How can I measure tree height?

[chep]

The most accurate way to measure is to go to Treebuzz.com and put up a post that offers any arboristin hte area to come climb your trees and drop a tape from the top. That is definetly the best way to get a height. If these trees are as big and neat as they sound, I am sure that some squirrel would love to be part of a measurement mission. You can always offer them cold refreshments once they are done.  If I lived near ya I would be up those trees asap!
Good luck with the math

chep

[Dodgy Loner]

Here is a visual demonstration (not to scale) of why my method is better.  It gives you the same results as SD's method, with no math.  It is based on similar triangles, a fundamental principle of geometry.

[SwampDonkey]

It's actually the same as my method 1. However in mine the math I typed is simply the proof, just to show it's not necessary at all if 45 degree angles are used. Only requires adding the horizontal distance from the observer to the tree to the height from the ground up to the horizontal distance line. Your using a fixed angle of 45 degrees which has a tangent of 1. Your forming an isosceles triangle (two angles and two sides equal). Just have to make sure it's dead level.

[jeffreythree]

If I hold my yard stick at the 27" mark because my arm is holding it 27"s from my eye, I will be achieving the same measurement, right?  And then I would need to make sure my arm is perfectly level so I am measuring straight up the tree, and add the height of my arm to the distance from the tree?  I tried Kevin's tree height gauge, but I managed to mangle it in transit to my place.  Or maybe the state forester finally coming out next week for my free state forestry plan has a clinometer and doesn't mind a few minutes measuring a tree or 2.

[SwampDonkey]

Not precisely, you need to measure at eye level or add the height from shoulder to the eye onto that vertical stick. Everything has to be level both horizontal and vertical. Stand back until top of stick sites on tree top. Your arm is level and the vertical stick is level (up and down). More accurate with a square and a level. This assumes you or flat ground like in my pictures. On a strong slope, for example, horizontal distance from the observer eye could be 10 feet up the tree or 5 feet below, depending if your up or down hill on the slope from the tree. Neither position you can directly measure because they are out of reach, unless in short segments of measuring horizontal distances and add them up or use slope correction by finding the angle of the slope line, find it's COS and mult. by slope distance measured.

[jeffreythree]

Well,  I am going out to try both the angle and stick methods this weekend.  Evidently the old Texas nutmeg hickory champ last measured in '74 is no longer around and the new one is smaller than my tree and mine may score bigger than the national champ .  I measured 84" circumference and it has a good crown spread.  I will get pics.

[pappy19]

I measured thousands of trees on a 2 year contract job for a large land excahnge between the USFS and Boise-Cascade using an angle guage and a Sunto. With heights, the most important thing was to use a steel tape and measure to your eye. A cloth or nylon tape will stretch and will be inaccurate. On the check cruisers from both FS and B-C, I was in the 98%. They all used a Relascope.

[Beweller]

With a clinometer measure the angle to the base of the tree.  Take one-half of this angle and add it algebraically to 45 degrees.  Move toward or away from the tree until the top of the tree sights at this angle.  Re-measure the angle to the base of the tree and if the angle has changed, repeat the procedure.  Rarely will you have to do this more than once.  The slant distance from the tree to your eyeball is the height of the tree.

Many methods require you to be standing a known distance from the tree.  This can be established with a prisim or gap gage.  For example, with a 10-to-1 prism or gage, when the tree just fits the prisim or gage,you are 33 diameters from the tree.  Walk up to the tree and measure the diameter and you have the distance.

[SwampDonkey]

With a clinometer measure the angle to the base of the tree.  Take one-half of this angle and add it algebraically to 45 degrees.  Move toward or away from the tree until the top of the tree sights at this angle.  Re-measure the angle to the base of the tree and if the angle has changed, repeat the procedure.  Rarely will you have to do this more than once.  The slant distance from the tree to your eyeball is the height of the tree.

Yeah, that will work assuming your on constant slope. Might be the quicker method for sloped ground in some instances, assuming your not standing on a bench/ground break in the hill. Or the hill isn't like a cow bell.
 

Many methods require you to be standing a known distance from the tree.  This can be established with a prisim or gap gage.  For example, with a 10-to-1 prism or gage, when the tree just fits the prisim or gage,you are 33 diameters from the tree.  Walk up to the tree and measure the diameter and you have the distance.

Horizontal distance yes, not slope distance. Known as Limiting Distance of the tree.

[Beweller]

Swampy,  No.  Using the prism or gage returns the distance along what ever your line of sight is.  If you sight on the tree at your eye height, it gives the slant distance (including the special case where the slant angle is zero).

Note that this eliminates the problem of un-even slopes, mounds or gulleys, between you and the tree.

[SwampDonkey]

Ah, yes true. Hopefully you can reach up to where the gauge hit the trunk to measure the diameter when there is a hump in front of the tree.

[jeffreythree]

I just wanted to thank everyone on this matter.  Finally got the nutmeg hickories measured, both beat out the 160 point state champ with the bigger at 68" circumference, 91' height, and 45' average spread for 170 points.  The other is 168 points.  Now if I could just find the 84" circ one again.  Now I need to go fill out that entry form .