[...]
The outer surface, shown on Chatham Airport Zoning Plan No. 36-011 86-08, Sheets 1 to 9 inclusive, dated January 28, 1987, is an imaginary surface located at a common plane established at a constant elevation of 45 m above the elevation of the airport reference point, except that, where that common plane is less than 9 m above the surface of the ground, the outer surface is an imaginary surface located at 9 m above the surface of the ground.
[...]