The 27 (24 active and 3 backups) satellites making up the GPS network over earth send microwave signals at light speed to communicate positions. For years, the military has used GPS coordinates to locate people, targets, set navigation and establish meeting places. Today, people use GPS for hiking, driving, SCUBA diving, golf and other applications where specific locations are needed. Many hand-held GPS units are accurate to within 12 inches or less. You can learn to read GPS coordinates to better understand GPS devices.
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Imagine the Prime Meridian and International Date Line as an equator splitting the earth into east and west. The Americas are located in the west and most of Africa, Europe and Asia are in the east when you read GPS coordinates.
Divide the earth into the northern and southern hemispheres for the first number when you read GPS coordinates. For example, N 20 degrees stands for the imaginary latitude line 20 degrees North of the equator. The coordinates S 75 05.235' represent a line slightly more than 75 degrees South of the equator. Sometimes, South is represented by a minus sign.
Split the earth into an imaginary east and west along the Prime Meridian. The Prime Meridian runs from the North Pole to the South pole through the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Togo, Ghana and Antarctica. The 180th meridian (half of 360 degrees, which represents a full circle) is the International Date Line and helps to establish east and west.
Read the second set of numbers in the GPS coordinates to determine the east or west line. For example, W 60 degrees stands for 60 degrees west of the Prime Meridian for a location in the western hemisphere. The coordinates E 15 degrees 07.55' relates to just over 15 degrees to the east of the Prime Meridian at a location in Europe or Africa. Sometimes, West is shown by a minus sign.
Find the point where the two numbers (for North/South and East/West) intersect to establish the GPS location. For example, the coordinates N 37 degrees 43.69, W 97 degrees 28.39 point to Wichita, Kansas. GPS coordinates can be specific down to about 30 cm.
Tips and warnings
- GPS coordinates use minutes and seconds to establish points between degrees. You may see the time represented as 07' 27" or 7 minutes and 27 seconds or 7.450 minutes or .124167 (7.45 divided by 60).
- GPS coordinates can be presented in at least four different formats, making it difficult to understand the coordinates.