In the late 16th century, a Dutch scholar and instrument maker named Gemma
Frisius suggested that a good surveying instrument could be made by attaching a
magnetic compass to the back of an astrolabe. Building on this idea, Jan Dou
designed an instrument with two pairs of fixed sights attached to a graduated
circle, and another pair of sights attached to either end of a movable alidade.
Dou published an account of this instrument in Dutch in 1612, and the form
became popular with surveyors in the Netherlands. The name Holland Circle was
coined in the 19th century. The Holland Circle is similar to but easily
distinguishable from the common theodolite.
