Figure 1.

(A) A known fraction, the section sampling fraction, ssf, is chosen. In this case five sections (lines are representing sections) are chosen from the object of interest, and (B) a step length = (x, y) and a counting frame area = a(frame) are applied. After placement of a 2D unbiased counting frame, a(frame) in the first predetermined x,y interval, the remainder of the positions of the counting frame in the x,y intervals are repositioned using a stepping motor. (C) Each black square is an optical disector with a fixed height, h. Modified from Figure 5.19 in Howard and Reed (2010).