Meridian altitude is a method of celestial navigation to determine the latitude of an observer. It notes the altitude angle of an astronomical object above the horizon at culmination.
Meridian altitude is a method of celestial navigation to determine the latitude of an observer. It notes the altitude angle of an astronomical object above the horizon at culmination.
The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure vertical angles. They were designed to allow for their use on boats in rough water and/or in heavy winds, which astrolabes are ill-equipped to handle. It's notable for its role during the Age of Exploration where Portuguese and Spanish navigators used it to great success. In the sixteenth century, the instrument was also called a ring.