Accuracy of Trupulse 360 & Centurion

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KoutaR
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Re: Accuracy of Trupulse 360 & Centurion

Post by KoutaR » Wed Dec 12, 2018 4:41 am

Brett,

Is Centurion growing on sloping ground? The small differences like that between the 2014 Sillet measurement and the 2016 Thomas measurement can easily derive from differing definitions of the average ground level. The photos also show piles of debris around the trunk - how to define the average ground level to a cm?

Kouta

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Erik Danielsen
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Re: Accuracy of Trupulse 360 & Centurion

Post by Erik Danielsen » Wed Dec 12, 2018 8:59 am

Brett, thanks for the additional information. It's disappointing that they have gone forward while knowing about the 2016 tapedrop (not mentioned in their report) and against your recommendation- where you are cited in their report it does bring up a source of possible error but otherwise sounds like an endorsement of the results. The 360's potential overestimation can of course be compensated for with thorough testing of the unit and calibration of the results, but they seem to have relied on the fact that the unit was new to ensure that it was accurate to spec regardless of distance.

Bob, fortunately they did not use the height routine. Their document indicates all the work was done in VD mode, therefore sine. In my correspondence with them about error sources I recommended that they spend time working with a laser collecting SD and INC separately for precise measurements, since working in VD only can make it hard for the user to recognize that that "exciting" figure they get once in every ten fires is just due to an intermittent hand shake altering INC, or similar scenarios, and that averaging multiple incorrect figures does not yield a more accurate figure. You're right that the challenges in that setting are no doubt greater; while I've used segmenting here in the east to assess whether a challenging tree is tall enough to be worth measuring precisely, I've had the luxury of finding a viewpoint to both top and base for any important measurements.

I'd like to see them do it better in the future. All the effort at documentation suggests to me that they thought they were getting all the important parts right and then got swept along by the excitement. Being immediately confronted with a major problem as simple as hand-triggering probably tripped them up pretty hard in the midst of their social media victory lap. There are some things you have to learn by getting it wrong a few times.

I am curious about Kouta's question, and do have a speculative question of my own to add; is the leader they measured to, as shown in the photos, the same leader that has been measured as "tallest" in previous measurements? All the speculation to date assumes the same leader between measurements. NY's tallest sycamore has put on rapid growth in the several years following its original highest leader breaking off at which point a less dominant leader put on a growth spurt and has since surpassed the original. If it's unclear whether the same leader is the top each time, there may not be much point in speculating about specific growth rates.

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mdvaden
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Re: Accuracy of Trupulse 360 & Centurion

Post by mdvaden » Wed Dec 12, 2018 12:19 pm

KoutaR wrote:Brett,

Is Centurion growing on sloping ground? The small differences like that between the 2014 Sillet measurement and the 2016 Thomas measurement can easily derive from differing definitions of the average ground level. The photos also show piles of debris around the trunk - how to define the average ground level to a cm?

Kouta
Your question emphasizes why a tree should be measured my the more experienced or most accurate means and equipment if the exact height is desired. Previously in this thread, I referred to the hemlock Tsunami for one example. We could also use the Ponderosa pine Phalanx that was the pine height world record of 2011.

Michael Taylor measured it with Impulse 200LR using cable trigger, tripods and prism. Ascending the Giants team climbed and used a tape drop. The two measures differed by about 2 mm or 2 cm .. like 8/10 or 8/100 of an inch !!!

With Centurion, an obvious reason for potential error is the laser model and how they triggered it. But in light of your question, what they chose for high and low grade could alter things even more. Ideally, if the same persons who measured in the past (accurately) could return, that would be very good for comparison.
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Brett Mifsud
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Re: Accuracy of Trupulse 360 & Centurion

Post by Brett Mifsud » Fri Dec 14, 2018 5:41 am

Centurion's base is half on a flat bench and half on a moderate slope. Regarding the difference between high and low points of ground: Yoav got 1.53m in 2018, my notes say I got 1.40m in 2008. The thing is, in 2008, the tape came down to the low point of ground, so I subtracted 70cm to get back to the midpoint. Using Yoav's number for the midpoint (76.5cm) that would make the tree 99.53m back in 2008 rather than the 99.60.

