A For most of history, maps were drawn by hand using reports from travellers and sailors. Many contained mistakes and imaginary islands.
B Accuracy improved with new instruments. Surveyors used a method called triangulation, measuring angles between distant points to calculate positions. National surveys took decades to complete.
C Mapmakers also had to decide how to show a round earth on a flat page. Every projection distorts something, whether the size of countries or their shape.
D Today, satellites and aircraft collect data, and digital maps update constantly. Volunteers contribute by adding paths, shops and buildings to open databases.
E Yet maps are still not neutral. Choices about names and borders can be political, and some areas remain poorly mapped because they are of little commercial interest.