When requested by the FAA :
– Any construction or alteration located on a public use airport or heliport regardless of height or location .
Part 77 also identifies the height at which an object may be considered an obstruction at a designated distance :
§ 77.17‐ Obstruction standards .
( a ) An existing object , including a mobile object , is , and a future object would be an obstruction to air navigation if it is of greater height than any of the following heights or surfaces :
( 1 ) A height of 499 feet above ground level at the site of the object .
( 2 ) A height that is 200 feet above ground level or above the established airport elevation , whichever is higher , within three nautical miles of the established reference point of an airport , excluding heliports , with its longest runway more than 3,200 feet in actual length , and that height increases in the proportion of 100 feet for each additional nautical mile from the airport up to a maximum of 499 feet .
( 3 ) A height within a terminal obstacle clearance area , including an initial approach segment , a departure area , and a circling approach area , which would result in the vertical distance between any point on the object and an established minimum instrument flight altitude within that area or segment to be less than the required obstacle clearance .
( 4 ) A height within an en route obstacle cle including turn and termination areas , of a F approved off‐airway route , that would incre obstacle clearance altitude .
( 5 ) The surface of a takeoff and landing are any imaginary surface established under § 7 77.23 . However , no part of the takeoff or la be considered an obstruction .
( b ) Except for traverse ways on or near an a operative ground traffic control service furn traffic control tower or by the airport mana coordinated with the air traffic control serv paragraph ( a ) of this section apply to traver be used for the passage of mobile objects o of these traverse ways are increased by :
( 1 ) 17 feet for an Interstate Highway that is System of Military and Interstate Highways are designed for a minimum of 17 feet verti
( 2 ) 15 feet for any other public roadway .
( 3 ) 10 feet or the height of the highest mob normally traverse the road , whichever is gre road .
( 4 ) 23 feet for a railroad .
( 5 ) For a waterway or any other traverse wa mentioned , an amount equal to the height object that would normally traverse it .
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