Lewis R. (Lou) Grosenbaugh (November 4, 1913 – April 22, 2003)[1] was a prominent U.S. Forest Service researcher and head of the Forest Service's first Pioneering Research Unit, in forest mensuration, in Berkeley, California.

Known for his contributions to the fields of forest inventory, forest measurement, and forest management, Grosenbaugh built on Walter Bitterlich's idea of estimating the density of a forest with timber cruising so that individual trees could be used to estimate various stand measures, such as volume per acre.

A notable contribution of Grosenbaugh was adapting Bitterlich's techniques to forest inventories throughout the US.

Grosenbaugh promoted the findings of European foresters and brought them the researchers and foresters in the US.

[3][4] Grosenbaugh had pioneered many original thoughts during his work in statistical sampling of trees in forests, including subsampling trees to obtain a volume to basal area ratio.