High solar clock. It is so named because the constructive parameter is based on the height of the sun. This brass ring is available in two versions: latitude 40º or 50º. In the fifteenth century the sailors found a way to estimate the Latitude to locate in the sea. They were based on a well-known fact: the altitude of the celestial bodies depends on the Latitude. Very soon other instruments joined the quadrant, the nautical astrolabe and the ballestilla. Pedro Nunes (Portugal) invented the nonius, a process of subdivision of scales and created other instruments of innovative design.