A quadrant is used for mathematics or astronomy and features a graduated arc that encompasses a quarter of a circle. This also is a 90 degree angle.

In 150 AD Claudius Ptolemy described a quadrant, although he referred to it as a plinth. This description included a shadow of a horizontal peg projected on a 90 degree graduated arc, set on the meridian plane to determine the sun's altitude at noon.

A mural quadrant is used for measuring astronomical objects' altitudes.

Navigators and surveyors use a tool called a geometric quadrant.

Navigators also used the Davis quadrant, which is a framed, compact quadrant that measures the altitude of an astronomical object.

Measuring the angular distance of astronomical objects can be done with the use of large, framed quadrants.

An altitude quadrant used a plumb line to measure the altitude of an astronomical object.

A Gunners quadrant is used to measure the depression angle of the elevation of a canon or mortar's gun barrel. This is a type of clinometer that helps to verify the firing elevation and correct alignment of fire control mounted weapons. This tool is used by an artillerist.

A Gunter's quadrant is an invention dating back to 1623. Edmund Gunter invented this quadrant to determine time.

Tycho Brahe, a Danish astronomer, built 2 meter radius quadrants in the 1580s on the isle of Hven at his astronomy observatory.

The Islamic quadrants include four types. The sine quadrant was used for astronomical observations and solving trigonometry problems. The universal quadrant was used for solving latitude astronomical problems. The horary quadrant used the sun to find the time. The astrolabe/almucantar quadrant was derived from the astrolabe and became a popular alternative.

The geometric quadrant is usually made of brass or wood, in a quartercircle panel. The earliest marine navigation geometric quadrants date to 1460. These quadrants had destination latitudes as opposed to degrees.

The back observation quadrant was developed to allow for sun altitude measurements.

Quadrants were the most important and most popular tool used for navigation in the mid1700s. It allowed the sailor to determine his position at sea by measuring the sun's angle over the horizon at noon. This made it possible to determine his latitude.

There are several famous quadrants located in various places including Tycho Brahe's mural quadrant in Uraniborg, in Hven, the Greenwich Observatory mural quadrant, and the John Bird mural quadrant at the Mannheimer Observatory.
