In armillary sphere …with diametric sight rules, or alidades, and it is likely that those made and used in the 12th century by Moors in Spain were the prototypes of all later European armillary spheres. Read More
astrolabes
In astrolabe …and a straight rule (the alidade), used for sighting objects in the sky. The alidade made it possible to use the astrolabe for surveying applications—e.g., determining the height of a mountain. Most astrolabes also had one or more plates (called climates) that were engraved with coordinate lines for different latitudes… Read More
plane table
In surveying: History …sights for accurate aim (the alidade) to the objects to be mapped—along which lines are drawn. It was the first device capable of recording or establishing angles. Later adaptations of the plane table had magnetic compasses attached. Read More
