Why is the rotation matrix used to represent the normal direction of MEG sensor?
How can I get this matrix?
MEG sensors measure a vector field. Position and orientation of sensors are therefore required.
HTH
Alex
Hi,
Just to add to what Alex said – the rotation matrix can be assembled from ch[‘loc’]. The first 3 elements are x, y, z, and then the subsequent elements are ex, ey, ez where ex, ey, ez are unit vectors in the x, y, z direction. Thus, you get 12 elements. The columns of the rotation matrix are ex, ey, ez.
Hope that helps,
Mainak
The OPM-MEG example program I run from this website, the data of one channel from ch[‘loc’] is shown in the figure
Does the matrix composed of the last nine elements represent the three measuring directions of an OPM?In fieldtrip (matlab), it seems that only one sensor sensitive direction is configured for a channel.I really appreciate your help.
The OPM-MEG example program I run from this website, the data of one channel from ch[‘loc’] is shown in the figure
Does the matrix composed of the last nine elements represent the three measuring directions of an OPM?In fieldtrip (matlab), it seems that only one sensor sensitive direction is configured for a channel.I really appreciate your help.
Hi – the measuring direction is likely z direction … that is defined in coil_def. The ch[‘loc’] just gives the coordinate system of the sensor, not the measuring direction of OPM sensors. I’m not sure how FieldTrip stores this information, it may be doing it differently.
Mainak