GPS (for Global Positioning System) is a satellite aided navigation system composed of several satellites in orbit around the Earth which are used by GPS units on the surface to get accurate positioning of vehicles and people in movement. The GPS units have an antenna which allows them to receive the signals from the satellites, and based on the position of those satellites (information provided in the signal), they obtain their current position.
This system is being used for several things, ranging for simple stuff, like street routing and sport activities recording, to more advanced things like fleet control, mapping.
Type of GPSs
There are a few kinds of GPS units, which you should choose depending on the use you are going to make out of it. The following sections explain the different types.
These are the simplest, and cheapest options, since they just provide an antenna and some interface to connect them to other hardware, like computers or cell phones.