A fix is determined by the intersection of at least two position circles. There is no argument when sights are simultaneous. Two transfer techniques are demonstrated in the ANM when sights are not simultaneous, the running fix technique (RFT) and the GHA-Dec updating technique (GD-UT). With RFT/LSQ*1 the transferred position line is thus supposed to represent a transferred position circle as the mathematical locus of all points on the original position circle transferred for a given run. This condition is met with GD-UT but as we will see it is not with RFT/LSQ*.

Past President of the Royal Institute of Navigation, Brian Calvert, was born in 1933 at Hankow on the Yangste in China (where his family was later interned by the Japanese during the Second World War) and educated at Stowe School, Buckinghamshire. He joined BOAC (now part of British Airways) in 1957, after National Service in the Fleet Air Arm. For his first two years with the airline he flew as a navigator, and this led to a lifelong interest in the subject.

The aviation-shipping analogy cannot be used as an argument for a decrease in the need for maritime pilotage. The increasing complexity and upsizing of modern ships, in combination with a vast variety in ship types, economic maximisation, crewing and technical standards, lead to marginal ship operations that require specialist knowledge and skill. On the other hand, modern commercial aircraft have very standardised equipment and operating procedures and they approach and land at airports which also use standard radio-navigation aids and procedures.