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  1. Pete w

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    I was flying a previously flown litchi waypoint mission and for some reason my p4 flew into a tree that it had previously flown over. My altitude was set to 30m and the trees i guess are around 25m. So i am wondering what went wrong, and how do i get my p4 back, given that i cant see it up in the tree tops from the ground.
    A review of my dji go app after the crash revealed that the imu needed recallibration ( litchi didnt mention anything). I didnt use dji go before the mission, and it wasnt running at the time of the crash, but for some reason, after the crash, i was still able to access the cached video feed showing some recognisable trees that it was focusing on at the time, giving me some sort of rough confirmation as to where it had flown.

    So i was able to get a live feed from the camera before the battery went dead, which identified the leaf of its resting place as an ash tree, this eliminates about 75 % of the trees as its resting place. The gps shows a large ash tree on the waypoint route that the p4 should have flown, so i am assuming that it did indeed fly its programmed mission. But there is still an element of doubt in my mind, for 2 reasons.
    1 i cant see the darn thing
    2 this "imu needing recalibration " according to the dji go ,issue.

    So my question is, given the imu needed recallibrating, how accurate is its last known location from the gps feed of the drone likely to be? What does the imu control? Altitude? Gps accuracy? Anything else?

    I wanted to get some feedback before i take the next step which will probably be to get a proffessional tree guy in to try to retrieve the p4.

    Thanks in advance for any thoughts and advice
     
  2. Meta4

    Meta4 Moderator
    Staff Member

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    The IMU is a collection of motion sensors, level sensors and the barometer.
    It's quite separate from the GPS so your GPS position should not be affected.
     
  3. RoyVa

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    Even thought you have flown the same way point before. He flight path can be off by a few feet on the 2nd or even third flight. I have noticed on flying repeat missions that I can be off a few feet or meters one direction or another. I also saw on film flying the same mission where I cleared a tree and on another mission of the same flight path I clipped a tall branch on the same tree. I had to adjust my altitude up a few more feet even though I had flow the same mission before. Don't know if it was due to wind drift, GPS satellite differences or what but the identical mission is not trulely identical. Just keep that in mind. I went up and checked all the trees in my area and found the height to say above 135 ft. But low and behold during flight I did find one lone tree at 150 ft and that was my altitude. When I review the video and checked my Phanton I had to remove some leaves/small branches from the landing gear. Boy was that close. Moral of the story ... Add a few feet to your altitude to be safe.
     
  4. Pete w

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    Thanks for both those replies. So I can be pretty sure then that the last indicated gps position is where the P4 is (given that i was able to reconnect and update location after the crash ie it wasnt a flyaway- is this even possible with litchi waypoint?) however altitude could be affected could it not?
    I suspected but didnt know for sure about the slight variations in flightpath with repeat missions. I suspect in this case- based on footage from previous missions where the P4 appears to clear comfortably the trees, that this might be related to the IMU.
     
  5. jstjohnz

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    Also keep in mind that if your takeoff point is at a slightly different elevation that will affect altitudes.
     
  6. Pete w

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    good point, and it was slightly lower so maybe that could have been a factor.
     
  7. Pete w

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    Finding the P4 is proving much harder than i anticipated. All things a pointing to a particular tree (very large) yet despite many hours with binoculars and other peoples eyes helping, the P4 cannot be seen. I am now starting to consider other methods such as using a thermal camera to find the P4 amongst all the leaves! Any other suggestions?
     
  8. normr

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    Do you know anyone who has a drone so you can try spotting it from the air?


    Sent from my iPad using PhantomPilots mobile app
     
  9. Pete w

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    Not really as I am visiting a foreign country (france)
     
  10. neven

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    Also it is a known issue that barometar for measuring altitude on Phantoms is not super accurate.
     
  11. Rlisch

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    Hasn't lit ho
     
  12. Rlisch

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    Use for all my P4 flying the FPV Camara App which includes "Flight Logs"
    Doesn't Litchi provide this module aswell?
    This would pin point your P4's location
     
  13. Pete w

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    i was using litchi Waypoint not FPV