I am looking around to see what are the units in which the “left_gaze_x”, “left_gaze_y”, “right_gaze_x” and “right_gaze_y” columns in the BinocularEyeSampleEvent file within the hdf5 file output, using a Tobii Pro Spectrum to record the eyegaze. I have seen that this is in Display Coordinate Type Units, but I don’t understand how this units translate either in pixels or in height units of this experiment, nor what the limits of these units are, and I have not been able to find any other information about them.
This is were I found the name of the units: Tobii — PsychoPy v2024.2.5
I would assume you need to look in the Tobii SDK to see what units are being used in calibration, then likely those units are used in your data output. Calibration - Tobii Pro SDK documentation.
The example shown in the above page shows it as the top left corner being 0,0 and bottom right corner as 1,1. Pixels should be quite obviously (as the numbers will be quite large or your calibration and tracking is very poor). But, I guess depending on your physical setup, pixels and mm might be similar? Other units can be found here Units for the window and stimuli — PsychoPy v2024.2.5. It might be the case that the eye tracker used the units in experiment settings, so whatever units the experiment is set as (you can see this in experiment properties window on the second tab, “screen”
The other way to determine what units are being used, make a really simple experiment that has a centre fixation and an object appearing for 1-3 seconds in varying position on the screen. For example, I use degrees, so my positions are (0,0), (0,5), (-5,5)… (-15, -10) etc, etc. And because I am fixating on a non-moving point for a period of time, I can easily determine how well calibration is.
Overall, just check to see what units the eye tracker are using, this will shown in the specific code component for your eye tracker either when it initializes, or in calibration. For example in the calibration for my eye tracker:
Issac