sextant
Sailor's horizon measurer
A sextant is a navigational instrument used to measure the angle between a celestial body and the horizon, allowing sailors and aviators to determine their position at sea or in the air.
The device uses mirrors and a graduated arc spanning sixty degrees—one sixth of a circle, hence the name.
Though largely supplanted by GPS, sextants remain valued as backup instruments and for their elegance: He took a sextant reading at noon to fix their latitude.
Location-finding via astronomical observation
- latitudeGeographic or personal freedom
- longitudeEast-west angular distance
- bearingPosture or orientation
- dead reckoningPosition-tracking via estimated motion
altitude · horizon · azimuth · nautical almanac · sight · chart · piloting · course
Geometric measure of rotation
- arcCurved line segment
- mirrorReflective viewing surface
- telescopeInstrument magnifying faraway objects
- vernierAuxiliary scale for fractions
drum · scale · graduation · limb · frame · adjustment · calibration · optics
Ancient altitude-measuring instrument
- quadrantFourth of a circle
- octantOne-eighth of circle
- cross-staffAltitude-measuring navigation instrument
- nocturnalActive during darkness
Hadley · exploration · chronometer · 18th century · Royal Navy · cartography · surveying · expeditions
Of the sky above
- starsLuminous celestial bodies
- constellationsRecognized celestial groupings
- zenithPoint straight overhead
- declinationAngular distance from equator
Polaris · horizon · almanac · ephemeris · celestial sphere · planets · moon · sun
Seagoing transport vessel
- deckShip's flat surface
- marinerOne who navigates ships
- captainOne who commands
- sailorSeafaring crew member
navigator · quartermaster · helm · bridge · voyage · ocean · nautical · sea
celestial navigation
Location-finding via astronomical observation
- latitudeGeographic or personal freedom
- longitudeEast-west angular distance
- bearingPosture or orientation
dead reckoning · altitude · horizon · azimuth · nautical almanac · sight · chart · piloting · course · waypoint
angle
Geometric measure of rotation
- arcCurved line segment
- mirrorReflective viewing surface
- telescopeInstrument magnifying faraway objects
vernier · drum · scale · graduation · limb · frame · adjustment · calibration · optics · brass
astrolabe
Ancient altitude-measuring instrument
- quadrantFourth of a circle
- octantOne-eighth of circle
- cross-staffAltitude-measuring navigation instrument
nocturnal · Hadley · exploration · chronometer · 18th century · Royal Navy · cartography · surveying · expeditions
celestial
Of the sky above
- starsLuminous celestial bodies
- constellationsRecognized celestial groupings
- zenithPoint straight overhead
declination · Polaris · horizon · almanac · ephemeris · celestial sphere · planets · moon · sun · ecliptic
ship
Seagoing transport vessel
sailor · navigator · quartermaster · helm · bridge · voyage · ocean · nautical · sea · merchant marine
angle measurement
Assessing angular magnitude
dip · refraction · parallax · correction · observation
- maritimeships, ship, boat, boats, anchors
- Maritime ExplorationColumbus, Magellan, voyage, navigator, Age of Discovery
- nauticalanchor, anchor chain, anchors, boat, boats
- nautical thingsanchor, rope, sail, compass, oar
- seafaringship, sailors, ships, sail, sailor
- stargazingtelescope, stargazing guides, night sky, stars, constellation
sextantGPS
Satellite-based location technology
satellite navigation · GPS receiver · guesswork · dead reckoning · lodestone