Different functions, including 1/ρ, more precisely 1/( ρ cos(α) ), were tested. The function bringing the curves to the closest overlap was (ρ cos(α))-0.16. In Fig. 4, right, the observations of Ex1-5 are shown. All intensity values were multiplied with (ρ cos(α))-0.16 to remove the influence of target reflectivity and angle of incidence. Then, the measurements were grouped in intervals of 2m width. For each class the mean, the standard deviation, and the coefficient of variation are plotted. For
comparison the best logarithmic model ( 0.22/ln( ρ cos(α) ) + 0.15 ) is shown, too.