Which calibration method should I use?

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Short answer: Unless brevity of calibration is important, you should use the Spiral calibration.

Spiral Calibration

Also known as Smooth Pursuit calibration, this is the standard calibration used in FOVE since v0.17. Prior to that, FOVE used a series-of-fixations style calibration, but it was deprecated and removed in favor of this calibration method.

Advantages of this calibration:

• Because the calibration dot is in motion, the user naturally follows it without instruction.
• Because the calibration captures the eye at a variety of angles and distances, it is more accurate than single point, especially towards the edges.
• Because we take many data points, we can filter out bad data, and thus is very robust.
  • While the user should try to look at the calibration dot the whole time, when the user does look away, those invalid segments are detected and filtered, and instead other sections are used to calibrate.

Disadvantages of this calibration

• It takes longer, and the motion can cause fatigue, especially calibration is run repeatedly.

1 Point Calibration

Sometimes called single-point, this calibration is included as part of FOVE Pro. The user looks at a single point near the middle of the screen for about a second or two, and the calibration is completed.

Advantages of this calibration:

• The shorter calibration time yields a better user experience.
• More users can pass calibration in less time, helpful in situations where you may have many people coming by to use the device, such as a kiosk.

Disadvantages of this calibration

• The accuracy is slightly lower in the center, and reasonably lower towards the edges.
  • Nonetheless, the accuracy may be sufficient for your application.

How is the accuracy impacted? The following heatmaps show the average accuracy across many users, in degrees, for FOVE0, for each section of the screen up to +/- 25 degrees from the center. 

In the center region, both calibrations yield very accurate eye tracker results. As the gaze moves towards the edges, the spiral calibration retains more accuracy than the single point calibration. Averaged across the whole range, the spiral calibration averages about 0.2 degrees better accuracy (as of late 2021).

If you are interested in our benchmarking methodology and how these figures are received, you can learn a lot more from this paper we published at ETRA '21 (the full text is available if you click on the PDF icon).