hsp : None  str  array, shape (n_points, 3)
If str, this corresponds to the filename of the headshape points.
This is typically used with the Polhemus FastSCAN system.
If numpy.array, this corresponds to an array of positions of the
headshape points in 3d. These points are in the native
digitizer space.
hpi : None  str  array, shape (n_hpi, 3)
If str, this corresponds to the filename of Head Position Indicator
(HPI) points. If numpy.array, this corresponds to an array
of HPI points. These points are in device space.
elp : None  str  array, shape (n_fids + n_hpi, 3)
If str, this corresponds to the filename of electrode position
points. This is typically used with the Polhemus FastSCAN system.
Fiducials should be listed first: nasion, left periauricular point,
right periauricular point, then the points corresponding to the HPI.
These points are in the native digitizer space.
If numpy.array, this corresponds to an array of fids + HPI points.
point_names : None  list
If list, this corresponds to a list of point names. This must be
specified if elp is defined.
unit : ‘m’  ‘cm’  ‘mm’
Unit of the input file. If not ‘m’, coordinates will be rescaled
to ‘m’. Default is ‘mm’. This is applied only for hsp and elp files.
transform : bool
If True, points will be transformed to Neuromag space.
The fidicuals, ‘nasion’, ‘lpa’, ‘rpa’ must be specified in
the montage file. Useful for points captured using Polhemus FastSCAN.
Default is True.
dev_head_t : bool
If True, a DevtoHead transformation matrix will be added to the
montage. To get a proper dev_head_t, the hpi and the elp points
must be in the same order. If False, an identity matrix will be added
to the montage. Default is False.
