Prime Meridian

Perhaps the first astronomer to determine the difference between geographical points in longitude was Hipparchus , who used Fr. Rhodes Ptolemy used the mythical “Islands of Fortune” , usually associated with the Canary Islands , as a starting point ^[3] .

In 1541, Gerard Mercator, on the earth globe he created, depicted the initial meridian passing through Fr. Fuerteventura (Canary Islands). On later maps, the Azores were used as a reference point, and when creating the geographical atlas of Abraham Ortelius in 1570, the Cape Verde. In 1634, at a conference convened by Cardinal Richelieu , it was proposed to use the westernmost island of the Canary Archipelago, Hierro (Ferro).

The Greenwich Meridian was first set to zero in 1851. It passes through the axis of the Passing Instrument of the Greenwich Observatory ^{[4] [5] [6]} .

International discussions

In 1871, the first International Geographical Congress took place in Antwerp , in one of the resolutions of which it was recommended to adopt the Greenwich Meridian as the zero meridian for sea charts of all countries, and over the next fifteen years. For mainland and coastal maps it was proposed to use their own zero meridian. By the early 1880s, twelve countries began to count longitude from Greenwich on newly published sea charts ^[3] .

Discussions about the Meridian Zero were spurred by an article called Earth Time, published in Canada in 1876 by Sanford Fleming , director of engineering for the Canadian Pacific Railway. The article expressed the idea of ​​using single time all over the world. In the years 1878-1879, Fleming gave two lectures at the Canadian Institute in Toronto . The first was called "Time Calculus" and was prepared on the basis of article 1876. The second lecture, entitled “Longitude and Timekeeping,” was subtitled “A few words about the choice of the prime meridian common to all states in connection with timekeeping”. In this lecture, in particular, the choice of the meridian, which is 180 ° away from Greenwich, was justified as a zero reference. Fleming's lectures aroused interest in the scientific world, and the opponents came up with their own proposals for the zero meridian, for example ^[3] :

• the Cheops Pyramid in Egypt (Professor Piazzi Smith, Royal Astronomer of Scotland);
• Jerusalem (astronomers of Bologna);
• Bering Strait (Professor Beaumont, geographer from Geneva).

All these and other proposals were discussed at the congress in Venice in 1881. After the first International Geographic Congress, the issue of the zero meridian was one of the main issues discussed at the following international forums:

• 1875 - II International Geographical Congress (Paris);
• 1881 - III International Geographical Congress (Venice);
• 1883 - VII International Geodesic Conference (Rome);
• 1884 - Washington Conference (see International Meridian Conference ).

For convenience of comparison, the approximate (rounded) value of longitude in decimal degrees is indicated.

• Burgess, Ebenezer (2013), "Translation of the Surya-Siddhanta", Journal of the American Oriental Society , vol. 6, Google, p. 185  

• Dolan, Graham The Greenwich Meridian before the Airy Transit Circle (neopr.) . The Greenwich Meridian (2013).

• Dolan, Graham WGS84 and the Greenwich Meridian (Neopr.) . The Greenwich Meridian (2013).

• Hooker, Brian (2006), A multitude of prime meridians , < http://zeehaen.tripod.com/unpub_2/multitude_meridians.htm > . Retrieved January 13, 2013.  
• Norgate, Jean and Martin (2006), Prime meridian , < http://www.geog.port.ac.uk/webmap/hantsmap/hantsmap/meridian.htm > . Retrieved January 13, 2013.  
• Sobel, Dava & Andrewes, William JH (1998), The Illustrated Longitude , Fourth Estate, London  

• “Where the Earth's surface begins — and ends” , Popular Mechanics , December 1930
• scanned TIFFs of the conference proceedings
• Prime meridians in use in the 1880s, by country
• Canadian Prime Meridian