Model Specific Notes

Intermet iMet-1 / iMet-4

iMet sondes do not transmit their serial number within their telemetry packets. This makes life somewhat difficult, as we need a unique identifier for the various mapping systems (sondehub.org / APRS / Chasemapper) to be able to distinguish between different radiosondes.

As a way around this issue, auto_rx generates a unique ID for each received iMet sonde by using:

• The reported time and telemetry sequence number to calculate the power-on time of the sonde;
• the transmit frequency of the sonde, and
• a user-defined 'station code'.

These three bits of information are concatenated, and a SHA256 hash is calculated. The last 8 characters of the hash are used for the Sondehub ID, and the last 5 for the APRS callsign. The code that calculates the ID is available here.

It is recommended that users who observe iMet sondes and have a good idea of their launch location to edit the [location] -> station_code field in their station.cfg file to match either the World Meteorological Organisation station code, or the ICAO code of the (probably) nearby airport. This code will appear in the sonde comment field on sondehub.org, so multiple users within range of a launch site can coordinate appropriately.