Extimation of displacement in Frontal plane from sagital plane

[btd]

estimation of displacement in Frontal plane from sagital plane

Hello everybody,
I hope I am posting this under right topic.
I am running a research project and we are recording videos of subjects from both frontal (back) and saggital (side) plane while they are walking on the treadmill.
I put 10cm long calibration marker on the back of the subject. This way, when I analyze the video recording I can calculate how much center of mass displaced during walking. But the problem is subjects do not walk on the same spot on the treadmill all the time. They go front and back and this makes my 10 cm, 8cm or 12cm (estimation) on the recording
I am just wondering if I measure the displacement from saggital recording, can this help to calculate how much it makes change on 10 cm in frontal recording.

or is there a another way?
Thanks
Tanner

 

[HallsofIvy]

I would suggest that you choose some point on the torso and subtract off the horizontal distance from that point to your control point to correct for movement of the torso.

(But if you are measuring from a marker on the back of the subject, that should already allow for movement of the body.)

 

[btd]

Thanks a lot for your answer,
Actually, what I am trying to do is calculating the displacement of center of mass (located at S2 vertebrae) from a fixed point on the torso with just one camera recording frontal movements.

Would you explain what you mean by saying "subtract off the horizontal distance from that point to your control point"?

I really appreciate your help

Cheers