[FieldTrip] question of planar gradient decomposition

[qi li]

Hi,

We have a axial ctf 1st order gradiometer. So it measures the axial
gradient of the the magnetic field-(dB/dr). If I do the planar gradient
transformation by 'sincos ,distance,' your codes looks like computing
d^2B/d(theta) and d^2B/d(phi) where theta and phi are azimuth angle and
polar angle respectively. It is well known in a spherical coordinate, there
is no way to derive the tangential components from axial component, so what
is the purpose of your linear transformation?

Compared to neuromag which does pick up the planar gradient, is there any
advantage for you to do so?

Thanks a lot!

Happy new year!

Qi




*
*<http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAA&url=http%3A%2F%2Fmailman.science.ru.nl%2Fpipermail%2Ffieldtrip%2F2008-July%2F001657.html&ei=1d39Tv_WHqj10gGj_emgAg&usg=AFQjCNGS3mBlohQrrRTW5gW_JcB9014Ldg>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20111230/c8ac884c/attachment-0001.html>