Abstract

The geometrical structure of a vegetation canopy determines the amount of foliage presented to a sensor and the form of the relationship between reflectance and vegetation amount. The aim of this study was to develop a practical measure of vegetation amount that was sensitive to canopy geometry. This measure was termed the radiometric leaf area index (RLAI) and comprised measurements of leaf area index (LAI), leaf inclination or curvature and the area of the canopy visible to the sensor. RLAI, evaluated on simulated and laboratory-derived data, was sensitive to canopy geometry but, like LAI, suffered from a high measurement error. Primarily as a result of error in these data sets reflectance was similarly correlated to both RLAI and LAI and therefore RLAI offered no advantage over LAI for the measurement of vegetation amount. It was concluded that future formulations of RLAI should be more complex and accurate.