Which RTCM V3 messages are mandatory to get C94-M8P Development Board into RTK Fix Mode?

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I am feeding my C94-M8P Development Board with RTCM V3 Messages from an Online Ntrip Caster. This caster sends RTCM V3 messages 1004,1005,1008,1012,1029,1030,1031,1032,1033. Unfortunately, the C94-M8P supports 1005, 1007,1007,1009,1010,1011,1012,1074,1075,1084,1085,1087,1124,1125,1127 and 1230.

1. With this Setup, I get the rover into RTX Float Mode with only message type 1005. Do you know which messages are mandatory to reach RTK Fix Mode? Is there any possibility to extend the supported message types on the Ublox module?

Furthermore, with another test setup, I am feeding RTCM V3 messages from an external base station (Novatel O638) into the C94-M8P Rover. Unfortunately, the Novatel O638 Base Station doesn't support message type 1230, which prevents to Rover to go into RTK Fix Mode although we're sending messages 1004,1077 and 1087.

2.Is message 1230 mandatory for RTK Fix Mode?

3. Would it be a better test setup to feed an Ublox Base Station with RTCM V3 data and send the correction data to the Rovers from the Ublox Base station or is this not a better option than feeding the RTCM V3 data straight to the Rovers from the Caster or Novatel Base Station.


Thank you very much for your help!

by chrisyd asked Nov 8, 2018
0 votes
These types of experiments are hard and time consuming to set up


Sending 1005 + 1074 or 1077 is sufficient to get into RTK Fixed Mode. I can get ZEP-F9P devices into RTK Fixed with just L1 observations from a NEO-M8P.

I suspect the receiver is going to be a bit ambivalent about GLONASS data without the 1230, so I'd half expect it to stay in RTK Float as a "not sure" kind of situation, while having a CEP of a few cm that's still quite serviceable. I might experiment with this, as turning the message off is easy.

The MSM messages are arguably "observations" from the Base and not "corrections" in the true sense. The Rover is solving for both. The rover is supposed to accept the older and corrective variants of the RTCM3 messages

For best outcomes, and support, I'd probably use the ubox-to-ublox approach,. Third party equipment and infrastructure, with assorted firmwares, is a difficult to debug without dumping tools and real-time analysis of the data streams. Feeding data to a Base should allow you to survey its location more quickly and accurately.
by clive1 answered Nov 8, 2018
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