The high point of leaves measured seems to be the same for both the 2008 and 2014 measurements from photos. The team that climbed it in 2016 spent 2 days climbing it and carefully measuring it. Getting to within 1.9m of the top before lowering the tape. The sooner we can climb it and do another tape drop the better. Unfortunately, the tree next to it contains a Wedge Tailed Eagles nest. The Tasmanian sub species of Wedge Tailed Eagles are endangered (due to over logging of their favoured nesting habitat - large old Eucalyptus!) The breeding season is generally from August to January, however, climbing Centurion is not allowed until March/ April so as not to disturb the birds.

regards
Brett

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M.W.Taylor
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Re: Accuracy of Trupulse 360 & Centurion

Post by M.W.Taylor » Fri Dec 14, 2018 3:41 pm

Yoav's claim of Centurion is unsubstantiated. I used to have a Trupulse360 for many years and I would say accuracy is more like +,- 40cm, especially at a distance like from the window Yoav used to measure the top. Perhaps my TP360 was a lemon ? He used the bottom 1/4-20 mount on a tripod which induces pivot wobble on each measurement leg from the original window. He should have used the yoke mount to L Bracket. Without it you will induce further propagating error to the measurement. He did not use the foliage filer, nor a prism and pole. He did not use the remote trigger. I would give his measurement +,- 1m error at best. Centurion is a wind swept 500 year old tree with no competition and up on a ridge. I doubt it grew that much. It might have cracked 100m by now but I seriously doubt it. You'll notice Yoav makes money giving tree tours. This is why he prematurely announced it as being over 100m. He wants to generate excitement so he can make a few extra bucks. It's that simple.

Brett Mifsud wrote:Hi Mario
Yes, we really have no idea of its exact height. By the way, Steve Pierce and Yoav already knew about the 2008 and 2014 tape drop measurements and I alerted them to the 2016 tape drop. In spite of this knowledge they've gone ahead with publicising their measurement.

What I can tell you is this: When Tom climbed it in 2008 he got within 1.88m of the top before dropping the tape - and he's very keen to climb it again after all the current fuss! What we don't know is if the same publicity will be generated if the tree turns out to be closer to 99.6 than 100m.

It has even made news with our national broadcaster:
https://www.abc.net.au/news/2018-12-12/ ... n/10604588

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mdvaden
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Re: Accuracy of Trupulse 360 & Centurion

Post by mdvaden » Sun Dec 16, 2018 2:16 am

M.W.Taylor wrote:Yoav's claim of Centurion is unsubstantiated. I used to have a Trupulse360 for many years and I would say accuracy is more like +,- 40cm, especially at a distance like from the window Yoav used to measure the top. Perhaps my TP360 was a lemon ? He used the bottom 1/4-20 mount on a tripod which induces pivot wobble on each measurement leg from the original window. He should have used the yoke mount to L Bracket. Without it you will induce further propagating error to the measurement. He did not use the foliage filer, nor a prism and pole. He did not use the remote trigger. I would give his measurement +,- 1m error at best. Centurion is a wind swept 500 year old tree with no competition and up on a ridge. I doubt it grew that much. It might have cracked 100m by now but I seriously doubt it. You'll notice Yoav makes money giving tree tours. This is why he prematurely announced it as being over 100m. He wants to generate excitement so he can make a few extra bucks. It's that simple.
Michael, when Centurion is measured properly instead of this duct tape & bailing wire thing, what would you think of a combo measure with climbing + laser Impulse 200LR ??

A proper climb measure will dial-in the real height. If it were also measured the same day with laser, with two reference tags, wouldn't that streamline more accurate tracking year by year? In the redwoods mainly one tag was attached. But two would offer more insurance in case something fell over or a branch knocks a tag loose. If I'm not mistaken, the laser measure would only need the difference between tallest top and the tag, because the climb team could supply the rest.

..
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M.W.Taylor
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Re: Accuracy of Trupulse 360 & Centurion

Post by M.W.Taylor » Sun Dec 16, 2018 3:05 pm

Kouta, Centurion is on a slope. Sillett-Mifsud ground level was 1.4m difference between high and low side. Yoav got 1.57m difference so for the average we get .085 higher for the total measurement. Why did Yoav get a bigger difference from high to low side ? Well, the ground level is a subjective measurement to some degree and perhaps the tree's lower base could have been compressed by walking around it. Even with the extra .085m it is extremely unlikely this tree grew 71.5 cm in 2 years (Yoav got 100.5m in 2018 vs. Sillett tapedrop of 99.7m in 2016). Centurion is a 500 year flat top tree growing high up on a ridge. Nearby there was a recent clear cut. The post by Yoav states Centurion experienced a recent growth spurt. Again, extremely unlikely. Yoav, a rookie at tree measurement, ignored the advise of people who have spent decades refining their tree measurement accuracy.
KoutaR wrote:Brett,

Is Centurion growing on sloping ground? The small differences like that between the 2014 Sillet measurement and the 2016 Thomas measurement can easily derive from differing definitions of the average ground level. The photos also show piles of debris around the trunk - how to define the average ground level to a cm?

