GPS

1. Use of the GPS

1.1. civil

1.1.1. time service

1.1.2. social networking

1.1.3. navigation

1.2. commercial

1.2.1. measurement

1.3. military

2. History

2.1. Transit

2.2. Timation

3. How it works

3.1. Function

4. disadvantages

4.1. error souces

4.2. not cheap enough for everyone

5. advantages

5.1. identify the route

5.2. be applied in urgent situation