[FieldTrip] Neuromag coordinate transformation

parham hashemzadeh ph442 at cam.ac.uk
Fri May 13 20:21:59 CEST 2016

Dear All
  I have read in some data (MNE-sample data set). I have this command in 
the script
hdr = ft_read_header(raw_data_filename); %your fif-filename

hdr.grad gives the below structure

ans =

      balance: [1x1 struct]
      chanori: [306x3 double]
      chanpos: [306x3 double]
     chantype: {306x1 cell}
     chanunit: {306x1 cell}
      coilori: [510x3 double]
      coilpos: [510x3 double]
     coordsys: 'neuromag'
        label: {306x1 cell}
          tra: [306x510 double]
         type: 'neuromag306'
         unit: 'cm'
It says that I am in "neuromag coordinate" system. The corresponding 
number for this coordinate system is device=1.0.
I have a transformation matrix T14.trans (coord system=1 to coord 
system=4) that takes me to head coordinate system i.e
T14 =

      from: 1
        to: 4
     trans: [4x4 double]

When I apply the transformation, to the coil position, the sensor array 
looks tilted to one side.
But, without the transformation, it looks more reasonable (visually). 
Maybe he was tilting !!! My question is:
Is it anyway possible that the transformation T14 has already been 
applied  by the function hdr = ft_read_header(raw_data_filename);
I have attached a picture of what I am describing.

many thanks
best regards parham hashemzadeh

-------------- next part --------------
A non-text attachment was scrubbed...
Name: coilpos.jpg
Type: image/jpeg
Size: 72267 bytes
Desc: not available
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20160513/7f282cd2/attachment-0002.jpg>

More information about the fieldtrip mailing list