How to use deviceMotion attitude values (roll,pitch and yaw) to detect a motion

Question

I'm using coreMotion in my app to detect a motion of iOS device. I know how to get the different sensor's data from coreMotion. I am getting roll, pitch, and yaw data as follows from the deviceMotion:

 float pitch =  (180/M_PI)*self.manager.deviceMotion.attitude.pitch];
 float roll = (180/M_PI)*self.manager.deviceMotion.attitude.roll];
 float yaw = (180/M_PI)*self.manager.deviceMotion.attitude.yaw];

How can I use these data to detect a motion? What are the calculations that I need to do for this?

Sir, What are you trying to do with these values? If you are trying to monitor these values when the device moves then, you could display these as labels. — iSeeker, Sep 30 '13 at 08:55

score 10 · Answer 1 · edited May 23 '17 at 12:16

The attitude values need the device motion updates to be started as:

startDevicemotionUpdates

To monitor attitude values when device moves, use the attitude values to be displayed in labels:

[self.cmMotionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue mainQueue] withHandler:^(CMDeviceMotion *devMotion, NSError *error) {

float pitch =  (180/M_PI)*self.manager.devMotion.attitude.pitch];
float roll = (180/M_PI)*self.manager.devMotion.attitude.roll];
float yaw = (180/M_PI)*self.manager.devMotion.attitude.yaw];

self.rollLabel.text = [NSString stringWithFormat:@"%f", roll];
self.pitchLabel.text = [NSString stringWithFormat:@"%f",pitch];
self.yawLabel.text = [NSString stringWithFormat:@"%f",yaw];
}

Also it is better not to use roll, pitch and yaw(aka Euler Angles). Use Quaternion or Rotation matrices for better accuracy. Euler angles have the tendency to be in a situation called gimbal lock which results in unreliable data.

Please check this link for how to use quaternion, and convert that value to the roll, pitch and yaw values: SO link

How to use deviceMotion attitude values (roll,pitch and yaw) to detect a motion

1 Answers1