In regards to the aircraft seat testing process in which the occupant's center of gravity is required, I am quite interested to know how people calculate the C.G. of an Anthropomorphic Test Device (commonly known as crash test dummy) It would also be really helpful if I could get relevant resources in the answer.
I would expect that the manufacturer would be able to provide you with the location of the CG among the specifications of the dummy.
Unfortunately, the CG of a flexible object depends on the shape the object is taking at the moment. The CG is obvious for a uniform bar of steel, but bend it into the horseshoe and the CG is no longer located within the bar.
If I had an oddly shaped rigid object that I wanted to find the CG of, I would hang the object from multiple points. Draw a vertical line down the object from each hanging point. Where the lines cross is the CG.
The center of gravity of a standing human body is roughly about an inch below navel: https://www.sciencedirect.com/topics/physics-and-astronomy/center-of-gravity
For a seated person the CoG is shifted forwards and up of navel, total distance and angle will vary according to the specifics of the posture: https://www.researchgate.net/figure/Center-of-gravity-of-a-person-in-sitting-posture-Body-segmental-Lengths-are-reported-in_fig2_256203106
The antrophomorphic test dummies mimic the proportions, weight distribution and kinematics of a human body as close as possible, for obvious reasons: to accurately replicate the response of a human body to forces, the ATD must resemble it accurately, not just as a whole, but down to its individual part also.
Example information of THOR ADT: Anthropomorphic Test Devices; THOR 50th Percentile Adult Male Test Dummy; Incorporation by Reference
If you wish to build a more accurate model, here is an example of a further break-down of proportional masses of average human body parts (Source):
|Forearm & Hand||2.52%||2.07%|
|Leg & Foot||6.18%||6.68%|
There is no more need to calculate the CG of an Anthropomorphic Test Device than there is to calculate the actual CG of a live body.
Aircraft weight and balance calculations generally don't require that level of precision. Roughly centered on the seat, "X" inches from the datum is close enough.