Definition:Sextant/Historical Note

Historical Note on Sextant
The principle behind the operation of the sextant was invented by, and can be found in his unpublished writings.

The technique was reinvented (and implemented) independently by both and  in around $1730$.

Its main purpose in the context of navigation was to determine (terrestrial) latitude, by measuring the altitude of a particular celestial body, usually Polaris or the Sun at noon.

The advent of GPS has rendered use of the sextant more or less obsolete.