Aprs.fi Telemetry

This section of the aprs.fi user guide describes telemetry visualization functions of aprs.fi.

Telemetry

APRS stations can transmit measured analogue and digital telemetry such as voltages, temperatures, and switch / alarm statuses. aprs.fi collects the data and presents it on the info and telemetry pages. The telemetry page allows looking up historic data over the past year.

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  • VK3RPG-2, like many other Australian digipeaters, reports temperature, battery voltage and transmitter PTT keydowns using APRS telemetry.
  • OH2RCH, an igate running the aprx software, reports channel busy status and received packets.

Telemetry is currently only collected for stations which have transmitted a position packet. This is a bug and will be fixed in the future.

aprs.fi implementation of telemetry

aprs.fi supports a few extensions to the slightly restricted 8-bit-minded original telemetry format:

  • APRS Base91 comment telemetry allows compressed telemetry values to be embedded in the comment field of a position packet. It allows over 13 bits of resolution, and the sequence number in the telemetry is used by aprs.fi to detect duplicate and out-of-order packets.
  • Normal telemetry may contain up to two decimal digits ("123.45").

Kenneth's summary of telemetry format variations may be useful.

aprs.fi user guide