All drones except Pulse Drones have a local scanner, which they can use to detect nearby agents, even if they are in soft cover. A drone uses its local scanner to investigate an interest point, or when preparing to hunt.
The scan has a radius of 4 tiles measured by Euclidean distance; it detects agents or a rescued Courier or Prisoner if they are within range. The scan ignores soft cover, but is blocked by tall cover and hard cover. If more than one detectable target is in range, only one will be detected.