How do you measure the height of a tree?

[stickbilt]

 My 12 year old daughter and I are planning on making a map of our 5 acre lot to plot the trees that we have growing. It's sort of like a long term science project. We will measure maybe fifty trees of various height and diameter and monitor the growth over the years. She thinks it's a cool project and is very interested in math(has to be some geometry here). Who knows, maybe our map will be in the hands of my great grandchildren some day.
 How do you measure the height of a tree? When you have a timber survey done does the person doing the survey eyeball the length of logs in a tree? Who typically does a timber survey? I'm guessing a forester. Any help for our project would be appreciated.        Thanks, Stickbilt

[Frank_Pender]

Dad and doughter.   The most accurate instrument used for measureing tree heights is the hand abney, either with a scale for measuring the vertical angle or below the horizontal.    But, I suspect that this tool is a bit out of most peoples league and expense accounts.  Therefore  I have a much easier method for you to practice you different forms of math skills.   The Merritt hypsometer is similar in principle to the Biltmore stick, and the two are usually placed on a single stick of wood (like a yardstick in width andthickness) to form what is commonly called the "cruiser's stick".  The hysometer was devised ti measure the tree heights.   This system was designed to measure heights based on 16' log lengthfrom a distance of 1 or 1 1/2 chains.  ( a chain is is 66')  There are two sets of graduations, one is for each of the two distances.  In measuring tree heights, the hypsometer is used as follows:   1.  Chain off or pace off a distance of 1 or 1 1/2 chains from the base of the tree.  the taller th tree, the greater is distance.     2.  Hold the stick vertically  and at arms length with the zero-end down, and the graduations towards the operator.  3.  Raise or lower the bottom of the stick until it intercepts the line of sight from the eye to the base of the tree.  4. Without moving your head, sight down to the point on the tree to which the height is to be measured and notice where the line-of-sight intercepts the stick.  The gradduation on the stick at this point is the tree height.    You might want to check with you local extension service for a location of a "stick".   good luck

[Jeff]

Making and Using
 A Biltmore Stick

[Frank_Pender]

  Thank you Jeff.  A picture is worth a 1000 words.  I can lay a tree on an dime and give you 9 cents change if you want but I have not mastered this machine to place things like that on it to get my messages out there.  Perhaps one day.  Anyway thank you for you help, for the youngin and her father.      : :P                                                                                                                                                                                                        Frank

[Bibbyman]

Well,  you could cut the trees down and measure how long they are.  But that would only work once.  ;)

 ::)You could stand a yard stick vertical and measure the distance of the shadow it throws.  Then measure the distance of the shadow of the tree makes,  Using something called a formula,  you could figure out how tall the tree was.  'Course,  you'd have to do this when there was a shadow to measure and at nearly the same time.

 :P

[Ron Scott]

The Biltmore stick is an easy and reliable way and would add to the experience if you make your own. There are instruments to use for increased accuracy such as abney level mentioned, hypsometers, Spiegel Relaskop, etc., but they are expensive for limited use.

Biltmore Sticks can be purchased from Forestry Suppliers at a cost of $48.50 each plus shipping. I have a source that make mine for $18.50 if someone needs one. I guess shipping would be extra.

I go through a few each year in productive timber cruising, break them, leave them behind, lose them, run over them, the logger talks me out of one for his use, etc., so I go the cheaper route. They just don't have the fancy brass ends, but hold up well under normal use.

[swampwhiteoak]

I usually eyeball heights when I'm cruising.  Maybe I'll take a few height measurements to make sure my eyes are working like they should  ;).

If you're interesting in total growth and maybe updating 5 or so years later, I'd recommend using a diameter tape.  It will take a bit longer, but you will be able to record increased growth in a relatively shorter period of time.  Using a biltmore with 1 or 2 inch size classes, you might not notice a measurable difference in a short period of time.

Another advantage of doing it this way is you can record more accurate volumes for individual trees.  That way, if you do any crop tree release management, you can record the individual growth rate differences between those released trees, and unreleased trees.  I've got a landowner I work with that is an engineer (loves the math) and he does all kinds of comparisons in growth related to species and crown sizes on his small woodlot.  If he just used a biltmore, he wouldn't get the kind of accuracy he needs to show these changes.

If this is strictly a one-time thing and you're looking to get done quickly, use the biltmore/merritt hypsometer combo.  

[Ron Scott]

Yes, for needed accuracy to measure growth rate on an annual basis use a diameter tape. The Biltmore stick is not as accurate here for checking growth rates on a regular basis.

I use both Biltmore stick and diameter tape in cruising depending upon the cruise design, sample etc. I also use a 100" measuring stick to keep my eye accuracy in determining product tree heights.

[Jeff]

Ron, is this the same guy that makes the fold down sticks like we use for measuring cords on the trucks? Works for Weyerhauser?

[woodmills1]

hey stickbilt when ya come over to visit bring your daughter and i will teach you both how to make both of the measuring instruments like i do my science students. :P that wood be woodmills the teacher speakin :D

[Ron Wenrich]

I've always eyeballed my heights, as well.  If you are looking for volumes, you must get use the number of logs in a tree.  A log is 16' in length.  You use only to the nearest 1/2 log.  

