Bits of Map Projection History

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EARTH'S SIZE AND SHAPE IN TIME AND SPACE, by Lance Nelson

(The following are notes were prepared by Lance Nelson for the seminar in map projections.)

World maps, per se, don't exist in the most ancient times. Both ancient Egypt and Mesopotamia develop some kind of cadastral mapping, but they do not attempt to represent the earth beyond their realms except to diagram their relationship to a cosmos of some sort.

In western history we have records of some of the first speculations about the shape of a world in 7th century BC Greece.

As Europe enters the dark ages, these ideas about the world are gradually lost. Europe's view of the world is increasingly shaped by theological concerns and lack of contact with other places. Generally the map of the world became a theological rather than geographic statement. In Europe this was expressed in the development of the so-called T-O map, which had some recognizable geographic informations in all of its forms, but was heavily influenced by dogmas and theology. These were the main world maps for centuries in Europe, but the concept of maps as tools did not disappear. All through this period Itineraries and other kinds of route maps were published for crusaders and pilgrims. On the seas portolan charts were in constant use.

Meanwhile...

All through Asia and parts of Africa seafaring and overland trade is taking place. The ideas of the Greeks and Ptolemy are preserved in Arabic translation. Eventually due to trade and contacts these works start to re-enter Europe. The Book of Roger, commissioned by a Norman king in Sicily in the 12 century, had maps and a geography based on Ptolemy. Additional information, probably based on trade in the East was used to update the Ptolemaic maps.

China has had a bureaucratic mapping tradition for administering its realm since the 3rd century BC. A graticule was developed, but was not related to the idea of the earth as a globe. There was always a certain amount of knowledge about the wider world available in China, but world maps do not seem to have been of much interest to scholars or rulers. The only ones that are available seem to be similar to the European T-O in their focus on religious or philosophical ideas.

For various reasons Europe starts to look at the world in a different way. In addition to a willingness to accept some of the Classical ideas now becoming available, there is heightened interest in the seafaring trade to Asia.

In the 15th and 16th century Portugal circumnavigates Africa, Columbus uses Ptolemy and others to underestimate the size of the globe and sails for Asia, Magellan more or less circumnavigates the globe.

In 1525 Pernel tries to measure a degree of latitude in France.

In the 17th century there is the development of surveying equipment and triangulation methods, including the logarithms, theodolite, pendulum clock, and barometric level. In 1669 Picard develops a triangulation line near Paris and measures a degree of latitude. Newton develops the theory of gravity and proposes that the globe is actually an oblate spheroid due to angular momentum.

In the 1690's Cassini, father and son, propose triangulation to further verify the degree of latitude. Their southern routes gives a shorter degree than Picard, the son goes on to measure a northern route and finds this degree is longer. He propose a prolate spheroid as the correct shape for the earth.

1735 - 1743 - Expeditions are mounted to Lapland and Peru by the French to measure the length of a degree of latitude and determine the correct shape of the earth. The Northern expedition measure a longer degree, thus proving Newton's proposal of the oblate spheroid based on the theory of gravity.

In the 18th century there is a great race to accurately determine the longitude. John Harrison's chronometer No 4 is successful at sea in 1761.

In the 20th century the two major developments are the use of the geoid and other models for the earth's surface and the ability to use space to make measurements of the earth.

Over-all the history of the shape of the earth can be divided into three major eras, if one ignores the flat earth theory which still captures some adherents in moderns times. These three are the time of the spherical earth from ancient ideas, the ellipsoidal earth, where the major perturbations of gravity are included in the modeled shape of the earth and finally the geoid which includes many local perturbations in the general shape of the earth.

Claudius Ptolemy (90-170 AD) Dr. K. C. Clarke

(The following are notes were prepared by Dr. Clarke for the seminar in map projections.)

Major Works

ALMAGEST (From the Arabic translation "the greatest")

GEOGRAPHY Meaning: Cartography: Mapping of all the world and the phenomena it contains.

PTOLEMY'S PROJECTIONS

ONE

TWO

THREE

PTOLEMY's PARALLELS

PTOLEMY's MERIDIANS

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last updated 7/14/97

Comments - Karen Mulcahy kam@everest.hunter.cuny.edu