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Hi @vwgx3, thank you for your query. It is important in considering the various terminologies at use here to avoid confusion.
It is quite true that raw (or even lightly filtered) gaze data as received from the eye tracker whether it be EyeX or a more advanced model will always have an inherent jitterness of position location across time. This is in fact a natural consequence of how the human eye works and so is not a technological deficiency but rather an unavoidable biological characteristic.
A fixation however (as opposed to simple gaze location data) is quite different, as this is defined as a location of sustained attention over time. The calculation of a fixation is in fact rather dynamic and can have numerous interpretations and methods but suffice to say that a fixation is calculated using an algorithm ( or fixation filter) based upon the raw gaze data.
Further details on the fixation filter Tobii use in some of our software can be found @ https://www.tobiipro.com/siteassets/tobii-pro/learn-and-support/analyze/how-do-we-classify-eye-movements/tobii-pro-i-vt-fixation-filter.pdf
Along with further details on fixation concepts @ https://www.tobiipro.com/learn-and-support/learn/eye-tracking-essentials/types-of-eye-movements/
The resultant fixation therefore is not something that is subject to jitter in the standard sense but is well defined within a window of space and time, so I am therefore somewhat confused about what you mean by having jitter in your fixations.
It would therefore be helpful if you could kindly describe the calculations you are using to determine fixations based on data as received from your EyeX.
In any event, I hope the information above has proven useful in understanding the distinction between simple gaze data and fixation mode. Please let us know how we can be of further assistance and if you could also include details of your current project that would be appreciated.