It is known that most natural surfaces are scattering incident radiation anisotropically as a function of illumination and viewing direction. These bidirectional effects cause brightness variation to aerial and satellite images and they can be studied e.g. using field-operated goniometers. The Finnish Geodetic Institute has developed four goniometers of different generation assisting the studies of anisotropy of the targets. Larger targets can be studied with the aid of airborne and satellite-borne measurements.

The focus research areas within the topic include

• development of an automatic goniometer
• studies of target´s anisotropic characteristics
• modelling of the bidirectional effects
• correction of the bidirectional effects