Triangulation and Historical Surveying Methods

Triangulation is a surveying method that determines the position of a point by measuring the angles to it from two or more known reference points, rather than measuring distances directly, exploiting basic trigonometry: once one side and two angles of a triangle are known, the remaining sides and angles can be calculated. The Dutch mathematician Willebrord Snellius (Snell van Royen) is credited with pioneering the systematic use of triangulation networks for large-scale land surveying, publishing his method in Eratosthenes Batavus (1617) after using a chain of triangles across Dutch towns to remeasure the length of a degree of meridian arc, consciously echoing Eratosthenes's ancient project. The technique requires establishing at least one precisely measured baseline distance using direct physical measurement, after which an extending network of triangles, each sharing a side with its neighbor, allows surveyors to calculate positions across vast distances while measuring only a small fraction of that distance directly on the ground.