This is known as ‘return to home’ feature. It also determines and calculates the drone’s altitude in respect to the amount of power it consumes. Propellers Propellers are clove like blades structured to create a difference in air pressure.
When in motion, they cut through the air creating difference in pressure between the top of the rotors and the bottom. The top side is characterized by low pressure as compared to the bottom causing the drone to lift into the air.