Latitude and longitude
are angles that uniquely define points on a sphere. Together, the angles
comprise a coordinate scheme that can locate or identify geographic positions
on the surfaces of planets such as the earth.
Latitude is defined with
respect to an equatorial reference plane. This plane passes through the
center C of the sphere, and also contains the great circle
representing the equator. The latitude of a point P on the
surface is defined as the angle that a straight line, passing through
both P and C, subtends with respect to the
equatorial plane. If P is above the reference plane, the
latitude is positive (or northerly); if P is below the
reference plane, the latitude is negative (or southerly). Latitude angles can
range up to +90 degrees (or 90 degrees north), and down to -90 degrees (or 90
degrees south). Latitudes of +90 and -90 degrees correspond to the north and
south geographic poles on the earth, respectively.
Longitude is defined in
terms of meridians, which are half-circles running from pole to pole. A
reference meridian, called the prime meridian , is selected, and this forms the
reference by which longitudes are defined. On the earth, the prime meridian
passes through Greenwich, England; for this reason it is also called the
Greenwich meridian. The longitude of a point P on the surface
is defined as the angle that the plane containing the meridian passing through P subtends
with respect to the plane containing the prime meridian. If P is
to the east of the prime meridian, the longitude is positive; if P is
to the west of the prime meridian, the longitude is negative. Longitude angles
can range up to +180 degrees (180 degrees east), and down to -180 degrees (180
degrees west). The +180 and -180 degree longitude meridians coincide directly
opposite the prime meridian.
Latitude and
longitude coordinates on the earth are sometimes
extended into space to form a set of celestial coordinates.
That's about all there is to latitude and longitude coordinates! Here's some tips to remember:
That's about all there is to latitude and longitude coordinates! Here's some tips to remember:
- Latitude is always given before longitude (49° N 100° E)
- Latitudes are parallel, but longitudes are not
- Degrees West and South are sometimes referred to as negative degrees (-12° -23° is the same as 12 S 23 W)
- A place's latitude effects its climate, but its longitude does not
- Key longitude lines are the Prime Meridian (0°) and the International Date Line (180°)
- Key latitude lines include the equator (0°), tropic of cancer (23° 26' N), tropic of capricorn (23° 26' S), the arctic circle (66° 33' N), and the antarctic circle (66° 33' S)
- Find your location from your latitude/longitude at this page
