Prime Meridian

Longitude Zero

Since 1870, geographers and scientists of allied disciplines from all nations have been trying the possibility of fixing a common zero for longitude and time reckoning throughout the globe. And it was the Prime Meridian, which was the first to be discussed. Hipparchos was the first astronomer to determine the differences in longitude, of which he used Rhodes. Ptolemy , following the Marinus of Tyre, adopted a meridian through the Canary Islands, which marked the western boundary of the world, whereas, to the east, there seemed to be no such boundary.

In 1871 the first International Geographical Congress (IGC) took place at Antwerp. The view expressed was for passage charts for all nations, not necessarily coastal or harbour charts, the Greenwich meridian should be adopted as the common zero for longitude, and that this should become obligatory within fifteen years.  It was also recommended that, whenever ships exchanged longitudes at sea , they should be based on Greenwich. This did not apply to land maps and coastal charts, these should keep its own prime meridian.

However, the 2nd IGC in Rome in 1875 discussed the whole matter again without coming to any further conclusions. France did express that if we were to accept the metric system, then they would accept the Greenwich meridian. Eventually, it was agreed internationally that a prime meridian was needed, and that it should be Greenwich.

So after years of discussion, the conference hoped that if the entire world was to accept Greenwich as the prime meridian, Great Britain might be prepared to conform to the metric system.

Prime meridians in use in the early 1880s