To convert wind direction from magnetic to true north, the local magnetic declination must be determined at each observing location. This value accounts for the difference between magnetic north and true north and varies by location and over time.
To convert wind direction from magnetic to true, the magnetic declination at the specific observing location must be determined. Magnetic declination is the angle between magnetic north (the direction the magnetic compass needle points) and true north. This variation changes with location and over time.
In the context of flying, for example, pilots must account for the wind velocity along with the plane's orientation relative to magnetic north to successfully navigate. This compensation is critical to ensure accurate travel and safety, particularly when conditions are ripe for severe weather like tornadoes, which require precise predictions. Meteorologists use this data, along with navigation tables and observations, to calculate atmospheric rotation—crucial in tornado forecasting.
For practical applications such as sailing or flying, it's common to consult local magnetic declination charts or use instruments that automatically adjust for it.