FieldTrip

Note that this reference documentation is identical to the help that is displayed in Matlab when you type “help ft_datatype_sens”.

  FT_DATATYPE_SENS describes the FieldTrip structure that represents
  an EEG, ECoG, or MEG sensor array. This structure is commonly called
  "elec" for EEG and "grad" for MEG, or more general "sens" for either
  one.
 
  The structure for MEG gradiometers and/or magnetometers contains
     sens.label    = Mx1 cell-array with channel labels
     sens.chanpos  = Mx3 matrix with channel positions
     sens.chanori  = Mx3 matrix with channel orientations, used for synthetic planar gradient computation
     sens.tra      = MxN matrix to combine coils into channels
     sens.coilpos  = Nx3 matrix with coil positions
     sens.coilori  = Nx3 matrix with coil orientations
     sens.balance  = structure containing info about the balancing, See FT_APPLY_MONTAGE
 
  The structure for EEG or ECoG channels contains
     sens.label    = Mx1 cell-array with channel labels
     sens.chanpos  = Mx3 matrix with channel positions
     sens.tra      = MxN matrix to combine electrodes into channels
     sens.elecpos  = Nx3 matrix with coil positions
  In case sens.tra is not present in the EEG sensor array, the channels
  are assumed to be average referenced.
 
  The following fields are optional
     sens.type     = string with the MEG or EEG acquisition system, see FT_SENSTYPE
     sens.chantype = Mx1 cell-array with the type of the channel, see FT_CHANTYPE
     sens.chanunit = Mx1 cell-array with the units of the channel signal, e.g. 'T', 'fT' or 'fT/cm'
 
  Revision history:
 
  (2011v2/latest) The chantype and chanunit have been added for MEG.
 
  (2011v1) To facilitate determining the position of channels (e.g. for plotting)
   in case of balanced MEG or bipolar EEG, an explicit distinction has been made
   between chanpos+chanori and coilpos+coilori (for MEG) and chanpos and elecpos
   (for EEG). The pnt and ori fields are removed
 
  (2010) Added support for bipolar or otherwise more complex linear combinations
   of EEG electrodes using sens.tra, similar to MEG.
 
  (2009) Noice reduction has been added for MEG systems in the balance field.
 
  (2006) The optional fields sens.type and sens.unit were added.
 
  (2003) The initial version was defined, which looked like this for EEG
     sens.pnt     = Mx3 matrix with electrode positions
     sens.label   = Mx1 cell-array with channel labels
  and like this for MEG
     sens.pnt     = Nx3 matrix with coil positions
     sens.ori     = Nx3 matrix with coil orientations
     sens.tra     = MxN matrix to combine coils into channels
     sens.label   = Mx1 cell-array with channel labels
 
  See also FT_READ_SENS, FT_SENSTYPE, FT_CHANTYPE, FT_APPLY_MONTAGE, CTF2GRAD, FIF2GRAD,
  BTI2GRAD, YOKOGAWA2GRAD, ITAB2GRAD