A common SNIP message decoder question is…

I see a message type appearing in the RTCM3 decoder with ADVNULLANTENNA – what is this for?


This indicates a “null antenna” antenna type used (often by Trimble GNSS devices) to denote that the end user (the rover device) does do not have to deal with additional antenna offset corrections.

More precisely, it means all such calibration offsets have already been incorporated into the measurements which that data stream is providing.

This is used in a two places in the RTCM 3 messages as follows.  The type 1007 message  and the type 1033 message.  If it is not present, but a 1006 message is present, then each NTRIP Client Rover device knows to seek there for suitable offsets.

If another value is found here, it indicates the official name of an antenna which can then be used to lookup calibration factors for that model.    <add link>

Hint:  You can also quickly see the antenna type and any offsets that are present by hovering the mouse over the mountPt label for each stream.  The resulting tool tips summarizes key information about the Base Station from the RTCM3 messages. [This feature is present in Release 1.20 and on wards]

FYI, Rover device setups should also use the ADVNULLANTENNA setting in sending these message, if desired.

Do I have to send this message?

No it is not required, but it helps others to understand the Base Station setup.

If you determined your Base Station location by taking a long time average position of your antenna and submitting that to OPUS or some other service (as described here), then you have already incorporated these offsets into the measurements which that data stream is providing.

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