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3.3 Discussion
The deviation of gaze coordinates is from two main aspects which are the scene calibration
procedure and gaze procedure. The scene calibration procedure teaches how eye movements
relate to eye direction within the scene. The calibration is semi-manual procedure which inevi-
tably leads to deviation. Using more calibration points can improve tracking accuracy. The
other cause is head movements and nystagmus. We assume that scene image is not change in
gaze procedure, which means head must be kept still. Nystagmus is an involuntary eye move-
ment. Luckily, it affects little.
The results showed that the differences across subjects were narrow. Sub.5 did the best.
Other subjects performed nearly. The standard deviation of the last ...