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Height from where?

Discussion in 'Pro/Adv Discussion' started by Itay, Sep 2, 2015.

  1. Itay

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    Look at my beautiful drawing.
    The pilot is standing 50 meters above sea level at the bottom of a mountain that's 500 meters height.
    The phantom is 50 meters above the mountain.
    What is the real height? is it sea level to drone = 50 + 500 + 50? or is it mountain top to drone = 50? or it's pilot to drone= 500 + 50?

    Another interesting question is, will phantom 2 shown in the drawing be able to get good reception or it's impossible to fly behind the mountain and the pilot should always keep it higher?

    phantomheight.jpg
     
  2. Mal_PV2_Ireland

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    500m from take off point
     
  3. bbfpv

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    500m from take off point.
     
  4. MarkEngland

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    500m from take off point.
     
  5. rockydog

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    Height is always shown as above take-off point, and no, you won't be able to get reception behind the mountain.
     
  6. 43k

    43k

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    I think it is 500m from take off point.
     
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  7. Itay

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    If it's 500m from takeoff point, then I have no way of knowing how far am I from the ground currently below me (the top of the mountain).
    We need to ask DJI to add this parameter; Distance from current ground.
     
  8. N017RW

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    Everybody here is wrong!!!

    If you're 50 meters above a 500 meter tall mountain and you took off from the base of the mountain... the correct answer is 550 meters.

    HOWEVER, the on-board baro. altimeter is subject to error and drift so don't expect accurate repeatable results.
     
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  9. 43k

    43k

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    How would you do that? Radar? Laser?
    The phantom actually CAN detect ground using "sound-radar" (ultrasonic), but it need to be pretty close to the ground, like a couple of meters, to be able to do that.
     
  10. 43k

    43k

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    Yes, i.e. 500m from take off point.
     
  11. D4T_PoM

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    +1 to 500m from take off point
     
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  12. Itay

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    No need for a laser. I have gps, and I need a simple map that shows the surface level above sea level. Simple. No?
     
  13. N017RW

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    Please explain...

    50 meters above a 500 meter high mountain???
     
    #13 N017RW, Sep 2, 2015
    Last edited: Sep 2, 2015
  14. rockydog

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    I don't know where the 500 brigade are coming from......the drone is 550m above take off point.
    The 500 figure only relates to the top of the mountain.
     
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  15. N017RW

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    Roger that!

    That's why I added the qualifier regarding the take-off point... the OP was unclear IMO.
     
  16. Meta4

    Meta4 Moderator
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    Forget your ideas about sea level.
    The Phantom manages perfectly well without knowing what sea level is.
    Every other Phantom owner manages too.
    GPS is very inaccurate for altitude so it won't be much use anyway.
    Because GPS is so bad for altitude, DJI don't even get altitude data from the GPS.
     
  17. Itay

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    Where Dji gets the altitude from?
     
  18. Meta4

    Meta4 Moderator
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    Your Phantom gets its altitude from its take off spot.
    Home = zero
    It uses a barometer to tell how high it is above or below the home point.
     
  19. D4T_PoM

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    I believe its by calculating air pressure, I may be wrong but I think I read it somewhere.

    Someone correct me.

    META4 Thank you for correction :D
     
  20. N017RW

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    A barometer in side the MC measures air pressure. At take-off it equates the current pressure to ZERO feet/meters altitude.

    Any changes in pressure up or down are displayed as altitude... so yes it is possible to read negative altitude if you fly below your take-off point.