For the purpose of these rules, the airport hazard areas shall be divided into the following zones:
Each zone shall be the ground area underlying the airport imaginary surface described in §§ 19-12-5 and 19-12-6, i.e. the horizontal zone shall be the ground area underlying the horizontal surface; the conical zone shall be the ground area underlying the conical surface; etc.
Haw. Code R. § 19-12-4