The follow me mode makes it possible for you to have your copter follow you as you move, using a telemetry radio and a ground station. it’s easiest to use a phone or tablet as your Follow Me ground station. Follow Me mode uses the APM:Copter dynamic waypoint feature and MAVLink telemetry commands.
GPS signal in your Ground Station.
Warning: Like all other modes in which the autopilot is responsible for altitude hold (Loiter, AltHold), the barometer is used in the altitude calculation meaning that it can drift over time and the copter will follow the air pressure change rather than actual altitude above ground.