[FieldTrip] question on coil orientations for elekta systems
Thomas Hartmann
thomas.hartmann at th-ht.de
Tue Aug 21 10:24:25 CEST 2018
hi,
while diving into the import code for elekta systems, i noticed that
coil orientations are imported like this:
t = orig.chs(n).coil_trans;
grad.coilpos(kCoil,:) = t(1:3,4)+0.0003*t(1:3,3);
grad.coilori(kCoil,:) = t(1:3,3);
(full code is here:
https://github.com/fieldtrip/fieldtrip/blob/master/fileio/private/mne2grad.m#L321)
t (or coil_trans) is a 4x4 matrix, that if i understood it correctly, is
a 3x3 rotation matrix combined with xyz coordinates in the last column.
if i understand everything correctly, coilori is supposed to store a
unit vector pointing in the direction of the coil's orientation.
so, why is this the third column?
thanks a lot in advance!
thomas
--
Dr. Thomas Hartmann
Centre for Cognitive Neuroscience
FB Psychologie
Universität Salzburg
Hellbrunnerstraße 34/II
5020 Salzburg
Tel: +43 662 8044 5109
Email: thomas.hartmann at th-ht.de
"I am a brain, Watson. The rest of me is a mere appendix. " (Arthur Conan Doyle)
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