How did ancient cartographers calculate and draw the contours of their countries?

WORDS AILSA HARVEY

Today you can virtually visit almost any street or landmark in the world, viewing an accurately mapped layout of its placement on the planet. When navigating new roads, real-time updates about weather and traffic conditions can keep us constantly in the know. This combines satellite and street-level imagery, incorporating huge amounts of data quickly and accurately. But before computers and satellites could lend a hand, the work of cartographers and surveyors was far more laborious and less accurate.

Maps have long been an essential tool for human civilisation, helping our ancestors piece together the world around them, document borders and navigate new landscapes. The first maps of 600 BCE were carved into chunky clay tablets. As human understanding of the world grew beyond local territories, maps escalated from local representations to attempts to envisage the entire planet. For a map to hold any real navigational benefit, mountain ranges and roads have to be drawn to scale.

Before the assistance of advanced technologies like GPS, cartographers took considerable time to manually calculate and plot each observable distance. The invention of the compass made for more precise map-making, helping surveyors orientate themselves. Meanwhile, large areas could be mapped quickly using triangulation. This technique involved dividing the landscape into triangular segments for plotting and meant that significant distances could be calculated without needing to manually measure all sides of each triangle. Trigonometry and three distinct reference points were used to achieve this. These time-consuming data-collection tasks proved successful in the production of history’s first accurate large-scale maps.