Jerzy Cierniewski

The influence of the viewing geometry of bare rough soil surfaces on their spectral response in the visible and near-infrared range

Abstract This work is a supplement to the article “A model for soil surface roughness influence on the spectral response of bare soils in the visible and near-infrared range” [Remote Sens. Environ. 23:97–115 (1987)]. It contains new equations necessary to calculate the shadowing coefficient of bare rough soil surfaces observed by a sensor from arbitrary angles and directions.

Virtual surfaces simulating the bidirectional reflectance of semi-arid soils

Virtual surfaces of four semi-arid soils (regs, crusts, playas and sands), used to predict their bidirectional reflectance in the optical domain, are discussed in the paper. These surfaces are defined by the horizontal and vertical semi-axes of equal-sized opaque spheroids simulating their particles or aggregates. The spheroids are regularly dispersed in a net of squares of a given side length, on a freely sloping plane. They are absorbed into the ground with their tops projecting to a given height above the slope. The material of the vertical structure is additionally defined by its refractive index. Virtual surfaces determined in this way were used as part of the input data to a geometrical model, which predicts the soil surface normalized reflectance NR, expressed as the ratio of the total radiance of the simulated surface viewed from the off-nadir direction to the radiance viewed from the nadir.

Effects of Soil Surface Irregularities on the Diurnal Variation of Soil Broadband Blue-Sky Albedo

This paper quantitatively explores, in terms of roughness indices, the effect of soil surface irregularities on the diurnal variation of the broadband blue-sky albedo of a large range of soil properties. Field studies were carried out on cultivated and uncultivated soil surfaces in Poland and Israel that vary in roughness and brightness. It was found that these irregularities, formed by different agricultural equipment and modified by rain or sprinkler irrigation, can be quantified by two roughness indices. Soil roughness not only affects the overall level of the diurnal variation of the albedo, but also affects the intensity of the diurnal increase from the solar zenith angle (θs) at the local noon to about 75°- 80°. The roughness indices are variables that precisely determine only the albedo at the local solar noon of soils with the same color value. If the contents of soil organic carbon (SOC) and calcium carbonate are treated as the dominant variables, combined with one of the indices, these three variables together would significantly describe the albedo at the local solar noon of all soil surfaces. The soils, with their high irregularities, showed almost no rising values of albedo at a θs lower than 75°, while the smooth soil surfaces exhibited a gradual increase of the albedo at these angles. It is concluded that the roughness indices provide sufficient means to accurately describe the diurnal variation of the albedo of a wide range of surfaces, disregarding other soil properties.

Geometrical modelling of soil bidirectional reflectance incorporating specular effects

Abstract A geometrical model, taking into account the diffuse, as well as the specular component of energy leaving soil surfaces in the visible and near-infrared, is discussed here. The model computes the bidirectional, reflectance of soils illuminated by a single source. A rough soil surface is simulated by equal-sized spheroids regularly spaced on a horizontal surface. The model was tested using soil bidirectional reflectance data obtained in laboratory conditions by Jacquemoud et al in 1992. Two parameters describing soil surface geometry were used for modelling the soil relalive reflectance in laboratory conditions: the relative distance (d/ a) between spheroids (relative to their horizontal radii ( a )and the shape of spheroids (b/ a) ( as proportion of their vertical (b) to horizontal radii (a)) The simulation of reflectance for soil surfaces of pebbles and sand, containing simple dense particles with rounded edges, can be carried out using the d/ a and b/ a ratios which nearly described their aclua...

Effects of farming works on soil surface bidirectional reflectance measurements and modelling

A model describing the directional reflectance in the optical domain from cultivated soil surfaces, taking into account their farming direction, is presented in the paper. It is discussed on the background of the directional reflectance measurements of soil surfaces, being effects of farming works preparing the soil for colza sowing. The model considers a soil surface as equal-sized opaque spheroids of definite shape and size dispersed in a net of squares on a freely sloping plane. They are absorbed into the plane having with their tops at a height above it. Different values for this height, along and across the soil cultivation direction, are parameters which express the variation of soil surface irregularities caused by furrowed farming treatments. The structure is illuminated by direct solar and diffuse light. Wave energy is reflected from it taking into account the diffuse and the specular components. A set of geometrical parameters of the structure, the equivalent of the real rough soil surface, makes it possible to predict the soil directional reflectance in any illumination and viewing conditions. It was applied to trace the influence of the direction of furrows, caused by a seeder, on the soil bidirectional reflectance.

