[FieldTrip] inconsistent chanunit for Neuromag data

[Steve Patterson]

Hello,

I noticed that fieldtrip produces inconsistent channel units when I
read in Neuromag (vectorview) data.

For example:

%%%%%%%%%%%%%%%%%%%%%%%%

cfg                                = [];
cfg.dataset                   = 'example.fif';
cfg.trialfun                    = 'ft_trialfun_general';
cfg.trialdef.eventtype    = 'STI101';
cfg.trialdef.eventvalue  = [17 18 20];
cfg.trialdef.prestim       = 0.500;
cfg.trialdef.poststim     = 1.000;
cfg                                = ft_definetrial(cfg);
data                              = ft_preprocessing(cfg);

disp(data.hdr.chanunit(1:6));
'T/m'
'T/m'
'T'
'T/m'
'T/m'
'T'

disp(data.grad.chanunit(1:6));
'T'
'T'
'T'
'T'
'T'
'T'

%%%%%%%%%%%%%%%%%%%%%%%%

data.hdr.chanunit is correct and data.grad.chanunit is wrong.

data.grad.chanunit must take precedence in further analysis, because
I've noticed this causes problems downstream.

For example, when using ft_dipolesimulation, the simulated data on the
gradiometer channels is too small in amplitude by a factor of
1/(16.8E-3) (the distance between the gradiometer coil pair in
meters).

This is reflected in the grad.tra matrix, whose non-zero values are
all 1's and -1's, whereas they should be 1's (magnetometers), and +/-
1/16.8E-3 (gradiometers).

If you could fix this, it would be much appreciated!

thanks,

Steve