Translates from Quaternion to Yaw. 

    @param qw,qx,qy,qz: Quaternion values

    @type qw,qx,qy,qz: float

    @return Yaw value translated from Quaternion

def quat2Yaw(qw, qx, qy, qz):
    '''
    Translates from Quaternion to Yaw. 

    @param qw,qx,qy,qz: Quaternion values

    @type qw,qx,qy,qz: float

    @return Yaw value translated from Quaternion

    '''
    rotateZa0=2.0*(qx*qy + qw*qz)
    rotateZa1=qw*qw + qx*qx - qy*qy - qz*qz
    rotateZ=0.0
    if(rotateZa0 != 0.0 and rotateZa1 != 0.0):
        rotateZ=atan2(rotateZa0,rotateZa1)
    return rotateZ