Sundial Altitude Ring Pendant
Altitude sundial. Takes this name because the parameter of its construction is based on Sun’s altitude.
15th century mariners found a way to estimate their latitude to find their location in the sea. It was based on a well-known fact: the height of celestial bodies depends on the latitude. Soon various instruments joined the quadrant, the nautical astrolabe and the cross-staff or ballastella. Pedro Nunes (Portugal) invented the nonius, a process for subdividing scales, and created other instruments of innovative design.