iPhone leaning angle - use Gyroscope?

Question

I would like to know how many degrees is the iPhone leaning when being held upright - that is, if I point the iPhone up, I would like to know how many degrees it is looking up at? I think that I can use the gyroscope and core motion for this, and I think that it is pitch that I want, however, the pitch is a "rate of speed" in radians per second. I am not really interested in how quickly a user moved the iPhone, I am just interested in the leaning angle. So if I am pointing a phone up to take a picture, I would like to know the angle of pointing up - any ideas??

Thank you.

Answer 1

Gyro data is in radians per second, but what you are looking for is CMMotionManager.attitude property. It shows the attitude of the object in radians relative to a some frame of reference.

create class variable motionManager and init:

 motionManager = [[CMMotionManager alloc] init];
    motionManager.deviceMotionUpdateInterval = 0.1f;
    [motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *motion, NSError *error) {
        [self processMotion:motion];
    }];

process the updates, you are looking for pitch, but in this sample it will show you all three values so you can play around and decide what you need:

    -(void)processMotion:(CMDeviceMotion*)motion {
        NSLog(@"Roll: %.2f Pitch: %.2f Yaw: %.2f", motion.attitude.roll, motion.attitude.pitch, motion.attitude.yaw);
}

these are Euler Angles, you also have an option to get rotationMatrix, or quaternion format. Each with their own advantages and disadvantages.