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Is the 500m overall height limit enforced by the app or by the firmware?

Discussion in 'Pro/Adv Discussion' started by Trumple, Aug 19, 2015.

  1. Trumple

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    Hi all,

    First off, I don't condone flying more than 120m (400ft) AGL and breaking the law. However, there are situations where you could be >500m from your take off point yet still less than 120m off the ground, e.g. flying up the side of a mountain. In some countries, this would be legal (it would be illegal in the UK because you need to maintain VLOS).

    So, my question is: is the 500m max height limit enforced by the DJI Pilot/GO app or by the firmware? If it is enforced by the app, then 3rd party apps might make it possible again.

    I also did a quick calculation of the kind of height you can comfortably climb to if you're scaling the side of a mountain.

    (flight time) = (max height)/(ascent speed) + (max height)/(descent speed) + (translation distance)/(ground speed)
    F = H/A + H/D + T/G
    (to take into account ascending and descending at different speeds, and also some ground movement if you're flying to a point)

    We have a battery life of 20 minutes, lets call it 15 minutes for a bit of safety, or 10 considering we'd be maxing out the motors and we'd like some time to take footage.
    Let's also say we need to travel 1km along the ground as we're scaling this mountain.
    Ascent speed = 5m/s
    Descent speed = 3m/s
    Ground speed = 16m/s (assuming no net headwind)

    Going back to the original equation:
    10*60 = H/5 + H/3 + 1000/16

    Rearranging:
    H = 1008m

    So if my maths is correct, we could comfortably fly up a ~1km high mountain with these batteries.

    I understand why DJI set the limit, but it'd be really nice if it was possible, even if just on principle :)
     
  2. msinger

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    It's controlled by the Phantom firmware -- since the DJI GO app is not needed in order to fly.
     
  3. Trumple

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    That might be true but I have a number of reasons why that might not be sufficient evidence:
    1) I don't know of anyone who has flown to 500m high without the app connected and then been able to ascertain if the aircraft kept on climbing
    2) Certain values are set by the app then stored in the aircraft. This would prevent #1

    Given that the only app available is the DJI GO app, how do we know it's not that the app simply refuses to tell the aircraft any higher limit? The way I imagine it is a "jump - how high?" situation where the aircraft limits and settings will be controlled by the app. It's possible that the aircraft has no built-in limitation.
     
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  4. msinger

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    Easy enough. Fly to 500m, shut down the DJI GO app, and try to fly higher.
     
  5. Trumple

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    Again, #2 - it's my understanding that the aircraft would store the last value the app told it as a limit (500m). Perhaps if a 3rd party app told it something else, it would go higher
     
  6. msinger

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    Perhaps. And, if that turned out to be true, that "bug" would no doubt be patched in the next firmware release.
     
  7. Dronebow

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    It's a good question. Maybe there is a hack like the channels config file...
     
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  8. BenDronePilot

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    First, you're not "breaking the law" going over 400 feet above your take off point (depending on where you live, this includes the USA which there are no Laws governing this only recommendations).

    And the 500m limit is absolutely a function that's in the firmware, but the million dollar question is can it be over written within an app programmed to allow an input of a number greater than 500m. That's the million dollar question. I suspect the option in the firmware is defaulted to 500m as a max as welll but likely can be changed if a program is made to do so.
     
  9. rrmccabe

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    The fact 3rd party apps using the DJI SDK have higher than 500m limits tells me its not just the firmware. I think when you make the change it writes it to the bird in the same manner as switching to 4k video.

    My bet is it's software defined.
     
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  10. bbfpv

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    How would you know whether you were able to climb higher w/o the telemetry telling you the altitude?
     
  11. Trumple

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    Ohh, that sounds interesting, what's that about then?
     
  12. Trumple

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    How do you know for certain it's in the firmware?
    And yes you're right - it's possible that the app could force it to exceed 500m!
     
  13. Dronebow

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    The app reduces the 1 - 32 channels to only 8 available channels. 13 to 20. The hack reverses that limit so you have channels 1 to 32 available again. It will only Auto select 13 to 20 but if you have congestion on those channels you can manually set to some other channel with less congestion to get better video range. Works good.. ;-)
     
  14. Trumple

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    Interesting! How does one go about doing this "hack" then? :)
     
  15. Dronebow

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    There is a whole thread discussing it. Or just PM me and I'll help.
     
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  16. tcope

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    You can only change the number via app and the app contains a range of numbers (0-500). You can't input a number outside of that range. In this way, it's the app. But the number you choose is certainly stored on the Phantom as it can't be changed without being connected. However, it's not firmware as you don't modify the actual firmware... the data is stored on the Phantom and accessed when flying.

    Third party apps might be able to get around this limit, it just depends on how DJI sets up the SDK. I doubt they would allow a work around in the SDK though.
     
  17. Trumple

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    This was my thinking too. Shouldn't be impossible to fiddle with the SDK though ;)
     
  18. N017RW

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    Anybody have access to a vacuum chamber or some other make-shift type container?... which you could lower the pressure, read telemetry to determine [pressure] altitude, then do all the app. testing combos you can think of.
     
  19. Joao Carlos

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    I bet NASA has one. Or someone could take a Phantom for a ride (without props please) on an unpressurized piston aircraft and see what happens. You could set the record for altitude in the process!
     
  20. Chris Vedeler

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    I'm right there with you regarding the 500m limit. For those of us around mountains it sucks.

    The Litchi app does not have this limit. While I have yet to try it myself in the real world, the software allow limits well beyond 500m. If this is true, the 500m limit can not be in firmware.
     
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