Leonard Digges invented the theodolite in 1551. Digges was known for improving many tools for surveyors, carpenters and masons. He also invented the refracting and the reflecting telescope.
A theodolite is a surveying tool with a rotating telescope that measures horizontal and vertical angles. In older texts, the term diopter is used as a synonym for theodolite. The first time the word theodolite was recorded was in a surveying textbook called "Pantometria." The book was authored by Leonard Digges and was published posthumously by his son in 1571.
A theodolite is a calibrated optical instrument that is used to decide relative position in surveying, navigation and meteorology. It has a telescope mounted on a tripod fitted so that it can swing freely on its horizontal and vertical axes. Graduated scales then measure the amount of rotation.