| Confirmations
worth mentioning |
Robert
Leverett |
| Jan
10, 2007 13:13 PST |
ENTS,
Over the past several weeks, I've remeasured
several important white
pines in MTSF as an end of 2006 exercise and to see if I could
verify
the heights of important trees from new locations. The Jake
Swamp tree
is currently listed as 168.5 feet. At my new location, which is
on the
opposite side of the tree, I got 168.6. I'll stick with the
168.5
because I've also gotten measurements as low as 168.4. My
clinometer
readings are the culprits.
On these measurements, different equipment was
brought into play. So
I have verification from different spots and different
instruments.
Also, Will Blozan confirmed the readings with his equipment this
past
June. Outside of Will climbing the Jake tree, this is as good as
it
gets.
Lee Frelich's tree was remeasured. This
last measurement places
Lee's tree at 158.7 feet. It may make 160 next year, and if not,
for
certain the following year. My measurements are within 0.2 feet
of one
another for Lee's tree. I'm satisfied.
I found another location to measure the
Frank Decontie tree and got
160.4 feet. All my close measurements of this tree are within
0.3 feet
of one another. I'm satisfied with 160.4 because crown
visibility is
better at the new spot.
Finding multiple vantage points to
verify a tree's height is
important to tying down the height to with +/- 0.2 or 0.3 feet.
Shooting
from exactly the same location multiple times helps one resolve
problems
with bad clinometer and/or laser readings, but crown and base
visibility
don't change. You need to move around.
The crowns of white pines of include
nested tops. With nested tops,
lesser tops intercept one's line of sight and give readings that
may be
accurate for the point being measured, but don't measure the
true top.
This is a far more common problem than one might imagine. After
making a
few hundred mistakes, one develops a feel for where the top
should be
and hunts for a vantage point. Finding the best vantage point or
points
may not happen on the first outing. That is just the way it is.
One
shoots multiple tops from multiple spots on multiple occasions
to get a
height accuracy down to +/- 0.2 feet, but it can be done. That's
the
good news.
People who try to measure trees
with complicated tops with
clinometer and tape measure are destined to make errors and have
no good
way of figuring out which spot is the true top.
I'm working up a new PowerPoint
presentation to give in April at
the Cook Forest rendezvous. I plan to include all the popular
height
techniques, plus some for lengths, volumes, and error checking.
It's
going to be a doozy. Lots more depth than the last.
Bob
Robert T. Leverett
Cofounder, Eastern Native Tree Society
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