Intro: Tree Measurement: Biltmore Sticks
Create a Biltmore Stick to measure tree diameter and tree height.
Biltmore sticks, or cruiser sticks, were developed on the Biltmore Estate in North Carolina in the late 1800’s to measure tree diameter at breast height (DBH) and tree height. The Biltmore stick uses the principle of right triangles and sight lines to convert circumference into diameter for the user. It is a quick and easy way to estimate the volume of a tree with a minimal amount of math. With the volume of a tree, timber value or carbon sequestration can then be calculated. Because of the difficulty maintaining exact distance and keeping the stick absolutely vertical or horizontal, the stick only estimates DBH and height, and is not generally used by foresters for generating precise cruise data.
Step 1: Materials
- Tape measure/ruler
0.25” x 1.5” x 24” board (sold at Home Depot for $1.59 in 2016)
Alternative board: 0.25” x 2.5” X 48” ($6.35 at Home Depot in 2016)
Pencil and marker
Optional: wood burning tool
Step 2: Making It
At the distance in inches (left column), make the following Biltmore Equivalent marks on your board in pencil, left to right (see pictures).
On the other side to measure height, make a mark every 6 inches.
You can leave the pencil marks, or you can use permanent marker (it will likely bleed though). If you want it to look nice, you can woodburn the marks on both sides.
Step 3: How to Use It
- Standing in front of the tree you want to measure, hold the Biltmore Stick straight out, with your knuckles against the tree.
- Look to the left side, and move the stick so that the left end of the stick aligns with the tree edge from your view.
- Look to the right. Where the right tree edge falls on the stick, use that DBH (or round to closest line). This is your DBH.
- Tips: Make sure to keep a straight arm, knuckles touching the tree (fist bump the tree), and keep body in one place (be a tree).
- Note: Actual DBH is measured at 4.5 feet from the ground.
- Stand 50’ away from the same tree. You can use a measuring tape or pace out strides equivalent to 50’.
- Again, with a straight arm, align the bottom edge of the stick with the bottom of the tree.
- Decide where the usable “top” of the tree is. Don’t measure to the very top, but to where it would be reasonable to still get a board or two from the top of the tree. If the tree is taller than 48’, reset the bottom of your stick at that 48’ point and measure how many more 12’ logs would be in the remainder of the tree.
Step 4: The Math Behind It
A = the viewpoint
C--D = the Biltmore stick
C--B & D--E = from the viewpoint, the Biltmore Stick edge lines up with the tree edge
C ’--B ’ = the diameter/2
From a set distance of 50’, at A, the same angle degree from B--D and B’--D’ gives an equivalent measurement: every 6” on the Biltmore Stick is a 12’ log.
Step 5: Calculating Tree Volume
Using tree height in feet and DBH in inches, you can calculate the following tree volume in cubic feet.
For example, a 12’ tall tree with an 8” DBH, has 4 cubic feet of volume.
To get a more accurate tree volume in cubic feet, accounting for taper, divide by 4.
To estimate the volume in board feet (a board is 1’x1’x1” thick), divide by 12. To estimate monetary value of a tree online: *need to convert to 16’ logs http://www.timberbuyer.net/treevalue.htm
Some species of trees sell for $1/board foot, but others sell for $0.50/board foot.
To estimate the amount of carbon sequestered in a tree, use the following formula: (Mc= Mass of carbon; Mw= Mass of wood; Dw= density of wood) *Assumes that water makes up ~45% of tree mass and Dw=0.6g/cm3
MC = 0.5 x Mw
Mw=0.55 x Volume x Dw