Maps, compasses, astrolabes, and calipers
are among the early tools used by ocean navigators. In the modern era, these tools have been largely replaced by electronic and technological equivalents. Despite these early beginnings, it would take many centuries before global navigation at sea became possible.
The
traverse board
was used to approximate the course run by a ship during a watch. It consisted of a circular piece of wood on which the compass points had been painted. Eight small holes were evenly spaced along the radius to each point, and eight small pegs were attached with string to the center of the board.
The earliest navigation methods involved
observing landmarks or watching the direction of the sun and stars
. Few ancient sailors ventured out into the open sea. Instead, they sailed within sight of land in order to navigate. When that was impossible, ancient sailors watched constellations to mark their position.
Three main types of navigation are
celestial, GPS, and map and compass
.
To find the way home from a voyage, navigators
sailed north or south using the bearing of the sun or star, and veered left or right using calculations to maintain a constant angle to the heavenly body
. To figure out the right angular alignment, navigators in the 16th and 17th centuries used an astronomer’s quadrant.
Sir George Cayley
* ‘Father of aerial navigation’ (1773-1857)
The earliest navigation methods involved observing landmarks or watching the direction of the sun and stars.
Few ancient sailors
ventured out into the open sea. … Compasses, which indicate direction relative to the Earth’s magnetic poles, are used in navigation on land, at sea, and in the air.
The North Star moves in a very small circle above the north celestial pole, while all the other stars in the Northern Hemisphere rotate around it. Because
Polaris
appears stationary in the night sky, seafarers can easily find true north by locating the North Star.
The theoretical accuracy of celestial position fix is
within 0.1 mile of your true position
. In comparison, a modern GPS should be able to give you an accuracy of less than 1 meter. … While the theoretical maximum accuracy of a celestial fix is 0.1 miles, in reality you will probably never achieve closer than 1 mile.
Because
constellations change seasonally
, mariners had to know which constellations were visible in the sky at different times of the year in each hemisphere. Based on the location of certain constellations in the sky, sailors could determine what direction they were heading.
The field of navigation includes four general categories:
land navigation, marine navigation, aeronautic navigation, and space navigation
. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks.
Browse Encyclopedia
They include the
four Arrow keys, PageUp, PageDown, Home and End keys
. See modifier key.
The methods used in this chapter include
pilotage—navigating by reference to visible landmarks
, dead reckoning—computations of direction and distance from a known position, and radio navigation—by use of radio aids.
How did sailors calculate longitude?
Sailors
used a sextant
to determine their latitudinal position. Longitude lines run vertically across the globe and are used to measure distances east and west of Greenwich, England.
Solving Lunar Distances
During the first part of the 19th century only naval vessels, the largest merchant ships, and exploration vessels could afford to carry them. … A navigator could find his longitude without a chronometer by
using the moon as a giant clock
, working its way past sun and stars.
Pirates made
compasses at
sea by stroking a needle against a naturally magnetic rock called a lodestone. Having a compass helped, but the most useful of all was a sea chart. … Even if pirates could not see land, they could still judge their direction and distance by looking at the clouds and sea birds.
