BRDF Applications in Semiarid Grassland Monitoring with the AVHRRs

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backscatter direction fwdscatter direction

Examples of BRDF distributions in a single azimuthal plane
A longer arrow implies a higher radiance value.

In the first diagram, the distribution of outgoing radiance is equal over the hemisphere; this is the reflectance expected from a truly Lambertian surface. Very few natural surfaces exhibit this property.

In the second diagram (the one with arrows of differing lengths), the outgoing radiance is not equally distributed over the hemisphere; the radiance detected by a sensor would depend on the viewing angle of the sensor relative to the surface, as well as the angle of incidence of incoming radiation. This is what happens in practice!