What is the tallest man-made structure around Halifax? Ask students to brainstorm a few ideas. Students might suggest a tall building. Some of the tallest buildings around Halifax are the Maritime Centre 78 m (256 ft), Purdy's Wharf 88 m (289 ft) and Fenwick Tower, the tallest building in Halifax at 98 m (322 ft) tall. Students might also suggest one of the two harbour bridges. The towers on the MacDonald Bridge are 103 m (338 ft) high and the towers on the MacKay Bridge are 96 m (315 ft). The towers on the MacDonald bridge are taller than the tallest buildings in Halifax. An observant student might even suggest the red and white painted smokestacks at the Tufts Cove Generating station. The smokestacks are tall indeed. From the picture below, you can see that the smokestacks are taller than the bridge towers of the MacKay Bridge.
You might ask students how you know by looking at the picture that the smokestacks are taller than the bridge towers. This would be a fun opportunity to talk about perspective.
We can check out the height of the smokestacks by using a little trigonometry.
I found a spot across the harbour from Tuft's Cove to measure the angle to the top of the smokestacks using a clinometer. (My favourite school/education clinometer is the Invicta MK1 Clinometer... not only does it have a cool name, it looks really cool as well!) It was an angle of elevation of 8 degrees. Next I used Google Earth to see that my distance to the centre stack is approx. 1160 metres. So that means tan(8) = x/1160. Solving for x gives us x = 1160*tan(8) = 163 metres. I emailed Emera an they said that the stacks are actually 500 ft. (152.4 m) tall. So I'm about 11 metres off. Not bad considering that at this distance, a variation of 1 degree is about 20 meters. The actual angle should have been about 7.5 degrees vice 8 degrees.
So, how could I minimize the amount of error? As I get farther away, the tangent value gets smaller but the distance that I'm multiplying by gets bigger. At what angle does 1 degree of error create the least amount of difference in the height being measured?
But is this the tallest man-made structure in Halifax? I used to think so, but I was only considering free standing structures. There is a radio transmission tower that is taller but not free standing... the tower has guy wires to hold it up. The CBC radio tower on Geizer’s Hill is even taller than the smokestacks at Tuft's Cove.
So how tall is this tower? I drove up to the top of Geizer's Hill to find out. I found a spot level to the base of the tower at a distance of 475 meters along Washmill Lake Dr. From this spot, my clinometer measured an angle of inclination to the top of the tower of about 23 degrees. 475 x tan(23) = 201 meters (about 659 ft).
A bit of digging led me to a website that stated the antenna height above ground level for the CBC radio tower is 192 m (629 ft). My measurement was only 9 meters different from this height... pretty close. This is so far the tallest thing I've found around Halifax. Let me know if you find something taller!