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Laser/Clinometer Comparisons

Posted: Fri Feb 28, 2014 6:49 pm
by Matt Markworth
Patrick, Don,

Thanks for the questions! This is a great topic for discussion. I figured I'd post a new thread and see if others have thoughts. Here is the original thread if anyone needs to reference it in the future: http://www.ents-bbs.org/viewtopic.php?f=111&t=6142
pdbrandt wrote:Matt,

Nice work and great pictures! How did the Trupulse 200 and the Nikon 440 compare?
Patrick,

When shooting to a good target (tree trunk with no clutter), both of my units excel at being accurate to their displayed accuracy (Nikon 440: 1/2 yard, Trupulse 200: 1/10 yard). For the Nikon 440, I have some correction factors utilized at the clickover point that increase the accuracy beyond the displayed accuracy. When weak targets (small twig at the top of a tree or clutter) are present, it's a whole different ballgame. Here are my thoughts on the two types of weak targets commonly encountered:

Small Twig at the Top of a Tree

When shooting to a weak target, the Trupulse 200 will leave off the decimal. In this case, upon changing from yards to feet, the best displayed accuracy is 1 foot. The Nikon 440 gives consistent results (with displayed accuracy of 1/2 yard) whether I'm shooting to a good target or a weak target. When I'm measuring what I consider to be an important tree, I'll utilize both lasers as a way to double check my results. The Trupulse 200 is also extremely helpful when scouting for tall trees.

Shooting through Clutter

I am continually amazed at how well the Nikon 440 can penetrate very thick clutter, while the Trupulse 200 is rendered useless for finding distance in this situation. The Trupulse 200, however, is still extremely helpful for finding the angle in this situation.
Don wrote:Like Patrick, I'm wondering how the mechanical clinometer faired against the electronic clinometer of the Trupulse 200? I'll expose my bias, my current thinking is that the electronic clinometers (based on accelerometers detecting motion) outperform the Suunto/Brunton types...what do you guys think?
Don,

When they're held completely steady, I arrive at the same angles with the Trupulse 200 and the Suunto clinometer. However, I think that I'm more accurate with the Trupulse 200 when out in the field. I think I have a pretty steady hand, but I can't consistently get to a tenth of degree of accuracy with the mechanical device.

Matt

Re: Laser/Clinometer Comparisons

Posted: Sat Mar 01, 2014 12:26 am
by Don
Matt-
Excellent! Part of the Measuring Guidelines Working Group's charge has been taking a look at current and future equipment to be used in tree measurements...for height measurements, vertical angles are of interest, and there are a number of 'electronic' clinometers out now. Haglof, now Pecos have two similar units, and there are a couple of Smartphone Clinometer Apps that utilize the Smartphone accelerometers (movement detection in planes, geometric ones...).

I'm hoping that we'll be able to mount a serious investigation of the accelerometer-based clinometers, with their claims of 0.2 degree accuracy...it may be that mounting them on tripods may required to get that accuracy. At the national level, tripods may be warranted anyway. By the way, the iPhone Clinometer app was recently upgraded...the dial face (within the numbering ring) now features the camera viewfinder view. The same accelerometers that the Clinometer App uses, is used by the Theodolite App, a much more feature rich App, using iPhone GPS, email, wifi, accessess maps and satellite image bases, and much more.

Re: Laser/Clinometer Comparisons

Posted: Sat Mar 01, 2014 10:05 am
by Matt Markworth
Don wrote: By the way, the iPhone Clinometer app was recently upgraded...the dial face (within the numbering ring) now features the camera viewfinder view.
Don,

Very cool. I played around with the Clinometer app last year and didn't realize that they added the camera viewfinder. It's now extremely easy to use. I make sure that the vertical crosshair is completely vertical and I also use the locking button.

I tested it this morning against the angle from the Trupulse 200 and initially I was consistently getting 1/2 degree less from the Clinometer app. In an effort to increase accuracy, I made multiple attempts to calibrate the app, but now I'm consistently getting 2 degrees less with the app compared to the Trupulse. Any tips on calibration? I've been using the two-way calibration.

Matt

Re: Laser/Clinometer Comparisons

Posted: Sat Mar 01, 2014 8:59 pm
by pdbrandt
I have the ipad clinometer app and although I think it has a lot of potential in its latest version, I can not for the life of me figure out how to calibrate it. That's the main reason I haven't used it for measuring. A second reason that I doubt it's accuracy is my concern that the angle could be off a few tenths of a degree because it can not be held up to your eye. A real benefit of the line of sight clinometers (Suunto and Brunton varieties) is that you hold them the same way you hold the Nikon 440, so the angle to the target takes the same path as the laser reading. Depending on how you sight with the iPad/iPhone clinometer app that may not be the case.

Re: Laser/Clinometer Comparisons

Posted: Sat Mar 01, 2014 9:15 pm
by pdbrandt
Don Bragg, et al. published a paper in 2011 (http://www.nativetreesociety.org/specia ... g2011D.pdf) wherein they measured 42 trees with a TruPulse 200 and compared the height to that obtained by tape drop from the top. I'm in the process of doing a similar comparison (on a much smaller scale) with my NIkon 440 and Suunto clinometer and should be able to report back in the next couple of weeks.

Re: Laser/Clinometer Comparisons

Posted: Thu Nov 20, 2014 8:33 pm
by Don
Patrick/Matt-
My apologies for just now picking up on your thread, after such a good start...by way of explanation, we were off to Kauai celebrating our 25th wedding anniversary, and my thoughts were elsewhere!
Now that I've refocused, I can't add to the calibration conundrum, but have an additional electronic solution (it does share the iPhone as the electronic Clinometer App, but adds a digital zoom...that of the iPhone app "Theodolite"). I suspect it has a similar calibration routine...
To round out a comparison test, it would be great to add a Haglof electronic clinometer! I'll post an inquiry of our fellow Ents to see if anybody has one, and would like to contribute...
-Don