External Rtcm correction server, exactly wich message is sent?

Q&A forumExternal Rtcm correction server, exactly wich message is sent?
amorosik asked 3 months ago

As source rtcm corrections I am using an external server, rtk.cisas.unipd.it and I am enabled to use the mountpoints max3, imax3, nrt3
The question is: how to understand exactly which messages are received using max3 or imax3 or nrt3?
The second is, how to understand if the messages received from the corrections server are useful or irrelevant in order to improve GPS receiver precision?

2 Answers
clive1 answered 3 months ago

Some NTRIP clients will show you what’s received.
You can review messages delivered to the ZED via UBX-RXM-RTCM, I think uCenter flags those of use or not.
The ZED’s Interface Specification lists those it will recognize.
Mostly observations, not corrections per se, uBlox generally wants to see antenna position 1005/1006 type messages, and MSM messages
https://www.use-snip.com/kb/knowledge-base/rtcm-3-message-list/

amorosik answered 3 months ago

The indicated link contains very interesting information, many thanks
At this address

https://www.use-snip.com/kb/knowledge-base/an-rtcm-message-cheat-sheet/
I read that MSM7 looks like a superset of the MSM4 and therefore the next question is: if I send the message 1077 also includes the information contained in 1074 and therefore can I send ONLY 1077?
Or is it necessary both 1074 and also 1077?
Same thing for 1084/1087 and 1094/1097

clive1 replied 3 months ago

MSM7 just has higher precision than MSM4, same basic observations, you use MSM4 when you want the most compact message, for lower bandwidth transmission, or where the link has a smaller packet size limit.

For higher bandwidth networks use MSM7 variants.

Pick one