European voyagers far out at sea needed ways to figure out exactly where they were, how far they’d travelled, and how fast they were sailing. They also needed to be able to find their way to places they already knew about.
They knew that technical observation of the stars and planets could reveal a lot of information about time and location. This meant that navigation and astronomy became closely linked subjects.
From medieval times, a number of different navigational and astronomical instruments had been developed by Arab and European scientists. As the design of these instruments improved, long-distance voyaging became safer.
During Captain Cook’s time – the eighteenth century – navigators, scientists, and inventors were keen to work out ways for voyagers to pinpoint their exact position on the globe, especially their longitude. This had been difficult in the past, and had made long-distance voyaging extremely dangerous.