Issue with importation of mff with GeoScan coordinates.xml

[mamoran66]

I have a customer who is reporting a distortion of the channel locations when importing a mff that has had the coordinates.xml file replaced by the output of GepoScan, one of our 3D digitization systems. I believe I've ruled out any issues with the generation of the Geoscan file as the coordinates appear fine in net station. Please see the attached images, the coordinates seem rotated in the 3D view. I believe you might already be aware of this issue?

[arnodelorme]

It seems that the position is rotated by 90 degrees. This can easily be fixed in EEGLAB GUI (menu Edit > Channel location) then set the noze direction to +Y. Also, can you share the XML coordinate file. I might be able to read the noze orientation from the file.

[arnodelorme]

coordinates.xml.zip

[arnodelorme]

I have checked and rechecked and it seems that this MFF file was exported from EEGLAB with the electrodes rotated. However, this is because the coordinate were imported and not rotated in EEGLAB.

[mamoran66]

Dear Arno,

Let me make sure I understand, the coordinates are being rotated by EEGLab so there is nothing you can do?

It is curious the issue only happens with custom coordinates. But, the issue must be in EEGLab as the rotation only shows in EEGLab.

I did try adjusting the nose settings in EEGLab and that seemed to show the rotation was not a full 90 degrees, no settings produced correct coordinates.

Thanks,

Mark

From: Arnaud Delorme @.> Reply-To: arnodelorme/mffmatlabio @.> Date: Thursday, May 9, 2024 at 9:48 PM To: arnodelorme/mffmatlabio @.> Cc: Mark Moran @.>, Author @.***> Subject: Re: [arnodelorme/mffmatlabio] Issue with importation of mff with GeoScan coordinates.xml (Issue #53)

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I have checked and rechecked and it seems that this file was exported from EEGLAB with the electrodes rotated.

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[arnodelorme]

The file you have shared was an MFF file exported from EEGLAB and it had the electrodes rotated. My intuition is that the electrode positions were imported into EEGLAB, not rotated properly and then exported to MFF. I have checked several native MFF files and the electrodes were fine (not rotated).

[mamoran66]

Hi Arno,

Let me clarify a bit.

The coordinate file was generated using one of our 3D digitization systems, GeoScan and then inserted in the MFF as the “coordinates.xml” file before importing the file into EEGLab. So I don’t believe it was imported per se. Does that change your analysis of the issue? This is not a one-time issue, all of the files generated by GeoScan by this customer are rotated, looks to be about 30 degrees. The rotation is not seen in Net Station, though, otherwise we would suspect the error is with the GeoScan.

Thanks,

Mark

From: Arnaud Delorme @.> Reply-To: arnodelorme/mffmatlabio @.> Date: Tuesday, May 14, 2024 at 2:57 PM To: arnodelorme/mffmatlabio @.> Cc: Mark Moran @.>, Author @.***> Subject: Re: [arnodelorme/mffmatlabio] Issue with importation of mff with GeoScan coordinates.xml (Issue #53)

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The file you have shared was an MFF file exported from EEGLAB and it had the electrodes rotated. My intuition is that the electrode positions were imported into EEGLAB, not rotated properly and then exported to MFF. I have checked several native MFF files and the electrodes were fine (not rotated).

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[arnodelorme]

The coordinate file shows "Exported by EEGLAB." See screen capture. Would you mind attaching the original dataset with the scanned electrodes by GeoScan?

[mamoran66]

Hi Arno,

Here is a link to a file prior to importation, Sorry, it’s a bit large, might take a few minutes to download

https://electricalgeodesics.sharefile.com/d-sb9ed02c22a424a46832fc2d99e5530ef

Thanks,

Mark

From: Arnaud Delorme @.> Reply-To: arnodelorme/mffmatlabio @.> Date: Wednesday, May 15, 2024 at 6:52 AM To: arnodelorme/mffmatlabio @.> Cc: Mark Moran @.>, Author @.***> Subject: Re: [arnodelorme/mffmatlabio] Issue with importation of mff with GeoScan coordinates.xml (Issue #53)

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The coordinate file shows "Exported by EEGLAB." See screen capture. Would you mind attaching the original dataset with the scanned electrodes by GeoScan? Screenshot.2024-05-15.at.6.50.47.AM.png (view on web)https://github.com/arnodelorme/mffmatlabio/assets/1872705/620c7d66-ab34-4230-9654-810cf26f4764

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