latitude v. longitude

Transparent globe. Image courtesy of dreamstime.com Latitude is a measurement of angular distance north or south of the Earth’s Equator, with values ranging from 0° at the Equator to 90° at the poles. Lines of latitude run east to west and are referred to as parallels because they are all parallel to the Equator. Latitude directly affects climate, with average temperatures dropping with increasing distance from the Equator.

Longitude is a measure of angular distance east or west of the Prime Meridian, which runs from north to south through the Royal Observatory in Greenwich, England. The Prime Meridian marks 0° longitude. Moving east, longitude has positive values; moving west, it takes on negative values. The International Date Line is located opposite the globe from the Prime Meridian, and marks both 180° east and -180° west. Lines of longitude are drawn from north to south and are called meridians. Unlike parallels, whose circumference varies with latitude, and which don’t intersect, meridians all have the same circumference and intersect at the North and South Poles.

NationalAtlas.gov on latitude and longitude

iTouchMap.com - Determine the latitude and longitude of any point on the Earth

Wikipedia on the history of longitude