Samples

Sample lines contain time, position, and pupil size data. For EyeLink 3 recordings, sample lines also contain head position and rotation data, and head-in-space and eye-in-head data, and optionally, velocity, resolution, and pupil ellipse data may be included. Each sample line begins with a timestamp. The time stamp field is followed by X and Y position pairs and pupil size data for the tracked eye, and optionally by X and Y velocity pairs for the eye, resolution X and Y values, and, for EyeLink 3, the extended head tracking data and eye position data. Missing data values are represented by a dot ("."), or the text specified by the "-miss" option to EDF2ASC. Optionally, velocity and resolution data may be included. Several possible sample line formats are possible. These are listed below.

Essentially, each sample line begins with a timestamp. This is followed by X and Y position pairs and pupil size data for each eye, and optionally by X and Y velocity pairs for each eye, and resolution X and Y values. For binocular data, the resolution is the average of the left and right eye values. Missing data values are represented by a dot ("."), or the text specified by the "-miss" option to EDF2ASC.


SAMPLE LINE FORMATS (EyeLink I, II, 1000, 1000 Plus, Portable Duo)


Data notations:
Field Content
<time > timestamp in milliseconds
<xp > <yp > monocular X and Y position data
<xpl > <ypl > left-eye X and Y position data
<xpr > <ypr > right-eye X and Y position data
<ps > monocular pupil size (area or diameter)
<psl > left pupil size (area or diameter)
<psr > right pupil size (area or diameter)
<xv > <yv > instantaneous velocity (degrees/sec)
<xvl > <yvl > left-eye instantaneous velocity (degrees/sec)
<xvr > <yvr > right-eye instantaneous velocity (degrees/sec)
<xr > <yr > X and Y resolution (position units/degree)
<tx > <ty > X and Y position of the target in camera coordinate
<td > Distance between the target and camera (in millimeters).

Samples recorded in P-CR Mode (EyeLink II, 1000, 1000 Plus, Portable Duo)

If the data file being processed was recorded using corneal reflection mode, each sample line has an added 3 (monocular) or 5 (binocular) character fields after all other fields (including resolution and velocity if enabled). These fields represent warning messages for that sample relating to the corneal reflection processing.

  • MONOCULAR Corneal Reflection (CR) Samples
    "..." if no warning for sample
    first character is "I" if sample was interpolated
    second character is "C" if CR missing
    third character is "R" if CR recovery in progress

  • BINOCULAR Corneal Reflection (CR) Samples
    "....." if no warning for sample
    first character is "I" if sample was interpolated
    second character is "C" if LEFT CR missing
    third character is "R" if LEFT CR recovery in progress
    fourth character is "C" if RIGHT CR missing
    fifth character is "R" if RIGHT CR recovery in progress

Samples Recorded in the Remote mode

If the data file being processed was recorded in the Remote mode, extra columns will be recorded to the sample lines to encode the target distance, position, and eye/target status information. The first three columns are:

< target x >: X position of the target in camera coordinate. Returns "MISSING_DATA" (-32768) if target is missing.
< target y >: Y position of the target.
< target distance >: Distance between the target and camera (in millimeters). Returns "MISSING_DATA" (-32768) if target is missing.

In a monocular recording, the next thirteen fields represent warning messages for that sample relating to the target and eye image processing.

  • "............." if no warning for target and eye image
  • first character is "M" if target is missing
  • second character is "A" if extreme target angle occurs
  • third character is "N" if target is near eye so that the target window and eye window overlap
  • fourth character is "C" if target is too close
  • fifth character is "F" if target is too far
  • sixth character is "T" if target is near top edge of the camera image
  • seventh character is "B" if target is near bottom edge of the camera image
  • eighth character is "L" if target is near left edge of the camera image
  • Ninth character is "R" if target is near right edge of the camera image
  • tenth character is "T" if eye is near top edge of the camera image
  • eleventh character is "B" if eye is near bottom edge of the camera image
  • twelfth character is "L" if eye is near left edge of the camera image
  • thirteenth character is "R" if eye is near right edge of the camera image

For a binocular recording, there will be seventeen target/eye status columns, with the last eight columns reporting the warning messages for the left and right eyes separately.


