Dear list members:

In the reply to the 3D camera angle question, Jesus Dapena identified
the use of surface markers. As he pointed out, there is a camera set
up problem in relation to the use of surface markers.

However, I would like to add to the discussion on this point:

I have always wondered, why somebody would like to use surface markers
in 3D analysis? If you are using surface markers, then you are not
digitising the motion centres ie. joint centres and you will get
"unrealistic" results (unless you have a software, which can
correct for and calculate surface marker digitising to the joint centres,
but very few of us have this). Additionally, there will be this accuracy
problem from the camera angle as already mentioned.

Thus, what is the value of use of surface landmarks in 3D analysis?

Aki Salo
Research Fellow
Brunel University College
Middlesex, UK