Bidirectional reflectance of bare soil surfaces in the visible and near‐infrared range

Abstract A deeper understanding of interactions of electromagnetic radiation with interpreted objects, as well as technological advance, is important for a further improvement of remote sensing methods. It also concerns soils, which like many natural objects, show variation in their brightness due to the direction of irradiating solar energy and the direction along which the reflected energy is detected. On the one hand, the knowledge of the interaction mechanisms, verified by laboratory and field measurements of soil spectral properties, enables us to define optimum source and sensor configurations for practical purposes. On the other hand, it makes possible the conversion of the remote sensing data collected with different illumination and viewing conditions to be standardized, which contributes to improved interpretations. The goal of this paper is to review physical principles of surface interactions with radiation in the visible and near‐infrared range, as well as the measurement of soil bidirectiona...

Furrow Microrelief Influence on the Directional Hyperspectral Reflectance of Soil at Various Illumination and Observation Conditions

This paper describes the results of an experiment designed to investigate the effects of furrow microrelief on the soil hyperspectral directional reflectance collected at various illumination and observation conditions. The reflectance of four soil surfaces formed by the same sandy material, one smooth and the others with furrows of different depth, were measured by a laboratory prototype goniometric spectral device. The most notable effects of the furrows on the hyperspectral bidirectional reflectance factor of the surfaces were observed along the vertical plane perpendicular to their furrows at high view zenith angles (as degrees from the nadir), particularly if the light-source zenith angle θs is extremely high, and its beams reach the furrows at the horizontal angle of 90°. It was also found that the absorption features of the soil material used in the experiment, located at around 1420 nm, become less visible with the increase of the θs, independent of the shape of the surfaces.

Effects of Sun and view geometries on cotton bidirectional reflectance. Test of a geometrical model

Abstract During the MAC-VI campaign, bidirectional reflectance measurements were taken on a cotton crop in order to analyze the effects of sun and view geometries in the wavebands and in the viewing vertical plane of the SPOT High Resolution Visible (HRV) instrument. The bidirectional reflectance was measured using a CIMEL SPOT simulation radiometer fixed on a goniometric apparatus 2 m above the top of the crop. Data are presented in terms of bidirectional reflectance factors relative to nadir reflectance for 15 view angles (− 70° to + 70°) and for 12 solar zenith (73-26°) angles. Results show major variations according to Sun position and backscattering or forward scattering observations. The relative reflectance factor of the cotton varies from 0.7 to 1.9 throughout one day. Measurements are compared to the output of a geometrical model where cotton rows are simulated by spheroidal cylinders sitting on an horizontal surface. The relative reflectance factor is calculated according to the global structure of the rows which is divided into illuminated and shaded facets viewed by the radiometer for each view and solar angle. The analysis of comparative results shows a good agreement between predicted and measured data in the three SPOT HRV wavebands.

Approximating the average daily surface albedo with respect to soil roughness and latitude

The present study explores the diurnal variations in blue-sky albedo (α) of soils under clear sky conditions with respect to surface roughness. Three roughness levels of ploughed and unploughed soil surfaces, developed from the same loessial material, were examined. The relation between α of the surfaces and the solar zenith angle, determined during the experiment, enabled us to predict the diurnal α variation of the surfaces throughout the year at a given latitude, between 75° S and 75° N. The optimal time (T O) for measuring the soil albedo by an instantaneous observation was considered as the best represented time for the daily averaged value within an error lower than ±2%. It was found that the T O, falling at different times depending on the soil surface roughness, limits the possibilities of data achievement by remote-sensing satellites along one of their sun-synchronous orbits.

Effects of Soil Surface Roughness on Soil Reflectance Measured in Laboratory and Outdoor Conditions

Various remote sensing methods, including diffuse and contact reflectance spectroscopy (DRS and CRS, respectively) as well as proximal soil sensing (PSS), have been widely used for obtaining information about the soil properties. The influence of soil surface roughness on soil spectra obtained with a FieldSpecPro (ASD) spectroradiometer using three measurement techniques was investigated. The PSS spectra in outdoor (PSS-O) and laboratory (PSS-L) conditions were collected and then compared with the spectra of the same soil recorded using Muglight (ML) adapter. PSS measurements of each soil sample were taken at three surface roughness levels: the lowest roughness level, representing the rolled surface, the second representing a moderately rough (MR) surface of medium-sized clods and aggregates, and the third level with the highest soil surface roughness, where the clods and aggregates, with size beyond their assessed mean size for a given soil. The roughness indices height standard deviation (HSD) and tortuosity (T3D) were closely related to the size of the aggregates and clods forming the soil surface. The ML spectra of ground samples were more strongly correlated with the PSS-L spectra than with the PSS-O spectra, and mean coefficient of determination (R2) for the spectra obtained at three levels of roughness was 0.99 and 0.95, respectively. With the increase of surface roughness, the differences between the level of ML and both PSS-L and PSS-O spectra increased. The relative difference (RD) calculated for PSS-L and PSS-O spectra in relation to ML spectra was better explained by the T3D (R2 = 0.82), than the HSD (R2 = 0.68).