Lesson Note On GPS

What is GPS?

 The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the US government made the system available for civilian use. Prior to 1990, GPS signals were deteriorated so a user could not achieve accuracy better than 10 meters. However, this has been changed and now any standard GPS unit can provide a precision of 4 to5 meters or 12- 15 feet. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. 

However, tall building s or thick forest cover may block the GPS signal and result in a less precise accuracy. 

The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are traveling at speeds of roughly 7,000 miles an hour. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. 

The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map. 

As GPS receivers track satellites and calculate your position this process is referred to as Triangulation. Any organization or agency that requires accurate location information can benefit from the efficiency and productivity provided by GPS technology. GPS units are used to collect point, line or polygon data on program activities by recording the latitude and longitude of activity sites, or tacking roads or walking/driving perimeter locations. 

The type of GPS unit used by USAID/Malawi does not provide data measurements necessary for land tenure processes and data collected should not be used for any legal purposes or land dispute as it is not to the required accuracy.