The on-board flight controller circuitry receives information from sensors that provide data about the craft in flight. Some of the possible sensors that determine the attitude, altitude, and direction of flight include:
A gyroscope that determines the attitude of the craft including its pitch and roll. This indicates the rotational motion of the craft.
An accelerometer that determines the rate of change of velocity of the craft with respect to the three axes.
An altimeter or barometer that determines the altitude of the craft above ground. At low altitudes, a down-looking sonar sensor may be used to determine altitudes up to several meters or more.
A magnetometer that serves as a compass to indicate the craft's direction by using the Earth's magnetic field as a reference.
The accelerometer and magnetometer need calibration to initialize their readings to the conditions where the flights will take place. For each quadrotor it is therefore important to follow...