Lost GPS signal scare

[Gumby]

On a flight yesterday tracking with 17 satellites maximum signal.. 8 minutes into the flight get a "weak GPS" message on the controller and attempt to head back. Controller still shows 17 says but weak red GPS signal. I could not control the aircraft... drifted for over 2 minutes and ended up about 1,000 feet down wind.. I was able to see and rotate the camera and gimbal the whole time - but could not control the aircraft. RTH did not work. I could only watch as it drifted downwind.

Finally (after 2 or 3 long minutes) the GPS signal returned and RTH worked perfectly.

Now I'm a little gun shy to fly very far. Any idea what could have caused this? I was flying over my neighborhood at 375 feet and was about 2,200 away
When this happened. Signal was a solid 3 bars

Thoughts?





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[msinger]

Did you try checking out your flight log? You can upload it and view it here.

 

[Gumby]

Here is the link...

HealthyDrones.com - Innovative flight data analysis that matters

Any idea why it suddenly lost GPS??

Thanks for the help

Bill



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[msinger]

Please upload your TXT flight log here and post a link back here.

 

[erkme73]

Just a shot in the dark, but I'm guessing you have the same issue being discussed here. At a minimum, please watch that thread - and ideally, post your experience there so that DJI sees this is not just an isolated few people.

 

[BudWalker]

Here is the link...

HealthyDrones.com - Innovative flight data analysis that matters

Any idea why it suddenly lost GPS??

Thanks for the help

Bill



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The information that HealthyDrones provides won't help much when trying to determine what happened in your flight. To learn a lot more about your incident take the .txt file you submitted to HealthyDrones and upload it here. After that site analyzes the flight post the link that it produces here so that others can take a look. Alternatively, you could attach the .txt to your next post here.

 

[Anthony]

On a flight yesterday tracking with 17 satellites maximum signal.. 8 minutes into the flight get a "weak GPS" message on the controller and attempt to head back. Controller still shows 17 says but weak red GPS signal. I could not control the aircraft... drifted for over 2 minutes and ended up about 1,000 feet down wind.. I was able to see and rotate the camera and gimbal the whole time - but could not control the aircraft. RTH did not work. I could only watch as it drifted downwind.

Finally (after 2 or 3 long minutes) the GPS signal returned and RTH worked perfectly.

Now I'm a little gun shy to fly very far. Any idea what could have caused this? I was flying over my neighborhood at 375 feet and was about 2,200 away
When this happened. Signal was a solid 3 bars

Thoughts?





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You are not the first person to report this .... i would open a support ticket once you have all the flight data as dji need to be made aware of this issue and it may need to be returned....

If this happens again and it turns into a flyaway dji may not help at that point ...

 

[Gumby]

see the flight log in the link below. I have no idea why it changed to atti mode when it had 15 plus sats at the 6 minute mark

Phantom Log Viewer - PhantomHelp.com

 

[BudWalker]

On a flight yesterday tracking with 17 satellites maximum signal.. 8 minutes into the flight get a "weak GPS" message on the controller and attempt to head back. Controller still shows 17 says but weak red GPS signal. I could not control the aircraft... drifted for over 2 minutes and ended up about 1,000 feet down wind.. I was able to see and rotate the camera and gimbal the whole time - but could not control the aircraft. RTH did not work. I could only watch as it drifted downwind.

Finally (after 2 or 3 long minutes) the GPS signal returned and RTH worked perfectly.

Now I'm a little gun shy to fly very far. Any idea what could have caused this? I was flying over my neighborhood at 375 feet and was about 2,200 away
When this happened. Signal was a solid 3 bars

Thoughts?





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Although the number of satellites was adequate the gpsHealth dropped from 5 (the max) to 1 which is the reason for the weak GPS message and switch to ATTI. This occurred at time 366 and lasted until time 626 where a switch GPS_ATTI was made.

gpsHealth probably includes both vertical and horizontal dilution of precision values. I don't know why this happened in your flight. It is extremely rare in the case of the P3.



The question remains as to why gpsHealth dropped in this interval. Could you please provide us with the .DAT for this flight. It will contain more information than the .txt file you submitted.

To retrieve a Mavic .DAT file use DJI Assistant 2 and go to the Flight Record tab. After confirming that it's OK to put the Mavic in Flight Data mode a list containing the recent flights will appear. Select just the Flight Control File of the incident flight and then press Save To Local. Ultimately a file with a name something like DJI_ASSISTANT_EXPORT_FILE[2016-10-27 22-40-28].DAT will be created.

The .DAT will be large add can't be directly attached here. You'll need to Dropbox it and provide the link.

 

[niclariv]

Beyond the lack of GPS, note that he says he had no control of it. I think this issue is worrisome because not only is it happening to people unexpectedly, but they also often have no control of the Mavic when it does. I'm surprised there hasn't been a post yet of someone's Mavic crashing when this happened. Mine is still on the way, but I'm watching these posts intently hoping that DJI is made aware of all these incidents and fixes the Mavic quickly. If it's unreliable to use that really limits the flying spaces to big open fields where it's ok for it to drift, not exactly what I, and everyone else who payed all that money, signed up for.


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[BudWalker]

@niclariv It seems that loss of control didn't happen in this incident.

@Gumby I know you stated that you didn't have control of the Mavic during the weak GPS interval. But, it looks like there was a minimum of control inputs.


The aileron and throttle inputs at 537 can be seen here


Maybe it felt like there was no control because the Mavic was moving (i.e. drifting with the wind) without stick input.

 

[Gumby]

It could be that I had control but could not tell as the camera did not appear to show any movement of the craft as I tried to manually fly it and the gps location screen was useless at that stage.

 

[niclariv]

If it happens again could you try raising the altitude? While DJI is sorting this out, it would be good to know if you are still able to make it fly higher, potentially avoiding collisions while drifting. As an actual fix I think some other people with the same issue have had some success with an imu calibration + compass calibration (don't only do imu)


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[Kilrah]

It could be that I had control but could not tell as the camera did not appear to show any movement of the craft as I tried to manually fly it and the gps location screen was useless at that stage.

The gimbal being stabilized hides any "quickly visible" effect your actions have on the aircraft. You have to work out the correct orders to give and assume they're working and not just give up, it will take significant time (seconds) of input and good concentration on the image to actually see the effect, which will never show as tilting or such of the image, but in change of speed/direction with regard to ground.

 

[Gumby]

I did both an IMU and compass re-calibration and will try a flight in the morning. Fingers crossed it doesn't happen again.

 

[BudWalker]

I did both an IMU and compass re-calibration and will try a flight in the morning. Fingers crossed it doesn't happen again.

An IMU and/or a compass calibration won't help with a gpsHealth issue such as the one in this flight.

Will you be able to retrieve the .DAT for this flight. There is a good chance more could be learned about the cause of the gpsHealth issue. And, how to prevent it on future flights.

 

[BudWalker]

If it happens again could you try raising the altitude? While DJI is sorting this out, it would be good to know if you are still able to make it fly higher, potentially avoiding collisions while drifting. As an actual fix I think some other people with the same issue have had some success with an imu calibration + compass calibration (don't only do imu)


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In this incident pushing the throttle forward resulted in an altitude gain.

 

[niclariv]

Thanks, good to know.. hopefully that's the same in the other similar incidents


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[Gumby]

I have not been successful retrieving the .dat file... DJI Assistant won't recognize the craft




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[BudWalker]

I have not been successful retrieving the .dat file... DJI Assistant won't recognize the craft




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Maybe the USB cable is defective.