Effect of surface roughness, wavelength, illumination, and viewing zenith angles on soil surface BRDF using an imaging BRDF approach

Abstract

Compared to non-imaging instruments, imaging spectrometers (ISs) can provide detailed information to investigate the influence of scene components on the bidirectional reflectance distribution function (BRDF) of a mixed target. The research reported in this article investigated soil surface reflectance changes as a function of scene components (i.e. illuminated pixels and shaded pixels), illumination and viewing zenith angles, and wavelength. Image-based BRDF data of both rough and smooth soil surfaces were acquired in a laboratory setting at three different illumination zenith angles and at four different viewing zenith angles over the full 360°azimuth range, at an interval of 20°, using a Specim V10E IS (Specim, Spectral Imaging Ltd., Oulu, Finland) mounted on the University of Lethbridge Goniometer System version 2.5 (ULGS-2.5). The BRDF of the smooth soil surface was dominated by illuminated pixels, whereas the shaded pixels were a larger component of the BRDF of the rough soil surface. As the illumination zenith angle was changed from 60°to 45°and then to 30°, the shadowing effect decreased, regardless of the soil surface. Soil surface reflectance was generally higher at the backscattering view zenith angles and decreased continuously to forward scattering view zenith angles in the light principal plane, regardless of the wavelength, due to the Specim V10E IS seeing more illuminated pixels in the backscattering angles than in the forward scattering angles. Higher soil surface reflectance was observed at higher illumination and viewing zenith angle combinations. For both soil surface roughness categories, the BRDF exhibited a greater range of values in the near-infrared than at the visible wavelengths. This research enhances our understanding of soil BRDF for various soil roughness and illumination conditions.

Characterizing Land Surface Anisotropic Reflectance over Rugged Terrain: A Review of Concepts and Recent Developments

“…Generally, topography alters the illumination and viewing geometry and generates a relief shadow, observation masking, and multiple scattering, this results in the intense topographic dependence on total incident and reflectance radiance, which distorts BRDF characteristics [4,21]. The BRDF characteristics varies with wavelength and shows a BRDF wavelength dependence in surfaces of greater roughness [22,23]. Without considering the topographic effects on the land surface BRDF, the anisotropic reflectance estimation relative errors could be larger than 58% [24].…”

Retrieval of Sediment Fill Factor by Inversion of a Modified Hapke Model Applied to Sampled HCRF from Airborne and Satellite Imagery

“…Physical properties of a sediment surface such as density, grain size, surface roughness, and moisture content influence angular dependence of spectral signatures, specifically the Bidirectional Reflectance Distribution Function (BRDF) [3][4][5]7,[16][17][18][19][20][21][22][23][24][25][26][27]. Models based on radiative transfer equations can relate the angular dependence of the reflectance to these geophysical variables [3,5,7,[17][18][19][20]28,29].…”

A Seven-Parameter BRDF Model with Double-Peak Characteristic Suitable for Sandy Soil

“…Bidirectional Reflectance Distribution Function (BRDF) has been widely used in the fields of agricultural remote sensing, atmospheric radiation transmission, spectral scattering characteristics of rough surface targets, and material diagnosis [1][2][3]. In the fields of agricultural remote sensing and digital agriculture, BRDF is used to study the spatial distribution characteristics and spectral characteristics of the reflected light of object, as shown in Figure 1.…”