Single Scattering

The total first-order scattering from a flat, uniformly lit, homogenous slab (Jensen et al. 2001). Single-scattering is most appropriate for scattering optical thicknesses less than about 0.1 when there is no absorption, but can be applied to thicker media as the single scatter albedo is lowered (American Meteorological Society). Single scattering can be calculated by utilising the BRDF model.

Multiple Scattering

The scattering of light by an array of objects each of which is excited to scatter not only by an external source but also by the scattered light from other objects in the array (American Meteorological Society).

Optical Thickness

The line integral of the absorption coefficient, or the scattering coefficient, or the sum of the two along any path in a scattering and absorbing medium (American Meteorological Society). In plain terms, this is a measurement of the extinction and/or scattering of light for a given material.

Isotropic

Having the same properties in all directions (American Meteorological Society).

Anisotropic

Not isotropic (American Meteorological Society).

Differential Solid Angle

Relates to the raw stream of photons (flux) to the intensity of light. It represents the angular size of a beam as well as its direction (Jensen 2001, p. 16).

Albedo

The ratio of reflected flux density to incident flux density, referenced to some surface.