1 / 23

Navigation

Navigation. Atlantic Wind Patterns. In the early fifteenth century, Europeans sailed out of sight of the coastlines of Europe for the first time and ventured into the Atlantic Ocean.

jerzy
Télécharger la présentation

Navigation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Navigation

  2. Atlantic Wind Patterns In the early fifteenth century, Europeans sailed out of sight of the coastlines of Europe for the first time and ventured into the Atlantic Ocean. In order to navigate, sailors had to learn to harness the wind systems of the Atlantic, which produce a clockwise wind carousel north of the equator and a counterclockwise wind carousel south of the equator. Christopher Columbus used the northern carousel to reach the West Indies in 1492. Vasco da Gama used both to circumnavigate the Cape of Good Hope and enter the Indian Ocean in 1497.

  3. The Canary Islands

  4. The Monsoons Generally from November until the following March, monsoons blow from the north and northeast. Any moisture they carry falls onto the northern slopes of the Himalayas. Little rain falls on India during this season. The wet season, called the southwest monsoon, occurs from mid-June through October, when southwesterly winds carry warm, moist air from the Indian Ocean. Water vapor in the air condenses to form clouds and rain. Heavy rains fall along the coastal plains, but sparse rainfall is typical of the land behind the Western Ghats. The lower Ganges Valley and the eastern Himalayas receive the heaviest rainfall. These regions lie directly in the path of the monsoon. In most of India, much of the year's rainfall comes with the southwest monsoon. Europeans discovered a very different wind system dominating the Indian Ocean. Monsoon winds, formed as a result of air warming or cooling over the Asian continent

  5. Quadrant The quadrant, was an apparatus/instrument used to determine the altitude of celestial objects, and thus one’s latitudinal position. It consisted of a quarter circle measuring 0 to 90 degrees marked around its curved edge. Its straight edges had tiny holes or sights on each end. A plumb line hung from the top. The navigator lined up the sights on the Pole Star and the plumb line would hang straight down over the curved area at a particular point. This would indicate the height of the star in degrees latitude.

  6. English Astrolabe, Ca. 1325 Astrolabe Instrument used for measuring the positions of heavenly bodies, consisting of a circle/section of a circle, marked off in degrees, with a movable arm pivoted at the center of the circle. When the zero point on the circle has been oriented with the horizon, the altitude of any celestial object can be measured by sighting along the arm. If, for example, the star measured forty degrees above the horizon, the sailor would know that he was at a latitude of approximately forty degrees north. The astrolabe was probably first used by the ancient Greek astronomer Hipparchus. In the 16th century, shortly before the invention of the telescope, the Danish astronomer Tycho Brahe, whose amazingly accurate observations made possible the formulation of the present theories of the solar system, constructed an astrolabe with a radius of 10 ft. Until superseded by the SEXTANT, during the 18th century, smaller types were the main instruments used by navigators. Astrolabes also had elaborate calendars and could be used to solve complex problems in astronomy. Astrolabe. Funk & Wagnalls. 2010.Discovery Education. 20 December 2010http://streaming.discoveryeducation.com/ An English astrolabe, ca. 1325..  2005. Image.20 December 2010. <http://www.discoveryeducation.com/>.

  7. Illustration of a steel sextant from Tycho Brahe's observatory, ca. 1598. The sextant was used to measure angular distance between celestial bodies and altitude. "Sextant." Image. Brahe, Tycho, Astronomiae Instauratae Mechanica, 1598. World History: The Modern Era. ABC-CLIO, 2010. Web. 20 Dec. 2010.

  8. This 1557 woodcut shows European sailors using instruments of navigation to calculate their latitude. At the center is an astrolabe, an instrument developed in the preceding centuries by Muslim navigators.

  9. Portuguese explorers soon discovered that as they traveled closer to the equator, the North Star dropped closer to the north horizon and it became difficult to fix exact latitudes. Rather than navigating by the North Star, sailors then turned, quite literally, to the sun. By observing and measuring the height of the mid-day sun, a pilot could calculate the ship's latitude and, with the aid of tables, determine the distance and direction to be sailed to arrive at the intended destination.

  10. A compass is a navigational instrument for determining direction relative to the Earth's magnetic poles. It consists of a magnetized pointer (usually marked on the North end) free to align itself with Earth’s magnetic field. The compass greatly improved the safety and efficiency of travel, especially ocean travel. A compass can be used to calculate heading, used with a sextant to calculate latitude, and with a marine chronometer to calculate longitude. It thus provides a much improved navigational capability. A compass is any magnetically sensitive device capable of indicating the direction of the magnetic north of a planet's magnetosphere. The face of the compass generally highlights the cardinal points. Often, compasses are built as a stand alone sealed instrument with a magnetized bar or needle turning freely upon a pivot, or moving in a fluid, thus able to point in a northerly and southerly direction. The compass was invented in ancient China around 247 B.C., and was used for navigation by the 11th century. The dry compass was invented in medieval Europe around 1300. This was supplanted in the early 20th century by the liquid-filled magnetic compass. Most ships equipped with a magnetic compass that was kept on deck in a binnacle that could be illuminated at night by means of a lamp burning olive oil. Although the compass was in wide use, most captains did not know why its needle pointed north. In fact, many captains preferred to keep the existence of a compass on board a ship secret because superstitious crew members would think that the ship was being guided by sinister forces.

