DIRECTIONAL REFLECTANCE OF VEGETATION MEASURED BY A CALIBRATED DIGITAL CAMERA

Obtaining directional reflectance information for vegetation canopies is often an expensive and time-consuming process. We present here a si mple approach based on the use of an inexpensive digital camera equipp ed with a wide-angle lens. By the imaging of a large homogeneous area, a single image captures multiple views of a vegetation canopy. This g ives a directional reflectance distribution fully sampled for view dir ection and free of variations in Sun elevation and azimuth. We determi ned the radiometric response of the camera sensor CCD's at the focal p oint and then extended this calibration to the full CCD array by using averaged images of clear blue sky. We evaluated the utility of the sy stem by obtaining directional reflectance distributions of two vegetat ion targets, grass (Lolium spp) and pine forest (Pinus radiata), for r ed visible light. The precision of the derived biangular pattern of re flectance was +/- 7%. (C) 1997 Optical Society of America.