25 vs RD 1000
10, 2006 06:31 PST
Will and Jess,
I ran some more tests on the Macroscope 25 vs
the RD 1000 at long
distances and less than ideal visibility - a kind of worst case
for the instruments. The results are summarized below.
Dist Diam Error Instrument
Rng-ft Rng-in Rng-in
226-312 14-44.7 0.170 Macroscope
226-312 14-44.7 1.220 RD 1000
At 0.17 inches, the average error for the
macroscope reflects the bad
visibility rather than the instrument. I was fairly pleased with
1000's performance. I feared that the average error might be
at great distance.
For the range of work we do, for the
Macroscope 25, it boils down to
visibility. If we can see it, we can accurately measure it. With
this Sunday, I hope to measure this past season's growth of the
Swamp tree. Should be able to do it to the nearest half inch.
Robert T. Leverett
Cofounder, Eastern Native Tree Society
Macroscope 25 vs RD 1000
10, 2006 22:57 PST
Are those numbers and error ranges for width or diameter? If
are not all that meaningful for absolute error.
to Will with buried question for Pamela
13, 2006 06:12 PST
ANSWER TO WILL'S QUESTION:
They were diameters, and as a consequence, I completely agree
that they aren't very meaningful. I did more tests over the
NEW MACROSCOPE VS DENDROMETER TESTS:
Actual diameter: 13.8"
RD 1000 12.8"
% error of act 7.3%
Macroscope 25 13.1'
% error of act 5.1%
on same birch tree (flat target)
Actual diameter: 11.0"
RD 1000 10.8"
% error of act 1.9%
Macroscope 25 11.1
% error of act 0.9%
on cottonwood (flat target)
Actual diameter: 18.0"
RD 1000 19.7"
% error of act 1.9%
Macroscope 25 18.1'
% error of act 0.9%
When the target is well
defined, I'm consistently getting errors
of under 1% for the Macroscope 25. Based on your and Jess's
expected that. I probably won't get quite the results that you
until I get new glasses. However, bad vision and all, the error
as low as 0.3% for significant distances. The Dendrometer's
usually around 2%, sometimes a little less. With a better
might slightly reduce the error for both instruments.
One lesson that comes through over
and over (not that we didn't
already know it) is that trees are NOT circular in cross section
that any serious attempt to model the volume of a trunk or a
take lack of circularity into account. The wide variation that I
from taped circumferences converted to diameters as compared to
measurements of diameter that I'm getting with the Macroscope 25
the very narrow variation in actuals versus measured for flat
serves to further illustrate how often trees are out of round.
Instruments that are designed around assumptions of a circular
section are going to lead to measurement errors. I suppose that
rely on a lot of averaging out over large numbers, so that over
trees maybe the volume errors are negligible, but not as applied
individual trees, so that volume tables that assume circularity
standard rate of taper are of no value to ENTS. I discovered
myself about 9 years ago, but wasn’t so confident then in
the inapplicability of table data to single tree measuring. But
was missing something. However, time and testing by the three of
(you, Jess, and me) has amply shown that we weren’t missing
are sentenced to ahve to go it alone.
15, 2006 14:46 PST
You have made a couple of recent posts concerning the asymmetry
trunks. What kinds of things could be looked at in this
asymmetrical are individual trees? Do some species tend to have
asymmetrical trunks than others? Does the degree of asymmetry
age/ What about other factors like stand density? Height to diameter
Is the asymmetry oriented in a preferred direction - north/south
upslope/downslope? Tree canopies are often asymmetrical. Does
asymmetry of the trunk relate to the asymmetry of the crown? Are
equally asymmetrical along their entire height? How does asymmetry
through time (you could measure cookies to determine this one)
lots of potential things to measure...
Lowes & Cannon Creeks, GSMNP, TN
15, 2006 22:23 PST
One way to look at this issue is to assume that in the East,
broadscale windevents and other climatological extremes, a
forest grows one
tree at a time...as one senesces (from whatever
one has an opportunity to fill the void, fresh exposed rich
soil, new dose of
sunlight, to the victor seed goes the spoils (space).
Where that seed that grows most successfully falls, determines
its 'space' and
its space determines how the tree fills it. Seed fall may
chance, but seed germination/growth success, probably doesn't.
aspect affect solar incidence angle (warmth, energy) and tipover
microtopography probably has significant impact on success.
Once the tree roars up into its space, its neighbors constantly
remind it of
its space constraints, as they 'wear' at each other.
Assymmetry should be expected, and the lack of it cause
trunk asymmetery, Macroscope 25, more tree conversations
16, 2006 06:14 PST
Whew! You've given us a decade's worth of measuring
your enumeration of asymmetrical possibilities. As it is, I'm
behind the plan I had for myself to begin simple measurements of
asymmetry. Haven't forgotten it though. Will and Jess, HELP!
Will and Jess,
On another measuring theme, yesterday ENTS reached another
After missing a Forest Reserves meeting, I consoled myself and
MTSF to measure the prior year's growth of the Jake Swamp tree
Macroscope 25. The weather was perfect.
instrument worked marvelously well. I measured 8
growth candles atop Jake's crown. The distance to the targets
from 66.5 to 69 meters and the reticle values varied from 0.3 to
millimeters (I use the metric scale with the Macroscope 25).
to English units, the two highest candles had surprisingly
lengths: 10.6" and 17.7". The full list of candle
10.6", 17.7", 11.2",
16.9", 17.6", 10.4", 15.5", 10.9".
