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GPS bad signal health


I have noticed during two flights yesterday that we received a warning stating GPS bad signal health while in the middle of a flight. This has never happened and am wondering if it is an upgrade to plane 3.9 issue? The person monitoring the GCS did not notice a drop in satellites from 18 or around that number.




Hello Justin!

Which type of GPS do you use? I have exactly the same problem.
But i also get in on the ground, maybe a minute after cold start.
I use the ublox m8n with 3.01 firmware. GPS, GLONASS and GALILEO active.
Hardware: Pixhawk 1 (orignal 3DR)
Same behaviour on 3.9.1 and 3.9.2 beta (3?), even switching back to Nuttx does not help.
26 Sats, HDOP 0,5.
Baudrate 115k, GPS type: ublox
To be able to arm the plane, i disabled GPS check in EKF2 & EKF3.

First observation was, the error appears with “DGPS” status. But i am not absolutely sure.
I am going to upload a log file.

Best regards

The message you are seeing is only seen in newer versions of copter/plane. It’s basically because the GPS must maintain at least a 5 Hz update rate for the EKF to be happy. If the GPS goes below 5 Hz update rate they consider that unhealthy. You can look at the GPS.Delta field to get the time interval from the data flash log.

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Thanks Arjun!

My M8N is set to 10Hz output rate, but i think it doesn’t reach the desired rate.
Do you mean GPA.Delta? I got values between 180 and 340, increasing with higher count of SATs visible.
So the ublox M8N seems to be too slow for GPS+GLONASS+GALILEO…

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Official M8N documented rate for your configuration is 3Hz (not supported by arduxx).


GPS+SBAS is 10Hz


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Alright Marc, thought it is faster… I don’t understand why the M8Q ist faster than the M8N!
Now i have GPS+GALILEO+SBAS and no error message anymore. Going to check the GPA.Delta in the log file but it must be below 200msec now.

Hi Guys,
I have heard from many people that the “Bad GPS Signal Health” indicator only shows up when the GPS message rate drops below 5 Hz. In my case, I see this message when I lose all satellites.

In other words, if I cover the GPS with my hand, the GPS sats drops to zero, and I see “Bad GPS Signal Health” in MP. When I uncover the GPS and allow it to see the sky, the message goes away once the GPS reacquires satellites. Is this the expected behavior?

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