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Inspire 1 Altitude variance from take off to landing at same location

Discussion in 'Inspire 1 Discussion' started by Cheeky Monkey, May 16, 2015.

  1. Cheeky Monkey

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    Hi Fellow pilots, have any of you encountered issues with your altitude readings from the time you take off to the time you land? I recently flew along Chesil Beach on Dorset Jurassic Coastline, at my take of point I'm approx 10m above sea level and the DJI Pilot app states I take off from zero meters, I fly out to a distance of approx 2200m and return home with plenty of battery life, on my return home I notice whilst flying that the drone appears to be getting lower and lower, almost to the point it drops into the sea, after I manage to fly the Inspire without it sinking into the drink I notice on the App screen that I'm now flying at zero meters even though the Inspire is about 10 meters below its take-off point. At the point of landing at exactly the same height as take-off my height readings are 12.1m. My Inspire has essentially changed its take off altitude by 12m during this flight.

    This really concerns me. Any ideas
    Inspire 0m.jpg Inspire 12.1m.jpg

    Take off Inspire 0m.jpg
    Landing
    Inspire 12.1m.jpg
    Link to Youtube video showing evidence of flight/issue:



    Happy and safe flying peoples
     
  2. insectorchird3

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    i have never trusted the altitude on the app but you my want to contact dji
     
  3. kenny kustom

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    My alt has read -64 feet when flying before.


    Sent from my iPhone using Tapatalk
     
  4. Kirk Pleasant

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    I lose about 1 meter per minute of indicated altitude.
     
  5. Kilrah

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    Absolute altitude is very hard to measure precisely with many factors like atmospheric conditions playing a role, such variations are to be expected.
     
  6. damoncooper

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    Be careful at very low altitude over water for sure. That variance can be a killer, especially prior to the last few FW updates where we would bleed 2-3m altitude on a hard stop from a full speed run. Had some heart stopping moments. Sure glad they fixed that, but I'm still scared of it happening. I'm in recovery though :)
     
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  7. Cheeky Monkey

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    Hi guys, thanks for your messages, this is really concerning especially if you set you return to home height and don't leave any space for error. 12m could be the difference between hitting a tree, house or other object, I guess this is just another case of 'Buyer Beware'

    Damoncooper, you say they fixed the altitude bleed, i'm running the latest FW and still got the altitude variance.
     
  8. damoncooper

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    The issue I'm referring to is very specific: go full throttle straight line across in front of you then let go of the sticks when the bird is directly in front of you. The symptoms were that on braking, it would immediately and suddenly drop 2-3m. I tested this at some length recently and it was solid for me.

    The issue you are referring to I believe is a similar but separate issue.
     
  9. BroxAg

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    Hi cheeky monkey.
    I am also having problems with altitude being inaccurate. Ive sort of come to the conclusion that it is worse in windy conditions, I'm not sure if this concurs with other people's finding or not? The only reasoning that I can come up at this stage is that the barometric sensor is registering pressure changes during gusts of wind and this is affecting altitude readings.
    Your right though, kinda scary if you are relying on altitude for RTH.
    Would be interested to know others experiances also.
     
  10. InspiredOne

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    Reading on the forum elsewhere, I read that this measures "height" not true "altitude" as in a full size aircraft. Altitude is a measurement above sea level. What we're seeing is a measurement above the point of take off.

    I learned this first hand taking off from the top of a 10-story building (100 feet above the ground) to clear a dense grove of trees. The "altitude" reading prior to take off was 0 feet.
     
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  11. Mopar Bob

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    When I first got my Phantom, many months ago, I had this altitude issue. It was discussed in great length on that forum to no avail. DJI had no response that made any sense so I learned to accept it as part of the business of flying a DJI product. Now that I have the Inspire, I too found similar altitude issues but just learned to accept the error right off the bat. My recommendation is to recognize the altitude reading as just an approximation and give yourself plenty of extra height to avoid any collisions. If you think the reading is off by 10 feet, give yourself 30 feet to play with.
     
  12. sirnikolas

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    I've got my RTH set to 40 meters. The higher the better I say.
     
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  13. BroxAg

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    This was the conclusion I had come to also Mopar Bob.
     
  14. Cheeky Monkey

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    Thanks guys for all your comments, glad to hear its not just me, also taking it on the chin, I guess its like anything, you have to take every flight with good planning, care and cover yourself for every possible failsafe moment.
     
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  15. dogear

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    I have 3 Inspire 1 Pro's and all of them are at least 20ft off at the end of a flight. Shutting down and starting back up zero's the altitude but as the flight progresses the altitude error gets worse, usually showing that the aircraft is higher than it actually is. Misery loves company?
     
  16. Richard-Inspire

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    dogear, does your inspire pro hold a solid altitude? i watched mine just dip 2-3 metres of its own accord whilst attempting a hover test in the garden. Pretty sure my last one (x3) didn't do that, and nor does my P3P. Am wondering if I've got a duff model and should send back. Midway through that flight I watched the app show a steady altitude of 7m even though I was descending to, and then did, land. After landing I disengaged and the altitude jumped back to 0m again.
     
  17. dogear

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    It kinda depends how windy it is. I have 3 Inspire 1 Pro's and they all do it somewhat but one is a little worse than the others. I have seen the 2-3 meter altitude loss. From what I can glean on these forums thats kinda normal, especially is you are flying in some pretty good wind or horsing the machine around. I am also flying at 6100ft MSL and I think the thinner air may have something to do with performance. Cant advise you on sending your drone back but any way I can avoid DJI customer service I will take. If it were me I'd just live with it. I've seen it explained elsewhere in these forums, with regards to real helicopters, that whenever the pilot does a pedal turn or in some way change the attitude of the machine it's necessary to pull a little pitch to compensate for the loss of lift in that vector. Thats because the lift vector is being split between two axises and to make up for that it's necessary to add pitch to the rotor system. With these machine you add a little power to counteract the loss of thrust as its being used to turn the machine. Not very well explained but suffice it to say loss of altitude whilst changing attitude is expected. Hope that helps.

     
  18. Richard-Inspire

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    yeah I've done an IMU calibration and it seemed a little better just now. I will test some more. Just alarming that it jostles around in the way it does. I guess i'm noticing it for a number of reasons:
    1. the FOV of the camera is narrower and so it shows a lot more on the screen that it is not stationary - also i'm in a garden near my house so everything is close
    2. i've been using the P3P a lot and that has better hover accuracy, according to the DJI specs.
    3. The X5 camera makes it worse, as really the Inspire was probably designed for the X3 and the X5 is quite a bit of extra weight.
    I was planning on doing some flying low over water, and really the last thing you want is the bird dropping a metre or two of its own accord. Now clearly I won't be flying 1m over water, but I was thinking maybe 2-3m, so i'm not keen for it to lose that altitude on its own. The phantom is so accurate, that perhaps I've become a bit spoiled.

    I will test some more and make a decision in a day or two.

    Generally speaking, though, do you feel confident in the craft? Your pro that has the bigger problem - do you find that you still trust it with whatever you might throw at it?

    cheers,

    Richard
     
  19. dogear

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    I feel pretty confident with it, I don't usually fly it below 3 meters, haven't had the need. Glad you saw some improvement after calibrating the IMU. Cheers