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  1. Cogito

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    I was flying the trusty Typhoon H for a TV show today and set up my waypoints and when I flew the saved CCC the drone was always in perfect position but was lower by maybe 5'. This is not the first time I've seen this behavior, four questions:

    1) Have any of you experienced this same CCC altitude problem?

    2) If so, was it remedied by any of the firmware updates? I'm still using the original firmware from when I bought the drone last May.

    3) Can anyone who has the RealSense version tell me do the added sensors help with altitude position?

    4) Do other drones you've flown have the same issue when playing back a recorded flight path?

    Thanks, as always, for your help.
    -C
     
  2. BillyTexas

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    I had a ccc i flew a couple months ago and when i flew it again about a week ago i believe it flew same altitude but seemed to be off coordinates quite a bit. It was flying the route and 30 ft west of original path.

    Bill W.
     
  3. Cogito

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    Thanks for replying Bill, interesting data point. In my situation this morning I flew the waypoints only 10 mins after I'd recorded them, I thought they'd hold for that long.
     
  4. Steve Carr

    Steve Carr Moderator
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    There are a few things that come into play with CCC. First, the GPS needs to have an exact fix before launching. Depending on how far you traveled since your last flight and how many weeks, an accurate GPS fix may take from 2 minutes to several minutes. Even though the readout may show 15 sats, the accuracy continues to build over several minutes. So it's a good practice to let the H sit for several minutes before starting the motors to build accuracy. The H will use very little battery power until the motors are running.

    Altitude is much less accurate than GPS. The altimeter is a rough instrument and can't be used for reading a few feet of difference. Even 20' of variation is reasonable. This is simply a barometer which is affected by barometric pressure changes and temperature. So a good practice is to allow plenty of altitude when flying a route especially near any trees or buildings.
     
  5. Cogito

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    Thanks for the info Steve, I will try a longer time before launch to gain a more accurate GPS fix. Are you saying the Typhoon H has a separate barometric altimeter and doesn't use GPS altitude? That never occurred to me.
     
  6. Steve Carr

    Steve Carr Moderator
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    I'm speculating about which it uses, but GPS altitude would take more processing power and still may not produce a very accurate reading. The barometer reacts quickly to changes and it gets zeroed out on each boot so it always starts at 0' altitude. The altitude readout on the ST16 is from the barometer and not from GPS.
     
  7. RiverRunner

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    GPS altitude is not very accurate either.
     
  8. Tuna

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    It's true that the Typhoon uses barometric altitude, which will drift.

    In addition, the Typhoon treats your takeoff point as 'zero altitude'. That is, it resets the altitude to zero when you start the motors.

    Therefore, if you take off from a different point, the Typhoon will fly at a different height. This is why UAV Toolbox requires you to specify your takeoff point when editing CCC routes, to remind you that altitudes are relative to where you start.

    The recommendation is to always start from the same location, and fly your route immediately to avoid drift becoming an issue.
     
  9. Cogito

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    Good information, thanks. Anyone fly the other drones and is altitude more reliable?
     
  10. BillyTexas

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    Thats a good question

    Bill W.
     
  11. SoCalDroner

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    I can tell you that the P4 uses a barometer as well and I watched one that was flying a demo indoors and when the air conditioning came on, it went from a 5' hover and slowly descended until the skids were touching the ground, all in about 60 seconds. The operator even commented on why it happened.
     
  12. Tuna

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    Yup, it seems that barometric altitude is the standard for most 'consumer' drones unless you have very specific needs. For many users, absolute accuracy is not as important as simple steady flight - i.e. slow drift.
     
  13. Steve Carr

    Steve Carr Moderator
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    Each of us has to understand the limits of the machines we fly and then fly within those limits. None of these are precision instruments. Neither is any aircraft. Programming autonomous modes requires a lot of extra clearance to avoid a crash. If you need greater precision you have to fly manually.
     
  14. PatR

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    The most accurate altitude I have personally experienced with an affordable multirotor was provided by APM and Pixhawk based flight controllers. They are very accurate, but not perfect. There are extremely accurate systems out there but they have not migrated down to the consumer level yet, if they ever do.

    If DJI did their latest multi GPS unit flight controller right they have the ability to generate extremely accurate position and altitude references but they will need to have linked the flight system GPS to another GPS unit at the ground station. All of the GPS units would need to communicate with each other and reference data through some specialized software.
     
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  15. Cogito

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    Another data point. I recorded and flew a CCC shot on the show today but waited 10 mins or so with both ST-16 and TH on and 17 satellites acquired before taking off. Flew path multiple times with repeatable altitude levels within a foot or two. May have been lucky, barometric pressure levels may have been more stable, or some other variable but got the shot today.
     
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  16. Steve Carr

    Steve Carr Moderator
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    Great to hear it went well. I'm impressed the altitude held that good. All the planets must have been aligned.:):):)
     
  17. Cogito

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    The planets weren't aligned today, the wind was 15G20kts so didn't fly, had to get show open shots with jib. Next week should be better. Thanks everyone for the help.
     
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