What is 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.

Source: Geographic Information Systems Training Module I through 4