Longitude always in motion relative to one another. For example, the longitudinal difference between a point on the Equator in Uganda, on the African Plate, and a point on the Equator in Ecuador, on the South American Plate, is increasing by about 0.0014 arcseconds per year. These tectonic movements likewise affect latitude. If a global reference frame (such as WGS84, for example) is used, the longitude of a place on the surface will change from year to year. To minimize this change, when dealing just with points on a single plate, a different reference frame can be used, whose coordinates are
History of longitude 2nd century BC Hipparchus was the first to use such a system to uniquely specify places on Earth. He also proposed a system of determining longitude by comparing the local time of a place with an absolute time. This is the first recognition that longitude can be determined by accurate knowledge of time. In the 11th century Al-Biruni believed the earth rotated on its axis and this forms our modern notion of how time and longitude are related. Determining latitude was relatively easy in that it could be found from the altitude of the sun at noon (i.e. at its