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Longitude
Lines of Longitude (Meridians) run from zero degrees at the Greenwich Prime Meridian to +180 degrees East and -180.0 degrees West.
Latitude
Latitude lines are parallel to the Equator (by definition the Equator lies at 0.0 degrees). Latitude or parallel lines run from the Equator up to +90.0 degrees North of the Equator (North Pole), and -90.0 degrees South of the Equator (South Pole).
Miles
Kilometers
Latitude 1 Longitude 1 Latitude 2 Longitude 2
The longitude and latitude of Greenwich Prime Meridian, England is 0 , 51 29  N
The longitude and latitude of Hawaii, USA is 155 40 17 W, 19 59 06 N 
Longitude and Latitude of World Cities
 
The haversine formula is an equation important in navigation, giving great-circle distances between two points on a sphere from their longitudes and latitudes.

Presuming a spherical Earth with radius R (see below), and that the locations of the two points in spherical coordinates (longitude and latitude) are lon1, lat1 and lon2, lat2, then the Haversine Formula:

dlon = lon2 - lon1
dlat = lat2 - lat1
a = (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2
c = 2 * atan2(sqrt(a), sqrt(1-a))
d = R * c

will give mathematically and computationally correct results. The intermediate result c is the great circle distance in radians. The great circle distance d will be in the same units as R.
Haversine Distance Formula