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# CMAttitudeReferenceFrame

Constants that indicate the frame of reference for attitude-related motion data.

```
struct CMAttitudeReferenceFrame
```

## Overview

When you start a service that reports the device’s attitude in three-dimensional space, Core Motion establishes a frame of reference for reporting pitch, roll, and yaw values. All subsequent data values specify the device attitude relative to this frame of reference. To get a list of the currently available reference frames for the current device, call the [`availableAttitudeReferenceFrames()`](/documentation/CoreMotion/CMMotionManager/availableAttitudeReferenceFrames()) class method.

When starting services, it’s your responsibility to specify a reference frame that’s available on the current device. Services that don’t let you specify a reference frame explicitly rely on the value in the [`attitudeReferenceFrame`](/documentation/CoreMotion/CMMotionManager/attitudeReferenceFrame) property of [`CMMotionManager`](/documentation/CoreMotion/CMMotionManager).

## Topics

### Getting the reference frames

[`xArbitraryZVertical`](/documentation/CoreMotion/CMAttitudeReferenceFrame/xArbitraryZVertical)

A reference frame where the Z axis is vertical and the X axis points in an arbitrary direction in the horizontal plane.

[`xArbitraryCorrectedZVertical`](/documentation/CoreMotion/CMAttitudeReferenceFrame/xArbitraryCorrectedZVertical)

A reference frame where the Z axis is vertical and has improved rotation accuracy, and the X axis points in an arbitrary direction in the horizontal plane.

[`xMagneticNorthZVertical`](/documentation/CoreMotion/CMAttitudeReferenceFrame/xMagneticNorthZVertical)

A reference frame where the Z axis is vertical and the X axis points to the magnetic north pole.

[`xTrueNorthZVertical`](/documentation/CoreMotion/CMAttitudeReferenceFrame/xTrueNorthZVertical)

A reference frame where the Z axis is vertical and the X axis points to the geographic north pole.

### Initializers

[`init(rawValue:)`](/documentation/CoreMotion/CMAttitudeReferenceFrame/init(rawValue:))


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