Quadcopter follows you...active RFID? or other method?

[tlocus]

Hello,
I'm building my quad from scratch. A friend bought a ready made one or ready to fly one that he uses to follow him in his boat when he fishes.
It stays at a given height and distance while under way (offshore fishing).
I asked him what sensor, etc... his quad had to do this but he didn't know.
Would it be like an active RFID, or something else?
Any info on how/what to use would be greatly appreciated.

tlocus

 

[holtneil]

Some use the transmitter to lock on to and follows this , there was a company made a drone called Lilly this had a wrist transmitter the drone would lock onto this and follow it , shame they went bust

 

[tlocus]

Some use the transmitter to lock on to and follows this , there was a company made a drone called Lilly this had a wrist transmitter the drone would lock onto this and follow it , shame they went bust

Thanks for the info! Will see if I can find out more on how it would lock on transmitter.