TruPulse 200 Test   Robert Leverett
  Sep 01, 2006 06:32 PDT 

ENTS,

Last evening I conducted a simple test of LTI's TruPulse 200's laser.
It was a hurried test and only the first of several that will be
conducted over the next 5 days. In this first test, I compared the
TruPulse with my old Bushnell 800 and my Nikon Prostaff 440. My Bushnell
is what I commonly call "old reliable". It is aging, but still very
accurate. It has been a workhorse.

The following table shows the results of a sample of 10 tests:

No.

Object        

Act  Dist 

TruPulse

Bushnell

Nikon 

Target Reflec

1

Tree trunk

xxxx

98.5

99.0

99.0

 low

2

Tree trunk

55.5

 55.5

 57.0

55.5

moderate

3

Tree trunk

 xxxx

192.5

192.0

195.0

 moderate

4

Container

39.5

39.5

 xxxxx

42.0

low

5

Tree trunk

65.0

65.0

66.0

66.0

high

6

Tree trunk

90.0

89.5

90.0

90.0

high

7

Canvass        

62.5

63.5

63.0

64.5   

moderate

8

Canvass    

100.0

100.0

99.0

102.0

moderate

9

Door        

201.0

200.5

201.0

201.0

high

10

Canvass        

128.5

128.0

129.0

130.5

moderate

 

 

 

 

 

 

 

Average (10)

xxxx

103.3

 xxxxx

104.6

 

Avg (9)

xxxx 

110.3

 110.7

111.5

 

Avg (8)

100.4

100.3

100.7

101.4

 


   Of the 8 trials on which I got a taped distance, the TruPulse
performed outstandingly. On average it was only 0.1 feet off the taped
distance. That is very, very impressive. I was able to make a comparison
on 9 of the 10 trails for all 3 instruments. My Bushnell won't register
a target at 39.5 feet distant, so I could get only 9 trials for it. It
registers at between 55 and 60 feet. The Nikon will register at about 33
feet. I haven't tested for the minimum of the TruPulse.

   As to the averages for the Bushnell and Nikon, the Bushnell was off
taped distances by a mere 0.3 feet and the Nikon was off by a
respectible 1.0 foot. I have two other Bushnells on loan. Based on past
trials, each would likely have been off by an average of about 2 feet,
one over and the other under.

   So, on this first, admittedly crude test, the TruPulse passes with
flying colors. Now, if we could just get Laser Tech to program in the
more accurate sine top - sine bottom computing algorithm as an
alternative to the tangent-based method, LTI could legitimately tout the
best height-measuring device for the price range available. But so long
as the makers of instruments such as the TruPulse fail to understand
that the shortcut tangent-based methods that they program into their
instruments inevitably lead to a lot of height errors (trees are not
vertical telephone poles in level parking lots), ENTS will need to
continue with its drum beat for accuracy.

   Over the Labor Day weekend, I hope to continue testing the TruPulse's
laser and then turn to its inclinometer. A report will be forthcoming on
Tuesday or Wednesday of next week.

Bob   

Robert T. Leverett
Cofounder, Eastern Native Tree Society
TruPulse 200 - more tests   Robert Leverett
  Sep 05, 2006 05:48 PDT 

ENTS,

       Over the long weekend, I continued with the testing of the LTI
TruPulse 200 laser-inclinometer and I am pleased to report that it is a
solid instrument. In 25 accuracy trials, the averaged absolute deviation
of the TruPulse distance from the taped distance was only 0.2 feet. That
is very good, To get better, you have to pay several thousand dollars.
The inclinometer is also good with accuracies to about a tenth of a
degree. While the built-in height routine is tangent-based and subject
to the known biases, there are features that allow one to compute the
height equivalent of the sine top - sine bottom method. There are 3
distance modes built into the TruPulse, Slope Distance (SD), Horizontal
Distance (HD), and Vertical Distance (VD), which can be in meters,
yards, or feet. There is an inclination mode (INC), which is in degrees,
and there is a height calculation mode HT. When you aim at a target and
fire the laser, you can be in any of the modes. If you are in SD, HD, or
VD modes, the reading shown on the LED is for the chosen mode, but
repeatedly hitting the down arrow button cycles through the other
choices, showing the result on the LED. So if you are in HD mode when
the laser is fired, the distance shown on the LED is the horizontal
distance to the target. Cycling to VD shows the vertical component of
the distance and SD shows the actual straight-line distance to the
target or the slope distance as TruPulse calls it. The INC gives the
angle to the target, and HT is set to allow you to take three
measurements, a horizontal distance, a top angle, and a bottom angle.
The tangent-based height is then shown.

     The key point here is that if you are in VD mode when you fire the
laser at the top twig of a tree, you get the height of the twig above
eye level. You can then shoot to the base in VD mode to get the height
of the target between eye level and the base. Does that sound familiar?
Adding the two numbers gives the height of the tree based on right
triangle trigonometry. The process isnít necessarily identical to how we
have been doing the sine top-sine bottom method because we donít know
what the internal mathematical routine is being used inside the TruPulse
to do the calculations, i.e how does it compute the sine of the angle?
However, the differences between the TruPulse routine and calculating
the sine with a scientific calculator is likely to be very small to
negligible.

     One difference of the TruPulse method over what we do with two
instruments is that when a spot is chosen as the top or bottom, and the
laser fired at that point in SD, HD, or VD mode, the angle is
concurrently taken by the TruPulse. The angle computed is that to the
target. This would seem to be an advantage over shooting the distance
and angles with separate equipment, especially if the top of the tree is
complex. It is possible to misidentify the top point when changing from
using the laser to the clinometer.

When you turn the TruPulse off and turn it back on, it remembers the
settings that were in effect when you powered down. You can select from
3 target modes, continuous, closest, and farthest. When the firing
button is held down, the laser acquires multiple targets, but displays
either the most recent one (continuous mode), closest target (closest
mode), or farthest target (farthest mode). However, the unit I am
testing does not seem to be doing this.

The good news for me is that my other two mainstay lasers still perform
very well especially the old Bushnell. The Nikon is more temperamental,
especially when the target is highly reflective. The Nikon tends to
shoot long on a highly reflective target. It appears that about 30% of
the distances returned using the Nikon are high by about 2 feet.

The design of the TruPulse is solid and it fits well in the hand. It is
as small as it should be. Letís hope that the LTI engineers donít screw
up a winning design like the Bushnell folks did by continuously fiddling
around with the size, positioning of the buttons, and piling up the
features and producing in such high volume that quality goes out the
window. I guess the message here is that now is the time to purchase, if
you can afford the substantial price of around $700.

There are features of the Bushnell models that I especially like. The
rain mode is one of them. Does the TruPulse have a rain mode? No, not
that I can discover, but I did get reliable readings through a light
rain with the TruPulse. More testing is needed to determine the
sensitivity of the TruPulse in slightly heavier rain.

       With the Bushnell, the rain mode can sometimes be used to shoot
through brush. It does not always work, but when it does, I can
penetrate to a distant trunk through a fairly narrow opening. So, how
does the TruPulse compare with the bushnell when it comes to penetrating
brush? Well, so far, the only disadvantage I found with the TruPulse is
that it doesnít perform well shooting through clutter. I will run more
tests to determine how to best get through brush. I may not have found
the right combination of settings, but there aren't that many, so I
should soon have the measure of the TruPulse's brush-penetration power.

Bob


Robert T. Leverett
Cofounder, Eastern Native Tree Society