Tuning Movi for acceleration...

Discussion in 'Movi Technical' started by Christian Robinson, Oct 3, 2018.

  1. Christian Robinson

    Christian Robinson New Member

    Oct 2, 2018
    Likes Received:
    Hey Movi Forum,

    General tuning of the Movi has been covered, but I have not been able to determine if it's possible to tune the Movi to maintain a level horizon while experiencing strong acceleration.

    Closest scenario would probably be akin to a chase car situation.

    I know Movi Pro, Carbon, and XL overcome this challenge, but I'm not sure if it is solved with tuning or by using tools like the Fowcine Blackarm.
  2. Rorick Edge

    Rorick Edge Active Member

    May 11, 2018
    Likes Received:
    Hi Christian,

    Andy may weigh in on this, but here's what I know...

    Two people have posted that the Movi will not remain level under acceleration and deceleration. The first case involved a New York City subway train braking before a station and accelerating when leaving a station. The second case involved acceleration and deceleration in a truck. I have myself run into this problem on the NY subway.

    You may find it useful to read the thread in which the subway and truck problems were discussed: https://forum.freeflysystems.com/in...ing-from-a-train-iphone-starts-to-roll.12409/ That thread also contains discussion of workarounds. The workarounds are low-tech and in some cases just might work for you.

    I think that this is distinct from another issue, which is that some people found that their Movi was not level on setup. As I understand it, Freefly has addressed this issue in the latest beta by making it possible to adjust the Movi's horizon. I mention this because there are several threads on this issue that will come up if you do a search for "horizon", and you probably won't find it helpful to read them. I stand to be corrected, but I doubt that this horizon adjustment will do anything to solve the problem that you are talking about.

    The way I see it, acceleration/gravity is a powerful force and the Movi is David before Goliath, except that Goliath is going to win.
    #2 Rorick Edge, Oct 3, 2018
    Last edited: Oct 4, 2018
    Edrolfo Leones likes this.
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Jul 31, 2012
    Likes Received:
    Christian: The problem is this: Acceleration and Gravity are indistinguishable. The Movi has accelerometers that figure out which was is up -- well, more correctly which way is down (gravity exerts an acceleration of 9.8 meters per second per second towards the center of the Earth).

    When you accelerate/decelerate the Movi, that generates a confusing second force that looks like a variation in gravity and the Movi's sensors now detect a different value for gravity in a slightly modified direction (but not straight down towards the center of the earth) -- but the Movi does its best to keep the phone "level" such that "gravity" (well, actually it's now "gravity + acceleration or deceleration") still points down. But that actually results in the Movi tilting the phone over slightly because the detected "down" is not really straight down.

    It was Einstein who first pointed this out and it's really hard to solve the problem without a very sensitive GPS receiver that can detect (by successive readings) that the Movi is in motion (and thus can computer what the accelerating/decelerating is doing to mess up the "gravity vector"). Even then, it's really hard to null out the effects of acceleration/deceleration.

    If you can think of a solution, I'll call the Nobel Prize Committee for you! <evil grin>


    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limitâ„¢
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
    Rorick Edge likes this.

Share This Page