Latitude, Longitude and Projections

Because the world is round, it is divided like a circle into 360 degrees. Imaginary lines drawn in the north-south direction mark this division.

On the map longitude lines may be drawn at intervals (for example, 10 or 20 degrees of longitude). Look at a globe and notice that the lines are farther apart at the widest part of the earth and that they come together at the north and south poles. Longitude lines are numbered, starting at the Royal Observatory in Greenwich, England (where the line is called the Prime Meridian) and progressing around the globe from east to west until reaching the 180 degree line (on the opposite side of the globe). A similar pattern of numbers move from the Prime Meridian to the west. When referring to longitude, use the E and W letters to designate the line's location in the Eastern or Western hemisphere.

The globe is divided in a similar fashion by latitude lines drawn around the globe at right angles to the longitude lines.

The most important of these is at 0 degrees--the line drawn around the widest part of the globe, called the equator. Latitude numbers get smaller as they approach the north and south poles, where they are 90 degrees. When mentioning latitude, you must include a reference to north or south, because the same number is found in both the Northern and Southern hemispheres.

Look on a world map to find the "Equator," "Arctic Circle," "Antarctic Circle, "Tropic of Cancer," and 'Tropic of Capricorn." These latitude lines record important factors in the movement of the Earth relative to the Sun [I won't get into the details here]; they divide the globe into Tropical, Temperate and Arctic climate zones.

A point where latitude and longitude lines cross can be used to describe the precise location of any point on the globe.

What is the location of Atlanta? Tokyo? Paris? (Remember to include the N or S in the latitude designation. and the E or W in the longitude number.)

Map projections are attempts to take the spherical globe and flatten it out without distorting the resulting image in undesirable ways. Think of an orange peel, flattened out: it has a lot of tears in it. Alternatively, think of balloon with a picture on its surface, cut open and stretched into a flattened, rectangular shape; it has to stretch in some areas and shrink in others, thus distorting the picture on the surface.