Note 1 to entry: The equivalent diameter is generally calculated as: ${\displaystyle D_e=\sqrt{\frac{4A}{\pi }}{D}_{\text{E}}=\sqrt{\frac{4A}{\pi }}}$, where A is the projected capture area as illustrated in Figure 3.

X

Key

A	projected capture area	h	height	w	width
DE	equivalent diameter	R	radius

Figure 3 – Equivalent diameter calculations for various projected capture areas