Biltmore stick
n.— «He wore a backpack with a G.P.S. receiver and carried, in one hand, a data collection unit resembling a portable credit card machine, and in the other, a strip of wood known as a Biltmore stick.…The Biltmore stick, for example, was developed around the middle of the 18th century to determine a tree trunk’s diameter.» —“A Newfangled Way to Count the Trees in the Park” by Lily Koppel New York Times Apr. 6, 2008. (source: Double-Tongued Dictionary)
From http://www.cradleofforestry.com/ :
“The Cradle of Forestry in America is the site of the first forestry school in America – the Biltmore Forest School, founded in 1898 by Dr. Carl Schenck, chief forester for George Vanderbilt’s Biltmore Estate.”
Dr. Schenck probably originated the term, directly or indirectly.