Automatic Packet Reporting System (APRS) is an amateur radio based system for digital communications, most commonly used to automatically report the position (GPS coordinates) of a person or object, or weather data at a remote location. It was developed by Bob Bruninga, callsign WB4APR, at the United States Naval Academy. The acronym "APRS" was originally derived from his callsign, and subsequently expanded to "Automatic Position Reporting System". As the system was modified and expanded to handle non-position packet data, the meaning of the "P" in the acronym was again changed to "Packet" rather than "Position". Today, it is common for hams to use either expansion of the acronym. Amateur radio station with modern solid-state transceiver featuring LCD display and DSP capabilities Amateur radio, often called ham radio, is a hobby that uses various types of radio broadcasting equipment to communicate with other radio amateurs for public service, recreation and self-training. ... In broadcasting and radio communication, a callsign or call sign (also call letters) is a unique designation for a transmitting station. ... The United States Naval Academy (USNA) is an institution for the undergraduate education of officers of the United States Navy and Marine Corps and is in Annapolis, Maryland . ...

Purpose

APRS is a real-time tactical digital communications protocol for exchanging information between a large number of stations covering a large (local) area. As a multi-user data network, it is quite different from conventional packet radio. Packet radio is a form of digital data transmission used in amateur radio to construct wireless computer networks. ...

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 attached Global Positioning System receivers, APRS is also capable of transmitting a wide variety of data, including weather reports, short text messages, radio direction finding bearings, telemetry data, short e-mail messages (send only) 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. Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... For the geological process, see Weathering or Erosion. ... Radio Direction Finding, or RDF, is the technique of locating the direction to a radio transmission. ... Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... This article is about the machine. ...

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(AFSK) on frequencies located within the amateur 2-meter band: AX.25 is a data link layer protocol derived from the X.25 protocol suite and designed for use by amateur radio operators. ... The Bell 202 modem was an early modem developed by AT&T. It used audio frequency-shift keying to encode and transfer data at a rate of 1,200 bits per second, half-duplex (one-way). ... Audio frequency-shift keying (AFSK) is a modulation technique by which digital data is represented as changes in the frequency (pitch) of an audio tone, yielding an encoded signal suitable for transmission via radio or telephone. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ...

• North America: 144.390 MHz with 144.990 occasionally used as an alternate input frequency for local low power stations
• Australia: 145.175 MHz with 144.390 MHz available for as a secondary frequency, primarily for satellite and DX work.
• New Zealand: 144.575 MHz (National APRS) and 144.650 (digipeaters) -- check with locals for details
• Argentina: 144.930 MHz
• Brazil: 145.570 MHz
• Europe: 144.80 MHz

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 and the International Space Station are capable of relaying APRS data. North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... For other uses, see Europe (disambiguation). ... A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ... An Earth observation satellite, ERS 2 In the context of spaceflight, satellites are objects which have been placed into orbit by human endeavor. ... “ISS” redirects here. ...

Equipment Settings

An APRS infrastructure comprises a variety of Terminal Node Controller (TNC) equipment put in place by individual Amateur Radio operators. This includes soundcards interfacing a radio to a computer, simple TNC's, and "smart" TNC's. The "smart" TNC's are capable of determining what has already happened with the packet (unit of information) and can prevent redundant packet repeating within the network.

There are a few radios on the market which include a built-in AX.25 Terminal Node Controller and APRS software, and are capable of working with or without the need for an external GPS device. Two common models are the mobile Kenwood TM-D700A, and the handheld Kenwood TH-D7AG.

Reporting stations use a method of routing called a "path" to broadcast the information through a network. In a typical packet network, a station would use a path of known stations such as "via n8xxx,n8yyy." This causes the packet to be repeated through the two stations before it stops. In APRS, generic callsigns are assigned to repeater stations to allow a more automatic operation.

