[Suggestion] Making CoordinateSystem mandatory if Pos3D is present

[Edouard2laire]

Hello,

Is your suggestion related to a problem? Please describe.
The main objective of having access to Pos3D (sourcePos3D, detectorPos3D) is to be able to coregister the montage with a template or the subject anatomy. This can however become tricky without information about the coordinate system used.

Additionally, the co-registration can be made much easier with access to landmark position (nasion, left/right ear...)

Describe the solution you'd like

Have the coordinate system be mandatory if sourcePos3D and detectorPos3D are present.

Have landmarkPos3D and landmarkLabels be recommended if sourcePos3D and detectorPos3D are present.

Additional context

The description of the coordinate system is required when including nirs data in a BIDS dataset: https://bids-specification.readthedocs.io/en/stable/modality-specific-files/near-infrared-spectroscopy.html#coordinate-system-json-_coordsystemjson