length vs height

General discussions of measurement techniques and the results of testing of techniques and equipment.

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sradivoy
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length vs height

Post by sradivoy » Tue Aug 04, 2015 12:08 pm

Not always the same thing. For example, on a leaning tree the height (its vertical axis) will be different from its length. The formulas for determining volume and AF point should be based on length and not height. Also, I don't think determining mid-slope (where the seed presumably drops) is relevant when determining the vertical height of the tree above ground level. The two relevant reference points, in my humble opinion, is the top of the vertical axis of the tree and the base at the highest ground level (up-slope) position. That said determining mid-slope (where the seed drops) is very relevant when determining the biological length/volume/pts of the tree. At least that's how I look at it.

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Will Blozan
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Re: length vs height

Post by Will Blozan » Tue Aug 04, 2015 4:49 pm

Midslope NEVER changes; upslope does. It is a constant- the only constant in a tree measurement...

Will

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sradivoy
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Re: length vs height

Post by sradivoy » Wed Aug 05, 2015 6:29 am

Will Blozan wrote:Midslope NEVER changes; upslope does. It is a constant- the only constant in a tree measurement...

Will
But how accurately can that be determined? ... especially when you have exposed roots down-slope that gradually blend into the trunk of the tree. Also, where the seed has taken root long ago requires a certain degree of interpretation.

Sure, up-slope can erode away eventually, but by that time the tree would need to be remeasured again anyway.

An ideal fiducial reference point, in my view, should be unambiguous. It shouldn't be open to subjective interpretation or calculation, but rather observed empirically through direct observation.

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bbeduhn
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Re: length vs height

Post by bbeduhn » Wed Aug 05, 2015 8:36 am

Not all trees fit the formula.

The length of a curving tree is not so easy to determine. I've seen some crazy leaning and curving sycamores and leaning river birches. The height is how much the tree is fighting gravity. The length depends somewhat on fighting gravity but not nearly as much as height.

Midslope works in almost all situations. On steep slopes, it may be a bit off at the point where exposed roots meet the trunk. It's also very difficult to measure cbh on a steep slope. This is an exception to the midslope rule. It's not an exact science determining the midslope on a steep slope. Yes, there can be ambiguity and different measurers will have slightly different results, much like crown spread. It's just not practical to get a consensus on every steep slope midslope.

If we went with only upslope, some trees would be shortchanged over 10 feet in height. Using the upslope side would keep things more consistent but it's simply not as accurate as using midslope, which is an average of the base of a tree. I believe Ohio's champion tree rules are based on the upslope side, like you're suggesting.

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dbhguru
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Re: length vs height

Post by dbhguru » Wed Aug 05, 2015 10:33 am

Gents,

Interesting discussion, but a point I feel I need to mention, not relevant to measurement for national champion determination. The rules have been established in the American Forests Measuring Guidelines Handbook. Most states follow the national lead, and eventually all of them will, if they want to remain relevant. Mid-slope is the rule for height and circumference measurements. As Will points out, it is what doesn't change, and yes, there is some judgement involved.

In volume measurements (we will eventually cover them in the guidelines) it will be trunk length. In the methods we now employ for volume, trunk curvature is not a problem because we take short sectons (frustums), compute their individual volumes, and add them all up. We can use a variety of frustum formulas with the conical frustum being the most common. Volume determinations go astray when long sections of trunk are taken. Long sections often reflect one or more changes in curvature so that a single frustum formula doesn't do the job.

As a point to those familiar with approaches taken in forest mensuration, a classic trunk form for volume determinations is the paraboloid, but while it works for well-behaved plantation trees, it fails for many big tree/champion tree shapes. So long ago, we abandoned this classic volume model.

For volume modeling eastern trees, Will Blozan is the all time modeling champion. I have no idea how many trees Will has climbed and modeled, but the number is huge, and he took the discipline to a whole new level with frame-mapping in Tsuga Search where accurate determinations were made of cross-sectioanl areas, especially in the vicinity of a trunk split. This is all well documented. So, I won't go into details here.

The problem with these kinds of discussions is that tree measuring quickly becomes complicated when we truly get serious. Methods increasingly become mathematically driven, which sends a lot of folks running for the door and paying little attention to what is described in the literature.

