Servers by jDrones

Loss of all GPS Satellites on HERE 2 GNSS and almost fly-away

Hello @Andrew_Tridgell @rmackay9
We had a issue with HERE2 GNSS today. According to the log, there was complete loss of satellites for very short period and we almost had a fly-away. Log also says Ublox detected at baud 115200 just after the loss of satellites including EKF error due to loss of satellites. Has the GPS rebooted? I’ll attach the log below. Please have a look. Board voltage seems to be alright, there was no short or anything. We flew the aircraft before an hour with stable satellite count. We have been flying this aircraft from a long time and never had a issue.
Thanks in advance!


The only thing I can tell from the log is that the flight controller completely lost communication with the GPS for a bit. This is evidenced by the sudden stop of GPS data and the GPS 1: detected as uBlox at 115200 baud event message that appears once the GPS data returns. This means that GPS device was completely lost, then detected again.

Hard to know what could have caused this. The GPS receiver rebooting for some reason could be possible; a hot-start could probably recover all 21 satellites within the ~15 second blackout we see here. A bad cable or connector interrupting the power or serial communication could definitely cause this.

1 Like


z vibe/ alt increase is about the same and spike just before the GPS goes out.
This looks a bit high to me.


The copter was pitched -20 deg too. This could cause a GPS glitch.

A GPS glitch is recorded as one. I’ve had a setup that was glitching alot. NSats dropped, vertical estimates went crazy - coupled with Z-axis vibes going up.
But I never, ever, encountered a re-detection of the GPS in the logs.
This looks like either serial comms drop or GPS hot-restart.

The vibration part was just after loss of GPS where there was sudden change in position when it regained the sats. Copter moved last location to latest location at very high speed and recovered. This can be seen in GPS log.

GPS Glitch never causes complete loss of satellites. I’ll check my cables first.

By saying glitch I think a power loss too. Your voltage looks great so the cable/connectors vibrating seems probable. It looks to me like your copter was vibrating and pitched hard just before the drop in sv’s. It’s also doing a yaw rotation.
These things happened just before the GPS reset.
position loss @4:49.22. When did you notice the fly away?
A glitch and the position recovery that fast should not cause a fly away to last more than a few seconds. Am I thinking wrong?
I have had a detailed review of your log and compared to my flyaway a few months ago.
The events are similar in hardware, a GPS glitch, EFK errors, flyaway & clipping.
I am sorry I don’t have great answers but I want to know why these fly away situations happen. I have had to ground the FC until It’s figured out. Below is a link to my flyaway for comparison.

Hey! My vibrations were just under first bar. There was no clipping at all. I completely lost GPS after reaching way point one. It moved to next GPS location which it received after reboot at around 80+kmph. Till it reached that point, say 3 to 4secs, it was on flyaway condition. It regained the sats after that and started hovering. I took it to manual and bought it back. I noticed there was no error after that and here2 was blinking green and was able to switch to loiter too. You can notice loss of GPS in GPS log and in map if you click “show map” option. I’m actually running some tests by putting new cable and plugging GPS to one more cube.

Hi @Mallikarjun_SE,
Were you able to know the reasons for the sudden loss of GPS?
In my case too, similar incident happened and even after changing the GPS, it again happened.
https://drive.google.com/file/d/1A96bNNLvo5B6Qx7fT3pvnODYLdjrolO9/view?usp=sharing

Servers by jDrones