SAMPLE LINE FORMATS (EyeLink 3)


Monocular recording:
<time > <xp > <yp > <ps >[ <xv > <yv > <xr > <yr >] <xhr > <yhr > <zhr > <xhp > <yhp > <zhp > <hisx > <hisy > <eihx > <eihy > [ <hisxr > <hisyr > <eihxr > <eihyr >] [ <pex > <pey > <pema > <pemi > <pea >]

Note that


Binocular recording:
<time > <xpl > <ypl > <psl > <xpr > <ypr > <psr > [ <xvl > <yvl > <xvr > <yvr >] [ <xr > <yr >] <xhr > <yhr > <zhr > <xhp > <yhp > <zhp > <hisx > <hisy > <eihlx > <eihrx > <eihcx > <eihly > <eihry > <eihcy > [ <hisxr > <hisyr > <eihxr > <eihyr >] [ <pelx > <pely > <pelma > <pelmi > <pela > <perx > <pery > <perma > <permi > <pera >]

Note that


Data notations:

Field Content
<time > timestamp in milliseconds
<xp > <yp > monocular X and Y position data
<xpl > <ypl > left-eye X and Y position data
<xpr > <ypr > right-eye X and Y position data
<ps > monocular pupil size (area or diameter)
<psl > left pupil size (area or diameter)
<psr > right pupil size (area or diameter)
<xv > <yv > instantaneous velocity (degrees/sec)
<xvl > <yvl > left-eye instantaneous velocity (degrees/sec)
<xvr > <yvr > right-eye instantaneous velocity (degrees/sec)
<xr > <yr > X and Y resolution (position units/degree)
<xhr > <yhr > <zhr > Rotation angle (in degrees) of the head around the X-axis (pitch), the Y-axis (yaw), and the Z-axis (roll)
<xhp > <yhp > <zhp > Translational movements along the X, Y, and Z axes
<hisx > <hisy > Head position X, Y in screen pixel coordinates
<eihx > <eihy > X, Y rotation of the monocular eye within the head projected onto a virtual screen (in screen pixel coordinates)
<eihlx > <eihly > X, Y rotation of the left eye within the head projected onto a virtual screen (in screen pixel coordinates)
<eihrx > <eihry > X, Y rotation of the right eye within the head projected onto a virtual screen (in screen pixel coordinates)
<eihcx > <eihcy > X, Y rotation of the "cyclopean" eye within the head projected onto a virtual screen (in screen pixel coordinates)
<hisxr > <hisyr > Angular resolution (in screen pixels per visual degree) along the X-, or X-axis at the current head-in-space position.
<eihxr > <eihyr > Angular resolution (in screen pixels per visual degree) along the X-, or Y-axis at the current eye-in-head position.
<pex > <pey > X, Y position of the pupil ellipse for the monocular eye in camera coordinate
<pelx > <pely > X, Y position of the pupil ellipse for the left eye in camera coordinate
<perx > <pery > X, Y position of the pupil ellipse for the right eye in camera coordinate
<pema > Major axis (in camera pixels) of the monocular pupil ellipse.
<pelma > Major axis (in camera pixels) of the left pupil ellipse.
<perma > Major axis (in camera pixels) of the right pupil ellipse.
<pemi > Minor axis (in camera pixels) of the monocular pupil ellipse.
<pelmi > Minor axis (in camera pixels) of the left pupil ellipse.
<permi > Minor axis (in camera pixels) of the right pupil ellipse.
<pea > Angle (in degrees) between the major-axis and x-axis for the monocular eye.
<pela > Angle (in degrees) between the major-axis and x-axis for the left eye.
<pera > Angle (in degrees) between the major-axis and x-axis for the right eye.

Samples recorded in P-CR Mode (EyeLink 3)

If the data file being processed was recorded using Pupil-CR mode, each sample line has an added 4 (monocular) or 6 (binocular) character fields before the head tracking data. These fields encode any warning messages relating to the corneal reflection processing that were present for that sample.

Status of Marker Tracking (EyeLink 3)

EyeLink 3 sample lines also provide a string that encodes the status of the Marker tracking for the head tracking data. They are useful for the interpretation of the head tracking data.

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