APRS.TXT AUTOMATIC PACKET/POSITION REPORTING SYSTEM (APRS)
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Document version: 8.5.3 (10 year anniversary update)
Document dated: 18 Sept 2002 (Previous version was 1 Mar 2000)
Author(s): Bob Bruninga, WB4APR@amsat.org
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Home page: www.aprs.org or www.ew.usna.edu/~bruninga/aprs.html
APRS is a real-time tactical digital communicatons 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.
APRS is different from regular packet in four ways. First by the
integration of maps and other data displays to organize and display
data, second, by using a one-to-many protocol to update everyone in real
time, third, by using generic digipeating so that prior knowledge of the
network is not required, AND FORTH, since 1997, a worldwide transparent
internet backbone, linking everyone worldwide. APRS turns packet radio
into a real-time tactical communications and display system for emergencies
and public service applications (and global communications). Normal
packet radio is useful in passing bulk message traffic (Email) from point-
to-point, but it does not do well at real time events where information
has a very short life time and needs to get to everyone quickly.
APRS is a LOCAL RF network. Although the Internet monitors APRS worldwide,
this is not the primary objective. But like all of our other radios, how
we use APRS in an emergency of special event is what drives the design of
the APRS protocol. Although APRS is used 99% of the time over great
distances, and benign conditions, the protocol is designed to be optimized
for short distance real-time crisis operations on RF.
APRS provides universal connectivity to all stations in the net by avoiding
the complexity and limitations of a connected network. It permits
any number of stations to exchange data just like voice users would on a
voice net. Any station that has information to contribute simply sends
it, and all stations receive it and log it. Secondly, APRS recognizes
that one of the greatest real-time needs at any special event or emergency
is the tracking of key assets. Where is the Event Leader? Where are the
emergency vehicles? Whats the Weather at various points in the County?
To answer these questions, APRS transmits and captures the location and
status of all stations. It can be used over any 2-way radio system
including HAM, CB, Marine Band, etc. See CB.txt, Boats.txt, Aircraft.txt.
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