Lost GPS signal scare

Discussion in 'Mavic Pro Help' started by Gumby, Nov 30, 2016.

  1. Gumby

    Gumby Member

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    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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    #1 Gumby, Nov 30, 2016
    Last edited: Nov 30, 2016
  2. msinger

    msinger Well-Known Member
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    Did you try checking out your flight log? You can upload it and view it here.
     
  3. Gumby

    Gumby Member

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  4. msinger

    msinger Well-Known Member
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    Please upload your TXT flight log here and post a link back here.
     
  5. erkme73

    erkme73 Well-Known Member

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    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.
     
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  6. BudWalker

    BudWalker Well-Known Member

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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.
     
  7. Anthony

    Anthony Well-Known Member

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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 ...
     
  8. Gumby

    Gumby Member

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  9. BudWalker

    BudWalker Well-Known Member

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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.
    upload_2016-12-2_7-59-3.png
    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.

    upload_2016-12-2_7-58-42.png

    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.
     
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  10. niclariv

    niclariv Well-Known Member

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    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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  11. BudWalker

    BudWalker Well-Known Member

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    @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.
    upload_2016-12-2_10-48-16.png

    The aileron and throttle inputs at 537 can be seen here
    upload_2016-12-2_10-49-30.png

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

    Gumby Member

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    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.
     
  13. niclariv

    niclariv Well-Known Member

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    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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  14. Kilrah

    Kilrah Well-Known Member

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    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.
     
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  15. Gumby

    Gumby Member

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

    BudWalker Well-Known Member

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    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.
     
  17. BudWalker

    BudWalker Well-Known Member

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    In this incident pushing the throttle forward resulted in an altitude gain.
    upload_2016-12-2_14-42-58.png
     
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  18. niclariv

    niclariv Well-Known Member

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


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  19. Gumby

    Gumby Member

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




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  20. BudWalker

    BudWalker Well-Known Member

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    Maybe the USB cable is defective.
     
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