The Plumb line method.

A few weeks ago, I put together I put together an article for Torontoist on Toronto’s geographic centre. With the help of Marcel Fortin, a GIS librarian at the University of Toronto and a GIS program called ArcMap, we determined that Toronto’s exact geographic centre is at 33 Wanless Crescent, a quaint, English-style style house in Lawrence Park.

In the article, I go into quite a bit of detail about Fortin’s method, but I thought I might talk a little bit more about the cut and paste methods that I used.

1) The plumb line method [PDF]:

How to:

1. Cut out the object you want to find the centre of mass for.
2. Using a pin make three small holes at three random locations long the edge of the object.
3. Attach a string with a weight on the far end and hang it from each point, one at a time.
4. Trace each path the string forms.
5. The point where the lines intersect is the object's centre of mass.

This method produced almost the exact same results as the computer program, which surprised me, as I wasn’t convinced of the accuracy of the map I was using, and my cutting job was less than stellar (take a look at the Toronto Islands). Oddly, this didn't really have much of an impact on the final result.

2) Balancing Method:

How to:

1. Cut out the object you want to find the centre of mass for.
2. Cut out a equal sized piece of cardboard and glue it on the back.
3. Balance the cut-out on a pencil, or another point object until you find its centre of mass.

This is method that Londonist used (one of Torontoist's sister sites, and the inspiration for this project). I tried this method twice, and got two different results—most likely the result of my poor cutting around the Toronto Islands.

Photo by Stephen M.