Coordinate system

[dienece]

I wanted to understand when a Brainvision file (.eeg, .vmrk, .vhdr files) is imported into Brainstorm how the channels are converted. What formula is used. I read the Coordinate systems tutorial but I didn't understand much.

[Raymundo.Cassani]

Hi @dienece,

The Coordinates in a BrainVision BrainAmp are spherical coordinates in degrees, they are first converted to spherical coordinates in radians and then to Cartesian coordinates. This is done here:

https://github.com/brainstorm-tools/brainstorm3/blob/d6f680f430a5e37974e4106bdb74290cf1537907/toolbox/io/in_fopen_brainamp.m#L112

For co-registration of channel positions and subject's anatomy, see this

Sensor coordinates in BrainVision vhdr files are not imported

Hi Chie, I fixed the import code for reading realistic 3D positions from the .vhdr files. Please update Brainstorm (menu Help > Update Brainstorm) and try again. Can you make sure that the orientation of the cap is correct (left on the left)? Note that the electrodes will not be correctly registered on the subject’s head because the .vhdr file does not contain the anatomical landmarks necessary to convert automatically the electrodes coordinates to the Brainstorm coordinates system (NAS,LPA,…

Best,
Raymundo

[dienece]

thanks a lot Raymundo