The average of the above is 13.8 inches. There
is little doubt that
Jake will reach 168 feet this year. With luck, it will make 170
end of 2008, 2009 at the latest.
After measuring Jake, I measured 3
candles on the Massasoit tree:
13.8, 11.5, and 9.2 inches. A white pine in front of the Nature
yielded 14.8 and 14.9 inches for its two very conspicuous tops.
The reticle is ideally suited to measure
candle growth. More on
geometry considerations using the reticle for vertical
an angle as opposed to horizontal ones in the next e-mail.
With the confirmation of the Macroscope as
reliable for new candle
growth measurement atop our tallest trees, I can finally make
good on my
promises to DCR. Lots of new possibilities. When will it ever
1000 vs Macroscope 25
07, 2006 04:46 PST
Will, Jess, Ed, et al:
I've added a few more tests of the RD 1000
versus the Macroscope 25.
Through 30 tests, the average of the absolute values of the
between the two instruments is 1.07 inches. That average covers
that are from 8 to 34 inches in diameter and shot from distances
to 312 feet. The difference between what the two instruments
most pronounced for large diameter objects. For example, the
difference for targets 24 inches or more in diameter is 1.99
That is almost double the overall average. This makes me
of my volume modeling of the big pines and hemlocks that I've
far in MTSF, MSF, Ice Glen, Bullardwoods, etc. Yet, it is a cut
dried issue. I got almost exactly what BVP modeled for the
In fact, my number was slightly lower than his. So, since the
not uniform, I cannot say for sure that all my big tree models
by a certain percent.
The RD 1000 is a fun instrument to use and
definitely has a role in
what I'm doing, but some kind of compensation factor must be
to correct for large objects and long distances. The difference
the two instruments illustrates the problems we encounter with
on sophisticated, versatile instruments. Internal algorithms and
tradeoffs can compromise accuracy without trusting users being
One needs to be aware of how much accuracy they are willing to
in order to enjoy a plethora of "Gee Whizz, it makes coffee
Having said this, use of the RD 1000 at
distance of 65 to 85 feet on
targets of 6 to 20 inches does yield good results.
08, 2006 05:33 PST
Will, Jess, Don, Lee, et al:
More comparison tests of the RD 1000 vs the
Macroscope 25 were
conducted last evening. The edition of 4 tests puts the average
difference between the two instruments at 1.1 inches and that
represents 4.86% of the Macroscope average diameter.
If more larger objects are shot at a distance,
the average difference
between the Macroscoope 25 and RD 1000 will grow. But if the
classes stay well mixed, the average difference (actually the
the absolute values of the differences) will likley stay around
At present, that's the number I'm keeping in my noodle.
How does the accuracy of each instrument
compare with the direct
measurement of the target objects? Well, a tree trunk measured
evening with a D-tape was 32.52 inches. The Macroscope 25
32.72 and the Rd 1000 was 33.3. The 0.2 inch difference for the
Macroscope represents 0.6% of the taped diameter. The 0.78 inch
difference for the Rd 1000 represents 2.3% of the taped value.
Since the tree trunk isn't absolutely
circular, the D-tape
measurement yields only an approximate value so that comparisons
0.2 versus the 0.78 inch differences is a little misleading.
Measuring control objects that are either
circular or flat is showing
that the maximum absolute error from the Macroscope does not
inch and that the average error is less than half that -
than a 1/10th of an inch. The Macroscope is consistent. Large
tend to be problems with seeing the target. However, the maximum
absolute error of the Rd 1000 can reach 3 inches, although that
extreme and is for large targets seen at distances of over 100
average error is around 1 inch.
The bad news from all this is that the volumes
of the larger trees
that have been modeled with the Rd 1000 are highly likely to
overstated. So it's hi-ho back into the forest I go to figure
out a new
set of volumes for an old set of trees.
Rd 1000 vs Macroscope 25
08, 2006 10:25 PST
With one exception, the 35 measurements are
comparable only among one
another. I was not clear on that point in my communication.
I've now tested the Macroscope 25 many times
measured objects and am very confident that its error range is
+/- 0.5 inches for distances approaching 300 feet. Errors in the
0.5 range are due to human error as opposed to instrument
Target visibility is the biggest source of error. However, most
Macroscope 25 measurements are accurate to +/- 0.2 inches on
between 100 and 250 feet. Objects that are too close are not
the monocular, so one does have to maintain one's distance.
Once I start re-measuring the pines, I'll
consider the Macroscope 25
as providing the equivalent of a direct measurement, but I'll
re-shoot with the RD 1000 so I'll have a side by side comparison
each tree to report.
Despite its limits, I really like the RD 1000
and see its utility for
jobs that fit into distance and diameter windows, with distance
to 100 feet and a diameter being 6 inches to 30 inches. The 6
be dropped to 4 and the 30 can be increased to 36 if one is
accept a larger error.
I'm anxious to re-measure the Grandfather pine
in MSF. I have a
feeling that the volume is going to go down by 75 to 100 cubic
That would drop it below 1000 cubes. Rats!! If the weather
out, it may be off to MSF old Bob goes this Sunday.
Don Bertolette wrote:
Stupid question time...are these measurements
only, or are you comparing these two measures against