Comparing instruments for measuring diameter

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dbhguru
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Comparing instruments for measuring diameter

Post by dbhguru » Thu Apr 11, 2019 9:05 am

Ents,

How many instruments are available to us to measure the diameter of the trunk of a tree? There is the DTape, of course, but also calipers, Biltmore stick, monocular with range finding reticle, LTI RD1000, LTI TruPoint 300 and its Leica equivalent, and photographic analysis to name some others. But are they all equal? The DTape is the traditional tool, but requires physical contact with the trunk. So do calipers. Presumably, These tools are the gold standard - or are they? Calipers work on trees up to about 36 inches in diameter. The DTape computes an average diameter, which for some purposes is what we want, but not all. Then there are those situations where we can't measure diameter directly, such as well above the base (unless the tree is climbed).

If we want to comprehensively compare the above instruments, beyond accuracy, we should identify the strengths and weaknesses of each, where each best fits, and conversely, where each doesn't. The attachment is the start of the process. It is a work in progress. Suggestions are welcome.

Bob
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ReticleCalipersDTapeTruPoint.xlsx
(19.35 KiB) Downloaded 47 times
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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bbeduhn
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Re: Comparing instruments for measuring diameter

Post by bbeduhn » Thu Apr 11, 2019 12:57 pm

Bob,
You have quite the data set! I'm not surprised that different methods yield different results but they're still quite close. I'd be comfortable using any method, depending on the situation. I still feel it's best to use hands on methods whenever possible but using hands on methods in computing volume is quite laborious and should be reserved for just the elite few trees. I measured a tulip with a reticle and it took just 30 minutes or so for my very first attempt.
Brian

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Re: Comparing instruments for measuring diameter

Post by dbhguru » Sat Apr 13, 2019 7:16 am

Ents,

Attached is an updated spreadsheet on instrument comparison. I realize that this isn't a hot topic among most NTS members. The Measurement and Dendromorphometry forum is where we can keep our methodology explained and updated.

Bob
Attachments
ReticleCalipersDTapeTruPoint.xlsx
(20.47 KiB) Downloaded 31 times
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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dbhguru
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Re: Comparing instruments for measuring diameter

Post by dbhguru » Sat Apr 20, 2019 3:44 pm

Ents,

Here is the latest version of the spreadsheet on instruments to measure diameter. Please take note of the second worksheet. The bottom line is going to be that the TruPoint 300 has a useful, easy to use diameter measurement routine. However, the monocular with reticle (and supporting laser rangefinder) is still the more flexible set of tools. The camera on the TruPoint is very useful when you can see the target clearly through it, but the camera is definitely a limitation. In addition there are size-distance limitations. For example, at a distance of 112.43 feet, a diameter smaller than 0.71 feet won't work at 4x, 1.42 feet at 2x, and 2.86 feet at 1x. This is because the function allows you to move vertical bars on the image over to encapsulate the trunk. The bars move only so far for each power selected, i.e. 1x, 2x, or 4x.

Bob
Attachments
ReticleCalipersDTapeTruPoint.xlsx
(34.36 KiB) Downloaded 18 times
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: Comparing instruments for measuring diameter

Post by Don » Sun Apr 21, 2019 8:39 pm

Bob-
It seems that every solution has a compromise...this isn't a problem, if you know the compromise, and can mitigate the shortcoming. 4x, that's what they put in kid's play binoculars...there must be a reason for limiting the 300 to 4x?
-Don
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Re: Comparing instruments for measuring diameter

Post by Don » Fri Jun 14, 2019 1:23 pm

Looks like the quick reply got lost in the down time...are we back on? (June 14, 2019)
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:
http://www.akbigtreelist.org

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Re: Comparing instruments for measuring diameter

Post by Don » Fri Jun 14, 2019 1:24 pm

As Bob would say, "YEEEEHAAAW !!!"
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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Re: Comparing instruments for measuring diameter

Post by Don » Fri Jun 14, 2019 9:41 pm

Does anybody else see a similarity between Apple's new Face ID security measure with it's 3D identification of facial features, and the technique that Michael Taylor uses when using digital imagery to create a 3D image of a tree's bole? I'm thinking that there might be developers soon working on apps that we might be interested in!
-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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