RTK Postcard RTK fix makes no difference in accuracy

GPS/GNSS
1

Hi there,

I have recently purchased an RTK Postcard and have “evaluated“ the LG290P quite a bit, going as far as writing custom software for the esp32 for my use case. The RTK accuracy has previously worked fantastically, giving me DOPs in the mm range, so I believe my unit is working.

Yesterday, I once again tried evaluating the RTK performance when I realized that the unit does indeed receive correction data, the RTK LED does blink and then stay on when a fix solution has been found and the NMEA indicates an RTK Fix, but the accuracy does not change whatsoever.

The NMEA and PQTM DOPs and also real testing show a 0.3m accuracy, which stays the same with or RTK Fix or Float and with “only“ DGNSS, even the “error characteristics“ don’t seem to change when providing corrections.

I have tried reinstalling the latest and even an older LG290P firmware, using a different NTRIP host/provider, switching to an open field with near perfect signal, changing the power source of the postcard from a laptop to a phone to a power bank, using the original RTK Everywhere firmware and changing a few of the “PQTM“ settings over serial.

Is there perhaps a magic ruleset of settings or a specific but not so obvious setting that prevents or allows RTK accuracy similar to what’s currently being shared with the Galileo HAS firmware version or have I overlooked something that would be obvious to the more experienced user?

I am kind of out of ideas what to try and would greatly appreciate your help and ideas.

Greetings and thank you in advance

Geno

2

Hi Gennos and welcome! You are running your own firmware on the ESP32 on the Postcard, correct? That’s very cool! It sounds like you are doing well if you are seeing the RTK LED illuminate.

giving me DOPs in the mm range,

DOPs are unit-less so I think you are confused.

Are you using our LG290P library? See get2Derror(). If not, please see the PQTMEPE command for the estimated error in meters.

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3

Hi Sparky,

Thank you for the clarification, the position error data is exactly what I was looking for, I indeed got the DOPs completely mixed up with errors, the DOPs mostly correlated with what I expected in meters of accuracy, so I didnt challenge that assumption :slight_smile:
As it is already very late, I will have to test the accuracy tomorrow, but I expect it to be as good as when I measured it on an app using the RTK Everywhere firmware, this correctly gave me the errors in mm.

4

No problem! There are many people here who have taught me many things as well. Let us know how your firmware and project go. Perhaps I can learn something from you!