Type of heading
1. True heading (TH-True Heading): The angle at the north end of the true meridian where the aircraft is located is measured clockwise to the heading line.
2. Magnetic heading (MH-Magnetic Heading): The angle at the north end of the magnetic meridian at the aircraft's position is measured clockwise to the heading line.
3. CH-Compass Heading: Measure the angle from the north end of the compass line clockwise to the heading line.