed, recheck the deviation to make sure it is within acceptable limits.

Additional Tips for Maintaining a Marine Magnetic Compass

• Keep the compass clean and free of dirt and debris.
• Avoid placing ferromagnetic materials near the compass.
• If the compass is damaged, have it repaired by a qualified professional.
• Have the compass calibrated and adjusted at least once a year.

Conclusion

By following these tips, you can help to ensure that your marine magnetic compass is providing accurate readings and that your vessel is safe to navigate.