How does RealEye.io compute fixations?
Fixation is a series of gaze points, that are very close in terms of time and space. To determine, whether such a cluster of gazes is a fixation or not, some parameters need to be defined:
- minimum fixation duration,
- noise reduction,
- gaze velocity threshold.
There are all set by default, but you can change them to suits your needs.
Minimum fixation duration is a minimum time of gaze cluster (pause of the eye) that may be called a fixation. It typically ranges from 100 to 300 milliseconds.
Noise reduction using the moving median algorithm is a way to reduce the influence of noise on the actual results. Each point is replaced by a median of a number of points (called noise reduction level). If a noise reduction level is set to 3, that means we calculate a median for three consecutive points. This is how it looks like for X and Y eyes position with noise reduction level set on 21.
To enter this plot, go to an item heatmap, choose one of the participants from the list and you'll see a "Show Fixation Chart" button.