GPS

1. History

1.1. 1973

1.1.1. U.S.airforce and navy

1.1.1.1. decided to build a navigation system

1.2. 1979

1.2.1. system tests

1.3. 1980

1.3.1. financial crisis of the system

1.3.1.1. doubtful sponsors

1.4. 1993

1.4.1. a anouncement of free of charge for all

1.5. 2004

1.5.1. lauched th 50th satellite

2. Disadvantages

2.1. system fail

2.2. inaccurate

2.3. weak signal when using in satellite

2.4. doesn't function indoor

2.5. poor reception whiling there is something block the signal e.g. tall building

3. How GPS function

3.1. Satellite in the space sends signal to the devices.

4. Advantages

4.1. good for navigation

4.2. no weather condition limitation

4.3. low cost

4.4. wide spectrum of application

5. Application

5.1. provide military and civil usage

5.2. provide information

5.3. usage in satellite

5.4. provide location