How Often Should You Check Magnetic Declination While Hiking?

Understanding Magnetic Declination

Magnetic declination is the difference between the magnetic north and the actual geographic north. It varies depending on your location and can change over time due to the Earth’s magnetic field shifting. In the contiguous United States, declination can range from 13 to 24 degrees, while in Alaska, it can be as much as 30 degrees. It’s essential to know your declination to ensure accurate navigation with a compass.

Checking Magnetic Declination

You can check magnetic declination by consulting a reliable map or a website that provides declination values for your specific location. The USGS provides a declination calculator on their website, which allows you to enter your location and retrieve the current declination value. You can also check the declination value on your compass, as many modern compasses have a declination adjustment feature. If you’re planning to hike in an area with significant declination, it’s a good idea to bring a map or a GPS device with pre-loaded declination data.

Adjusting for Declination

To adjust for declination, you’ll need to add or subtract the declination value from your compass reading. If the declination is east, you’ll need to add the value to your reading, while a west declination requires subtraction. For example, if the declination is 15 degrees east and your compass reading indicates a bearing of 270 degrees, you’ll need to adjust the bearing to 285 degrees (270 + 15). Make sure to double-check your calculations to ensure accurate navigation.