2. Medieval and Renaissance learning and practice

‘Medieval and Renaissance learning and practice’ describes the techniques used by the three major cultures of ambitious development in navigation—Chinese, Arab, and European. It begins with the ‘Arab compass’ that used horizon astronomy, the kamāl, and latitude sailing. It then describes the Chinese use of the magnetic compass, believed to have been first used at sea during the 11th century. By the 15th century, the Chinese were using the compass alongside dead reckoning and so could choose between coastal and latitude sailing. The use of portolan sea charts and sets of tables (toleta) in the Mediterranean and quadrants and astrolabes in the Atlantic in the 14th‐15th centuries is also described.

6. The electronic age

The application of radio waves triggered a wholly new approach to navigation at sea. ‘The electronic age’ begins with Radio Direction Finding introduced at the start of the 20th century with radio beacons established to transmit signals, so that a direction-finding antenna could determine a bearing to a known transmitter on shore. Examples of this technology were the short-distance Decca Navigator System and Loran (long-range aids to navigation). Radio detecting and ranging (radar), using shortwave radio signals, is also discussed along with the development of the inertial navigation system. Global satellite navigation systems have transformed the art of navigation, yet there is no immediate prospect of old techniques being abandoned.

3. A mathematical science

‘A mathematical science’ shows that the idea of navigation taking on techniques from other disciplines is reinforced by the appearance of instruments from these disciplines modified for seaborne use. The mariner’s astrolabe had only the altitude scale and was more robustly made to withstand the rigours of use at sea. The cross-staff, and then backstaff, replaced the astrolabe. These instruments made familiar the concept of latitude in degrees. Seamen also used the nocturnal to find local time from the rotation of the stars around the celestial Pole. The new role for mathematics in navigation is nowhere better exemplified than in the development of nautical charts—particularly the 16th-century Mercator projection.