Navigation, science of finding the position and directing a marine, air, or space vessel from one place to another. Ocean navigators were dependent on landmarks and observations of the heavenly bodies until the invention of the compass around the 12th century gave them an independent means of determining direction. Latitude has been found using the astrolabe, cross-staff, and quadrant since the Middle Ages, and longitude has been determined with the chronometer and the sextant since the 18th century. Radio signals and satellites are now used.
21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Mudpuppy to Nebula