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Word of the Month – Viewshed

By Ian Brown, Editor

June 2021 – This is probably a new word to all of us. Transport Canada recently sent out circular AC 601-006 titled VIEWSHED ANALYSIS FOR AIRCRAFT DETECTION SYSTEM (ADS). Unless you've been following this more closely than I have, you'll be interested to know that this is all about automated lighting systems for wind farms. Viewshed analysis attempts to resolve the risks associated with the design of automated lighting systems, turned on by sensing approaching aircraft with radar. The problem of always-lit nighttime lighting on wind turbine towers and the environmental problems associated with sometimes very bright lighting invading people's bedrooms while they're trying to sleep is somewhat mitigated by these systems.

Viewshed analysis is the idea that you use an analysis tool to look at the geography and figure out if certain approach areas around a wind farm could be masked by surrounding terrain. Flatlanders may not need to worry too much about this, and it's unlikely to see wind farms in the high Rockies, but there are certain areas like Quebec and Ontario that have pop-up mountains that would certainly shadow a radar looking for approaching aircraft. The Viewshed analysis is an attempt to examine the radar shadowing risk and calculate the resolution of this by raising the radar or installing another radar.

Avoiding collisions with wind farm turbines is certainly more of a concern for GA than for commercial traffic, though fortunately we don't have to get into the lighting design process that this AC addresses.

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