What is APRS ?
Also known as Automatic Packet Reporting System, APRS was developed by Bob Bruninga, WB4APR, and is an amateur radio based digital communications system for local, tactical, real-time exchange of information among all members of a net, including map based displays for situational awareness.
APRS is used to transmit real-time information including messages, bulletins, announcements and the locations of any station or object via packet radio protocols. Real-time reporting of station position for mobiles is facilitated using the Global Positioning System (GPS). APRS is capable of transmitting a wide variety of data including weather reports, short text messages, radio direction finding bearings, telemetry data, and storm forecasts. These reports can be combined with a computer and mapping software to show the transmitted data superimposed on a variety of map displays and special radios.
With various implementations and additions APRS has expanded to a world wide network, though it's fundamental objective still remain the same. See Bob Bruninga's description for more details.
The Automatic Position Reporting System, APRS, allows mobile users and objects to report their current position over radio. This enables the objects position to be automatically displayed and updated on computers or special radios running APRS mapping applications. APRS can have many uses, some amateurs have even used it to track their stolen cars