core-motion

I need to calculate iphone velocity in space, punch speed for example. My first question is: Are the acceleration values accelerometer:didAccelerate with this filtering actions: gravity_x = acceleration.x * kFilteringFactor + gravity_x * (1.0 - kFilteringFactor); gravity_y = acceleration.y * kFilteringFactor + gravity_y * (1.0 - kFilteringFactor); gravity_z = acceleration.z * kFilteringFactor + gravity_z * (1.0 - kFilteringFactor); float gravityNorm = sqrt(gravity_x * gravity_x + gravity_y * gravity_y + gravity_z * gravity_z); accelX = acceleration.x - gravity_x / gravityNorm; accelY =

I have a CMRotationMatrix *rot and i would like to get the pitch, yaw, roll from the matrix. Any ideas how i could do that? Thanks iSeeker Its better to use the Quaternion than Euler angles.... The roll, pitch and yaw values can be derived from quaternion using these formulae: roll = atan2(2*y*w - 2*x*z, 1 - 2*y*y - 2*z*z) pitch = atan2(2*x*w - 2*y*z, 1 - 2*x*x - 2*z*z) yaw = asin(2*x*y + 2*z*w) It can be implemented as: CMQuaternion quat = self.motionManager.deviceMotion.attitude.quaternion; myRoll = radiansToDegrees(atan2(2*(quat.y*quat.w - quat.x*quat.z), 1 - 2*quat.y*quat.y - 2*quat.z*quat

I can use this method of the Core Motion framework: - (void)startAccelerometerUpdatesToQueue:(NSOperationQueue *)queue withHandler:(CMAccelerometerHandler)handler as an alternative to the - (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration UIAccelerationDelegate method of UIKit. There, I have to specify the frequency of updates. I want to get acceleration data as fast and accurate as possible. Is Core Motion my friend here? What's the frequency of readings I can expect from that method of Core Motion? The documentation doesn't talk about it. Edit

I see that I can retrieve CMAttitude from a device and from it I can read 3 values which I need (pitch, roll and yaw). As I understand, this CMAttitude object is managed by CoreMotion which is a Sensor Fusion manager for calculating correct results from compass, gyro and accelerometer together (on Android it is SensorManager Class). So my questions are: Are those values (pitch, roll and yaw) relative to the magnetic north and gravity? If above is correct, how can I modify it to give me results relative to the geographic north? If a device (such as iPhone 3GS) doesn't have an gyroscope, do I

In my root controller I have a property with the CMMotionManager @property (strong, nonatomic) CMMotionManager *MManager; In its getter I do lazy instantiation. When the controller's view loads, I call this method - (void)reloadAccelerometer { NSLog(@"Away we go"); self.MManager.deviceMotionUpdateInterval = 10.0/60.0; [self.MManager startDeviceMotionUpdatesToQueue:self.queue withHandler:^(CMDeviceMotion *motion, NSError *error) { NSLog(@"Y values is: %f", motion.userAcceleration.y); }]; } I see "Away we go" in the NSLog and then immediately the app crashes and I get this thread log libsystem

I'm getting CMDeviceMotion objects from CMMotionManager . One of the properties of the CMDeviceMotion is timestamp, which is expressed as a NSTimeInterval (double). This allows for "sub millisecond" timestamp precision, according to documentation. [motionManager startDeviceMotionUpdatesToQueue:motionQueue withHandler:^(CMDeviceMotion *motion, NSError *error) { NSLog(@"Sample: %d Timestamp: %f ",counter, motion.timestamp); } Unfortunately, NSTimeInterval is calculated since last device boot, posing significant challenges to using it in its raw form. Does anyone have a working code to convert