La. Admin. Code tit. 55 § III-1102
Basic Plane-a plane through the centers of the right and left external ear openings and the lower edge of the eye sockets (§1131. B Figure 1) of a reference headform (§1131. C Figure 2) or test headform.
Helmet Positioning Index-the distance in inches, as specified by the manufacturer, from the lowest point of the brow opening at the lateral midpoint of the helmet to the basic plane of a reference headform, when the helmet is firmly and properly positioned on the reference headform.
Mid-Sagittal Plane-a longitudinal plane through the apex of a reference headform or test headform that is perpendicular to the basic plane (§1131. D Figure 3).
Reference Headform-a measuring device contoured to the dimensions of one of the three headforms described in §1131. F -M. (Table 2 and Figures 5 through 8) with surface markings indicating the locations of the basic, mid-sagittal, and reference planes, and the centers of the external ear openings.
Reference Plane-a plane above and parallel to the basic plane on a reference headform or test headform (§1131. C Figure 2) at the distance indicated in Table 2.
Retention System-the complete assembly by which the helmet is retained in position on the head during use.
Test Headform-a test device contoured to the dimensions of one of the three headforms described in §1131. F -M (Table 2 and Figures 5 through 8) with surface markings indicating the locations of the basic, mid-sagittal, and reference planes.
La. Admin. Code tit. 55, § III-1102