Inertial Measurement Unit

An inertial measurement unit comprising:

• a three-axis angular velocity sensor that measures a three-axis angular velocity along three axes orthogonal to each other for each first period;
• a minute posture change calculation portion that calculates a posture change quaternion representing a posture change in the first period based on the three-axis angular velocity measured by the three-axis angular velocity sensor;
• a posture increment calculation portion that calculates a posture quaternion by combining the posture change quaternions for each first period, and calculates a posture increment quaternion representing a posture increment in a second period longer than the first period;
• an angle increment calculation portion that calculates an angle increment in the second period based on the posture increment quaternion;
• and
• an interface portion that transmits the angle increment to an external device for each second period.