Trees: the cross section area of a tree stem in square feet commonly measured at breast height (4.5' above ground) and inclusive of bark, usually computed by using d.b.h. or tallied through the use of basal area factor angle gauge.
The basal area factor is the number of units of basal area per acre (or per hectare) represented by each tree. The fornula for basal area = (3.1416 x DBH^2)/(4 x 144). This formula simplifies to: basal area = 0.005454 x DBH^2