How to convert magnetic bearings to true bearings easily?

Understanding Declination

To accurately convert magnetic bearings to true bearings, you need to account for the declination, which is the difference between magnetic north and true north. Declination varies by location and is influenced by the Earth’s magnetic field. Check a declination chart or website like the National Geophysical Data Center for the current declination in your area. For example, in the northeastern United States, the declination is approximately 20 degrees east, while in the northwestern United States it’s around 20 degrees west.

Calculating True Bearing

To convert a magnetic bearing to a true bearing, you can use the following method: magnetic bearing + declination = true bearing. If the declination is east, you add it to the magnetic bearing. If it’s west, you subtract it. For instance, if your magnetic bearing is 270 degrees and the declination is 20 degrees east, the true bearing would be 270 + 20 = 290 degrees. Be aware that declination can change over time due to the movement of the Earth’s magnetic field.

Using a Compass with Declination Compensation

Some compasses come with built-in declination compensation or adjustable declination dials. These allow you to directly account for the local declination without needing to calculate it manually. If your compass has this feature, adjust the declination to match your location’s value. This will provide you with true bearings directly from the compass, eliminating the need for separate calculations.