Locating a point on the Earth’s surface so that everyone agrees on exactly where that point is can best be achieved by using coordinates known as latitude and longitude. These two are measured in degrees calculated from the angle whose apex is the Earth’s center.

Latitude Imagine that the effective axis on which our world spins has at its ends the North Pole and the South Pole. At an equal distance from either pole, the Equator is a line drawn around the earth’s waist, and it is assigned the value of 0 degrees, making it the starting point for latitude values. The angular distance between the equator and points either south or north of it is the latitude value of that point. Imaginary lines on the earth’s surface, parallel to the equator and circling the globe, all having the same latitude are known as lines of latitude, or parallels. From the equator, and on the north and on the south of it, there are 90 degrees of latitude. So, the North Pole is at 90 degrees north, while the South Pole is, predictably, at 90 degrees south.

Longitude Tracing paths along the earth’s surface perpendicular to the latitude parallels are lines on longitude, known as meridians, which all run through both the north and the south poles. While there is no obvious logical meridian to be called 0 degrees, by international convention, the meridian that runs through Greenwich, England is designated as 0 degrees, also known as the Prime Meridian. All longitudinal values are measured from this line, either east or west.

Since the earth is a sphere, it is divided into 360 degrees, half of those being east of the Prime Meridian and the other 180 degrees to the west of it. Imagine then that 180 degree meridian is exactly opposite of the Prime Meridian on the globe. Dividing the earth into equal degrees yields about 69 miles per degree. Minutes, of which there are 60 per degree, are about 1.15 miles and seconds, of which there are 60 in a minute, are a mere 100 feet.

By understanding these universally accepted standard measurements on the earth’s surface we can all agree on precisely where we are. If one knows the coordinates of both latitude and longitude of a spot on the earth, there is no mystery nor controversy of where that particular spot is located.