Estimating Tree hieghts??

[Shane]

I am a little geeky when it comes to these things but mathematical way of working it out is pretty straightforward.

 

Imagine a triangle (lets assume the tree is pretty much upright/without lean). You want to know the height side of the triangle or the 'opposite'. What you can easily work out from the ground is how far away from the tree you are standing by pacing backwards. This gives you the 'adjacent' length. From the the point you are standing you measure angle by eye between the base of the tree and the tip. Just use a simple 99p school protractor and a bit of string/pencil. Then using a calculator type in the angle you measured then press 'tan'. You then multiply this number by the distance you are standing from the tree. Add on your own height and you've got a roughly calculated height of the tree.

 

So as an example - I pace 20 metres from the base of a tree. I hold the protractor flat at my eye level and look at the top of the tree. Lets say the angle is 50 degrees. type in 50 press 'tan' gives me 1.91 which i times by the 20 metres giving 23.8 meaning, I am 1.94 so add together you get a tree that is 25.8 metres tall. Sounds complicated but you can do it in a minute.

 

This calculation is based on a right angle triangle but it will give you a pretty accurate figure. If you are on a significant slop the maths starts to get a bit trickier.

 

The point for most of us is - If you cant walk back far enough to get a 45 degree angle, you aint got room to fell it.

[Lucan]

I'd recommend the clinometer made by Suunto. Bit pricey but a great piece of kit. Gives more accurate and reliable readings than holding a stick, especially when dealing with trees on gradients.

 

If money is no object you can buy clinometers with inbuilt lasers that measure the distance to the tree, angle, height for you . These are more for suited to when you are needing to measure hundreds of trees a day though.

[hedgesparrow]

If I followed the method given here, wouldn't it depend on the length of the stick? If it was a two foot stick I'd end up further away than if I used a three foot stick, wouldn't I?

 

Maybe I'm missing something. The way I was taught in the scouts was to get a stick walk back until the stick ends were level with the base and the top and then spin the stick to the horizontal, keeping the bottom end still in line with the base - thus forming a right angle triangle - note where the end of the stick appears on the ground and then measure or pace it off.

 

the stick is from your shoulder to your wrist. then with it upright you get top of tree and bootom of tree together were you stand it should fall not bomp proof but it worked with a ceder we dropped. out by a 1inch

[csservices]

Way I do it is to hold my arm out and bend it upright at the elbow with your fingers outstretched upright now walk backwards til your fingertips are level with the top of the tree then if you swing your arm over in the direction you want to fell it your finger tips will line up with where the top of the tree will end up, give or take a couple of feet.

[countrryboy]

I wish i put this question up 3 days ago, :lol:had 3 douglaus firs climbed and preped for knocking the tops off but needed some extra help to rig and lower them.

 

Knocked the 3 over full hieght tonite in no time, left a bit of polyprop up so could pull my rope over and tifor'd them down. Landed exactly where i thought and where the method said too.

 

Without going into deep maths and protarctors etc, if ur stick is same length as ur arm then that gives u 2 sides of the equal length on a 90 degree small triangle, so meaning the big triangle ie tree hieght (vertical) and the distance to u (horizontal) should also be equal length.

 

A few of the later replies have confused me a wee bit, but i'm over the moon with the stick method as u can never forget it and confident it works.

 

Up till now i have alo just guesstimated how many men(6ft) or a smaller tree as more accurate on smaller trees and its worked fine

But when u get u to 50-60ft u only have to be a man or 2 out and ur 12ft out, couple off the trees have been pushing 100ft and a few of the big 1's will have been over it (ran out of climbing rope on 1) and the space has been quite tight.

 

Cheers again folks, must admit when i was a kid sure it was only a 8-10 inch stick and u had to add ur hieght but very happy with the biger stick approach, nice and simle and it works

[Bren.]

Suunto clinometer.

Easy.

[penfold]

Impulse laser. Again pricey but does all the work for you and pretty accurate too (0.3m at 200m iirc)

[oldwoodcutter]

Well the old fc cutting boys had a much simpler way,ive seen them walk away from the tree and bend down and look through their legs,and when they could see the top tips of the tree through their legs they stopped and dragged a heel on the ground,and after it went over those tips would be on his boot mark. Those old boys all gone now.

[slack ma girdle]

hold your arm at 45 degrees, walk back until the top of the tree is visable by your fingertips, add a couple of feet, and that will be where the tree will fall. (Unless you mess up the hinge)

[mdvaden]

Easy --- Easy !!

 

But if $2800 (US) is too much, same company makes one for about $700 or less if you look for used.

 

Got it for exploring coast redwood forests, but also use it for dropping small trees that don't need climbing, when I want to approximate where the top will land.