[Eeglablist] electrode location coordinates
Darren Weber
dweber at radmail.ucsf.edu
Wed Dec 20 15:31:05 PST 2006
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I have a matlab function called elec_sph2cart. This is the help:
elec_sph2cart - convert spherical to Cartesian coordinates
Convert from spherical (theta,phi,r) to Cartesian rectangular (x,y,z)
coordinates.
Useage: [X,Y,Z] = elec_sph2cart(theta,phi,r,[degrees])
theta is counterclockwise rotation from +x in x-y plane
(azimuth),
phi is elevation with respect to z-axis (eg, Cz in 10-20
system),
r is radius,
degrees: 0=radians (default) or 1=degrees for theta & phi
Result: (X,Y,Z) are double floating point
Note: Conversion from spherical to Cartesian coordinates, given
angles in radians, is:
x = r .* sin(phi) .* cos(theta);
y = r .* sin(phi) .* sin(theta);
z = r .* cos(phi);
+ve x-axis from origin through T4 (right ear)
+ve y-axis from origin through Nasion (at theta = +90degrees)
Results from this routine are not the same as those from
the inbuilt sph2cart matlab function. Phi here is
elevation with respect to z-axis. The matlab function
sph2cart uses elevation with respect to xy plane.
Maybe that will help.
Best, Darren
Maro Machizawa wrote:
> Dear Johannes,
>
> Thank you very much for your reply and the file, but I'm afraid M10 and
> M11 have different
> arrangements; M10 is more like 10/20 system but M11 is equidistant
> system. I've got easycap's
> theta/phi coordinates for M11; however, I am not quite sure how to
> implement those values into
> EEGLAB.
> I attached their M10 theta/phi coordinates file. Can anyone help me to
> create a location file out of
> this?
>
> Best regards,
> Maro
> ----- Original Message ----- From: "Sarnthein Johannes"
> <Johannes.Sarnthein at usz.ch>
> To: "Maro Machizawa" <m.machizawa at ucl.ac.uk>; <eeglablist at sccn.ucsd.edu>
> Sent: Monday, December 18, 2006 8:10 AM
> Subject: Re: [Eeglablist] electrode location coordinates
>
>
> Dear Maro,
> here is a .loc file I made for easycap M11,
> maybe you can adapt it to M10.
> Best,
> Johannes
>
>
> -----Ursprüngliche Nachricht-----
> Von: eeglablist-bounces at sccn.ucsd.edu
> [mailto:eeglablist-bounces at sccn.ucsd.edu] Im Auftrag von Maro Machizawa
> Gesendet: Mittwoch, 13. Dezember 2006 13:45
> An: eeglablist at sccn.ucsd.edu
> Betreff: [Eeglablist] electrode location coordinates
>
> Dear Users,
>
> I have a problem registering electrode location in EEGLAB. I have a set
> of theta and phi angles (coordinates); however, they don't match with
> EEGLAB's one.
>
> I attached a text file contains theta and phi coordinates. (we have
> easycap's M10 cap).
> Theta is the angle between the Z-Axis and the connecting line from the
> origin of the coordinates and the electrode position. In the left
> hemisphere Theta is less than zero, in the right hemisphere it is larger.
> Phi is the angle between: 1. the projection of the connecting line from
> the origin of the coordinates and the electrode position onto the
> XY-plane and 2. the X-axis. Phi is greater zero in the front right and
> rear left quadrant and smaller zero in the front left and the rear right
> quadrant.
>
> I just need to input electrode locations in EEGLAB and create location
> file. If anyone can help me to go through this step, it will be greatly
> helpful.
>
> Best Wishes,
> Maro
>
> Site Theta Phi
> 1 0 0
> 2 23 90
> 3 23 30
> 4 23 -30
> 5 23 -90
> 6 -23 30
> 7 -23 -30
> 8 46 90
> 9 46 66
> 10 46 33
> 11 46 0
> 12 46 -33
> 13 46 -66
> 14 46 -90
> 15 -46 66
> 16 -46 33
> 17 -46 0
> 18 -46 -33
> 19 -46 -66
> 20 69 90
> 21 69 66
> 22 69 42
> 23 69 18
> 24 69 -6
> 25 69 -30
> 26 69 -54
> 27 69 -78
> 28 -69 78
> 29 -69 54
> 30 -69 30
> 31 -69 6
> 32 -69 -18
> 33 -69 -42
> 34 -69 -66
> 35 92 90
> 36 92 68
> 37 92 45
> 38 92 22
> 39 92 0
> 40 92 -22
> 41 92 -45
> 42 92 -68
> 43 92 -90
> 44 -92 68
> 45 -92 45
> 46 -92 22
> 47 -92 0
> 48 -92 -22
> 49 -92 -45
> 50 -92 -68
> 51 115 35
> 52 115 10
> 53 115 -15
> 54 115 -40
> 55 115 -65
> 56 115 -90
> 57 -115 65
> 58 -115 40
> 59 -115 15
> 60 -115 -10
> 61 -115 -35
>
>
> ------------------------------------------------------------------------
>
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- --
Darren L. Weber, Ph.D.
Postdoctoral Scholar
Dynamic Neuroimaging Laboratory,
UCSF Department of Radiology,
185 Berry Street, Suite 350, Box 0946,
San Francisco, CA 94107, USA.
Tel: +1 415 353-9444
Fax: +1 415 353-9421
www: http://dnl.ucsf.edu/users/dweber
"To explicate the uses of the brain seems as difficult
a task as to paint the soul, of which it is commonly
said, that it understands all things but itself."
Thomas Willis (The Anatomy of the Brain and Nerves, 1664)
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