Automatic Position Reporting System
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Automatic Position Reporting System (APRS) is an amateur radio based automatic position reporting system for tracking and digital communications, and was developed by Bob Bruninga, callsign WB4APR, at the United States Naval Academy.
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Capabilities
In its simplest implementation, APRS is used to transmit real-time reports of the exact location of a person or object via a data signal sent over amateur radio frequencies. In addition to real-time position reporting capabilities using the Global Positioning System, APRS is also capable of transmitting a wide variety of data, including weather reports, short text messages, radio direction finding bearings, telemetry data, and storm forecasts. Once transmitted, these reports can be combined with a computer and mapping software to show the transmitted data superimposed with great precision upon a map display.
Technical Information
In its most widely used form, APRS is transported over the AX.25 protocol using 1200 baud Bell 202 audio frequency-shift keying on frequencies located within the amateur 2-meter band - usually 144.39 MHz in the United States, 145.175 MHz in Australia and 144.80 MHz throughout Europe. An extensive digital repeater, or "digipeater" network provides transport for APRS packets on these frequencies. Internet gateway stations (i-Gates) connect the on-air APRS network to the APRS Internet System (APRS-IS), which serves as a worldwide, high-bandwidth backbone for APRS data. Stations can tap into this stream directly, and a number of databases connected to the APRS-IS allow web-based access to the data as well as more advanced data mining capabilities. A number of low-earth orbiting satellites are also capable of relaying APRS data.
History
Bob Bruninga implemented the earliest ancestor of APRS on an Apple II computer in 1982. This early version was used to map high frequency Navy position reports. In 1984, Bruninga developed a more advanced version on a Commodore VIC-20 for reporting the position and status of horses in a 100-mile endurance run. During the next two years, Bruninga continued to develop the system, which he now called the Connectionless Emergency Traffic System (CETS). Following a series of FEMA exercises using CETS, the system was ported to the IBM PC. During the early 1990s, CETS, now known as the Automatic Packet Reporting System, continued to evolve into its current form. As GPS technology became more widely available, 'Packet' was replaced with 'Position' to better describe the most common use of the system.
Related systems
The APRS protocol has been adapted and extended to support projects not directly related to its original purpose. The most notable of these are the FireNet and PropNET projects.
APRS FireNet is an Internet-based system using the APRS protocol and much of the same client software to provide fire fighting, earthquake, and weather information in much higher volume and detail than the traditional APRS system is capable of carrying.
PropNET uses the APRS protocol over AX.25 and PSK31 to study radio frequency propagation. PropNET 'probes' transmit position reports, along with information on transmitter power, elevation, and antenna gain, at various frequencies to allow monitoring stations to detect changes in propagation conditions.
External links
- WB4APR web site (http://web.usna.navy.mil/~bruninga/aprs.html)
- www.findu.com Web-based access to worldwide APRS real-time data
- APRS World (http://www.APRSworld.net) Open Source web-based APRS database
- APRS Specification (http://www.tapr.org/tapr/html/Faprswg.html) Official APRS specification document
- KCAPRS Organization (http://www.kcAPRS.org/) Getting started in APRS
- PropNET Homepage (http://www.PropNET.org) If the band is open and no one is active, does anybody hear it?da:APRS