##### Measuring Big Trees

The New Jersey Forest Service Big Tree Conservation Program uses the American Forest 3-Point formula to determine the potential Big Tree Champions:

Total Points = Circumference of trunk (in inches) + tree height (in feet) + 1/4 average crown spread (in feet)

Start by measuring the circumference of the tree at 4 1/2 feet off the ground in inches, or if the tree sits on a slope, 4 1/2 feet from the uphill side. If the tree has a branch or abnormal swelling at 4 1/2 feet, take the measurement where the trunk returns to normal size. If you measure below 4 1/2 feet, make sure to include the actual height where the measurement was taken.

For example: 182" or 15’-2” circumference at 3 feet.

There are numerous ways to measure the height of a tree. You can purchase a clinometer or a rangefinder, which will mechanically do the math for you, or you can use the Biltmore stick method that is described below.

Biltmore Stick Method

1. Hold the stick or ruler at its base vertically, making certain that the length of the stick above your hand equals the distance from your hand to your eye.
2. Move away from the tree while sighting the trunk base above your hand while staying on ground level (or on the same contour as the base of the tree).
3. Stop when the top of the stick is level with the top of the tree.
4. You should be looking over your hand at the base of the tree and, moving only your eyes, looking over the top of your stick at the top of your tree.
5. Measure how far you are from the tree and that measurement - in feet - is the tree's height.

Clinometer

1. Measure out 66 feet (also referred to as one chain in the forestry world) from the base of your big tree.
2. Place the clinometer to your eye and shoot an imaginary line to the top of the tree.
3. Once you are lined up with the top of the tree, read the number on the right side of the clinometer. Let’s say the number is 95’.
4. Now shoot a line with your clinometer to the base of the tree. Let’s say the number is – 5.
5. Now let’s determine the total tree height. Take 95’ + 5 = 100”

Note if the number at the base of the tree is negative, you add it to the number at the top of the tree and if it’s positive you subtract it from the number at the top of the tree.

Rangefinder
Digital Rangefinders, also known as digital clinometers, are the most expensive of the three height measuring tools but they are quick and easy to use, and they are the most accurate. The nice thing about a digital rangefinder is that you can be any distance away from your tree and it will give you the tree’s height.

Measure the crown at its widest (A-B) and narrowest widths (C-D). Find the average crown by adding the two measurements and dividing by two.

Please note that September 1st is the cutoff date for big tree measurements and that tree measurements resume in the spring of each year.

Clinometer:
an instrument used for measuring the angle or elevation of slopes. The height of NJ big trees is measured 66 feet away from the tree. This allows the forester to use the numbers directly off the right side of the clinometer without having to use the formula to calculate height.

h = (A-B) * (d * .01)

Rangefinder/hypsometer:
A rangefinder/hypsometer provides accurate range, height, and angle measurements.

Logger’s Tape:
Loggers tapes are designed and manufactured for professional loggers, forestry specialists, and arborists. They come in a variety of blade lengths and scales including English, English/Metric, All metric, and Diameter. New Jersey Forest Service foresters typically use a 75’ tape because they are long enough to pull out 66’ (one chain) to measure tree height and circumference.

200’ Fiberglass Tape:
The crowns of big trees can be enormous. That is why it is necessary to be equipped with a 200’ fiberglass tape.

Cruising Vest:
A cruising vest is handy for foresters because it is a highly visible orange and it has many grommets for tying forestry tools like their clinometer and compass. It also has numerous pockets for carrying flagging and small field notebooks.

Smartphone:
Smartphones have become such a useful technology over the years. About four years ago the Big Tree Conservation Program switched over to logging field data with smartphones and it has proven to be more efficient than the past dataloggers.