Figure 2-6: Example Drift Check/Drift Correct Screen - SR Research EyeLink Portable Duo User Manual

Figure 2-6: Example Drift Check/Drift Correct Screen

2.4.4.1 Drift Check/Drift Correct Screen Purpose
The Drift Check/Drift Correct screen displays a single target to the participant
and then measures the difference between the computed fixation position and
the current target. As with the EyeLink 1000 and 1000 Plus, the default "drift
check" configuration of EyeLink Portable Duo leaves the calibration model
unmodified. The purpose therefore, is to check whether the calibration model is
still accurate. If the error between the measured location of the fixation and the
drift check target is large, the experimenter is prompted to acquire another
sample. If the error remains large (i.e., the prior sampling error was
reproduced), the drift check will fail and another calibration will be required
(see Section 3.11 for more details).
To perform a drift check/correction, have the participant look at the first
fixation point and click the 'Accept Fixation' button, or press ENTER or the
Spacebar, to evaluate the adequacy of the calibration parameters.
Important: In EyeLink I and II systems, the fixation error calculated during
drift correction was used to shift/correct the calibration map. This linear
adjustment often greatly improved the overall accuracy for the upcoming
recording. However, with the EyeLink Portable Duo eye tracker, the default
behavior in the pupil-CR mode is to report the calculated fixation error without
altering the calibration map in any way. Therefore the procedure is better
viewed as a "Drift Checking" procedure in the EyeLink Portable Duo, though a
true drift correction can be easily enabled (by toggling on the "Apply Correction"
button after entering in the Drift Check screen; see also section 3.11).
2.4.4.2 Drift Check/Drift Correct Screen Main Functions
Click to go to the 'Setup' screen.
Keyboard Shortcut: ESC = exit to Setup screen
Whether a correction will be applied to the calibration mapping. If
"Apply Correction" is toggled on, a true drift correction will be
performed; otherwise, the tracker just reports the error without
correcting for it.
Keyboard Shortcut: D = Toggles on/off the "Apply Correction" button
Click to terminate the drift correction/drift check and exit to the
Setup screen
Press to accept fixation value, after the participant's gaze is stable
on the target.
Keyboard Shortcuts: ENTER, Spacebar = 'Accept Fixation'
EyeLink Portable Duo Host Software
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