Trupulse 200 Distance Tests

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#1)  Trupulse 200 Distance Tests

Postby Matt Markworth » Wed Jan 01, 2014 10:38 pm

All,

I performed an indoor and an outdoor distance test on my Trupulse 200 today and am very pleased with the results. Average difference from the true distance was less than 2 inches and all of the measurements were within the displayed accuracy of .1 yards.

When using the tripod mount as a reference point, it consistently shoots just a little bit short, which makes me question the reference point or makes me wonder if the internal calculation is truncating the decimal place instead of rounding. Either way, it's very accurate in the conditions that I tested.

Indoor Test
- Comparison made to the super accurate Bosch DLR130
- Unit was handheld
- Reference point for the Trupulse 200 was the tripod mount, reference point for the Bosch DLR130 was set to the back of the unit, the reference points were lined up for the measurements
- All targets were white or off-white

               
                       
TP 200 indoor test.PNG
                                               
TP 200 indoor test.PNG (15.02 KiB) Viewed 1922 times
               
               


Outdoor Test
- Comparison made to a tape that was stretched out straight on top of the grass on a flat football field (impossible to get tape perfectly straight, which introduces some error)
- Unit was mounted to a tripod, the tripod mount was used as the reference point for the measurement
- A pole was attached to the bottom of the tripod center column and extended down to the ground and touched the tape (impossible to get it perfectly lined up, which introduces some error)
- Target was a 10" x 10" piece of brown cardboard at eye level
- Weather: Partly Cloudy, 48°F, sun was behind me therefore directly hitting the target

               
                       
TP 200 outdoor test.PNG
                                               
TP 200 outdoor test.PNG (10.08 KiB) Viewed 1922 times
               
               


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#2)  Re: Trupulse 200 Distance Tests

Postby Karlheinz » Thu Jan 02, 2014 7:03 am

Hello Matt,
that's very enlightening!

Your test suggests: the measurement accuracy in direct distance is the same for TP200 and TP200X, only the display steps were refined from 10 cm to 1 cm.

Karl
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#3)  Re: Trupulse 200 Distance Tests

Postby dbhguru » Thu Jan 02, 2014 11:45 am

Karl, Matt, Kouta, et. al.,

  Over the years I've tested both the TruPulse 200 and 360 many times and in many environments. I discovered early on that the particular laser put into the TruPulse series is more accurate than claimed by LTI. They claim an accuracy of +/- 1 foot for typical targets. They've given reasons for being conservative in their specifications, but it has long been apparent that we can do better on height measurements than their accuracy specifications and even better than the 0.5 feet on the display.

   Recently, Will told me that he sets his TruPulse to yards because the display reads to tenths of a yard. That means the distance and height measurements are reflected to increments of 0.3 feet. In most of the tests I've done, where I adjusted for changeover, accuracies have been between 0.2 and 0.35 feet.

Matt,

  You may have one of the better instruments if you can maintain a distance accuracy to +/- 2.0 inches at changeover. There is some variation between instruments, though not much. All in all LTI quality control is very good.

Bob
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#4)  Re: Trupulse 200 Distance Tests

Postby Matt Markworth » Mon Feb 08, 2016 9:04 pm

All,

I ran another test on my Trupulse 200 this weekend and remain pleased with it's performance.

The unit was mounted on a tripod with a plumb bob touching a stretched 100m tape on a football field. Slope distance was measured in meters with the unit. Three targets were used: semi-gloss white cardboard, black cherry bark, and a white pine sprig. I have included a photo of the targets below.

The Trupulse got the same distance as the tape in 12 out of the 30 measurements. It came to within 1/10 of a meter in 17 out of the 30 measurements, with one measurement to within 2/10 of a meter. It should be noted that the displayed measurement can change a little with each firing of the laser, but after several measurements there is usually one particular reading that repeats itself the most. For example, if the laser was fired 8 times in a row the result would be something like this: 29.9, 29.9, 29.8, 29.9, 30, 29.9, 29.9, 29.9. In this case I would only record 29.9 as the measurement and discard the two outliers.

In this table the yellow background shows measurements that were slightly short, with the orange background showing measurements that were slightly long. 60m - 70m on the bark and pine sprig were the sweet spot for getting the measurement dead on. At 30m - 40m and closer the unit will shoot just a little short, and at 80m and beyond it will shoot a little long.

               
                       
TP 200 test.JPG
                                               
TP 200 test.JPG (44.42 KiB) Viewed 1473 times
               
               


The 3 targets:

               
                       
IMG_5529.JPG
                                       
               


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#5)  Re: Trupulse 200 Distance Tests

Postby Don » Mon Feb 08, 2016 11:19 pm

Matt-
I guess I'm a nerd, as my first thought was "What fun!"
Early in my forestry career, my vocational drift took me into forest engineering, land survey and corner restoration. For the original corner restoration, we used the same type of survey transit as used by the original surveyor in 1880's (this was in eastern Oregon, in the late 1960's), using the same type of steel tape (with topographic adjustments in concert with topographic abneys), and magnetic declinations adjusted to reflect as close to possible, the duplication of their survey, and using their readings from their original notes (just absolutely great job for a budding young forester just outta school, away from home!!!).

I'll spare you the details, but for the findings involving steel tapes.  Usually modern day survey quality steel tapes are in 200, 250, 300, and rarely 500' lengths.  I used to think that laying them on the ground (when flat) was the most accurate. It turns out that they are calibrated to reflect the catenary curve that gravity causes, when the tape has specific poundage of pull per distance.  We would have a spring scale to measure the pull, and only set points when that was reached. Another issue was laying the tape on pavement/ground usually was 10-25 degrees hotter than when suspended in air.

