Conceptual models from experience and intuition from past fires can be used to anticipate the future. Many semi-empirical fire spread equations, as in those published by the USDA Forest Service, Forestry Canada, Nobel, Bary, and Gill, and Cheney, Gould, and Catchpole for Australasian fuel complexes have been developed for quick estimation of fundamental parameters of interest such as fire spread rate, flame length, and fireline intensity of surface fires at a point for specific fuel complexes, assuming a representative point-location wind and terrain slope. Based on the work by Fons's in 1946, and Emmons in 1963, the quasi-steady equilibrium spread rate calculated for a surface fire on flat ground in no-wind conditions was calibrated using data of piles of sticks burned in a flame chamber/wind tunnel to represent other wind and slope conditions for the fuel complexes tested.