A UAS performing a property inspection will need to operate inside parcel boundaries, over and around the structures while avoiding trees, utility lines and the structures being captured. Obstacle avoidance systems will help prevent collisions with obstructions that could not be accounted for in the flight planning. A UAS obstacle avoidance system may implement multiple sensor types to overcome the weaknesses of any one sensor. Ultrasonic transducers and laser range finders are examples.
In the event that obstacle avoidance and human intervention fails it will be important for the UAS to detect collisions and handle them appropriately. For example, a multicopter with exposed propellers might shut the propellers down to minimize the amount of damage done. A multicopter with fully enclosed propellers may simply bounce off the obstruction and dynamically map the obstruction location in the flight plan.
A lot of obstacle avoidance and collision detection testing can be done indoors but eventually there is a point where real outdoor flight testing needs to be done. This is another area where a netted enclosure can provide a real-world testing environment and prevent the UAS from running away in the event of a failure