A tree that has 24' of merchantible timber would be 1 1/2 logs high.

Don't estimate limb wood in your volume estimate.  Many times they will break during felling, and give you an unrealistic volume.

Typically, foresters do surveys.  But, most landowners never have this done.  

On 5 acres, you probably could measure all of the trees.  Foresters often use point sampling.  It is a method of taking plots to come up with a represntative sample of the entire forest.  Usually, only 10-12 trees would be measured per plot.

After combining the data, you can have a pretty realistic idea of the volume, the number of trees, species, and size distribution.  From that, you can do some pretty good management work.

If you're interested in point sampling, try this link:

http://forestry.about.com/library/weekly/aa121398.htm?once=true&;

It is an article I wrote on point sampling for another web site.  It is a 3 part series.

You have any problems with your project, just give a holler.

[Ron Scott]

No Jeff, this is a professional wood worker and builder here in Cadillac, a retired Forest Supervisor.

[stickbilt]

You guys are awesome. Wait till my daughter sees all this information. She'll be tickled pink. This is going to be great project for the two of us. We both are getting an education here. I'll have to get her on here to thank you guys.

 Thanks a million(fbm),  ;D Stickbilt

p.s. She has really seen the light on how important math is in everyday life. We got into a big conversation about pi (3.141...)
last night and we ain't talkin' apple. :D

[Don P]

Its good to hear math interests her. It was hard for me to see the practical application of alot of what they were attempting to teach us. Too bad you couldn't frame a roof while doing geometry :D.
One instrument that you may have came to mind...Gotta transit?

[stickbilt]

Hi Don,
 I have what "I" call a transit. It is an old Sears model that used to be my stepfathers. I use it occasionally to shoot grades but beyond that I don't know how to use it. It does have the ability to tilt with a scale for degrees. I can almost visualize using it for measuring the height of trees. If I tape off a distance from the tree and set it up. I will think of it just like framing a roof. I'm no genius with algebra so it would be easier if I had say, a 45 degree angle.
 
The distance from the base of the tree = run
The angle of the transit when pointed at the top = slope
The distance the transit is off the ground = add to final # (?)

I might need a little help here. Do you have a simple way to figure it?  Stickbilt

[Roger_T]

Hi Stick,

I believe what you are asking for is Trigonometry.  Just been sitting here brushing up on my trig since reading your post.  

This should be your equation,

Tan (whatever the asmuth on the transit says, ie: 60degrees)=X divided by known distance from tree

Tan 60*= X/known distance

So using the Tangent tables

Tan 60* =1.735

Lets say known distance to your transit is 100 ft.

So your equation now looks like this  

X = 1.735 x 100

hence  x = 173.5 feet tall  now add in the height of the transit, approx 5 feet.

tree now equals 178.5 feet

Now if this is clear as muddy water, you got one up on me....  hadda go to my sons for help on this one.  but seriously, get a copy of a basic highschool or college math book that has trig equations in it and have a ball.  Who knows, you might be creating another Einstein!!

 8) 8) 8)

Roger

I really absorbed math in school, usually by havin my head firmly planted on the textbook. ???

[Gordon]

Go figure, I just climb the tree and drop the tape measure down. :D :D :D

I do like the transit idea, never even thought of that. Might be a pain to haul around in the woods but, using it for a tree here and there would be great.

Gordon

[John_Boisselier]

Train up those kids and make them practical  ;D with common sense  :P and they may actually get somewhere in this deficient society of ours and maybe even have a real sense of humor   .    A simple way to get approximate heights of trees without going to any expensive instruments or a biltmore stick is to make a simple gauge mark at a known height on the tree (say approximately 6' or so), walk away from the tree to a spot that is in the ballpark range of the height of the tree. Turn around and hold a scale of some kind up in front of you about arms length so that the bottom of the scale is sighted to the bottom of the tree.  Note what mark on the scale is sighted against the gauge mark on the tree, and what mark is sighted against the point on the tree that you want to measure, divide the first measure into the second and multiply times the known height of the guage mark with the resulting figure being about as accurate as your arm stability and eyesight will permit for a fair estimate of tree height.  Another mechanical/mathematical means is by relationships.  Take a string, stick, etc  and from about the same location as above sight out the optical positions of the base of the tree and the top of the tree.  At the same distance from your eye tilt your measuring device horizontally and sight out the same distance on your scale along the ground from the tree to a spot on the ground about the same distance from you as the tree.  Note the spot, and walk over and measure to the base of the tree.  Again fairly close to reality.  
  Only significant changes in tree height really affect volume of marketable timber in a tree.  After a certain point in maturity, many trees only gain minimally more in terms of height depending on stand density, soil conditions , and weather etc..  As stated above, the best way of measuring volume changes in a tree is by measuring the girth of the tree in relationship to the total number of marketable logs in that total tree height.  Have fun, and don't forget to actually harvest some of those trees for actual use.  Practical forestry protects, manages, culls, sustains, harvests and actually utilizes and/or markets the raw material in your crop of trees.