Another way to measure height is to hold a stick or pencil at arm's length, sighting on the thing you want to measure, moving your thumb along the stick to match the perceived tallness; then rotate your hand to the horizontal, and measure that distance on the ground. Works for stuff of moderate height, such as a tree (is the tree going to hit the house when I cut it down? Answer: It's going to fall the other direction and take out your neighbor's garage). Does not work on tall buildings or mountains or space satellites or the moon. Well, maybe you could use it on a building: how many blocks long is the building's height? How is this information of any use to anybody?
Another thing that can screw you up is parallax. In the woods, we wanted to check out the diameter of a huge red cedar. Larry wanted to stand in front of it and have me determine how much wider it was than his arm span. "Parallax, Larry, parallax," I said.
Have Larry stand on a marked position with his arms out. Move to a position where his fingertips seem to reach the sides of the trunk. Mark your position. The ratio of widths will equal the ratio of distances from you.
At the farm I once dropped a tree on a fence because the ground sloped enough to fool my eyeball estimate of which way gravity would take it. After that, I d estimate by walking around a tree with a plumb bob suspended at arm's length.
In town I wanted to take down a Bradford Pear 22' from the house. It was also 10' from a stop sign, 10' from a street, 20' from another street, 22' from the house, 20' from one tree, 30' from another tree, and 38' from the mailbox. To measure the trunk, I tapped in a nail at breast height, tied a string to it, ran the string around the trunk, marked it at the nail, straightened it, and measured from the mark to the nail: 60". That meant the diameter was 19".
I needed to know the height exactly and reliably. I tapped two marking nails into the trunk, one 6 feet above the other. I backed up to where the nails were 3cm apart on a ruler at arm's length. The tree measured 20.5 cm. I knew now that it was 41 feet tall.
There was no space wide enough for the fallen tree, so I cut off a lot of limbs with a 21' pole saw. Even then, the only place to fell it was straight toward the mailbox. Because my cut would be 5 feet off the ground, I'd have 2 feet to spare.
In the past I'd made slapdash notches and used ropes, cables, or chains when necessary. Now too much depended on precision. I made sure that the back cut aligned perfectly with the vertex of the wedge and that no cut went even 1/4" too deep. I used 4 wedges. I chose a windless day with a fair forecast. As the wedge came down to an inch thick, a squall came out of nowhere. I was pretty scared. When it passed, I felled the tree so precisely that I wished I'd put a can 30 feet from the stump so I could crush it.
I measured and calculated that the squall had been no threat. A wooden hinge offers tons of resistance to falling anywhere except where intended.
