3D fix but bad gps health

I had 14 to 15 Sats and HDOP 0.71 to 0.75.
The message “bad gps health” appeared periodically.
What’s wrong and how can I fix it ?

ArduCopter 4.0.3
Matek F405 CTR
GPS BN-180

dataflash log

Good day l, just keep the module far from power sources… receivers and antennas.
You can also shield the module… its like create a Faraday cage

yes, sure.
But 15 sats and hdop 0.71: what can “bad gps health” be ?

might be your GPS temporarily dropping below 5 Hz update rate. check your log‘s GPA.delta message for intervals above 200ms. did you maybe set any non-default config in GPS_GNSS_MODE?
btw it might help to set your log‘s donwload link public.

Yes, that seems to be the problem.
Every 20 s the update rate drops from 200 to 300 ms.


Sorry, the dataflash log link is public now.

now that the problem is figured out how can I fix it ?

That GPS is not good. Seeing a lot of posts lately of people using that and similar GPS’s (different brands, but pretty sure they’re all the same GPS) and having trouble. I never had success w/ them in the past.

But… Something you could try…
Disable Glonass… Try just GPS/SBAS. More constellations can slow it down.

a navigation rate drop below the required 5 Hz in non-default multi-GNSS-modes, especially with galileo enabled, afaik is an inherent limitation of the ublox M8N chipset. iirc it does 10 Hz on single, 5 Hz on double and 3 Hz on multi-GNSS-modes / galileo.
i personally am running my M8Ns (including a couple of BN-180s) on defaults with good results though and don’t see any functional limitations with that default setting. this depends on individual use case obviously.

I have changed GPS_RATE_MS from 200 to 140.
Error message is gone.
100 to 140 works, anything above 150 does not work.

Regarding the BN-180 update rate:
The manual says:
Single GNSS: 1Hz-18Hz
Multiple GNSS: 1Hz-10Hz, Standard 1Hz

i can’t really wrap my head around how setting a higher rate in ap would fix this, doesn’t really matter as long as it works though!

this is the delta i get from my BN180 on defaults:

i wonder if there’s that much benefit in the multi setting?

cheers from hamburg!

In my understanding AP wants gps messages at least every 200ms.
To my surprise the peaks in delta (200 to 300) disappeared with the higher rate.
With GLONASS enabled I usually get 50% more sats.

Are you in Hamburg/Germany ? Me too.

that spot in your log is just half a liion discharge away from where i work :wink:
used to shop RC parts at staufenbiel barsbüttel quite frequently, seems they didn‘t survive cov19 lockdown though…

cheers, basti.