| TruPulse360
and Macroscope 45 |
dbhg-@comcast.net |
| Aug
30, 2007 19:08 PDT |
Ed,
Unfortunately, I don't own it yet. It is only
borrowed. However, by mid-September when LaserTech announces its
availability, my order will be one of the first.
On
the serious side, the TruPulse 360 is a potentially very
valuable instrument to us. It adds easy 3-dimensional measuring
to our reparatory of methods. Imagine two points in space with
no particular orientation. Add a third point representing the
measurer. There is no requirement as to the location of the 3rd
point with respect to the first two. The TruPulse 360 allows the
measurer to determine the linear distance between the first two
points. The 360 also returns the vertical distance and
horizontal distance between the the points and azimuths from the
observer's position.
The
two points could be the ends of a limb or the extremities of the
opposite sides of a tree representing the maximum crown spread.
The 360 could be used to create a 3-dimensional map of a tree.
Although, the TruPulse 360 will not perform like an Impulse
Laser, it is sufficiently versatile to allow us to efficiently
explore 3-dimensional territory. In the next several days, I'll
be testing the 360 for a limited type of ground-based canopy
mapping and dutifully report the results.
The
weakness of the TruPulse is that it doesn't shoot through narrow
canopy gaps. With reflectors, that might be less of a problem,
but reflectors can't be put on the ends of branches 50 feet up
in the air. So, additional mathematics will be necessary.
Nonetheless, for us, the 360 appears to be a big addition.
Unfortunately, it is expensive, costing $1,600. Were it priced
at half that, it would be a steal, but $1,600 is expensive for
the level of accuracy it allows for distance (within a foot),
azimuth (within a degree), and vertical angle (within 0.25
degrees).
On
to another gizmo. My new Macroscope 45 is proving to be a
challenge. Its reticle is scaled to 3 millimeters instead of 5
like the Macroscope 25, so one must be farther from a tree to
get the same diameter coverage. The factor used to compute width
is not 75, as it is with the Macroscope 25, but appears to be 45
(3/5*75?). I say appears to be. I have to get more exact
measurements to know.
At
this point my advice to any of you contemplating a purchase is
to stick with the Macroscope 25.
Bob
|
| True
Pulse 360 |
dbhg-@comcast.net |
| Sep
01, 2007 07:44 PDT |
Dendromorphometrists,
Well, yesterday was a highly productive
day for me. Monica and I went to visit a friend in Stoddard, NH,
and while the ladies had a chance to renew their long
friendship, I skipped out with the TruePulse 360 on my belt and
a 200-foot taper measure in my hands. The day's objective was to
test the horizontal angle measurer of the 360.
The first couple of hours proved
to be wasted. I got bizarre results for horizontal distances
with the TruPulse and had to go through the recalibration
process before the instrument settled down. The instructions for
recalibrating miss a point or two, but eventually I figured out
what the authors of the instructions intended to be done. After
recalibration, it was all goodness and light. I did 14 carefully
setup experiments to measure the horizontal, vertical, and slope
distances between two points in space as measured from a third
location- namely where I was at. The three points can be
oriented in any fashion. So the experiments were useful to test
the feasibility of making crown and limb measurements
measurements.
The results of the
experiments were encouraging. The average horizontal distance
from the tape measurments for the 14 separate situations was
14.1 feet. The average of the best laser measurements for teh
situations was 14.4 feet. The average of the best was used
because I took multiple readings and often saw patterns that
indicated that I had missed the sometime indistinct targets.
Also, interference from power lines, cars, etc. can throw off
the internal compass readings. One, must be very conscious of
one's surroundings when using the horizontal angle measurer. The
average of all the instrument readings for the tests was 13.0.
The difference of 1.1 feet is consistent with the expected level
of accuracy for 3-dimensional calculations over a wide variety
of field conditions. However, being careful or using a tripod, I
think the average would have been closer, perhaps +/- 0.5 to
0.75 feet.
The uses to which we can put
the 3-dimensional capability are many. The following is a mere
sample.
