This section of the aprs.fi user guide describes telemetry visualization functions of aprs.fi.
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.
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 supports a few extensions to the slightly restricted 8-bit-minded original telemetry format:
Kenneth's summary of telemetry format variations may be useful.
aprs.fi user guide