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Understanding Latitude and Longitude
Just as the equator is an imaginary line around the circumference of Earth, latitude and longitude are also imaginary lines that run horizontally and vertically around the globe. Latitude and longitude are used for determining location. GPS devices use data transmitted by satellites to determine the exact latitude and longitude of a given point, as well as the point’s height above sea level. Long before GPS, however, sailors relied on a variety of skills to navigate the oceans. Celestial navigation was a common way to determine position. Sailors used the North Star, which is located directly over the North Pole, as it appears in the night sky. Sailors used a tool called a sextant to measure the angle of elevation of the North Star. The angle of elevation was the equivalent to a point of latitude on a map. Today, NASA (National Aeronautics and Space Administration) still uses celestial navigation for many missions that take place outside of Earth’s atmosphere. • Latitude is measured from the equator and runs north to south. Longitude is measured from the Prime Meridian and runs west to east. • Determining latitude and longitude is similar to using a coordinate grid to plot points. The y-­‐axis is latitude (vertical) and the x-­‐axis is longitude (horizontal). The center point (zero) is where the prime meridian and The Contiguou s United States
the equator intersect. • Measuring latitude and longitude is also similar to using a number line. Points going north and east are positive values and points going south and west are negative values. For example, 115 degrees west longitude, 40 degrees north latitude is -­‐
115 degrees longitude, +40 degrees latitude. • Latitude lines are numbered from 0° to 90° north and south. Zero degrees is the equator; 90° north is the North Pole and 90° south is the South Pole. • Longitude lines are numbered from 0° to 100°. Zero degrees longitude is located at Greenwich, England. It is called the prime meridian. The degrees continue 180° east and 180° west until they meet. This imaginary line where they meet is the International Date Line. A degree of longitude is widest at the equator at approximately 69 miles apart and shrink to 0 miles at the poles. • Latitude lines are also known as “parallels” since they are an equal distance apart at any point. Each degree of latitude is approximately 69 miles apart. There are variations in this number because Earth is slightly egg-­‐shaped and not a perfect sphere. ©2014 QUICK SMART™ Geography Level 2 newtoneducationgroup.com 90