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
Mercator 1569 world map 12 by using compass roses on the equator and it is only in Legend 10 that he introduces the Organum Directorium and also addresses the inverse problems: given the initial point and the direction and distance of the second find the latitude and longitude of the second. Mercator's construction is simply an evaluation of the rhumb line distance in terms of the latitude difference and the azimuth as If the latitude difference is expressed in arc minutes then the distance is in nautical miles. In later life Mercator commented that the principles of his map had not been understood by