General Navigation
General navigation questions test direction, distance and position on the Earth's surface, plus the chart work needed to get from one to the other. Start with the Earth model and the graticule.
Key concepts: latitude and longitude, the great circle and the rhumb line, and when each is used; the difference between true, magnetic and compass directions; variation and deviation; the nautical mile (1 minute of latitude) and the relationship between nautical miles and kilometres; the convergency of meridians and how it affects rhumb-line tracks; chart projections (Mercator, Lambert conformal conic, polar stereographic) and their properties; and the calculation of track, heading, drift and ground speed from the wind triangle.
Traps: confusing great circle and rhumb line distances; forgetting that a Mercator chart exaggerates scale with latitude; applying variation in the wrong sense; and mixing nautical miles and statute miles.
Worked example: a flight from 10°N 000°E to 20°N 000°E along the meridian covers 10° of latitude = 600 nm. If the same latitude change occurs along a rhumb line away from the meridian, the distance is longer than the great circle. Rule of thumb: 1 minute of latitude = 1 nm, and 1° = 60 nm.