Developed by Bob Bruninga, WB4APR, the Automatic Packet Reporting System "was designed to support rapid, reliable exchange of information for local, tactical real-time information, events or nets. The concept, which dates back to the mid 1980's, is that all relevant information is transmitted immediately to everyone in the net and every station captures that information for consistent and standard display to all participants."
APRS uses amateur radio packet technology to transmit position reports, weather reports and messages between users. When combined with GPS technology, mobile radio stations can transmit accurate, regularly updated position reports which enables accurate tracking of the vehicle.
Using a frequency of 144.800Mhz., the radio range of individual stations, particularly when mobile, can be considerably enhanced by the use of "digipeaters" which in effect receive an individual station's signal and re-transmits it over a wider area, a process that can be repeated several times. A station known as an "igate" can feed information received by radio to the Internet where it can be seen by not only radio amateurs (or "Hams"), but by internet users worldwide.
The map available below shows realtime APRS activity in the Merseyside area. If I'm active on APRS around the time you're watching this page, I'll be on the map with the callsign G7GFU