Finding the Top

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

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#1)  Finding the Top

Postby dbhguru » Mon Feb 15, 2016 3:57 pm

NTS,

   A tulip tree growing down hill from our back door is with a fine target for practicing measuring from our upstairs bedroom window. The base of the tulip has a horizontal distance of 100.5 feet. The base is 43.2 feet below eye level. The top is not less than 84.5 feet above eye level, but that determination is not easy to arrive at. First a look at the whole tree.

               
                       
MTT-1a.jpg
                                       
               


   As can be seen, the tree is arrow-straight and its crown still exhibits a somewhat flattened spear-shaped top. Let's see the top from a closer perspective.

               
                       
MTT-2a.jpg
                                       
               


 What point would you select as the highest point from this vantage point? Let's move closer.

               
                       
MMT-3a.jpg
                                       
               


 Can you see what the orange arrow is pointing to? It isn't the highest looking top, but one slightly to the left. Let's take a final look.

               
                       
MTT-4a.jpg
                                       
               


 Neither my eyes or the lens of my TruPulse 200X or Cannon XS260 HS has the depth of field to show that the target top is behind the higher looking branch. It took my Zeiss 10 x 40 binoculars to do that, and it was clear as a bell. The near branch has a horizontal distance of 87.9 feet. The true top has a horizontal distance of 98.8 feet. The tops of hardwoods are not easy to decode. Binoculars with a good depth of field are worth their weight in gold.

  BTW, a plumb line dropped from the true top falls to the right of the base and slightly in front of it. Since this is still a relatively young tulip tree growing in competition with tall oaks surrounding it and with fairly good wind protection, it remains a good candidate for the Tangent Method. But which top would a tangent measurer select? The odds of the true top being selected are slim.

  The angle difference between the highest appearing top and the true top is 0.2 degrees, amounting to 0.6 feet using a 100.5-foot baseline 100.5 x [tan(40.8)-tan(40.6)]. The difference would reduce the overall error of 2.2 feet to 1.6 feet. Either the tangent measurement to the false top or true top is pretty good because the tree is straight, the crown relatively narrow, the high points more toward the center, and the eye 43.2 vertical feet above the base. Had the tree been measured 100 feet from the trunk on level ground, the results from the Tangent Method would not have been so close.

Bob
Robert T. Leverett
Co-founder and Executive Director
Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest

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#2)  Re: Finding the Top

Postby Larry Tucei » Mon Feb 15, 2016 8:01 pm

Bob-  Great example of where the top really is vrs where your eye tells you it is. Wow! I saw where New England had record cold. Broke all the records from 60 years ago! Burr= warm down here! 60's-40's.  Larry
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#3)  Re: Finding the Top

Postby dbhguru » Mon Feb 15, 2016 8:11 pm

Larry,

  Yep, pretty cold. The valley in Westhampton below Hanging Mountain made -20 degrees. It was about -12 here at the house. Charlemont was -16. That's cold enough. Brrrrr. Mount Washington, NH made -40 degrees.

Bob
Robert T. Leverett
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Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
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#4)  Re: Finding the Top

Postby Don » Mon Feb 15, 2016 8:48 pm

Bob-
Any impact on accuracy when shooting through glass? Either obliquely or at an angle?
-Don
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#5)  Re: Finding the Top

Postby dbhguru » Mon Feb 15, 2016 9:52 pm

Don,

 Supposedly not, but I plan to conduct experiments to answer the question decisively.

Bob
Robert T. Leverett
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Native Native Tree Society
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Friends of Mohawk Trail State Forest
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#6)  Re: Finding the Top

Postby Erik Danielsen » Mon Feb 15, 2016 11:30 pm

Of course, with trees of less "ideal" form the actual highest point is often quite a surprise when it's finally picked out of the crown! More and more I find that measuring trees on a steep slope is actually the easiest, since you can ascend and find a viewpoint that gives a better sense of the shape of the crown and consequently its highest points.
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#7)  Re: Finding the Top

Postby Matt Markworth » Wed Feb 17, 2016 6:07 pm

Bob,

Very cool, what a great example. Did the TruPulse 200X gate functionality come in handy for the distance to the top from that vantage point? I'm not sure if my TruPulse 200 could "see past" that one twig that is nearly in the way and hit the actual top.

It's supposed to warm up this weekend so I may get out and test the gate functionality on my new (new to me) Impulse 200LR.

Matt
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#8)  Re: Finding the Top

Postby dbhguru » Wed Feb 17, 2016 10:06 pm

Matt,

 The gate was absolutely critical to confirming the true top. Without it, I would have had no chance of hitting that twig.

Bob
Robert T. Leverett
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#9)  Re: Finding the Top

Postby tomhoward » Sun Feb 21, 2016 2:15 pm

Bob, NTS,

The twig you highlighted as the tallest is the one I would have chosen. I've seen many crowns like this in central NY.

Speaking of cold last Sun. Feb. 14 - it got really cold here in Syracuse. The temperature was -23 at Syracuse Airport, the coldest it has been in over 20 years here, and coldest in Feb. since 1979. It's been a very mild winter before this year, and it is now mild again.

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#10)  Re: Finding the Top

Postby Don » Sat Apr 30, 2016 2:22 am

While my topic is peripherally related to "finding the top", I was browsing through Apple's accessory site and came up with the following solution that's waiting for someone wanting to elevate tree height measuring...; ~ }
Go to:
http://www.apple.com/us-hed/shop/product/HJWF2/dji-phantom-4-camera-drone?fnode=79
and consider the quality offering!
Mike Taylor has shown us the way, back when quadcopters were somewhat more primitive...while digital solutions abound, I envision the DJI flying up to the top with a tape, and once the DJI levels off on the operator's screen, they read the tape at the bottom. Of course, laser rangefinders, if stripped down for less weight would do as well or better.
Just saying!
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