Skill and Practices

Question 1

Strengths of GPS

Answer 1

Quick and Easy to Use
Works in all Weather
No prior knowledge or skills needed
Works anywhere on Earth

Question 2

Weaknesses of GPS

Answer 2

GPS may fail due to certain reasons
GPS systems last only 8-12 hours before needing a battery replacement.
GPS accuracy is related to the quality of signal reception
GPS may not work due to obstacles to the signals, for example; solid structures, trees, extreme atmospheric conditions

Question 3

Explain the process of Trilateration

Answer 3

1. GPS satellite transmits data that indicates its location and the current time. The signals, moving at the speed of light, arrive at a GPS receiver.
2. The distance to the GPS satellites is determined by estimating the amount of time it takes the signals to reach the receiver. It needs the distance from four GPS satellites to calculate the position of the GPS receiver
3. The receiver picks up the satellite’s transmission and compares the time the signal was transmitted to when the signal was received.
4. The time difference tells the GPS receiver how far away the satellites are and the positions the signal was transmitted. Enabling the GPS receiver to determine its location

Question 4

Differences between Trilateration and Triangulation

Answer 4

Trilateration uses distances and time to work out location, whereas Triangulation uses angles and bearings to work out the location.

Question 5

How many satellites are needed to determine the location of the GPS receiver

Answer 5

3 satellites are needed to work out the longitude/latitude position-2D position fix. 4 satellites are needed to work out the longitude, latitude and altitude-3D position.