BIDS Validation Error EEG BrainVision

Hello everyone,

I’m using Brain Visions BV2BIDS tool, and I’m getting an error in validation:

sub-06_ses-fmri1_task-awak_coordsystem.json0.067 KB | application/json

Invalid JSON file. The file is not formatted according the schema.

.EEGCoordinateSystem should be equal to one of the allowed values

The coordinatesystem json file is as follows:

  "EEGCoordinateSystem": "BESA",
  "EEGCoordinateUnits": "mm"

Isn’t BESA an allowed value? Please let me know if more information is required.

Thanks in advance,


Hi @tomvanasse, "BESA" is not a valid entry as a EEGCoordinateSystem.

This one is tricky, because it used to be in the specification, but was later identified as a “bug” and therefore removed. Coincidentally, @robert and I noticed this “bug” in a phone call with Brain Products, so I am surprised that their tool is now writing “BESA”.

It would definitely be worth it to raise this as an issue on Brain Product’s code repository for BV2BIDS: GitHub - brain-products/BVTools: BV2BIDS is a command line tool that creates the EEG-BIDS folder hierarchy from BVCD files. (once you did this, please make sure to link the issue here, and also link to this post from the newly opened issue).

You can find the valid inputs for "EEGCoordinateSystem" here: Coordinate systems - Brain Imaging Data Structure v1.6.0-dev

In your case, this could be "Other" and you then supply a free text description in the "EEGCoordinateSystemDescription" field, which is mentioned here: Electroencephalography - Brain Imaging Data Structure v1.6.0-dev

Thanks, @sappelhoff

I’ve created an issue on the BV2BIDS page (EEGCoordinateSystem · Issue #2 · brain-products/BVTools · GitHub).

I appreciate the workaround you suggested.

1 Like