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Speed discrepancy - DJI Go v. Healthy Drones

Discussion in 'Pro/Adv Discussion' started by jonebk12, May 7, 2016.

  1. jonebk12

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    So I went out and flew my P3 over a nearby lake today. It may have been a little windy, but nothing crazy. P mode the entire flight. When I checked out my Healthy Drones log after, it said my max speed was 40mph which I figured could be normal if I had a bit of a tailwind even in P mode. Out of curiosity, I also watched the flight log play out in the DJI Go app, where it shows the bird flying around on the map and displays all the telemetry data. What surprised me was that at various points in the flight, the log showed the quad sustaining speeds of around 50mph, and occasionally exceeding 50mph. Again, I was in P mode the entire flight. What's going on with this discrepancy? Doesn't Healthy Drones and the DJI app draw from the exact same data? I'm curious if I was actually hitting 50mph+ on a relatively calm day, wind-wise (at least on the ground, I understand conditions can be quite different 400 feet up). During the actual live flight, I didn't pay much attention to the telemetry data, but I definitely will from now on.

    Edit: I just watched parts of the flight again in DJI Go, and I was sustaining 50mph going in exact opposite directions at various times in the flight, which I feel somewhat rules out a tailwind.

    Also, I thought I was posting this in the P3 advanced/professional section. Mods, feel free to move it.
     
    #1 jonebk12, May 7, 2016
    Last edited: May 7, 2016
  2. ianwood

    ianwood Taco Wrangler
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    Healthy drones calculations are flawed.
     
  3. alokbhargava

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    I also feels so.
     
  4. jonebk12

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    15mph is a huge discrepancy, I'm surprised Healthy Drones has it so off. Not saying I don't believe you, I'm just surprised. And if DJI Go is accurate, that means I was sustaining speeds of 50 mph, in P-mode, flying both North and South. Anyone have an explanation or thoughts on that?
     
  5. ferraript

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    if you can, share with us your DJI GO flight log
     
  6. jonebk12

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    Here's the text file. I ran it through your converter, ferraript, and it indeed shows a max speed of about 40mph (like Healthy Drones). But here's also a screenshot from the DJI Go app, same flight, clocking me at 50+mph.
     

    Attached Files:

  7. flyNfrank

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    It's been that away for some time. The developer must either not be familiar with the issues, or he just doesn't care. I've seen other developers admit there was currently some sort of issue in their system, but also they were working to find a fix.

     
  8. flyNfrank

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    Max Speed 40.24mph
     
  9. jonebk12

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    Which is exactly what Healthy Drones is telling me...

    DJI Go, on the other hand, has me exceeding 50 mph.

    Could the flaw not be with DJI? Both HD and the text file ran through the converter say 40.24.
     
  10. flyNfrank

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    Maybe one was displaying in Fps(Feet per second)?
     
  11. ferraript

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    yes, you got it :)
    according to my converter, at that moment (flightTime 5:32, travelled 10517 ft), speed was 35.05 mph and that's exactly 51.4 ft/s