Invented by the Greeks around 240 B.C., several different types of quadrants have been used over the past 2500 years. Quadrants were often designed for a specific use. Artillery officers used a simplified quadrant known as a gunner's quadrant for aiming their guns and measuring distance.

How was the quadrant made?

invention by Hadley

…of Philadelphia, Hadley invented a quadrant (actually a double-reflecting octant) for measuring the altitude of the Sun or a star above the horizon to find geographic position at sea. His double-reflecting principle made accurate determinations of location much easier.

Who invented the quadrant and sextant?

Captain John Davis conceived this instrument during his voyage to search for the Northwest Passage. It was described in his Seaman's Secrets published in 1595. It was called a quadrant because it could measure up to 90 degrees, that is, a quarter of a circle.