DJI’s obstacle sensing system is designed to create a 3D map with help from ultrasonic sensors that bounce signals back to the drone. Just like how a Ford with PCS initiates brakes once a pedestrian is detected, the Phantom 4 stops and hovers or goes around an obstacle once it spots an object is in its way.

Photo credit: DJI.
Developing technology
Even though obstacle avoidance systems are made to prevent crashes, there is still a chance collisions can happen. Uber was recently under fire after their self-driving car test resulted in a cyclist’s fatality, and DJI quadcopters can still crash when something like an eagle comes out of nowhere and strikes the drone, so this technology must be further developed and extensively tested, especially when human lives are on the line.

Drone taxis, which are already being tested in places like Dubai, need to have some sort of obstacle avoidance system to operate by themselves.
As technology advances, fully autonomous vehicles and drones will be designed to rely more on obstacle avoidance systems to prevent collisions. Even though obstacle avoidance systems today are proven to work in most situations, it’s only a glimpse of what to expect from tomorrow’s technology.