1. Definitions
Latitude – Distance north or south from the equator measured in degrees
Longitude – Distance east or west of the Prime Meridian measured in degrees
Degree – Unit of measurement on latitude or longitude (°)
Equator - An imaginary line drawn around the earth equally distant from both poles, dividing the earth into northern and southern hemispheres and constituting the parallel of latitude 0°
Prime Meridian - A planet's meridian adopted as the zero of longitude. The earth's zero of longitude, which by convention passes through Greenwich, England.
Hemisphere - A half of the earth, usually as divided into northern and southern halves by the equator, or into western and eastern halves by an imaginary line passing through the poles.

2. Equator and Prime Meridian