Tobii plugin gaze data file


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Hi,
We have a question about eye-tracking output we generated with the Inquisit Tobii plugin. The output file lists x,y,z coordinates of the gaze points of the eyes and coordinates of the eyes. Millisecond documentation states that both are reported 'in the 3D User Coordinate System'. Tobii SDK states this is in millimeters, as unit. Attached a recording plot of both variables (example from left-eye z-dimension). Unclear to us are the units and origin of the gaze data (y axis) in particular.  
Thanks for any clarification,
Estherhttps://www.millisecond.com/forums/uploads/images/c73213ce-d4f0-4106-810a-1db1.jpg


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Dave
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The Tobii documentation describes the 3D UCS as follows (highlights not in original):

User Coordinate System (UCS)
All the data available from Tobii Eye Trackers that describe 3D space coordinates are given in the so-called User Coordinate System or UCS for short. The UCS is a millimeter-based system with its origin at the centre of the frontal surface of the eye tracker (see Figure 1). The coordinate axes are oriented as follows: the x-axis points horizontally towards the user’s right, the y-axis points vertically towards the user’s up and the z-axis points towards the user, perpendicular to the front surface of the eye tracker.

https://www.millisecond.com/forums/uploads/images/ae3a890a-6250-4ead-a7e8-d4b9.png

To sum up: The unit is millimeters throughout, the origin point of the axes is the center of the eye tracker's front.
- lefteye (x,y,z) would reflect the left eye's position relative to the eyetracker.
- leftgaze (x,y,z) would reflect the left eye's gaze point on the calibration plane.

Hope this helps.

Edited 4 Years Ago by Dave
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Dave,
Sorry, I thought I be notified on reply. This is _very_ helpful (we did figure it out, too)!!

Thanks again,
Esther
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