Earth Location

LOCATION
Location is the geographic situation, or a point or position in space where objects, organisms and fields of force may be found or events occur. It is also the fact or condition of occupying a particular place. The mathematical system commonly used to describe location on the earth's system is based on a'series of imaginary lines arawnon a globe according to an agreed method.

The geographic grid is a network of intersecting lines on the globe, based on two natural points-the North Pole and the South Pole.

GREAT CIRCLE The great circle is any hypothetical circle on earth's surface, the plane of which passes through earth's centre, cutting it into two equal halves, Le. hemi­spheres. This intersection of the plane with the globe is the largest circle that can be drawn on it. The equator is a great circle. It divides the earth into the northern hemisphere and the southern hemisphere.

An infinite number of great circles can be drawn on a sphere. However, only one great circle can be found to pass through two given points on the surface of the sphere-unless the two points are the extremities of the same diameter, in which case any number of great circles can be drawn through them. Intersecting great circles bisect each other. An arc of a great circle is the shortest distance, following the surface, between any two points on a sphere; hence the use of the great circle routes by aircraft, e.g. over the North Pole region.

SMALL CIRCLE A small circle is a hypothetical circle made by a plane passing through the globe anywhere except through the centre. It cuts the globe into unequal
parts. The Tropic of Cancer at 23"30'N and the Tropic of Capricorn at 23"30'5 are small circles. The Arctic Circle is
66"32'N (often taken as 66.1 "N) and the Antarctic Circle is
21
66"32'5 (often taken as 662" "5). All parallels of latitude
except the equator arE! small circles.

Meridians and Parallels Rotation of the earth on its axis provides two natural points-the North and the South Poles. The set of north-south lines connecting the poles are called meridians. The set of lines running east-west are called the parallels. All meridians are halves of great circles, containing 1800 of are, spaced farthest at the equator and converging to common points at the poles. Parallels are equidistant circular lines, running parallel to the equator and to each other, intersecting the meridians at right angles. A meridian exists for any point selected on the globe as an infinite number of meridians may be drawn on a globe. Every point on the globe, except the North Pole and the
POINTS TO REMEMBER