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<p>dear jan-mathijs,</p>
<p>that is indeed the case. thanks for the quick reply!</p>
<p>best wishes,<br>
thomas<br>
</p>
<div class="moz-cite-prefix">Am 21.08.18 um 11:11 schrieb
Schoffelen, J.M. (Jan Mathijs):<br>
</div>
<blockquote type="cite"
cite="mid:5C9F995D-1ABA-4CC6-BD6A-FA59DDC62B66@donders.ru.nl">
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Dear Thomas,
<div class=""><br class="">
</div>
<div class="">I would guess that the 3x3 ‘rotation’ part of the
affine transformation matrix here describes the direction plane
of the sensor in the first two columns (x/y axis), and the
normal to this plane in the third column, which is the vector
perpendicular to the coil. Try and verify whether the
cross-product between the first two columns gives the the third.</div>
<div class=""><br class="">
</div>
<div class="">Best wishes,</div>
<div class=""><br class="">
</div>
<div class="">Jan-Mathijs</div>
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On 21 Aug 2018, at 10:24, Thomas Hartmann <<a
href="mailto:thomas.hartmann@th-ht.de" class=""
moz-do-not-send="true">thomas.hartmann@th-ht.de</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div text="#000000" bgcolor="#FFFFFF" class="">
<p class="">hi,</p>
<p class="">while diving into the import code for elekta
systems, i noticed that coil orientations are imported
like this:</p>
<pre class="">t = orig.chs(n).coil_trans;
grad.coilpos(kCoil,:) = t(<span class="pl-c1">1</span>:<span class="pl-c1">3</span>,<span class="pl-c1">4</span>)+<span class="pl-c1">0.0003</span>*t(<span class="pl-c1">1</span>:<span class="pl-c1">3</span>,<span class="pl-c1">3</span>);
grad.coilori(kCoil,:) = t(<span class="pl-c1">1</span>:<span class="pl-c1">3</span>,<span class="pl-c1">3</span>);
</pre>
<p class="">(full code is here: <a
class="moz-txt-link-freetext"
href="https://github.com/fieldtrip/fieldtrip/blob/master/fileio/private/mne2grad.m#L321"
moz-do-not-send="true">
https://github.com/fieldtrip/fieldtrip/blob/master/fileio/private/mne2grad.m#L321</a>)<br
class="">
</p>
<p class="">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.</p>
<p class="">if i understand everything correctly,
coilori is supposed to store a unit vector pointing in
the direction of the coil's orientation.</p>
<p class="">so, why is this the third column?</p>
<p class="">thanks a lot in advance!</p>
<p class="">thomas<br class="">
</p>
<pre class="moz-signature" cols="72">--
Dr. Thomas Hartmann
Centre for Cognitive Neuroscience
FB Psychologie
Universität Salzburg
Hellbrunnerstraße 34/II
5020 Salzburg
Tel: +43 662 8044 5109
Email: <a class="moz-txt-link-abbreviated" href="mailto:thomas.hartmann@th-ht.de" moz-do-not-send="true">thomas.hartmann@th-ht.de</a>
"I am a brain, Watson. The rest of me is a mere appendix. " (Arthur Conan Doyle)
</pre>
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</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Dr. Thomas Hartmann
Centre for Cognitive Neuroscience
FB Psychologie
Universität Salzburg
Hellbrunnerstraße 34/II
5020 Salzburg
Tel: +43 662 8044 5109
Email: <a class="moz-txt-link-abbreviated" href="mailto:thomas.hartmann@th-ht.de">thomas.hartmann@th-ht.de</a>
"I am a brain, Watson. The rest of me is a mere appendix. " (Arthur Conan Doyle)
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