Definition(s)
Limited obstacle sector (LOS)
Limited obstacle sector (LOS) is a sector extending outward which is formed by that portion of the 360° arc, excluding the obstacle-free sector, the centre of which is the reference point from which the obstacle-free sector is determined. Obstacles within the limited obstacle sector are limited to specified heights.
Source: IMO Resolution A.1023(26), Code for the Construction and Equipment of Mobile Offshore Drilling Units (2009 MODU Code), 2009. Global Standards
Limited obstacle sector
Limited obstacle sector is a 150º sector outside the take-off and approach sector that extends outward from a helideck where objects of limited height are permitted.
Source: IMO MSC.1/Circ.1431, Guidelines for the approval of helicopter facility foam fire-fighting appliances, 31 May 2012, International Maritime Organization, Regulatory guidance