???????? ???? ???????? ???? ???????? ????Dutch mathematician Willebrord Snellius (a.k.a. Snel van Royen) introduced the fashionable systematic usage of triangulation. In 1615 he surveyed the distance from Alkmaar to Breda, approximately 72 miles (116 km). He underestimated this length by three.5%. The survey was a sequence of quadrangles made up o