Channel Definition File Formats

Module information
Modules	BESA Research Basic or higher
Version	BESA Research 5.2 or higher

BESA Research can read 3 types of file to define channels. These are identified by different extensions:

• *.ela: Channel definition files containing labels and, optionally, channel types (ASCII, 1 label/line).
• *.elp: Channel definition files containing coordinates and, optionally, channel types and labels (ASCII). This is the format of the file written by the Channel Configuration Dialog.
• *.elb: Channel definition files stored by older versions of BESA Research (binary format). This format can still be read, but is no longer written by BESA Research.

Channel Label File Format (*.ela)

Files containing a list of channel labels are an alternative to editing electrode configurations in the application. These files can be edited using a standard text editor.

Electrode label files (.ela) require a sequence of lines corresponding to the sequence of channels in the data. Each line contains one label and an optional identifier. The format is [Identifier] {Label}, ([Identifier] can be omitted if the electrode label defines the type of signal)

Identifiers can be one of:

EEG	scalp electrode
SCP	scalp electrode
POL	polygraphic channel
PGR	polygraphic channel
ICR	intracranial electrode
MEG	MEG sensor
REF	reference electrode (this can only occur once, and must be the last item in the file)

Examples:

Fz	scalp electrode, coordinates assigned by default.ecd
Cz	scalp electrode, coordinates assigned by default.ecd
VEOG	vertical EOG, Polygraphic type is assigned by default
Exx	xx=01, 02.. electrode number, Polygraphic type is assigned by default
EEG xx	scalp electrode, coordinates must be assigned either by default.ecd or by a surface point file (*.sfp). An alternative to the "EEG" prefix is "SCP".
POL XX	identifier sets Polygraphic type - an alternative to the "POL" prefix is "PGR"
ICR A01	identifier sets Intracranial type to electrode A01 - do not use A1!
ICR A02	identifier sets Intracranial type to electrode A02 - do not use A2!
MEG M01	identifier sets MEG type to electrode M01 - do not use M1!
MEG M02	identifier sets MEG type to electrode M02 - do not use M2!
REF Cz	the label is assigned to the electrode reference, no channel is associated with this entry. This must be the last line of the file!

Channel Spherical Coordinate File Format (*.elp)

These files follow the same rules as the channel label files, with the addition of spherical coordinates (theta, phi) that follow the labels of EEG and MEG channels.

Labels can also be omitted. In this case, BESA Research will assign labels according to the nearest coordinate defined in the default.ecd file. To indicate that the coordinates have been assigned, the label will have a tick, e.g. Fz' instead of Fz.

Channels of other types (polygraphic; intracranial) are defined exactly as in the channel label (*.ela) file.