Have you ever wondered what method is used for measuring the Bruce Trail length?
According to the Bruce Trail article in Wikipedia, the length of the Bruce Trail is 885 km. We know that the length of the Bruce Trail varies over time due to re-routes, so how is the length is actually measured? Satellite photos? GPS? Perhaps someone walks the entire length with a measuring tape? (That would have to be a long measuring tape!)
I was curious about this myself, so I reached out to Scott Langley, GIS Cartographer for the Bruce Trail Conservancy.
This is what I learned from Scott:
When I first started working at the BTC ten years ago we were still measuring the trail with a measuring wheel. It was a custom made bicycle wheel which was easier to maneuver on the terrain. Please see the image attached.
Since 2004 we have been using GPS technology to capture the detailed route of the Bruce Trail. It took awhile to capture the entire Main Trail and Side Trails but it’s all GPS’d. When there is a reroute, we again use GPS technology to capture the new trail segment. The new GPS data is brought into my mapping system and the horizontal distances are measured for each segment within my geographic mapping system which is known as GIS (Geographic Information System).
GPS technology is not 100% accurate. In my experience the data location can swerve in and out up to a gross maximum of approximately 10 metres depending on the conditions. Between 2 to 5 metres is the general norm. In some cases, with the help of the GPS data as a guide I then use aerial photography to clean up some of the routes by screen digitizing the trails (or portions of) if the trails are evident on the aerial photography and don’t exactly match the GPS track.