CMAttitudeReferenceFrame

Enum constants for indicating the reference frames from which all attitude samples are referenced.


typedef enum {
     CMAttitudeReferenceFrameXArbitraryZVertical = 1 << 0,
     CMAttitudeReferenceFrameXArbitraryCorrectedZVertical = 1 << 1,
     CMAttitudeReferenceFrameXMagneticNorthZVertical = 1 << 2,
     CMAttitudeReferenceFrameXTrueNorthZVertical = 1 << 3
} CMAttitudeReferenceFrame


CMAttitudeReferenceFrameXArbitraryZVertical
: Describes a reference frame in which the Z axis is vertical and the X axis points in an arbitrary direction in the horizontal plane.

CMAttitudeReferenceFrameXArbitraryCorrectedZVertica
: Describes the same reference frame as CMAttitudeReferenceFrameXArbitraryZVertical except that the magnetometer, when available and calibrated, is used to improve long-term yaw accuracy. Using this constant instead of CMAttitudeReferenceFrameXArbitraryZVertical results in increased CPU usage.

CMAttitudeReferenceFrameXMagneticNorthZVertical
: Describes a reference frame in which the Z axis is vertical and the X axis points toward magnetic north. Note that using this reference frame may require device movement to calibrate the magnetometer.

CMAttitudeReferenceFrameXTrueNorthZVertical
: Describes a reference frame in which the Z axis is vertical and the X axis points toward true north. Note that using this reference frame may require device movement to calibrate the magnetometer. It also requires the location to be available in order to calculate the difference between magnetic and true north.

all available in iOS 5.0 and later.


source : Apple dev page.