Research Drone Collision Avoidance Techniques

What type of sensors can/should we use to achieve collision avoidance?
How are these sensors integrated into our drones?

The issue names no files, tests, or entry points. Begin by defining the collision-avoidance requirements for the drones, then research suitable sensors and how they could integrate with the existing system. Done means a documented, project-specific sensor recommendation and integration approach.

Written by the indexing model from the issue text.