I suspect you probably used 'rag tapes' (fiberglass?). They do stretch, they aren't calibrated for catenary pull, and yes as you note, it's difficult to lay down a tape perfectly straight when there's much distance invovled.

That said, your data seems to reflect relatively constant conditions, and your taking multiple readings and tossing the outliers, all sound good.
Good stuff!

What about a half dozen targets, all equidistant, but of different reflectivities, textures, colors?
-Don
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#6)  Re: Trupulse 200 Distance Tests

Postby dbhguru » Tue Feb 09, 2016 5:17 pm

Matt,

  I applaud your efforts to investigate TruPulse accuracy. When the first laser rangefinders showed up for wide public use, most were designed to read in either whole meters or yards -selectable. The manufacturer specifications usually stated an accuracy of +/- 1 meter or yard for their rangefinders. However, we soon discovered that if we moved forward or backward to the point where the reading on the display changed that we were accurate to around +/- a foot. This was a big leap forward. Later, most of those acquiring laser rangefinders were encouraged to check their accuracy at intervals of a yard or meter to determine if there were correction factors that needed to be applied for their particular instrument. During this time, we struggled with the challenge of hitting the target through clutter, and as you know, the Nikon Prostaff 440 came to our rescue. That instrument was the NTS preferred rangefinder until the accuracy and versatility of the LTI TruPulse product line won most of us over. The old 440s are still useful, but they will gradually fade from the scene.

   How far have we come from the early days? Michael Taylor opened my eyes to a combination of methods and instruments that would allow almost unimagined levels of measuring accuracy. His 3-triangle method for measuring height that uses angle measurers accurate to 1/60th of a degree or better, very accurate distances attainable by class 2 industrial lasers, and a computer program held promise of establishing the gold standard. Then came the LTI TruPulse 200X, which gives us accuracy and penetration through clutter, and I'm told by Steve Colburn that LTI has some gee-whiz products on the drafting board. I think they may be toying with the idea of adding a reticle and even a compass to the 200X. That would be cosmic cool.

Bob
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#7)  Re: Trupulse 200 Distance Tests

Postby Matt Markworth » Tue Feb 09, 2016 9:06 pm

Don,

Yep, I compared the laser to a Keson open reel fiberglass tape. My process for laying it flat was to secure the end in the ground and then use the goal post at the other end of the field as a landmark to walk towards to stay in a straight line. I gave it a little bit of a pull before securing the end with the handle in the ground. The set up with a steel tape calibrated for catenary curve sounds very appealing and much more precise. At some point I may get a longer distance Bosch Class 2 laser which will help with testing as well.

I agree that lots of targets is the way to go. Next time I'll mix it up a little and may also include a twig.

Bob,

Thanks to all of the trial and error you all did back in the early days, it's makes it a lot easier on the rest of us now. I imagine along the way there were lots of tests on lasers that didn't pan out or lost favor over the years. Identifying the preferable toolkit for tree measuring I think is a major accomplishment of NTS. I've certainly used that body of knowledge for my purchasing decisions. My first laser was the Nikon 440 and the second was the Trupulse 200, both very important tools in the ever expanding toolkit.

More tests are definitely on the way!

Matt
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#8)  Re: Trupulse 200 Distance Tests

Postby Don » Tue Feb 09, 2016 10:05 pm

Bob-
I involuntarily inhaled in surprise as I considered Sparky's reaction to a new and more cosmic LTI TruPulse 200X...you wouldn't, surely!
; ~ }
Don

dbhguru wrote:Matt,

  I applaud your efforts to investigate TruPulse accuracy. When the first laser rangefinders showed up for wide public use, most were designed to read in either whole meters or yards -selectable. The manufacturer specifications usually stated an accuracy of +/- 1 meter or yard for their rangefinders. However, we soon discovered that if we moved forward or backward to the point where the reading on the display changed that we were accurate to around +/- a foot. This was a big leap forward. Later, most of those acquiring laser rangefinders were encouraged to check their accuracy at intervals of a yard or meter to determine if there were correction factors that needed to be applied for their particular instrument. During this time, we struggled with the challenge of hitting the target through clutter, and as you know, the Nikon Prostaff 440 came to our rescue. That instrument was the NTS preferred rangefinder until the accuracy and versatility of the LTI TruPulse product line won most of us over. The old 440s are still useful, but they will gradually fade from the scene.

   How far have we come from the early days? Michael Taylor opened my eyes to a combination of methods and instruments that would allow almost unimagined levels of measuring accuracy. His 3-triangle method for measuring height that uses angle measurers accurate to 1/60th of a degree or better, very accurate distances attainable by class 2 industrial lasers, and a computer program held promise of establishing the gold standard. Then came the LTI TruPulse 200X, which gives us accuracy and penetration through clutter, and I'm told by Steve Colburn that LTI has some gee-whiz products on the drafting board. I think they may be toying with the idea of adding a reticle and even a compass to the 200X. That would be cosmic cool.

Bob
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#9)  Re: Trupulse 200 Distance Tests

Postby dbhguru » Wed Feb 10, 2016 3:52 pm

Don,

 Sparky is king of the hill. Always will be. Newbies will have to prostrate their beams in his presence.

Bob
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