1. Crown spreads
(maximums and averages)
2. Limb lengths
3. Crown
point-horizontal offsets
4. Trunk segment
lengths
5. Trunk widths
(error level may be too high)
6. Crown volume
calculations
7. Full tree
mapping (error level may be to high)
8. Vegetative
surveys where location of each tree/species is desired
9. Location of a
tree relative to an established landmark
10. Angle of limb departure
from trunk (with law of cosines)
The biggest disadvantage of
the TruPulse is that it doesn't thread the needle when there is
clutter in the way. In addition, if the target is small with
items around it, you can never be sure that you are hitting the
most distant point. For example, if you are trying to measure
the length of a limb structure, you may be okay where the limb
joins the trunk, but hitting the end of the foliage section
where there are multiple targets is a crap shoot. I need to do
more testing to determine sensitivity.
Well, on to the day's
testing with results to be reported later. Oh, by the way, the
ML (missing line routine allows you to compute the height of a
tree via the sine top-sine bottom method without that being a
specific intention of theirs. It gets around the limitations of
their built in, tangent-based height routine.
The TruPulse 360 is way
cool.
Bob |
| TruPulse
360-final report |
dbhg-@comcast.net |
| Sep
04, 2007 09:52 PDT |
ENTS,
Today the TruPulse 360 that has
been loaned to me for testing goes back to its home at LaserTech.
All in all, I'd say that the instrument performed well and it
has many potential applications for us. I need lots more time
for testing, but appreciate the opportunity I've been given. I
will most likely buy a TruPulse 360, but I'm hesitant to
purchase from the first run of models. If the TruPulse 360 is
like the RD1000, the first models don't have all the kinks
worked out.
For quick shots of the opposite
sides of tree crowns to get crown spread, or the opposite ends
of a limb to get limb length, the TruPulse could be invaluable.
It can even be used for some crude trunk modeling, but I would
emphasize that we need to keep approximating methods distinct
from more exacting methods such as what we can accomplish with
the Macroscope 25/45.
One of the tests performed on the
360 was of its relative azimuth feature - the azimuth of point
#2 as measured from point #1.If the points are ground-based, you
can go the the first point and shoot to the second point with a
compass or the 360 to get the azimuth of point #2. If both
points are in the canopy of a tree, that may not be possible.
However, if both points are in the first quadrant and arranged
in a configuration with the second point at a higher azimuth
reading and a greater distance, then the following formula
provides the relative azimuth.
d1 = horizontal distance to point
#1
d2 = horizontal distance to point
#2
a1 = azimuth of point #1
a2 = azimuth of point #2
A = azimuth of point #2 from point
#1
A = 180 + a1 - arccos[(d1-d2*cos(a2-a1))/sqrt(d1^2+d2^2-2*d1*d2*cos(a2-a1))]
There are many possible
configuration of points and I'm unsure to how many the above
formula applies. There will be quadrant adjustments leading to a
family of formulas. All in good time. They will be incorporated
into the dendromorphometry guide that some of us are working on.
I'll soon be turning my attention
to the Macroscope 45. I'm pretty confident that the better
choice is the Macroscope 25, but hopefully, I'll find
applications for the 45.
Bob
|
| Testing
the TruPulse 360 Horizontal Angle Measurer |
dbhg-@comcast.net |
| Sep
06, 2007 01:37 PDT |
ENTS,
The specified accuracy for the
compass built into the TruPulse 360 is listed as +/- 1 degree.
That isn't too good if you want to use the 360 to measure
diameters of trees. Howeevr, I think that most readings are more
accurate, perhaps to +/- 0.5 degrees. To test how well the
instrument works for diameter measurement, you can measure the
width of of a target object with a tape measure. Then from a
convenient distance, align yourself with a tree and measure the
distance to each side of the tree from the reference point.
Align yourself so that you are centered on the object. The
distances to the edges should be equal. Now calculate the angle
subtended by lines from the reference point to the edges of the
target as follows.
If D = distance
to an edge
W =
width of target
A
= angle subtended by sides of triangle from reference point to
sides of target
Then A = arccos(1 - W^2/D^2)
Now from the reference point, take
azimuth readings of each side of the target and subtract them.
Compare the result to A from the above formula. You may need to
repeatedly shoot the azimuth readings to be sure you are hitting
the outer edges of the target.
I didn't have time to do this when
testing the 360 loaned to me.
Bob
|
| Macroscope45 |
dbhg-@comcast.net |
| Sep
04, 2007 16:27 PDT |
ENTS,
Gary Beluzo and I decoded the Macroscope
45 today after I made a series of comical errors. However, the
final news is that the factor for the model 45 is 41.667. That
corresponds to 75 for the Macroscope 25.
Bob |
|