RECOMMENDED PATH: Throughout North America (and in many other regions) the recommended path for Mobiles or portable stations is now WIDE1-1,WIDE2-1. Fixed Stations (Homes, etc.) should normally use plain WIDE2-2 or less.

OLD PATH: Early on, the widely accepted method of configuring stations was to enable the short-range stations to repeat packets requesting a path of "RELAY" and long-range stations were configured to repeat both "RELAY" and "WIDE" packets. This was accomplished by setting the station's MYALIAS setting to RELAY or WIDE as needed. This resulted in a path of RELAY,WIDE for reporting stations. However, there was no duplicate packet checking or alias substitution. This sometimes caused beacons to "ping pong" back and forth instead of propagating outwards from the source. This caused lots of interference. With no alias substitution, you couldn't tell which digipeaters a beacon had used.

NEW PATH: With the advent of the new "smart" TNC's, the stations that used to be "WIDE" are now "WIDEn-N." This means a packet with a path of WIDE2-2 would be repeated through the first station as WIDE2-2, but the path will be modified (decremented) to WIDE2-1 for the next station to repeat. The packet stops being repeated when the "-N" portion of the path reaches "-0." This new protocol has caused the RELAY, WIDE path to become obsolete. Users are being asked to configure "RELAY" stations as WIDE1-1. This results in a new, more efficient path of WIDE1-1,WIDE2-1.

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 Position Reporting System, continued to evolve into its current form. As GPS technology became more widely available, 'Position' was replaced with 'Packet' to better describe the most common use of the system. The Apple II was one of the most popular personal computers of the 1980s. ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ... The VIC-20 (Germany: VC-20; Japan: VIC-1001) is an 8-bit home computer. ... New FEMA seal The Federal Emergency Management Agency or FEMA is an agency of the United States government dedicated to swift response in the event of disasters, both natural and man-made. ... IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...

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. PSK31 or Phase Shift Keying, 31 Baud is a digital radio modulation mode, used primarily in the amateur radio field. ...

Open Trac was created to provide an alternative to APRS that was cleaner and more functional than APRS.

See also

• Packet radio
• Automatic Identification System - Position reporting system used for marine traffic

Packet radio is a form of digital data transmission used in amateur radio to construct wireless computer networks. ... A United States Coast Guard Operations Specialist using AIS and RADAR to manage vessel traffic. ...

External links

• Queensland APRS Information
• WB4APR web site
• APRS Depot Build custom KML files of APRS Data. Home of the APRS Auto Response System
• APRS Wiki Site More specific APRS setup information
• APRS on PocketPC PDA options Using APRS with PocketPC PDAs
• www.findu.com Web-based access to worldwide APRS real-time data
• aprs.he.fi Automatically updating real-time APRS view using Google Earth and Google Maps
• OpenAPRS Web-based APRS real-time data using Google Earth Maps
• DB0ANF Web-based Access to APRS Station and Network Data
• HamHUD A message capable APRS "heads up display" with LCD. SmartBeaconing was first developed for the HamHUD.
• APRS Server List Publicly available servers hosting the APRS-IS
• APRS World Open Source web-based APRS database
• APRS Specification Official APRS specification document
• KCAPRS Organization Getting started in APRS
• PropNET Homepage If the band is open and no one is active, does anybody hear it?
• Northwest APRS Homepage Pacific Northwest APRS alternate Wiki
• APRS in Australia Australian (VK) APRS National Information Site
• APRS Argentina Group Argentinian APRS Group (Spanish)
• APRS in Brazil Brazilian APRS Network since 1998 (Portuguese)
• Peet Bros. Company, Inc. Homepage Weather Station Hardware with direct support for APRS / TNC Interface
• Official UI-View Site Roger Barker G4IDE SK was the author of UI-View
• UI-View M0CYP UI-View Web Resource, including registration
• Radioactive Networks GPS projects
• XastirA popular Open Source APRS client for Linux, Windows, Mac OS-X and more.
• APRS ON4SAXA free online visual tracker for APRS