Table 1. Examples of metrics that can be derived from the HIPOP.

Metric	Unit
Instantaneous head pitch angle	°
Rate of change of head pitch angle	°/s
Head pitch angle distribution	°
Head pitch angle amplitude	°
Head pitch angle cycle duration	s
Head pitch fixation angle	°
Head pitch fixation duration	s
Instantaneous head heading	°
Rate of change of head heading angle	°/s
Head heading angle cycle amplitude	°
Head heading angle cycle duration	s
Head heading fixation angle	°