[Eeglablist] Importing channel locations from Neuroscan (3DSpaceDX)

[Sara Graziadio]

EEGLab users,

I tried to import channel locations from Neuroscan (Scan 4.2) into
EEGlab but I have had some problems. I was wondering if you could help
me.
I recorded electrode positions and head shape with Fastrak (Polhemus)in
the 3DSpaceDX in Neuroscan and I saved them to a .3dd file. I tried to
import the data in EEGlab choosing the Polhemusx format (as I was
working in the X positive hemisphere) but I had an error: "readlocs:
error reading Polhemus coords. If Besa .elp file force file type to
BESA". I tried to save the data to a .elp file in Neuroscan and import
it again. When I imported the file in the Polhemusx format I had the
same error like before, whereas when I tried with Besa format (.elp), it
seems ok (I didn't had any error)but I didn't have my channel locations,
no XYZ coordinates, just numbers in the polar angles that looked like
random. I tried also to use autodetect when asked for file format but
nothing happened, no coords and these warnings on Matlab command window:

readlocs(): Inserting electrode labels automatically.
Warning: Reference to uninitialized variable eloc in readlocs at line
569.
Warning: Reference to uninitialized variable eloc in readlocs at line
584.
Warning: Reference to uninitialized variable eloc in readlocs at line
617.
Warning: Reference to uninitialized variable eloc in readlocs at line
625.
Warning: One or more output arguments not assigned during call to
'readlocs'.
Warning: Reference to uninitialized variable chans in pop_chanedit at
line 995.
Warning: Reference to uninitialized variable chans in pop_chanedit at
line 996.
Warning: One or more output arguments not assigned during call to
'pop_chanedit'.
Warning: Reference to uninitialized variable chans in pop_chanedit at
line 741.

Could anyone help me by any chance? 
Is there anyone that used the Polhemus device and had a good precision
in the localization of the electrodes? Because however I'm having
problems also in the calibration of the Fastrak, it seems to have 2cm of
error in the position recordings!

Thanks a lot in advance

Sara Graziadio



University of Newcastle
Queen Victoria Road 
NE14LP
Newcastle Upon Tyne
Uk