u-blox GPS satellite count capped at 12

Fumiya

Hi,

I'm using RaceChrono with a custom M5Stack Wi-Fi GPS logger and a u-blox NEO-M9N receiver.

The logger streams NMEA over TCP. I currently send GGA/RMC at the navigation rate and GSV at about 1 Hz. With GSV enabled, RaceChrono shows the satellite sky view correctly.

The satellite count display, however, stays capped at 12. This seems to come from u-blox GGA behavior: the GGA satellite count field appears to be limited to 0-12. On the same receiver I can see UBX-NAV-PVT numSV showing 15 satellites, while GGA still reports 12.

I also tried sending GNS at 1 Hz, but the displayed satellite count did not change. As a test, I modified only the live GGA sentence by replacing the satellite count field with the GNS/UBX-derived value and recalculating the checksum. Then RaceChrono showed 14 satellites.

So I would like to confirm:

Is the RaceChrono satellite count display based only on GGA numSV?
Does RaceChrono use GNS numSV?
Does the satellite sky view use only GSV, or also GSA?
What is the recommended NMEA setup for u-blox receivers where GGA is limited to 12?

Thanks!

aol

Yes, this is a known issue, but it is cosmetic only, the accuracy is not affected. Not many receivers use NMEA anymore, so this remains unfixed.

RMC+GGA+GSV+GSA & GGA+ZDA+VTG+GSV+GSA are the supported combinations at the moment.

Fumiya

aol

Thank you for the clarification!

That makes sense. I understand that the satellite count issue is cosmetic only and does not affect the recorded accuracy.

I'll use the supported NMEA combination, RMC + GGA + GSV + GSA. In my tests, adding GSV already restored the satellite sky view. I had also tested modifying the live GGA satellite count as an experiment, but based on your answer I will keep the GGA sentence unmodified and treat the 12-satellite count as a cosmetic limitation.

Thanks again for the quick answer!