Where is the top?

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dbhguru
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Where is the top?

Post by dbhguru » Sun May 17, 2015 3:10 pm

Hi NTS,

As part of the AF National Cadre training on measuring tree height, we want apprentices to think long and hard about the top and where it is located relative to competing twigs. For demonstration purposes, I frequently measure a white oak in my neighbor's yard. I can see the base, the first part of the trunk, then the crown. The image below points to base and top. You can see the top is offset to the right. Click on the photo to expand.
MaharOak-1a.png
In the next image, I point to the highest sprig, which is 100.1 feet. The HD values are the horizontal distances (HD returns of TruPulse 360) to tops that look higher. They are between 95 and 97.5 feet in height. Through binoculars, one can see depth better and the highest top clearly looks to be farther back into the crown. The two dimensional image below doesn't communicate this well. Click on the photo to expand.
Screen shot 2015-05-17 at 4.11.00 PM.png
One can see a difference in the size of the leaves in the above photo of competing tops. But the differences aren't great. There is an art to locating the highest top of a broad-crowned hardwood, or even a narrow one for that matter of fact.

In past posts, I've shown the crown of this tree and had the 97.5-foot top identified as the top. The true top didn't look like a viable candidate. This is a clear case of Oops! I'm sure everyone has them, but I went a long time before confirming the higher top. I guess old dogs can learn new tricks.

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: Where is the top?

Post by Will Blozan » Sun May 17, 2015 4:59 pm

Bob,

Excellent example of how standard baseline to trunk tangent methods simply do not work. Try to do this tree with the tangent method- it would take a lot of time with cross-triangulation and slope correction.

Time to give the TP 360 a hug!

Will

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Don
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Re: Where is the top?

Post by Don » Sun May 17, 2015 9:21 pm

Will-
Bob's mention of the binocular's ability to discern distance differences (depth of field) is spot on too! A foot or two? Maybe not. But 5', 10', 15'...absolutely.
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

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View my Alaska Big Tree List Webpage at:
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Larry Tucei
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Re: Where is the top?

Post by Larry Tucei » Mon May 18, 2015 7:39 am

Bob- Many times I'd get far as possible from the Crown of the tree I'm measuring to find the highest point. Sometimes you have to walk around the whole tree to see the differences. Many of the Oaks I've measured have an offset higest top, sometimes over 20-40' from the trunk. I'm not just talking about Live Oaks, all Oak and even some Conifers. I could see where Binoculars would come in handy to find the top much better than our eyesight. Good idea! Larry

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Matt Markworth
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Re: Where is the top?

Post by Matt Markworth » Mon May 18, 2015 7:44 am

Bob,

Great illustration! I really like how you included the horizontal distances - very strong piece of evidence for showing how difficult an accurate tangent-based measurement would be.

Matt

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dbhguru
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Re: Where is the top?

Post by dbhguru » Mon May 18, 2015 1:49 pm

Will, Don, Matt, et.al.,

Here is another look from a slightly different spot of the Mahar Oak. In this case, I show only the two competing tops: the one I originally chose as the highest and the true top. To get the full height of the tree, you must add 3.7 feet. The numbers shown below are for height above eye level.
MaharOak-3a.png
Here is a peek at the top, up close and personal.
MaharOak-4.png
You can see the leaf that needs to be hit to get the absolute top. It takes a number of trials to be sure that target is hit. Once you look at the canopy through binoculars, the spatial relationship of the competing tops immediately becomes clear. In fact, it is a revelation. Don, we owe you for pushing for binoculars as a standard part of the measuring repertoire.

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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