I'm unsure of what to do to improve the general understanding of volumes. Probably nothing can be done. But in terms of the National Cadre, we're looking for a greater level of comprehension. Don, Will, and I will be updating the AF Guidelines this fall and would welcome your critiques. What needs to be explained better? What additional topics need to be introduced? We do plan to expand pith testing and methods for determination functional circumference where multiple stems are involved. Also, Don's research on the definition of a tree will be expanded. So,alas, as we move forward, the guidelines will not get simpler, which I suspect is the direction that a lot of big tree hunters would like to see us go - especially some of the old timers who didn't pay much attention to accuracy. But we know where that led, and we don't want to go there again.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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Don
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Re: length vs height

Post by Don » Wed Aug 05, 2015 1:58 pm

And folks (Cadre, apprentices, interested 'bystanders'),
I'd like to reiterate what I think is a primary message in Bob's post above:

"in terms of the National Cadre, we're looking for a greater level of understanding. Don, Will, [Don] and I will be updating the AF Guidelines this fall and would welcome your critiques. What needs to be explained better? What additional topics need to be introduced?"

Please do take the time to provide input here, we very much do value your thoughts!
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

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Don
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Re: length vs height

Post by Don » Wed Aug 05, 2015 2:12 pm

sradivoy-
I don't think Will or Bob addressed your misconception in the paragraphbelow, italicized and bolded:
sradivoy wrote:Not always the same thing. For example, on a leaning tree the height (its vertical axis) will be different from its length. The formulas for determining volume and AF point should be based on length and not height. Also, I don't think determining mid-slope (where the seed presumably drops) is relevant when determining the vertical height of the tree above ground level. The two relevant reference points, in my humble opinion, is the top of the vertical axis of the tree and the base at the highest ground level (up-slope) position. That said determining mid-slope (where the seed drops) is very relevant when determining the biological length/volume/pts of the tree. At least that's how I look at it.
Bob does point out that volume does require length as you correctly inferred, but height when measured for American Forests' National/State Champion Big Tree formula, must be the height that is defined as the vertical distance between two horizontal planes that just capture the 1)highest tip top twig/leaf, and 2)the mid-slope of the tree's base. MOST all of the time, that WON"T be directly over the base. In a conifer, that infers that MOST of the time the tree will have some amount of lean. In a deciduous tree, that infers that their typically broad crown will have a highest point ALMOST ALWAYS NOT directly over the base, though that may not confer "lean" in the primary trunk.

In coming up with a definition for height for the AF formula, we needed to arrive at a rule that worked for ALMOST ALL tree types, irrespective of whether they were gymnosperms (usually needled conifers) or angiosperms (usually deciduous, broadleaf).

I'm not immune to your thinking that we should be measuring the uphill side of the tree's base...I did so from 1967 to about 1997 in a forty year career in forestry. But this old dog has learned new tricks, has "seen the light"...: ~ } Length as a measure for logs, was appropriate in the production of lumber and was used extensively. There were only a few forestry applications where height was the specific measure sought. And even then, it was OFTEN mis-measured for decades, until the arrival of the laser rangefinder which allowed the accurate measurement of the slope distance to the top of the tree, a measurement that stymied efforts for accurate height measurement calculations (heralding the increasingly prominent use of the Sine Method).
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
http://www.akbigtreelist.org

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dbhguru
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Re: length vs height

Post by dbhguru » Wed Aug 05, 2015 2:35 pm

Stefan,

In volume modeling, we don't use the official definition of height per our AF guidelines. We take the tree's form, whatever that might be and work with it. This allows for a fairly straightforward process with most conifers, but it is a beast of a challenge for large spreading hardwoods that may begin with a short fat trunk and then explode into maze of outstretched limbs.

Some of our volume modelings have dealt only with the trunk while others have added th major limbs. A few deal with the smaller branches down to a cutoff size. Lots of work!

Michael Taylor and I are planning on modeling the wedge at the base of the tree for trees growing on sloping ground. This gets us into integral calculus with double integrals. Each of us is waiting for the other to get started. Don't cross your fingers for a quick result.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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Will Blozan
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Re: length vs height

Post by Will Blozan » Wed Aug 05, 2015 4:37 pm

As for midslope, if all else fails and the base is a fluted mess- do a pith trace perpendicular to the slope. We had to do this in Panama as the trees just melted into the ground and midslope was not a spot near the trunk center.

Will

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Don
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Re: length vs height

Post by Don » Wed Aug 05, 2015 8:09 pm

Will-
Makes me wonder if you have any photos of 'fluted messes', Panamanian "trees just melting into the ground"?
We are definitely entering the assemble images phase of the next MG revision, and would be great to start tackling "non-standard forms".
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
http://www.akbigtreelist.org

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