| Title What if Ferdinand Magellan Had a GPS?
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Author Dawn Magnusson American River College, Geography 350: Data Acquisition in GIS; Spring 2009 | |
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Abstract This paper contrasts the medieval methods of navigation used by Ferdinand Magellan in the 16th Century with those used today. | |
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Introduction What if Magellan had a GPS and other modern navigation technologies available when he sailed in 1519? Would he have survived the trip, with all his ships intact? We will never know, but let's compare the methods Magellan used to those of today. Magellan used celestial navigation and dead reckoning, not computers and GPS units with satellites. Today we can take a look at Google Earth and get a preview of where we will be headed. Magellan had crude, inaccurate maps, and warnings that he could sail off the edge of the earth.
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Background Ferdinand Magellan set off from Seville, Spain on August 10, 1519 to find the Spice Islands. He sailed with five ships: The Trinidad- his flagship; the San Antonio- the provision ship; and the Victoria, Conception, and Santiago; collectively, "The Armada de Molucca" , and 237 men. From there he sailed past Cape Verde (14°N/23°W), the Equator, Rio de Janiero (22°S, 43°W), reaching Puerto San Julian on March 30, 1520 (49°S/67°W). He spent the winter there and left again on August 21, 1520. On October 2, 1520 he reached Cape Virgines at the southeast tip of Argentina, and on November 1, 1520 he reached the entrance to what he named the Strait of All Saints, (at 53° S/70W) since they entered the strait on All Saints' Day. This strait would later be named The Strait of Magellan in his honor.
The strait, with its 300 miles of fjords, twists and turns, and rough seas, took Magellan 28 days to pass through. After navigating the Strait, he reached the South Pacific on November 28.When he emerged from the strait into the Pacific Ocean, Magellan mistakenly thought that the Spice Islands lay a short distance away. A voyage of what he had believed would be two or three days turned out to be four months on open ocean. He then continued on north, past the Equator again, past Guam (13°N/144°E), and reached Cebu, Philippines on April 7, 1521 (10°N/123°E) where he was killed in battle on April 27, 1521.
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Methods Lacking the time and resources to retrace Magellan's trip, research for this project was done using two books: Over the Edge of the World - Magellan's Terrifying Circumnavigation of the Globe, by Laurence Bergreen, and A World Lit Only By Fire - The Medieval Mind and the Renaissance, Portrait of an Age, by William Manchester; and Internet sources. | |
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Results Magellan used medieval methods of navigation, employing dead reckoning, which is the process of determining position based on the speed and direction of travel. The ships' pages (young men at the bottom of the crew's division of labor), were employed to regularly turn an hourglass while measuring the time it took for a log other object to pass from one end of the stern to the other. The pages would turn the hourglasses (or ampolettas) every half hour or hour, while chanting prayers to the Virgin Mary to ensure a safe passage.
Each day at noon, the pilot of the ship would "shoot the sun" with a quadrant or crossbow to determine latitude. A quadrant is a quarter circle, which measures vertical angles, like the height of the sun or the North Star. This gave the measure of latitude. These calculations were recorded in the ship's log, and it was determined that Magellan's ships made daily runs of 50, 60 or 70 leagues per day, a league being equivalent to about 2.6 miles.
Today's maritime navigators still use Dead Reckoning to navigate. Modern ships use an Inertial Navigation System (INS) that uses a computer and motion sensors to continuously calculate via dead reckoning the position, orientation, and velocity of the ship. An INS gets its position and velocity from a source such as a human operator or a GPS satellite receiver. The INS needs no external references to determine its position, orientation, or velocity once it has been initialized. Celestial navigation involves reducing celestial measurements to lines of position using tables, spherical trigonometry, and almanacs. Magellan used a quadrant or backstaff to shoot the sun. Modern celestial navigation usually requires a marine chronometer to measure time, a sextant to measure angles, an almanac giving schedules of the coordinates of celestial objects, a set of sight reduction tables to help perform the height and azimuth computations, and a chart of the region. These methods may be used as a backup to Global Positioning System (GPS) receivers and LORAN Systems. The LORAN (Long Range Aid to Navigation) is a terrestrial radio navigation system using low frequency radio transmitters to determine location and/or speed of the receiver. The Apollo Command Modules were equipped with a fixed sextant, which could measure angles between the stars, earth or moon landmarks, and planetary horizons.
