Definition of fields in EEG.Chanlocs


The Fig 9.4 of your book “Analyzing Neural Time Series Data” used a EEG dataset sampleEEGdata.mat. After loading it into Matlab, it created a structure EEG.

I need help to confirm the coordinate system used in EEG.chanlocs. My current understanding is the following

  1. There are 2 coordinate systems: polar and cartesian
  2. The origins of both systems are at the center of the head (not on the surface)
  3. X axis points to the nose
  4. Y axis points to the left ear
  5. Z axis points up (top of scalp)
  6. Theta is the rotation around the Z axis following standard right hand rule, and the nose has theta=0, left ear = 90 degree
  7. Phi is the angle measured from the XY plan, + direction is towards the scalp, - direction is towards the feet
  8. What is the measurement unit for ‘radius’? e.g. cm, mm, inch etc
  9. What is the measurement unit for X, Y, Z?
  10. what is the measurement unit for ‘sph_radius’?

If there is a good documentation source, please share.



That’s eeglab format, so I recommend checking out their official documentation. A quick google search leads me to suggest the following two sites:

MIke, Thanks!

Happy new year!