In order to determine the Bi-directional Reflectance Distribution Function
(BRDF) of natural surfaces a CCD line camera is used. This allows measureme
nts under natural conditions with a high azimuth and zenith angular resolut
ion in a short time. The CCD line spans a field of view of 80 degrees as th
e zenith angle range. For covering the azimuth range, the camera is mounted
on a rotating device and an extendible boom provides an aerial platform. T
his set up allows the measurement of the [almost] complete reflectance dist
ribution of the surface below the camera for the 30-s rotation period of th
e camera. The camera used for this set up is the wide angle airborne camera
(WAAC), which was developed at the DLR for airborne stereo imaging purpose
s, This paper presents the radiometric calibration of the system and shows
the initial results of our approach in measuring the BRDF with high angular
resolution for a short period. (C) 2000 Elsevier Science B.V. All rights r
eserved.