// Calculate height
$h = 2.4527 * log([D:m]) + 5.3355;
// Return nearest half integer value
return floor($h * 2) / 2;

Approximates data in Table 3.2 by a logarithmic function (R² = 0.84).

Performs better than 2nd-order polynomial function (R² = 0.93), which gives a maximum height of ~15 m (D = 40-50 m) and than decreases yielding unrealistic values. Maximum height is ~17 m.

Original diameter range is 10.97-67.06 m (36-220 ft).