# Tag Archives: trig

## Felling a tree at 100 degrees F is insane…

but relying on a homemade surveying device and distant memories of trigonometry might take this over the edge.

Last year something has come through Kansas killing a ton of pine trees. Our problem is that one of these is pretty close to the house and the dead branches have begun to droop so low that they scrape the car when we drive under it. That’s a problem by itself, but then there’s the fact that the branches have become so brittle that I really worry about it toppling over onto us, our cars or the house.

With that in mind I decided that it had to come down. The strategy was to tackle the problem head-on first thing in the morning. I started by removing all the lower branches (I would have kept going, but I could feel the sway of the tree and I kept thinking…’brittle.’ So, I didn’t finish off the top.

Oh, right – I forgot to mention that a couple weeks ago someone broke into our garage/shop and stole my chainsaw, so this whole process is being undertaken with just an axe and bow – saw.

Once the lower branches were off, it was decision time. The last tree I took down I took off the branches and then the top of the tree before chopping down the trunk. It was a pretty scary process, because high in the tree I cut the top and despite all my efforts, the top came down in a way that hit both me and the ladder I was on pretty hard. This time around, I was remembering that clearly while deciding on my next step.

My solution was that I needed to get a good measurement of how tall the tree was to know if it was even safe to bring it down all in one piece or if I just needed to face the prospect of knocking myself off the tree or otherwise hurting myself. But how to measure this?

That’s where high school trig came to mind.

The tangent of an angle equals the opposite over the adjacent sides. So, if I could measure the angle to the top of the tree from any point a known distance away, then I could compute the opposite side (the height of the tree).

How do you measure angles? With a protractor – damn, I don’t have one…. but I can make one!!

Then I need to be able to sight my angle…how about using a straw as a sight?!? And from where on the tree am I measuring the height? I wanted to use a laser pointer, but that didn’t work, so I just sighted that as well.

Here’s the device I used in the hands of my helper:

tan 25 = tree height / 726″

tree height = about 9.5 yards

I worked for about three hours with a lot of breaks in the shade, but I’m still not finished. I hope it’s safe until tomorrow morning when it’s cool again.