|Latitude and longitude form a
system used for locating places on the surface of the earth. They are
measurements, expressed as degrees of a circle measured from the center
of the earth. The earth spins on its axis, which intersects the surface
at the north and south poles. The poles are the natural starting place
for the graticule, a spherical grid of latitude and longitude
Halfway between the poles lies the equator. Latitude is the angular
measurement of a place expressed in degrees north or south of the
Latitude runs from 0° at the equator to 90°N or 90°S at the
poles. Lines of latitude run in an east-west direction. They are called
parallels because they are equally distant from,
Lines of longitude, called meridians, run in a north-south direction
from pole to pole. Longitude is the angular measurement of a place east
or west of the prime meridian. This meridian is also known as the
Meridian, because it runs through the original site of the Royal
which was located at Greenwich, just outside London, England. Longitude
runs from 0° at the prime meridian to 180° east or west,
around the globe. The International Date Line follows the 180°
making a few jogs to avoid cutting through land areas.
|DEGREES, MINUTES, SECONDS
A degree (°) of latitude or longitude can be subdivided into 60
parts called minutes ('). Each minute can be further subdivided into 60
seconds ("). One degree of latitude equals approximately 69 miles (111
km). One minute is just over a mile, and one second is around 100 feet
(a pretty precise location on a globe with a circumference of 25,000
Because meridians converge at the poles, the length of a degree of
varies, from 69 miles at the equator to 0 at the poles (longitude
a point at the poles). The diagram at left is an example of a place
to the nearest second. It is written as: 42°21'30"N 71°03'37"W
This place is city center, Boston, Massachusetts.
|Which way up . . .
The north and south poles are the earth's geographic poles, located
at each end of its axis of rotation. All meridians meet at these poles.
The compass needle points to either of the earth's two magnetic poles.
The north magnetic pole is located in the Queen Elizabeth Islands
in the Canadian Northwest Territories. The south magnetic pole lies
the edge of the continent of Antarctica, off the Adélie Coast.
magnetic poles are constantly moving.