Distance moved by Accelerometer

Question

I want to move objects on iPhone screen (rectangle, circle and so on) by moving iPhone. For example, I move iPhone along X-axis and the object moves along X-axis. The same for Y,Z-axis.

How can I do this? Can I get algorithm for it?

Thank you.

P.S: I looked for a while and seems like it is possible using accelerometer.

score 15 · Accepted Answer · edited May 23 '17 at 12:00

You get position by integrating the linear acceleration twice but the error is horrible. It is useless in practice.

Here is an explanation why (Google Tech Talk) at 23:20. I highly recommend this video.

However the gyro mouse might work for your application, see between 37:00-38:25 in the video.

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score 3 · Answer 2 · answered Jul 11 '11 at 03:46

Not easy to do accurately. An accelerometer only reports acceleration, not movement. You can try (numerically) integrating the acceleration over time, but you're likely to end up with cumulative errors adding up and leading to unintended motion.

Pseudocode, obviously untested:

init:
    loc = {0, 0, 0}    ; location of object on screen
    vel = {0, 0, 0}    ; velocity of object on screen
    t = 0              ; last time measured

step:
    t0 = time          ; get amount of time since last measurement
    dt = t0 - t
    accel = readAccelerometer()
    vel += accel * dt  ; update velocity
    loc += vel * dt    ; update position
    displayObjectAt(loc)

So you are saying it is not practical thing to do on iphone? — MeIr, Jul 11 '11 at 14:18
Correct. The links in Ali's response show that this will probably not work usefully. — , Jul 11 '11 at 14:59

score 2 · Answer 3 · edited May 23 '17 at 12:02

2

Why don't you use the acceleration itself instead distance moved? For example; If your acceleration is 1.4G east, your object should move to east 14pixels per second until your acceleration changes.

So that object's movement is will be like it is under a relative force and I think it's more realistic. Faster moving device, bigger force to effect object.

Also look:

http://www.freescale.com/files/sensors/doc/app_note/AN3397.pdf

and

Using accelerometer, gyroscope and compass to calculate device's movement in 3D world

edited May 23 '17 at 12:02

Community

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answered Nov 27 '11 at 23:42

kubudi

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When you will make a movement, for example to the left, you will get output like this: -1g 0g 0g 0g 1g because when you will stop movement you will get force which will be negative to initial force which created movement. you need to somehow filter it and it isnt easy. – Kamil Orzechowski Apr 14 '17 at 21:26

Distance moved by Accelerometer

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