Quick Answer
To calculate your direction in relation to True North, you need to know the declination of your location, which is the difference between Magnetic North and True North. This can be found using a declination chart or online tool. You then adjust your compass bearing by the declination value.
Understanding Declination
Declination is the difference between Magnetic North and True North, which can vary significantly depending on your location. For example, in the United States, the declination value ranges from -14 degrees to 20 degrees, depending on the region. To find the declination value for your location, you can consult a declination chart or use an online tool such as the USGS’s Declination of the Earth’s Magnetic Field.
Adjusting Your Compass Bearing
Once you have determined the declination value for your location, you can adjust your compass bearing by subtracting or adding the declination value to your magnetic bearing. For example, if your magnetic bearing is 270 degrees and the declination value is -10 degrees, your true bearing would be 260 degrees (270 - 10). Conversely, if the declination value is positive, you would add it to your magnetic bearing. It’s essential to note that declination values can change over time due to the Earth’s magnetic field shifting, so it’s crucial to update your knowledge of declination values regularly.
Using a Compass with Declination Compensation
Some modern compasses come equipped with declination compensation features, such as a rotating bezel or a digital display that can be set to the local declination value. These compasses can simplify the process of determining your direction in relation to True North, but it’s still essential to understand the underlying principles and be able to adjust your bearing manually if needed.
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