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Tools of the hemispherical-directional reflectance model

Skylight determines constants of the empirical function describing the hemispherical skylight energy distribution depending on the solar zenith and horizontal angles and the normal optical thickness attributed to the wavelength.

Surface geometry fits geometrical parameters of the soil virtual surface to the soil measured hemispherical-reflectance data and evaluates errors of the fitting.

NDHRDF predicts distribution of the normalized hemispherical-directional reflectance function of a soil surface and its albedo, using the surface geometrical parameters and the surface illumination conditions defined by the sun position in relation to the surface and the normal optical thickness of the atmosphere attributed to the wavelength.

The work on these tools was carried out under the projects: Virtual surfaces for prediction of soil imageries in their variable illumination and viewing conditions and Sky irradiance distribution in the optical domain for modeling of the bidirectional reflectance from soil surfaces, supported by the Rector of Adam Mickiewicz, University in Poznan.

Didactic software

The didactic software has been created for deeper understanding the hemispherical-directional reflectance in the optical domain from soil and rocky surfaces of different roughness states under changed conditions of outdoor illumination. The software has been worked out in the form of tools explaining many aspect of the phenomenon, described by a new geometrical model (Cierniewski et al., 2004). Use of these tools, written in the Borland Delphi 6, needs to install drivers OpenGL minimum in the version of 1.2, and 32-bit colour depth.

Didactics ZIP archive (9.23MB) - Use the following link to download the latest version of the Didactics Tools. Make sure that SSE and OpenGL v1.2.1 (glBlendEquation) is available on your computer


Cierniewski J., Gdala T. and Karnieli A. (2004). A hemispherical-directional reflectance model as a tool for understanding image distinctions between cultivated and uncultivated bare surfaces. Remote Sensing of Environment, 90:505-523.