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

Spiral Calibration

Also known as smooth pursuit calibration, this has been the standard calibration method used in FOVE since v0.17. Prior to that, FOVE used a series-of-fixations calibration, but it was deprecated and removed in favor of this newer calibration method.

Advantages of smooth pursuit 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 toward the edges.
• Because many data points are taken, any bad data can be easily filtered out, resulting in a robust calibration method.
  • While the user should try to look at the calibration dot the whole time, if the user does look away, those segments are detected and filtered out. The other sections will be used to calibrate instead.

Disadvantages of this calibration

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

One 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 method:

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

Disadvantages of this calibration method:

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

How much is the accuracy impacted? The following heatmaps show the average accuracy in degrees across many different FOVE 0 users. Measurements were taken for each section of the screen, up to +/- 25 degrees from the center.

Smoot Pursuit Calibration

One Point Calibration

In the center region, both calibrations yield very accurate eye tracker results. As the gaze moves towards the edges, the spiral (smooth pursuit) calibration retains more accuracy than the one point calibration. 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 were taken, you can learn more from this paper we published at ETRA '21 (the full text is available if you click on the PDF icon).