Testing TruPulse 200 X

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

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dbhguru
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Re: Testing TruPulse 200 X

Post by dbhguru » Tue Dec 31, 2013 12:10 pm

Steve,

For the customary applications in NTS, there is that point of diminishing returns, and it legitimately applies to most of our members. It isn't necessary for every, or even most members to engage in such fine-tuned, obsession-driven measuring. I would not advocate the extra expense. The measuring that you and others do with lasers in the $100 - $400 range is the meat of our measuring program, of inestimable value.

The above said, there is an ancillary benefit to all from the obsessing few. Our eliteness allows members to speak with confidence about the integrity of our data. The confidence is justified from the extremes we go to to confirm the largest, tallest, etc. There are no equivalents in present-day champion tree programs. Field forestry does not require the lengths that we go to to obtain accuracy, and as Doug points out, some (such as Doug) have scientifically based reasons to go the extra foot.

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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Karlheinz
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Re: Testing TruPulse 200 X

Post by Karlheinz » Wed Jan 01, 2014 1:33 pm

Happy New Year Everyone!

Here are the results of direct distance measurement with my equipment!
TP200X-Messreihe-auf-Zieltafel-bis-210m-S1.jpg
TP200X-Messreihe-auf-Zieltafel-bis-210m-S2.jpg
Zieltafel.jpg
I measured on a nearly horizontal level towards the target board, shown in the photo. The readings ​​in the charts show the direct distance without involving the tilt sensor. The surface of the target plate (50 x 50 cm) is equipped with a polished aluminum sheet. The entire measuring beam impinges perpendicularly on the target board. The central red ring of the LED reticle appears in front of the target plate at 150 m with a diameter of about 50 cm (20 inches). These are optimum measurement conditions to a target of high reflectivity. I measured in the range of 1 m to 210 m (3 to 688 feet). This is only about a tenth of the total measuring range of TP200X (max. 2,500 m). But it covers all distances that are required for measuring European trees normally. I have divided the chart into three distance zones. It can be shown that the error of measurement is virtually independent on the distance. My average error value fits very well with Bob's results. Due to the inherent higher measurement accuracy (~40x) of the Leica the difference between the measurements of both devices must be fully assigned to the TP200X. Therefore I conclude that under the conditions of this test series the TP200X measures on average 28 mm (1.1 inch) too little. That this deviation over the entire investigated range of distance is constant, I think is a very good result.

It becomes very interesting when the laser is pointing to and sweeping over the vertical or horizontal pole of my target board. I get the impression that the measuring beam of the TP200X is already a pretty mace in comparison to the point-like beam of the Leica, at least not a closely focused beam. Unfortunately, as you know, I am missing still reliable comparisons between the laser spots of TP200, TP200X, Impulse200LR, Nikon440 and Nikon550. So far I have only seen statements of opinion or wordy descriptions, like I've just given. I hope that there will still be a discussion in ents-bbs, how to make visible and to document the laser spots for comparison!
When I move the measuring beam from the center of the pole away to side, apparently the measured value increases a bit. Particularly at the vertical pole I observed that the range within I get yet a reading, is not symmetrically distributed on both sides of the pole, which I think is a pity, because TP200X has no option as with the Impulse200LR to calibrate the crosshairs on the laser.
We will have to study all this in future in more detail, but unfortunately it is not easy to document.

Karl
Last edited by Karlheinz on Wed Jan 01, 2014 2:06 pm, edited 1 time in total.

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dbhguru
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Re: Testing TruPulse 200 X

Post by dbhguru » Wed Jan 01, 2014 1:46 pm

Karl,

Really good information. Do you want to send your data directly to LTI headquarters? I'm sure they would greatly appreciate seeing the results and would then perhaps answer your questions directly. It is frigid outside, so I won't do any outdoors testing today, but am pleased to see that what we've done closely matches.

I'm going to re-measure all the trees I can get to in my database using the 200X. I'm now up to 13. Only a few thousand to go.

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: Testing TruPulse 200 X

Post by Will Blozan » Wed Jan 01, 2014 4:05 pm

Karl, Bob,

I have an old camcorder that has a night vision option, in which it uses an infrared light to illuminate the scene that is recorded via an infrared sensor (I assume). I wonder if such a device could "see" or record the shape of the pulses on a flat surface? I am not sure mine works anymore but I'll dig it out and see if anything can be seen.

Will

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edfrank
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Re: Testing TruPulse 200 X

Post by edfrank » Wed Jan 01, 2014 6:02 pm

It might work in complete darkness, or at least in very very dim light because the sensors are capable of seeing infrared, but are more sensitive to visible light. I am not sure what wavelength of light the camera is capable of seeing because there is quite a broad bandwidth of what is called infrared light. Try it and see! It is worth checking out.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Karlheinz
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Re: Testing TruPulse 200 X

Post by Karlheinz » Thu Jan 02, 2014 5:16 am

Bob,

If LTI is approached with questions by Robert T. Leverett, Co-founder and Executive Director Native Native Tree Society, this has more weight.

Before I begin with re-measuring all trees, I must find out how reliable are the readings of my new device, what are the error tolerances and how I can produce accurate readings. First I must know my device exactly and I must be able to properly assess my measured values. The way to find out this, is to compare with known distances and heights. Measurement to target plates is only the first step. Measurements to tall trees whose height is already determined precisely by other measuring procedures or instruments, e.g. tape drop, must follow. With the re-measurement of may be inaccurate measured trees, I do not get ahead here. Most of European registered trees are measured with Nikon550. Who wants to correct these values, must first be able to evaluate the measurement results of his new device safely.


Will, Ed,

I read the thread"Laser beam viewing aid"and I think Infrared (IR) Sensor Cards are too little. M.W.Taylor used his night vision goggle to see the infrared beam. Photos from the laser spot for documentation apparently could not be made.

Matt Markworth idea to test trough a cardboard with a circle cut out, I find very interesting.


Karl

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KoutaR
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Re: Testing TruPulse 200 X

Post by KoutaR » Thu Jan 02, 2014 6:50 am

There are filters that pass infrared but block visible light.

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Karlheinz
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Re: Testing TruPulse 200 X

Post by Karlheinz » Sun Jan 05, 2014 9:58 am

I suggest the following test to determine the beam width of the TP200X (I have not yet tried):

Measure from variable distance to a round plate, which is standing a few meters in front of a wall (e.g. a round traffic sign with a house in the background). The distance to the plate you have to suppress with the filter functions Farthest and Gate in each case.
Since the beam has no sharply defined form, you can define the width differently. In this test the width is determined, from which ratio of distance to diameter the edge of the plate overrunning rays just begin to produce a measurable reflex.

Unfortunately you can’t get with this method comparative values of the other instruments without filter functionality (only with the Impulse200 devices it would still go).

Karl

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Karlheinz
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Re: Testing TruPulse 200 X

Post by Karlheinz » Wed Jan 08, 2014 6:38 am

The manual describes how to trigger the measurement by a remote cable with an open collector closure between pin 1 and pin 2 of the plug socket. I will use this feature to avoid shaking. This does not work. My dealer knows no advice. He waits for support from LTI.

Karl

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