This application helps you determine the true bearing based on your compass-based bearing. The compass points to the direction of the horizontal component of the magnetic field in its location, rather than to a specific point. To adjust your compass for the magnetic field in your area, you need to know the magnetic declination, which is the angle between the true north and the horizontal trace of the magnetic field. You can calculate the true bearing by adding the magnetic declination to the magnetic bearing. This works so long as you follow the convention that degrees west are negative (i.e. a magnetic declination of 10 degrees west is -10 and a bearing of 45 degrees west is -45). In this application, the magnetic declination is calculated using the most recent World Magnetic Model (WMM), World Magnetic Model High Resolution (WMMHR) , or the International Geomagnetic Reference Field (IGRF) model. The accuracy of these models is usually within 0.5 degrees. Sometimes, there are local magnetic field anomalies that can cause this angle to be off by more than 10 degrees, but this doesn't happen often. It's recommended that you register using the registration link on the top right to stay up-to-date on NOAA’s magnetic maps and models.