  11. The log line is an old instrument for measuring the speed of the ship. It consisted of a flat piece of wood (the log), which was weighted at the bottom edge to enable it to float upright in the water. To the log was attached a long rope (log line). The log line was wound onto a spool (log reel) so that it could be reeled out after the log was thrown into the water at the aft (rear) of the ship. The friction of the water held the log in place as the ship moved away from it. The log line was 150 fathoms (900 feet) in length and was marked with a piece of white bunting (duck) to start the measuring and after that by “knots” to represent the speed. The line was then let to run out for a given interval of time - the number of “knots” counted as the as the line reeled out during that time would show the speed of the ship. The log line, which is knotted every 47 feet 3 inches, was used to measure the ship's speed. Three seamen were needed for this task: one to hold the reel, one to heave the log line over the ships stern, the third to watch the twenty eight second time glass. As the line ran over the stern the knots were counted against the time glass. The number of knots counted = the ships speed in knots.1 knot =1 nautical mile per hour.1 nautical mile = 6,080 feet or 2,026.6 yards

  12. The Traverse Board was used as a memory aid by navigators as early as the seventeenth century, and would certainly have been used by the officers and crew on the Mayflower. With this simple device they were able to record how far and in what direction they had traveled during each four-hour watch. It consisted of a simple wooden board, equipped with pegs which were inserted into a series of holes. The upper portion of the board was marked out in the thirty-two points of the compass. Notice there are a series of 8 holes radiating out from the center to each of the thirty-two points of the compass on the outer circle. A set of eight pegs is attached to the center of this circle. At the end of each half-hour of the watch, the officer on duty would take a peg and stick it into the hole in the compass bearing on which the ship had run during the half-hour just completed. The first half-hour of the watch was represented by the first circle of holes nearest the center of the compass, and so on. At the end of the four-hour watch all of the pegs would have been used, with the last peg inserted in the outermost circle of holes. To record the speed at which the ship had been traveling, the rows of holes at the bottom of the board were used. At the center of this row of holes was another set of eight pegs on strings. The holes to the left side of the center were used for the first two hours of the watch, while those on the right side were used for the last two hours. At the end of the first half-hour of the watch, the officer in charge would insert a peg at the hole which represented the knots-per-hour at which the ship had been traveling. [Remember that this was determined by using the log-line.] If the ship had been traveling at four knots-per-hour, the officer would count over from left to right on the first row of holes and place the first peg in the fourth hole. At the end of the four-hour watch, the officer in charge would transfer this information from the traverse board onto a slate -- or perhaps a piece of paper. At the end of the day the master or captain of the ship would use this information to write up his log, which was a detailed record of the voyage. The navigator would use the same information to chart the progress of the voyage on his maps. Traverse Boards provided a simple and relatively foolproof method of recording information which could be used even the foulest weather.

  13. Until the problem of determining longitude was solved, most sailors relied on dead reckoning. This meant that the pilot had to estimate the ship's speed with a logline (before the use of a logline, the speed of a ship was calculated by having one member of the crew throw a chip of wood over side of a vessel and then judging how far the ship traveled before it hit the water to determine how fast a ship was moving), while time was measured with one-minute glasses (a one minute sand hourglass was the only reliable method of keeping time on board the ship - provided that a member of the crew did not heat the hourglass with the lamp, making the sand run faster, in order to shorten his shift). This information combined with the known direction of the compass helped to determine progress along longitudinal lines. Time, distance, and direction were measured each time the ship changed tack due to wind direction. This zigzag plotting was calculated with a traverse board. Dead reckoning also included observations of the surroundings. Cloud formations, and wave patterns and directions, as well as birds and floating debris were all taken into account. Clearly, dead reckoning was a complicated process and not the most reliable method a sailor could use to determine his course.

  14. For the most part, a good captain would rely on the ship's log, his lookout, and his leadsman to determine the location of the ship.

  15. Geography and cartography

  16. Rather rudimentary navigation techniques were used by early explorers—the charts used by early explorers, while showing bodies of water, landmasses and ports, were not drawn to a grid system of degrees, but were based on compass findings and estimated distances. Some cartographers (like astronomers) were interested in astrology and their main purpose was not to discover what actually existed but to rationalize their world around preconceived notions of religion and philosophy. Early influences on cartography included Claudius Ptolemaeus, or Ptolemy (below right), Massoudy, Edrisi, and several medieval European cartographers and geographers. In 151 C.E., Ptolemy published a work on map-making called Geographia. His envisioned world stretched from Iceland and the Canary Islands in the west, to Ceylon in the east, with a mass of unknown lands south of North Africa and beyond India. He believed that Africa connected with an undiscovered southern landmass which would have made it virtually impossible for a ship to reach Asia by rounding southern Africa. Ptolemy's ideas remained the basis for cartographers and geographers alike for centuries.

  17. Ptolemaic Map (1432)

  18. Massoudy and Edrisi In the tenth century, Massoudy, an Arabic scholar, suggested that a channel existed between southern Africa and the unknown land mass around the southern extremities of the world. Massoudy's work was continued by Edrisi, an Arab geographer in the service of King Roger of Sicily, in the twelth century. Edirsi's main contribution was to record the travels of his contemporaries in both the Christian and Muslim worlds and to include those discoveries in the maps he created. Abdullah el Idrisi (Edrisi)

  19. Cartography contd.

  20. Prince Henry the Navigator

  21. Transportation

  22. Caravels

More Related