How can aircraft save fuel by using a GPS navigation system?
There are three basic ways of navigating in the air. The oldest is the visual method. This is fine for local travel, where visual contact with the ground is possible – and knowledge of what the route looks like is in the pilot or navigator’s mind. More accurate than that is map navigation with compass. This is, once again, all right for short haul work. For long haul flights, maps are not quite as useful. This is because the shortest distance between two airports is not simply a straight line on the map. The Earth is a melon, not a pizza. The shortest possible distance between two surface points would be a tunnel between them. This is not a practical proposition, so planes and ships follow what is called great circle routes. One of these is a section of a slice across the globe – whose centre is the centre of the Earth. The two most obvious great circles, perhaps, are the Equator and the 0/180 degree meridian that passes through Greenwich. There is a great circle route connecting any t