The Apollo Spacecrafts were also equipped with an inertial guidance system called the Apollo Primary Guidance, Navigation, and Control System (PGNCS, pronounced pings). It allowed the spacecraft to carry out their missions when communications with Earth were interrupted.The Command Module and Lunar Module were both equipped with PGNCS, which consisted of the following:
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Analysis As I could not go and retrace Magellan's voyage or the Apollo missions, reasearch was done mostly with Internet sources. There is a wealth of information on navigation, both medieval and modern, available. The problem is paring down the information to what is pertinent and interesting. There are many technical articles explaining Dead Reckoning, Celestial Navigation, LORAN, GPS, and other navigational methods. Many are too technical and scholarly for the scope of this paper. The idea was to contrast the past with the present. I believe it is true that Magellan's voyage was just as risky and daring as any manned spaceflight. The research on Magellan was a bit less volumninous, but the books I read provided fascinating accounts of Magellan's adventure, and those of his surviving crew. | |
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Conclusions Ferdinand Magellan was killed in battle in Cebu, Philippines and never returned to Spain. On September 6, 1522, 18 of Magellan's 237 men returned in the ship Victoria, all malnourished and weak. Some had died of hunger or disease, some deserted at the island of Timor, and some had been put death - by Magellan - for crimes, mostly mutiny. The Victoria returned with 381 sacks of cloves. The expedition had circled the globe, and added 7000 miles to the Earth's circumference, and banished myths such as mermaids, boiling water at the equator, and a magnetic island that pulled nails from passing ships. Of the Apollo missions, 3 astronauts were killed in the Apollo 1 mission which never left the ground. It was destroyed by fire in a test and training exercise, killing astronauts Virgil "Gus" Grissom, Edward White, and Roger B. Chaffee. Apollo 13 experienced an in-space explosion but managed to splash back to earth with no fatalities. However, it never landed on the moon. The Apollo astronauts returned with a total of 841.5 pounds of lunar rocks. These rocks range in age from 3.2 billion years to 4.6 billion years. The Genesis Rock contains a geochemical known as KREEP which has no known terrestrial counterpart. These lunar samples have been used to infer that the moon was once completely molten. It is difficult to say which of these endeavors was more brave, or more terrifying. Magellan sailed off into waters as unknown as outer space was to the first astronauts. More men died on Magellan's voyage than on the space missions. Only time will tell if manned spaceflight will one day be as common as a cruise in the Pacific Ocean. | |
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References Bergreen, Lawrence, Over the Edge of the World - Magellan's Terrifying Circumnavigation of the Globe 2003, Perennial.
Manchester, William, A World Lit Only By Fire - The Medieval Mind and the Renaissance, Portrait of an Age, 1992, Little, Brown. "How Columbus and the Apollo Astronauts Navigated" http://er.jsc.nasa.gov/seh/navigate.htm "NASA - The Apollo Program" http://spaceflight.nasa.gov/history/apollo "The Mariners' Museum" http://www.mariner.org/educationalad/ageofex/magellan.php "Apollo PCGNS" http://en.wikipedia.org/wiki/Apollo_PGNCS "Apollo Program" http://en.wikipedia.org/wiki/Apollo_program "Dead Reckoning" http://en.wikipedia.org/wiki/Dead_reckoning "Ferdinand Magellan" http://en.wikipedia.org/wiki/Ferdinand_Magellan "Navigation" http://en.wikipedia.org/wiki/Navigation
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