TAG 20 Series manual Operating Your Tablet PC

The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter! In a sense it is like giving every square meter on the planet a unique address.

Here's how GPS works in five logical steps:

The basis of GPS is "triangulation" from satellites.

To "triangulate," a GPS receiver measures distance using the travel time of radio signals.

To measure travel time, GPS needs very accurate timing that it achieves with some tricks.

Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.

Finally you must correct for any delays the signal experiences as it travels through the atmosphere.

Five broad categories of GPS application:

Location – determining a basic position

Navigation – getting from one location to another

Tracking – monitoring the movement of people and things

Mapping – creating maps of the world

Timing – bringing precise timing to the world

Operating Your Tablet PC 2-27