Hi, I have been learning to simulate my own fixed-wing UAV using Gazebo. The LiftDragPlugin has a parameter called cma which is the slope of the (pitching) moment coefficient vs alpha curve. As far as the whole of the aircraft is concerned, I think the moment should be taken about body y-axis centered at CG of the aircraft. But I have to input the value for the parameter for the wing as well as tail. So, is the moment coefficient about the CG of the aircraft or CG of the individual link or other points such as the origin of the individual joint frame?

I dont have access into the plugin itself which would show how the cma is used. So, I would be grateful if you could provide some insights into how cma should be calculated. I have looked at example of cessna172. The cma=-1.8 for wing, to my knowledge, means the moment center is ahead of AC of wing but it doesn't reveral wehre. Thank you.

(Also, I am aware a similar question has been asked previously but the answer doesn't explain this topic.)