What is APRS?

In the words of its creator:

"APRS is not a vehicle tracking system. It is a two-way tactical real-time digital communications system between all assets in a network sharing information about everything going on in the local area. On ham radio, this means if something is happening now, or there is information that could be valuable to you, then it should show up on your APRS radio in your mobile. APRS also supports global callsign-to-callsign messaging, bulletins, objects email and Voice because every local area is seen by the Internet System (APRS-IS)! APRS should enable local and global amateur radio operator contact at anytime-anywhere and using any device."

-          Bob Bruninga, WB4APR (SK)

 

APRS can send many types of data, including, but not limited to:

 1.      Positions with speed, heading, altitude.

2.      Station capabilities.

3.      Voice frequency.

4.      Objects (usually on behalf of other entity).

5.      Weather Reports from individual stations.

6.      Weather Alerts forwarded from the National Weather Service.

7.      Telemetry.

8.      “Messages” addressed to specific stations, with automatic retries and acknowledgment.

9.      Bulletins sent to wider groups.

10.   Queries and Responses.

11.   Ham Radio of Things.   (like Internet of Things but with Ham Radio)

12.   User Defined data types.

 A more concise description could be, “APRS is an ecosystem for doing cool stuff.”

 It can be used directly between users with no infrastructure.

Digital Repeaters (“digipeaters”) retransmit packets to extend range.  The sending station specifies the desired number retransmissions, often called hops.

The International Space Station (ISS) and some amateur radio satellites carry APRS digipeaters.

Internet Gateway (“IGate”) stations forward radio communications to a global network of computers, called the APRS Internet Service (APRS-IS).  Messages, and other configured data, are forwarded to local radio networks.  You can send a message to someone on the other side of the earth and receive a delivery confirmation or failure alert.  

Some websites, such as aprs.fi and aprs.to , extract information from the APRS-IS servers and provide a map view, and other analysis, of APRS activity without the need for a radio.   Sample aprs.fi screenshot:

Besides communicating with other people, there are many automated systems which will provide a response to your message.  One popular service, called WHO-IS, performs a callsign lookup and responds with the result.  In this case, I sent a message with the callsign W1AW.

 

Kenwood, Yaesu, and a growing number of other manufacturers, recognize the importance of this mode, and build the capability into many of their radios.

  

You don’t need to buy expensive specialized equipment.  You can also participate with an ordinary transceiver and free software applications which often provide a map view and messaging capability.

 

Sample application screenshot, showing stations received over the air:

The key takeaway is that APRS is designed for local, radio-based communication, with the Internet playing a secondary role in long range messaging and data visualization tools like aprs.fi or aprs.to.

For more information, see https://how.aprs.works/00-aprs-resources/