| Tree
Height Measuring Accuracy |
Will
Blozan |
| Sep
26, 2005 14:40 PDT |
ENTS,
When discussing our tree height measuring accuracy, our sin+sin
based
methodology will mean nothing, I mean absolutely nothing,
without physical
verification of the actual tree height. That involves a tape
drop. To the
average person our numbers are no more significant than anyone
else's. We
have some numbers from our climbs but they are not displayed on
our website.
We need a page to back up the credentials we say we have.
Maybe it's time we invited professionals to "tag-team"
a champion tree that
we could get permission to climb. We could all measure it and
discuss the
methods and pitfalls as a training session.
Will
|
| Re:
Lots a stuff |
Edward
Frank |
| Sep
26, 2005 18:04 PDT |
Will,
I could not agree more. The single most
important thing we need to do in
order to upgrade the scientific demonstration of the
effectiveness of our
tree measuring methodology is to compile a table of tree
measurements taken
vie the laser/clinometer that were later confirmed by Will's (or
others)
tree climbs. Until this is compiled our methodology is
incomplete.
Bob wrote in a post on Sept 08, 2005: "At 66 feet my aging
eyes saw the
scale just covering the trunk at a scale reading of 32.7 inches.
Please
remember that I got this reading with the RD 1000 before I
actually measured
the tree. I didn't want prior knowledge of the diameter to
influence me in
settling on the scale width that just masked the trunk at the
66-foot
distance."
This demonstrates the need, even in our own minds, to show by a
comparison
of measurements that the methodology is valid. A listing of all
the climbs
is not important, perhaps twenty examples would be appropriate.
What were
the measurements taken by laser before the climb and what was
the actual
taped measurement taken during the climb. In some cases higher
tops were
found in the climbs than were seen from the ground. Including
some examples
of these with an explanatory note would be valuable in this
context.
Ed Frank
|
| Impulse
vs tape drop in Borneo |
Roman
Dial |
| Sep
26, 2005 22:39 PDT |
Will,
The Implse 200 LR was generally within 1 meter of the tape drop
measures. The tape drop measures were done by Tom Greenwood, who
is an
international caliber competitive tree climber. The guy
regularly
climbed to within 1-2 meters of the top! Now these Impulse 200
LR
measures were usually made by Brett, who's been doing big tree
measures
for like 10 years (albeit usually with a Bushnell, a clinometer
and a
calculator -- the humidity hurt his Bushnell). he took great
pride in
estimating his tree heights as a conservative X+. He'd say
"yep 82 plus"
using the laser and eyeballing midpoint of ground, then Tom
would climb
and drop the tape and after adding the small bit at the top the
number
would come out like 82.4 m. This happened all the time. We
climbed 14
trees on our 14 day expedition (all over 65 m) and Brett was in
all
cases but one (-2.7 m off) within 1.99 m and within 0.99 m for
at least
2/3. In essence, Tom checked Brett's measures (underestimates
when
lianas and woods tangled the view) and changed Brett's
"plus" to a
point. So, to answer you question, Will, the Impulse in the
hands of an
experienced user gives measures with 95% confidence intervals of
2 m (or
6 feet), and generally underestimate the true height by around 1
meter.
From my experience, the best pairing is a big tree hunter and a
big tree
climber. I'd be interested to know if you folks back East have a
BVP-Sillett or Mifsud-Greenwood pairing?
Nevertheless, I think it’s very important for the tall trees
to be
climbed as it gives the most precise and accurate measure of the
tree
height and more importantly the best view, looking down at the
world
below after the pleasure of getting over difficult parts of the
trunks
and forks.
Roman
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