Celestial navigation glossary
Longitude
Angle east or west of the prime meridian through Greenwich: 0° to 180°.
Where the course teaches it
Longitude, and why distance uses latitude, in the module Latitude and the nautical mile. Read a latitude, turn a difference in latitude into miles, and keep a dead reckoning position.
Taught alongside it
- Latitude
- Angle north or south of the equator, measured at the Earth’s center: 0° to 90°.
- Nautical mile (nm)
- One minute of latitude: 1,852 meters. Distances are measured on the latitude scale.
- Dead reckoning (DR)
- Position worked out from the last fix, the course steered and the distance run.
- Variation
- The angle between true north and magnetic north at a place; printed on the chart.