The Geographic Grid

The geographic grid is a system of imaginary arcs drawn in a grid pattern on Earth's surface. It allows us to pinpoint absolute location using longitude and latitude.  Longitude lines are also know as meridians, they run north to south.  Latitude lines are also known as parallels and they run east to west.  The prime meridian is a longitude line that separates the western and eastern hemispheres.  The equator is a latitude line that separates the northern and eastern hemispheres.  When you plot an absolute location, the longitude is first and latitude is second.  You also have to say N or S after the longitude and W or E for latitude.  For example, Washington D.C.'s absolute location is about 39०N, 77०W.