| 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 isn’t necessarily identical
to how we
have been doing the sine top-sine bottom method because we
don’t 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. Let’s hope that the LTI engineers
don’t 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 doesn’t 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
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