determine the current person’s head pose precisely in ARKit’s face recognition

Hi there, I'd like to accurately determine the current person's head pose in ARKit's face recognition. Here is my code, but it was not precise.

fileprivate func getCurrentDirection(faceAnchor: ARFaceAnchor) -> CommandDirection?{
        let transform = faceAnchor.transform
        let pitch = atan2(-transform.columns.2.y, transform.columns.2.z)
        let yaw = atan2(transform.columns.2.x, transform.columns.2.z)
        
        var direction: CommandDirection?
        var horizontalTurn = false
        if yaw > 0.5 {
            horizontalTurn = true
            direction = .right
        } else if yaw < -0.3 {
            horizontalTurn = true
            direction = .left
        }
        
        if(!horizontalTurn){
            if pitch > 0.5 {
                direction = .down
            } else if pitch  < -0.1 {
                direction = .up
            }
        }
        return direction
    }


 func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard let faceAnchor = anchor as? ARFaceAnchor, let currentRotationDirection = getCurrentDirection(faceAnchor: faceAnchor) else {
            return
        }
}