Distance sensors can be used for various purposes. One can design a GPS enabled drone which can reach a specific location. Collision avoiding drones also use distance sensors, to determine the obstacle in their path.
Following are some of the distance sensors:
A Laser Range Finder (LRF) sends out a laser beam at certain intervals. When these beams bounce off of objects, the LRF detects the time at which it takes for these beams to return to the drone to reflect the distance between the object and the drone.
Light Detection and Ranging (LiDAR): LiDARs create an LRF spin, which is especially useful for producing 3D constructions and surveillance required for aerial surveys and navigation purposes.
The frequency shift between a transmitter that emits a particular signal and the receiver antenna on the drone that detects its Eco is used to determine the speed and direction of the object in relation to the drone.
By sending out a sound wave at a specific frequency, the drone measures the distance by which a sound wave bounces off the object and back to the drone.