5. Finding Balance Through the Rule of Three

Before there was celestial navigation, there was the rule of marteloio, a technique applied by medieval mariners that essentially used compass markings and basic trigonometry to plot location and direction. This was an early version of triangulation, a term of wayfinding that takes readings from three known points to calculate location or distance. These are not old techniques lost forever in the mists of history. The mechanics behind the GPS app on your phone or the navigation system in your car is all about triangulation. It calculates your location by reading signals from a field of satellites parked in orbit around the Earth. It only needs to read the signals from three of these satellites to do the same thing medieval sailors did with compasses and sextants. Wherever you are on Earth, there are GPS satellites visible for your device to use.