The navigation board includes the sensors and a 40 MIPS microcontroller with a fast 12 bits ADC converter. The navigation board has one ultrasonic transceiver and one ultrasonic receiver to measure the height of the drone up to 6 meters / 20 feet. The altimeter provides a measure at a 25 Hz rate. A 3 axis digital MEMS accelerometer positioned at the center of gravity of the AR.Drone. The accelerometer is used in a +/- 2g range and digitalized by an on-chip 10 bit ADC. Data are sent to the microcontroller. A two axis MEMS gyroscope and a precision piezoelectric gyroscope for the yaw measurement and heading control. Both sensors measure up to 500 °/s. These are analog sensors digitalize by the 12bits ADC of the microcontroller. These sensors compose the inertial measurement unit. The fusion of these data allows computing the Euler angles of the AR.Drone. Euler angles are used for stabilization. The navigation board software may be updated when you update the AR.Drone software. This kit includes 1 navigation board and 4 screws.