John, Andrew, Will, ENTS,
What follows is something for us to really think about. To distant targets, my
Nikon 440 often shoots long by 0.5 yards. I'd say this happens about half the
time. When repeatedly shooting a target, I will usually get two populations of
bounces that differ by 0.5 yards. I can choose the higher, the lower, or
average the two. However, I often give the tree the benefit of it doubt,
especially when shooting a tree for the first time. The following table shows
conservative measurements where I've taken off 0.5 yards from each distance
measurement to the top and the base. Almost all original distances were the
longer of the two populations and all were taken while Andrew and team were
still climbing. I've left the angle measurements alone. They are from my very
accurate TruPulse 360.
CD = crown distance
CA = crown angle
HA = height above eye level
BD = base distance (to John's tag)
BA = base angle
HB = height below eye level
OFF = height of John's tag
TH = total height
CD CA HA BD BA HB OFF TH
51.00 41.60 101.58 39.50 24.60 49.33 4.50 155.41
54.00 34.10 90.82 47.00 25.30 60.26 4.50 155.58
51.00 41.70 101.78 39.50 24.60 49.33 4.50 155.61
54.00 34.20 91.06 47.00 25.30 60.26 4.50 155.81
57.00 29.00 82.90 53.50 25.60 69.35 4.50 156.75
59.50 29.20 87.08 53.00 24.00 64.67 4.50 156.25
61.00 27.80 85.35 58.50 22.40 66.88 4.50 156.73
72.50 17.20 64.32 75.50 22.90 88.14 4.50 156.95
0.00 0.00 0.00 156.14
The tape dop height was 156.1 feet. The average of the distance adjusted
measurements I took is 156.14. Using a similar method of averaging is how I
came to within 0.1 feet of the tape drop measurements for both the Jake Swamp
and Joe Norton trees. I have always recognized the need to take multiple
measurements, search for patterns, eliminate improbable measurements and
average the rest. I'm sure that I wanted to believe the Thoreau pine is not
less than 158 feet. I hoped for 160, but hav enever gotten that. So, in this
case, I didn't do my usual averaging, especially since John was getting similar
measurements to mine at the time we were comparing them.
My adjustments suggest that the top we measured is truly 156.1 feet above
mid-slope. We'll have to accept that Thoreau's 13.0-ft girth as making up the
difference. If we take a 13-ft girth, the 156.1-ft height, a form factor of
0.4, we get 839.7 cubic feet of trunk volume. It was measured at modeled to
around 816 cubes in 2004. So, 840 cubes now sound pretty close. Do I hear any
other volume bids? Going once, going twice - SOLD!
Bob
----- Original Message -----
From: "John Eichholz" <[email protected]>
To: [email protected]
Sent: Sunday, December 6, 2009 12:04:10 AM GMT -05:00 US/Canada Eastern
Subject: Re: [ENTS] Andrew Joslin and Henry David Thoreau
ENTS,
I was a nice day, as usual when out in the woods. the tape drop results were a
surprise. I can add some more information about the work we did. First,
attached is a photo of the pole location at the time of measurement. It is
blurry, since I was using a 55mm lens. The tip that the pole was at was the
exact one I measured. From where the photo was taken, the line of sight to the
crown was about 57 degrees. You can also make out Andrew as he leans out with
the pole. The top we measured was part of the main leader, which leans
uphill/downstream from the trunk. When the tape reached the ground, it was
perhaps 10' from the trunk due to the lean, and it did seem pretty straight. I
used a clinometer to sight level from the tape to the upper point of the base.
I got 137.9', and added 16' for the pole adjustment and 2.2' for the distance
from the upper base to midslope = 156.1. Using the midpoint between the upper
and lower base of the tree allows the cbh readings to be accurately repeatable.
I measured the tree from several locations, each time to the same tip and to a
pin located at 4.5'h. From each location my readings were repeatable, but I did
have a range of results: 158.4', 157.5' and 156.3'. There is definitely some
experimental error, especially with such long baselines where the clinometer
accuracy can have a greater effect on the result. I would report the middle
height, 157.5', in this case. I suppose a 1.4' error is plausible in the tree,
and perhaps equally plausible in the ground-based measurements. Bob's and my
readings were remarkably consistent, using different instruments, and using
photos of the crown we were able to agree on the tip we considered the highest.
This might just be a case of maximum variance between tape drop and laser
method measurement.
Bob reported on the sugar maple find already. Nearby that tree was another,
120.2'h, in an area that seemed to have more maples than average for the site.
I also found two hemlocks over 119', one next to the Thoreau Pine and one
opposite the trail on the way out. There is bound to be at least one more 120'+
hemlock somewhere in there.
Here is a link to a couple more pictures of the climb:
http://s835.photobucket.com/albums/zz274/treetop314/
Bart and Freddie, I can send you a CD of the rest of the photos if you like.
These are the best ones, though.
John
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