Since the beginning, the development of quadcopters and drones has been strongly influenced by sensors in combination with microprocessors. These flight systems would not be feasible without sensors, because gyros, acceleration sensors and inertial measurement units, for example, are absolutely necessary to make them fly. These are used for axis control. Others, such as the electronic compass, the air pressure sensor or GPS, make control considerably easier for the pilot. Together with sophisticated software, additional sensors such as ultrasonic, infrared or cameras allow additional functions such as automated take-offs and landings, obstacle detection or object tracing. All these sensors and their physical principles are explained in this booklet and their use and possibilities in quadrocopters and drones are discussed.
