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reference:ft_datatype_sens [2018/08/23 14:43] (current)
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 +=====  FT_DATATYPE_SENS =====
 +Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_datatype_sens"​.
 +  <a href=/​reference/​ft_datatype_sens><​font color=green>​FT_DATATYPE_SENS</​font></​a>​ describes the FieldTrip structure that represents an EEG, ECoG, or
 +  MEG sensor array. This structure is commonly called "​elec"​ for EEG, "​grad"​ for MEG,
 +  "​opto"​ for NIRS, or general "​sens"​ for either one.
 +  For all sensor types a distinction should be made between the channel (i.e. the
 +  output of the transducer that is A/D converted) and the sensor, which may have some
 +  spatial extent. E.g. with EEG you can have a bipolar channel, where the position of
 +  the channel can be represented as in between the position of the two electrodes.
 +  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 <a href=/​reference/​ft_apply_montage><​font color=green>​FT_APPLY_MONTAGE</​font></​a>​
 +  and optionally
 +     ​sens.chanposold = Mx3 matrix with original channel positions (in case
 +                       ​sens.chanpos has been updated to contain NaNs, e.g.
 +                       after ft_componentanalysis)
 +     ​sens.chanoriold = Mx3 matrix with original channel orientations
 +     ​sens.labelold ​  = Mx1 cell-array with original channel labels
 +  The structure for EEG or ECoG channels contains
 +     ​sens.label ​   = Mx1 cell-array with channel labels
 +     ​sens.elecpos ​ = Nx3 matrix with electrode positions
 +     ​sens.chanpos ​ = Mx3 matrix with channel positions (often the same as electrode positions)
 +     ​sens.tra ​     = MxN matrix to combine electrodes into channels
 +  In case sens.tra is not present in the EEG sensor array, the channels
 +  are assumed to be average referenced.
 +  The structure for NIRS channels contains
 +    sens.optopos ​       = contains information about the position of the optodes
 +    sens.optotype ​      = contains information about the type of optode (receiver or transmitter)
 +    sens.chanpos ​       = contains information about the position of the channels (i.e. average of optopos)
 +    sens.tra ​           = NxC matrix, boolean, contains information about how receiver and transmitter form channels
 +    sens.wavelength ​    = 1xM vector of all wavelengths that were used
 +    sens.transmits ​     = NxM matrix, boolean, where N is the number of optodes and M the number of wavelengths per transmitter. Specifies what optode is transmitting at what wavelength (or nothing at all, which indicates that it is a receiver)
 +    sens.laserstrength ​ = 1xM vector of the strength of the emitted light of the lasers
 +  The following fields apply to MEG and EEG
 +     ​sens.chantype = Mx1 cell-array with the type of the channel, see <a href=/​reference/​ft_chantype><​font color=green>​FT_CHANTYPE</​font></​a>​
 +     ​sens.chanunit = Mx1 cell-array with the units of the channel signal, e.g. '​V',​ '​fT'​ or '​T/​cm',​ see <a href=/​reference/​ft_chanunit><​font color=green>​FT_CHANUNIT</​font></​a>​
 +  The following fields are optional
 +     ​sens.type ​    = string with the type of acquisition system, see <a href=/​reference/​ft_senstype><​font color=green>​FT_SENSTYPE</​font></​a>​
 +     ​sens.fid ​     = structure with fiducial information
 +  Historical fields:
 +     pnt, pos, ori, pnt1, pnt2
 +  Revision history:
 +  (2016/​latest) The chantype and chanunit have become required fields.
 +   ​Original channel details are specified with the suffix "​old"​ rather than "​org"​.
 +   All numeric values are represented in double precision.
 +   It is possible to convert the amplitude and distance units (e.g. from T to fT and
 +   from m to mm) and it is possible to express planar and axial gradiometer channels
 +   ​either in units of amplitude or in units of amplitude/​distance (i.e. proper
 +   ​gradient).
 +  (2011v2) 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 <a href=/​reference/​ft_read_sens><​font color=green>​FT_READ_SENS</​font></​a>,​ <a href=/​reference/​ft_senstype><​font color=green>​FT_SENSTYPE</​font></​a>,​ <a href=/​reference/​ft_chantype><​font color=green>​FT_CHANTYPE</​font></​a>,​ <a href=/​reference/​ft_apply_montage><​font color=green>​FT_APPLY_MONTAGE</​font></​a>,​ CTF2GRAD, FIF2GRAD,