Kouta

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M.W.Taylor
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Re: Accuracy of Trupulse 360 & Centurion

Post by M.W.Taylor » Sun Dec 16, 2018 3:19 pm

Mario, It would be really hard to hit the top of that tree with the wide laser emitter of the 200LR. Your measurement would be conservative for sure. You would want to use the Trupulse200x to really nail it down. To survey the base however you could use the Impulse200LR in filter mode along with a prism and pole mounted on a tripod. Also should use a polarized filter so the Impulse200LR can only get a return when shooting at the center of the prism with no slop. Centurion might possibly be over 100m, but not likely in my opinion. Also very unlikely the tree experienced a recent growth spurt.
mdvaden wrote:
M.W.Taylor wrote:Yoav's claim of Centurion is unsubstantiated. I used to have a Trupulse360 for many years and I would say accuracy is more like +,- 40cm, especially at a distance like from the window Yoav used to measure the top. Perhaps my TP360 was a lemon ? He used the bottom 1/4-20 mount on a tripod which induces pivot wobble on each measurement leg from the original window. He should have used the yoke mount to L Bracket. Without it you will induce further propagating error to the measurement. He did not use the foliage filer, nor a prism and pole. He did not use the remote trigger. I would give his measurement +,- 1m error at best. Centurion is a wind swept 500 year old tree with no competition and up on a ridge. I doubt it grew that much. It might have cracked 100m by now but I seriously doubt it. You'll notice Yoav makes money giving tree tours. This is why he prematurely announced it as being over 100m. He wants to generate excitement so he can make a few extra bucks. It's that simple.
Michael, when Centurion is measured properly instead of this duct tape & bailing wire thing, what would you think of a combo measure with climbing + laser Impulse 200LR ??

A proper climb measure will dial-in the real height. If it were also measured the same day with laser, with two reference tags, wouldn't that streamline more accurate tracking year by year? In the redwoods mainly one tag was attached. But two would offer more insurance in case something fell over or a branch knocks a tag loose. If I'm not mistaken, the laser measure would only need the difference between tallest top and the tag, because the climb team could supply the rest.

..

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ElijahW
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Re: Accuracy of Trupulse 360 & Centurion

Post by ElijahW » Mon Dec 24, 2018 5:13 pm

Mario,

I appreciate your commitment to proper measurement methods for trees of the highest caliber. We all must be held accountable for our work, and especially for making extraordinary claims. Maybe this tree in question has exceeded 100 meters, maybe it has not. Hopefully these fellows will take the advice they’ve been given and do a more careful job on their next attempt.

I have to confess that, although I almost always use a tripod with my 200X, I rarely use the remote fire method. The reason is mostly to conserve battery life, both in my phone and in the laser (they’re connected via Bluetooth, for those not familiar with the Trupulse machines).

I assume this is also a touchy subject because of the “100 Meters” claim. Is that correct? Isn’t Coast Redwood the only tree species known to currently achieve that height?

Elijah
"There is nothing in the world to equal the forest as nature made it. The finest formal forest, the most magnificent artificially grown woods, cannot compare with the grandeur of primeval woodland." Bob Marshall, Recreational Limitations to Silviculture in the Adirondacks

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mdvaden
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Re: Accuracy of Trupulse 360 & Centurion

Post by mdvaden » Tue Dec 25, 2018 9:46 pm

ElijahW wrote:Mario,

I appreciate your commitment to proper measurement methods for trees of the highest caliber. We all must be held accountable for our work, and especially for making extraordinary claims. Maybe this tree in question has exceeded 100 meters, maybe it has not. Hopefully these fellows will take the advice they’ve been given and do a more careful job on their next attempt. ... SNIP
Elijah
It caught my eye when they commented at a forest related Facebook page by someone else, stating being transparent. But that immediately raised the question why they made no mention of others saying to hold off until climbing or a proper measure.

Regardless, accurate measuring is something I just faced !!!

It's been a few years since the Ponderosa pine Phalanx was measured. The one that was the record for a few years, found west of Grants Pass. I thought maybe when snow cleared I would drive up and remeasure it. Then I remembered the cable pins got messed up where the thing connects to my laser. With the only other option being hand triggering, I decided to skip it even though I have a prism and tripods.

I may start looking around for a replacement cable sometime. Maybe Michael Taylor has an extra in his boneyard that I can buy to fill the void.
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