Canadian Aviation Regulations

601.23 (1) For the purposes of this Division, any building, structure or object, including any addition to it, constitutes an obstacle to air navigation if

• (a) it penetrates an airport obstacle limitation surface as calculated in accordance with Chapter 4 of the document entitled Aerodrome Standards and Recommended Practices, TP 312E, published by the Department of Transport;

• (b) it is higher than 90 m AGL and is located within 6 km of the geographical centre of an aerodrome;

• (c) it is higher than 90 m AGL and is located within 3.7 km of the centreline of a recognized VFR route, including, but not limited to, a valley, a railway track, a transmission line, a pipeline, a river and a highway;

• (d) it is higher than 150 m AGL; or

• (e) in the case of any catenary wires crossing over a river, any portion of the wires or supporting structures is higher than 90 m AGL.

(2) For the purposes of subsection (1), an addition to a building, structure or object includes any vertical mast, pole, tower or other object erected on top of the building, structure or object and adding to its height.