Markings

Where an object, regardless of its height, has been assessed as constituting an obstacle to air navigation as per subsection 601.23(1) of the Canadian Aviation Regulation (CARs), it requires marking and/or lighting in accordance with the standards specified in CAR Standard 621.

Day marking of obstructions that are 150 metres above ground level (AGL) in height or less, such as poles, chimneys, antennas, and cable tower support structures, may consist of alternate bands of aviation orange and white paint. A checkerboard pattern may be used for water tanks, as shown below. Where a structure is provided with medium or high-intensity white flashing strobe lighting systems that are operated during the day, paint marking of the structure may be omitted.

Suspended cable spans, such as power line crossings, assessed as being hazardous to air navigation are normally marked with coloured balls suspended from a messenger cable between the tops of the support towers. The support towers are obstruction painted. When painting the support towers is not practical, or when additional warning is necessary, shore markers painted international orange and white will be displayed. In some cases, older marker panels that have not been updated are of a checkerboard design.