Way OT:measuring tree height

Got a question for the math gurus! I have a 130 (+ or - a few) year old oak tree in my yard that needs to come down and I'm trying to remember how to measure the height (without climbing of course!). Seem to remember something about using a pencil/wooden dowel of a certain length at arm's length/eye level and stepping back until you see the top. Any body here know about this? If it's not too cost prohibitive, I'll rent a boom lift(I am certified to use one) and take all the limbs off myself and get a friend to take the trunk down. thanks!

If you are able to bend over far enough to look between your own legs then do that while walking away from the tree. When you can see the top of the tree from between your legs, the distance you are from the tree is equal to the tree's height - plus or minus a couple of feet.

Tangent of the angle to the top times the distance to the tree.

Or (same thing) drive a pole into the ground then back up so from ground level the top of the pole appears at the top of the tree. Proportion of your distance to pole to tree is the same as proportion of pole height to tree height.

Google 'tree height'. Plenty of answers.
Richard in NW SC

We had a calibrated stick for this while working on forestry in the FFA.

Of course that was 33 years ago and I haven't seen one of those sticks since. Would be a handy thing to have though.

Yeah, but don't let anyone see you doing that.

(quoted from post at 16:26:24 04/06/14) Got a question for the math gurus! I have a 130 (+ or - a few) year old oak tree in my yard that needs to come down and I'm trying to remember how to measure the height (without climbing of course!). Seem to remember something about using a pencil/wooden dowel of a certain length at arm's length/eye level and stepping back until you see the top. Any body here know about this? If it's not too cost prohibitive, I'll rent a boom lift(I am certified to use one) and take all the limbs off myself and get a friend to take the trunk down. thanks!

Click to expand...

You may be thinking of a Biltmore Stick, although a Biltmore Stick also calculates how much lumber is in the saw logs but you can just use it to measure total height. Here is a link showing what measurements to mark on a stick

http://www.beaconlearningcenter.com/documents/2460_01.pdf

Check out page 2. Have someone measure the distance from your eye to where you naturally hold a stick at arms length. Pick the right distance on the right side of page 2. Make marks on a stick. Stand back 66 feet from the tree. Line up the base of the stick with the base of the tree and read the marks to tell you how tall the tree is. Teach a kid or grandkid what and how you are doing this, it’s a great lesson in math and for them to not just shrug their shoulders and hire somebody.

I keep 66 feet of string wound up on the stick so I always know where it is and don’t have to look for a tape measure. I made my mark for the base of the tree up a little on the stick and labeled it, and then if the stick wears, it’s still accurate. I also split the distances marked on the stick so instead of only 16 foot saw log measurements, I have 4 foot increments, that’s close enough for me but you could split it up smaller if you want. Good luck.

It Works.

On a nice sunny day, and the tree has a defined shadow, take a stake and put it in the ground so that one foot of it is above ground. Now measure the shadow from the stake. If the shadow is lets say 10", then one foot equals 10". now measure the shadow from the tree and you will know the height of the tree.

Only if you are looking at the tree at a 45 degree angle, think about it for a minute.

Might need a friend to help a little, but it's pretty straight forward. Measure the length of the pencil(call it p) and the distance from your eye to the pencil (we'll call this a) in your outstretched hand. Now step back until the pencil appears to be the same height as the tree and measure from your eye to the base of the tree(call it d). Then the ratio of arm length to pencil length is the same as the ratio of distance to the base to height of the tree(h).

a/p = d/h

As an example, let's say the pencil is 10 inches and you hold it 30 inches from your eye, then step back 120 feet from the tree.....

30/10 = 120/h would give you a tree 40 feet tall.

There's an easier way if you know a little trig. Simply measure the distance to the base of the tree and the angle of elevation to the top of the tree. h/d = tangent of the angle so if you multiply the tangent of the angle times the distance to the tree, you get the height of the tree.

If you were able to bend over far enough to put your head on the ground, it would be 45 deg. That's why this method is not 100% accurate but it will work for most applications.

Cut it down then measure it. Stan

You could be 100% right, Only ever tried it one time, Next time I tried it 40 years later I couldn't bend over far enough! Was perfect the 1st time.

Similar triangles. I second the shadow rule. You can do it with your shadow if ya know how tall ya are.

I was told to grasp a yardstick at the 1' mark and hold it at arms length. Face the tree and back up until you can see the base of the tree and the top of the tree in the length of the yardstick. At that point the top of the tree should land where you're standing.
I was skeptical but tried it. That method was within 18" of where the top of the tree actually landed.

Read The Musgrave ritual, by A cannon Doyle. It uses the shadow method, below...