Читать книгу Geography For Dummies - Jerry T. Mitchell - Страница 57

The longitudinal “starting line” is called the prime meridian, which signifies its importance as the line from which all other lines of longitude are numbered. Locating this line proved more problematic than locating the equator. Quite simply, no logical equivalent of the equator exists with respect to longitude. Thus, while the equator came into general use as the latitudinal starting line, mapmakers were perfectly free to draw the longitudinal starting line anywhere they pleased. And that is what they did.

Typically, mapmakers drew the prime meridian right through their country’s capital city. By the late 1800s, lack of a universal prime meridian had become a real pain in the compass. International trade and commerce were growing. Countries were claiming territory that would become colonial empires. But one country’s world maps did not agree with another’s, and the international climate made it increasingly advisable that they do so. I have a map hanging in my living room to prove the point! There are different longitude coordinates at the top of the map compared to those at the bottom. Both were given to aid a map reader more used to a coordinate system beginning with a different meridian.

As a result of this growing confusion, in 1884 the International Meridian Conference was convened in Washington, D.C. to promote the adoption of a common prime meridian. Out of that was born an agreement to adopt the British system of longitude as the world standard. Thus, the global grid’s prime meridian passes right through the Royal Greenwich Observatory (which is in the London suburb of Greenwich) as well as parts of western Europe and Africa, and the Atlantic Ocean. The British system was chosen largely because in 1884 Britain was the world’s major military and economic power, and also had a fine tradition of mapmaking.