How to Shield a Marine Compass from Magnetic Interference
- 1). Keep things such as knives, small radios, stereo speakers, your flashlight, or any tools away from the compass. These things either contain a magnet or an iron-based product that can influence your compass.
- 2). Permanently mount your compass as close to the center line of your boat as possible, so that the influence from the permanent steel parts of your boat is stable. If your compass is adjusted, then moved, the magnetic variation--the boat's effect on the compass--will change.
- 3). Spend a few hours on the water with a marine technician certified to adjust compasses. The technician will have you follow certain courses and make certain maneuvers while moving the magnets and iron bars in your compass that compensate for the magnetic variation induced by your boat.
- 4). Use the most current chart when planning your voyage and pay attention to the note on changes in the Earth's magnetic field located at the top center of the chart. This note will tell you how to adjust your course to allow for changes in the location of the North Magnetic Pole (the "North" your compass points toward) over time. The note will vary from chart to chart because the Earth's magnetic field isn't the same everywhere.
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