why do aviation things like charts and runways and such switch back and forth between true north and magnetic north? What’s the point of orienting anything to true north when all the instruments that can measure direction are only capable of using magnetic north?

Question

Seems like pilots have enough to worry about without having to memorize when to use which north, especially when they can only actually orient to one of the norths.

In: 2

Answer 1

Many use gyroscopic compasses and satellite navigation that don’t depend on the magnetic field.

The deviation of magnetic north from true north varies with position on the Earth. It also changes with time. The magnetic north pole is moving slowly across Alaska towards Russia. So in Britain currently the deviation is close to zero, the magnetic pole is behind the true pole from our viewpoint, whereas it is several degrees off to one side from the western US. The deviation angle is also less the closer to the equator you are while it can be significsnt in the northern part of the American and Asian continents. Then take into account that many flights between the continents take routes across the polar region and that deviation, together with the uncertainty of magnetic readings close to the pole, means that navigation based on true north is far easier.

Answer 2

Many use gyroscopic compasses and satellite navigation that don’t depend on the magnetic field.

The deviation of magnetic north from true north varies with position on the Earth. It also changes with time. The magnetic north pole is moving slowly across Alaska towards Russia. So in Britain currently the deviation is close to zero, the magnetic pole is behind the true pole from our viewpoint, whereas it is several degrees off to one side from the western US. The deviation angle is also less the closer to the equator you are while it can be significsnt in the northern part of the American and Asian continents. Then take into account that many flights between the continents take routes across the polar region and that deviation, together with the uncertainty of magnetic readings close to the pole, means that navigation based on true north is far easier.

Answer 3

Also, there are local magnetic anomalies that can alter the direction of magnetic north by several degrees for just a few miles. This is especially true in areas that have iron deposits in the crust.

Answer 4

Also, there are local magnetic anomalies that can alter the direction of magnetic north by several degrees for just a few miles. This is especially true in areas that have iron deposits in the crust.