Camera Gimbal

I hope this bit of the forum is correct for this subject, as I am a newbie here??

I have APM 2.6 and have built a 3 axis servo gimbal for my Skywalker 1900. I can get all three digital servos to operate on outputs 5,6 and 8 fine.

My problem is with tracking - I have assumed that the gimbals are designed to make stabilising corrections to mute the movements of the plane ,i.e. steady the camera. I can see that each of the roll, yaw and tilt servos will track to their limits of turn from a fixed first position (say North and horizontal), but they then seem to stay in those positions until I reposition the plane back to its start location. I just can’t see how (when the plane moves around) the servos adjust themselves?? Am I missing something here - sorry to sound thick, but my brain doesn’t get this!!

Best regards,