Technology behind camera drones with "follow" function

[greypilgrim]

Hi.
Most modern camera quadcopters (drones) have a "follow" function, allowing them to follow and film a person. The DJI Phantom 4 does this by optical tracking, most other brands require that the person carry a smartphone or other wearable.

How does this work? I assume the smartphone or wearable sends a signal, but how can a single drone determine its distance and direction from the source? Obviously not by triangulation.

Or is it that simple that both the smartphone/wearable and the drone must have GPS and the drone simply receives the coordinates of the sender, compares them with its own and follows? But is this fast and accurate enough? As far as I know GPS is only accurate to a couple of meters, which could bring the drone dangerously close to the person it follows so far away that the camera shots become useless.

 

[mfb]

I don't know what exactly the different tools are using, but GPS is precise enough. The absolute precision of GPS is not good, but the problem mainly comes from atmospheric effects - nearby GPS devices will have the same measurement errors so they cancel in the difference. Even if the receivers are kilometers apart this differential GPS can achieve an accuracy of about a centimeter.