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actual altitude?

Discussion in 'Pro/Adv Discussion' started by gringorio, Feb 2, 2016.

  1. gringorio

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    Yesterday I flew over a local landmark. I was more or less 170' agl over the location from my launch point according to the GO app. I did a few circuits over the area to make sure I captured useable video then headed back home.

    At one point on the way back to my home point I lost sight on the craft, but could still hear it. The DJI Go app said I was at +-170 feet and descending (as per my control) so I kept looking at that approximate area to relocate the Phantom as I descended toward my launch location. As the Phantom closed to within a couple hundred feet I could still not locate it, but I could hear it just fine. Then I realized it was actually closer to about 75' agl and I was looking to high. Any lower and it would have likely hit the local phone lines that must have been at about 40' agl.

    My visual of the Phantom's height (As compared to the telephone poles it was near) did not correspond with the DJI Go app's reported AGL which was much higher.

    Flying LOS is great until light conditions make it difficult and one has to depend on the Go App for heading, speed and altitude.

    I don't want to repeat this experience...

    Has anyone else experienced this apparently incorrect AGL info on the DJI Go App?
     
    Reed L likes this.
  2. Meta4

    Meta4 Moderator
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    I've not heard of it.
    Easy enough to check next time you take off. Does 10 feet look like 10 feet etc etc.
     
  3. Phill2

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    Mine says 3 metres when hovering about 1 metre
     
  4. alokbhargava

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    I know home point is at always at zero level even if you are standing at an altitude of 100'. All other locations are referenced to this home point. Its so difficult to judge the real altitude, we just need to believe the values shown on the Go App.

    I fly in open areas and always above the nearby trees or obstructions. Far you fly, lower it appears.
     
  5. gringorio

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    Thanks... That's my observation in general terms: At take off 10' AGL looks like 10' AGL but after flying a bit the Go app may say you're at 75' when you're actually at 40'.

    I'll try and capture this on video....
     
  6. gringorio

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    That's my point., it is an open area with no obstructions... If I trusted the values in the Go app I may have flown through the telephone wires... Or have hit them. After I lost visual I was looking way to high based on the Go apps estimation of AGL.

    I had that "oh ****" moment when I saw the quad approaching well below the AGL indicated by the Go app;.
     
  7. With The Birds

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    Very common for the phantom to be well below dji reported altitude when returning from a reasonable flight (in my case). I allow 10m+ error margin to be comfortable.
     
  8. Reed L

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    I've had a severe altitude drop over a canyon. I went out at 140' and when I came back it was maybe 40' tops but I was thinking that it must have been operator error until reading this because it was almost a horizontal los... I was looking up for it for maybe 5 minutes and couldn't find it and did the same thing. Listened, watched, figured that I had messed up...
     
  9. CactusJackSlade

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    When you say AGL... do you mean above your take off point?... or just above ground level where the copter was?

    FYI, I have noticed at least a 10-20 foot disparity on any typical occasion...
     
  10. Meta4

    Meta4 Moderator
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    If you are having problems with the altitude sensor, the first thing to do is calibrate your IMU inside on a perfectly level surface.