What is Latitude and Longitude?
Latitude is measured North or South of the Equator, resulting in a range of -90 (S pole) to +90 (N pole) degrees. The Equator is the parallel that divides the globe into two halves, the Northern and Southern Hemispheres. Any point on the globe below the equator has a negative value for latitude, while points above the equator have positive latitude values.
Longitude is measured East or West of Greenwich, and can be expressed in different ways. For example, 120 degrees West Longitude is also 240 degrees East Longitude, since the earth is round, and 360 degrees make a circle. The choice of sign for longitude is also somewhat arbitrary. Some uses require (+) for West, others use (+) for East.
Although a degree of latitude or longitude is about the same at the equator (60 nautical miles), this is not true as one approaches the poles, where a degree of longitude eventually becomes infinitesimally small. To determine the latitude of a particular location, geographers measure distance in degrees north or south from the Equator. The exact distance of a place north or south from the Equator can be written in degrees, minutes, and seconds; however, it is sufficient to determine distance within a minute or two, not worrying about seconds.
For example, the distance from the Equator to one of the Poles, a quarter of the way around the earth, is 90 degrees (since there are 360 degrees in a complete circle around the globe). For greater accuracy in pinpointing location, each degree is divided into 60 minutes (60') and each minute is divided into 60 seconds (60").
To determine longitude, geographers measure distance in degrees east or west of the prime meridian, which passes through Greenwich, England. For greatest accuracy, longitude is also given in degrees, minutes, and seconds.
The global address of any place on earth includes both latitude and longitude.