Developments in navigational science can be traced from beginnings twenty-three centuries ago when the Greeks tried to calculate latitude to the present when satellite systems can easily pinpoint positions to within millimetres. The history of navigational science offers vivid insights into the areas of human endeavour which have driven it: the need for discoverers such as Columbus to locate and claim distant lands for their sovereigns and paymasters; the need of merchants in a world of expanding horizons and trade for efficient and reliable shipping; the new and urgent needs of rapidly developing air travel where safety demands accurate and quick navigation in very difficult conditions; the deadly needs of the military in targetting missiles and sailing submarines in radio silence.