Data from: Smaller is better: drift in gaze measurements due to pupil dynamics

Camera-based eye trackers are the mainstay of eye movement research and
countless practical applications of eye tracking. Recently, a significant
impact of changes in pupil size on gaze position as measured by
camera-based eye trackers has been reported. In an attempt to improve the
understanding of the magnitude and population-wise distribution of the
pupil-size dependent shift in reported gaze position, we present the first
collection of binocular pupil drift measurements recorded from 39
subjects. The pupil-size dependent shift varied greatly between subjects
(from 0.3 to 5.2 deg of deviation, mean 2.6 deg), but also between the
eyes of individual subjects (0.1 to 3.0 deg difference, mean difference
1.0 deg). We observed a wide range of drift direction, mostly downward and
nasal. We demonstrate two methods to partially compensate the pupil-based
shift using separate calibrations in pupil-constricted and pupil-dilated
conditions, and evaluate an improved method of compensation based on
individual look-up-tables, achieving up to 74% of compensation.