1. GPS Survey Equipment City Planning Construction Environmental Studies

2. 24 GPS satellites in orbit around the earth at any given time at least 4 satellites are always visible each survey unit has a receiver which picks up radio frequencies sent from satellites all data is sent to a handheld device called a “collector” the collector stores the information until it can be downloaded to a computer with software to interpret the data GPS Receiver Collector

3. Each satellite has an individual code or PRN Each PRN contains a specific altitude and exact time so with each signal this information can be transmitted to the receiver The exact location of the GPS survey unit can then be calculated through a mathematical method called triangulation which uses the known altitudes (distance x speed of radio wave ≈ 186,000 miles/sec), the time the signal was sent and the time it was received from each satellite. Triangulation can become very complicated very quickly