Tree height - cruise stick

**dgc** · 09-02-2009, 01:29 PM

I've been looking for a quick/simple way to estimate the height of trees I've been reconnoitering. Using the handy-dandy Google as my guide, I have learned a little about biltmore sticks (timber cruising sticks). I found some pre-made ones online, and I have been thinking they would be a good way to estimate the height of a tree before cutting into it and without having to spend thirty minutes per tree measuring distances and applying pythagorean theorems. Does anybody else have any experience using these?

Also, since the biltmore stick is made to be used at a fixed distance from the tree, I wonder if you could use a laser rangefinder (like on a golfcourse) to quickly establish that distance without having to carry around a long tape measure or measuring wheel in your trunk. Anyone have any thoughts on that?

DGC

**loghousenut** · 09-04-2009, 03:40 PM

I've never used one. I kinda sorta have gotten a fairly rough estimate idea how tall a tree was (or the useable section of it) by using the arms-length-twig method from my old Boy Scout Fieldbook. For accuracy I've had a much better success ratio by cutting one tree down in an area and measuring the rascal while it's on the ground.

What I'm wondering about is this laser rangefinder you're talking about. Why couldn't you get a distance to the butt of the tree and another to the top of the useable part of the tree and calculate how tall the tree is by triangulation?

I'm hoping this is where Peter steps in and tells us how to really do it...

**tgb3** · 09-06-2009, 06:25 AM

I have never used a laser range finder but wouldn't it be more simple to stand at the base of the tree and point the laser to the spot or branch up where you want? No math, just read the range finder.

**loghousenut** · 09-06-2009, 08:12 AM

Never used a range finder either but I'm betting it's a rare tree that is bare enough for you to get a fix from the butt onto just the right branch at the 40' mark. I do like the triangulation theory though.

My Son thinks he knows what he is doing here and he says:
1... Stand a ways away from the tree on the level with the base of the tree. Try to make it work so the tree is fairly straight up and down.
2... Get a range to the bottom of the log that is in that tree.
3... Standing in the same spot, get a range to the top to the log that is in that tree.
4... Square each of those two numbers (multiply it by itself).
5... Subtract the big number from the other.
6... The square root of the answer is the length of your log.

His example is a 3,4,5 triangle:

If you were 40' from the base of the tree and your measurement to the top of the log was 50' then the log would be 30' long.

50x50=2500
40x40=1600
2500-1600 = 900
square root of 900 = 30

The real question is can you program you're cell phone to give you the answer by just plugging in the numbers. Personally, I have figured out how to dial a number if there is a signal.

**Yuhjn** · 09-06-2009, 11:17 AM

Originally Posted by loghousenut

The real question is can you program you're cell phone to give you the answer by just plugging in the numbers.

If your cell phone has a scientific calculator in it, sure!

a = tree length
b = distance to tree base
c = distance to tree top

a = sqrt(c^2 - b^2)

Pretty simple function, any scientific calculator will allow you to do that.

If you use an iPhone I can write an application for you that you can download in the appstore.

And actually if you like we can continue this discussion into solutions when the angle at the base of the tree is NOT 90 degrees. It's slightly more complicated but still quite easy for anyone with a basic understanding of algebra to understand.

**dgc** · 09-06-2009, 04:21 PM

All that math is what the Biltmore stick is made for. It has pre-measured segments for the estimation of feet. As I understand it, you can make your own with custom segments (to pick how far out you want to stand from the tree), or you can buy the pre-built stick and stand the prescribed distance from the tree for the pre-set scale on the Biltmore stick. The prescribed distance was where I wondered whether it would save time to use a rangefinder.

To do all that math, you have to measure out the distance from the tree, then calculate the angle using a separate instrument, then do the math. Biltmore sticks save you from doing the math and the angle calculation, but you still have to measure the distance from the tree. I'll get a Biltmore stick and tinker around with it to see how it works out.

DGC