Table 1.

Average Target Localization Error (TLE) of external and internal landmarks as measured by 3 different observers.

Measurement Points	Average TLE (mm) ± SEM
	Observer 1	Observer 2	Observer 3
Left earlobe	4.32 ± 0.25	5.69 ± 0.10	4.89 ± 0.11
Left lateral canthus	6.18 ± 0.36	1.65 ± 0.015	4.70 ± 0.17
Midpoint maxillary central incisors	9.23 ± 0.53	2.31 ± 0.05	5.98 ± 0.04
Midpoint maxillary central incisors	1.72 ± 0.10	2.04 ± 0.03	4.19 ± 0.17
Right earlobe	8.22 ± 0.47	4.13 ± 0.11	3.89 ± 0.19
Left IAC	7.65 ± 0.44	7.50 ± 0.06	7.04 ± 0.13
Right IAC	7.87 ± 0.45	9.50 ± 34	12.3 ± 0.15
Total Average	6.46 ± 0.37	4.69 ± 0.10	6.14 ± 0.14