| The Global Positioning System, commonly | | | | |
| called GPS, is a navigational system that | | | | The GPS system became fully functional in |
| uses satellites and computers to determine | | | | 1985. Today it is used for navigating on |
| the latitude and longitude of a receiver on | | | | land, sea and air. It is also used for |
| Earth. This is done by computing the time | | | | mapmaking, land surveying and scientific |
| difference for signals from different | | | | research. |
| satellites to reach the receiver. | | | | |
| | | | Over the last fifteen years, the accuracy of |
| GPS is the only satellite navigation system | | | | the GPS signal has improved steadily. Today, |
| that is fully functional. It uses a | | | | a GPS system can accurately pinpoint the |
| collection of more than twenty-four | | | | receiver on Earth to almost five meters of |
| satellites to send radio signals to | | | | its exact location. However, further |
| electronic GPS receivers. By doing so, the | | | | improvements and developments may increase |
| satellites are able to find the correct | | | | the accuracy to about 1 cm of the receiver. |
| location of the receivers. They get the exact | | | | This can be done using techniques such as |
| longitude, latitude and altitude of the | | | | differential GPS. A GPS also gives an |
| receiver. GPS systems work around the clock | | | | extremely precise time reference which is |
| under any weather conditions. | | | | useful in some scientific experiments. |