where, hF is flame height (metres), A is the flame angle
(degrees), and AT is the flame tilt angle (degrees). Flame
height represents the maximum vertical extension of the
flame front and does not consider the occasional flashes
which rise above the general level of the front (Fig. 1).
Flame angle is defined as the angle formed between the
flame front and the unburned fuel bed (Fig. 1). Flame tilt
angle is defined as the angle formed between the fire
front and the vertical (Fig. 1). At very low wind speeds
on level terrain, flame length is equatable to the vertical
flame height (i.e., A = 90" and AT = 0"). Ryan (1982)
has developed an inexpensive and reliable passive
sensor for measuring flame height which, along with an
estimate of A, can be used to estimate flame length and
frontal fire intensity, at least for low- to moderateintensity
prescribed and experimental surface fires.