Phase angle dependence of sand density observable in hyperspectral reflectance

Bachmann, Charles M.; Philpot, William; Abelev, Andrei; Korwan, Daniel

doi:10.1016/j.rse.2014.03.024

Cited by 22 publications

(41 citation statements)

References 42 publications

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“…A high-density scene and a low-density scene of mixed soil were created. The trends observed by Bachmann et al 11 were thought to be a byproduct of smaller magnetite grains physically mixed with larger quartz grains. Therefore, the distribution shown in Fig.…”

Section: Chemistrymentioning

confidence: 84%

“…Documentation reveals that changes in geometry and porosity have an impact upon reflectance. [5][6][7][8][9][10][11][12][13][14][15][16] Even so, the exact relationship between porosity and reflectance is still ambiguous. Laboratory studies have shown that reflectance does increase with density.…”

Section: Phenomenologymentioning

confidence: 99%

“…Bachmann et al measured beach sand samples of different densities to observe reflectance trends related to changing phase angle. 11 Phase angle is the angle subtended by illumination source, sample, and a sensor. It was observed that lower density sands had larger reflectance than higher density sands.…”

Section: Phenomenologymentioning

confidence: 99%

“…The virtual sensor used in this experiment was characterized by Gaussian-shaped response functions centered at 450, 550, 650, 868, 1000, and 1915 nm. Bachmann et al 11 also analyzed spectral reflectance at these wavelengths. Half nanometer spectral resolution was used.…”

Section: Radiometrymentioning

confidence: 99%

“…The directional hemispherical reflectance of pure materials is used to represent in-scene chemistry. Through the consideration of these three parameters, observed signature features [11][12][13][14][15][16][17] due to particle size, porosity, and physical mixing are closely analyzed through simulation. The ability to shed the need for functional data fitting is an important benefit of this technique.…”

Section: Introductionmentioning

confidence: 99%

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Soil signature simulation of complex mixtures and particle size distributions

2015

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Abstract. Soil reflectance signatures were modeled using the digital imaging and remote sensing image generation model and Blender three-dimensional (3-D) graphic design software. Using these tools, the geometry, radiometry, and chemistry of quartz and magnetite were exploited to model the presence of particle size and porosity effects in the visible and the shortwave infrared spectrum. Using the physics engines within the Blender 3-D graphic design software, physical representations of granular soil scenes were created. Each scene characterized a specific particle distribution and density. Chemical and optical properties of pure quartz and magnetite were assigned to particles in the scene based on particle size. This work presents a model to describe an observed phase-angle dependence of beach sand density. Bidirectional reflectance signatures were simulated for targets of varying size distribution and density. This model provides validation for a phenomenological trade space between density and particle size distribution in complex, heterogeneous soil mixtures. It also confirms the suggestion that directional reflectance signatures can be defined by intimate mixtures that depend on pore spacing. The study demonstrated that by combining realistic target geometry and spectral measurements of pure quartz and magnetite, effects of soil particle size and density could be modeled without functional data fitting or rigorous analysis of material dynamics. This research does not use traditional function-based models for simulation. The combination of realistic geometry, physically viable particle structure, and first-principles ray-tracing enables the ability to represent signature changes that have been observed in experimental observations. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Chemistrymentioning

confidence: 84%