Improved modeling of multiple scattering in hyperspectral BRDF of coastal sediments observed using the Goniometer of the Rochester Institute of Technology (GRIT)

Eon

Ambeau

et al. 2017

Self Cite

Abstract. We compare field hyperspectral bidirectional reflectance distribution function (BRDF) measurements acquired by a hyperspectral goniometer system known as the goniometer of the Rochester Institute of Technology (GRIT) during an experiment in the Algodones Dunes system in March 2015 with NASA Goddard's light detection and ranging, hyperspectral, and thermal imagery of the site acquired during the experiment. We augment our field spectral data collection with laboratory hyperspectral BRDF measurements of samples brought back from the Algodones Dunes site using GRIT and our second-generation goniometer GRIT-two (GRIT-T).In these laboratory experiments, we vary geophysical parameters such as sediment density and grain size distribution of the sediments that would typically impact observed BRDF with the goal of extending the range of applicability of our resulting BRDF spectral libraries. Geotechnical measurements on site confirm the variability of geophysical parameters such as density and grain size distributions within the dune system, and measurements with GRIT and GRIT-T demonstrate the impact on observed spectral variation. By augmenting field spectral libraries with laboratory BRDF, we show that a greater proportion of the dune system is more faithfully represented in the expanded spectral library. Beyond developing appropriate calibration data for airborne and satellite imagery of the Algodones Dunes, laboratory and field studies also support goals to develop reliable retrieval methods for geophysical quantities such as sediment density directly from spectral imagery. We consider approaches based on the Hapke model. Our approaches use the invariance of the observed functional forms of the single scattering phase function, which must be invariant to differences in the illumination geometry. Fill factor is retrieved and correlates with expected direct measurements of sediment density in a laboratory setting. © 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.

Section: Field Measurements Of the Angular Dependence Of Hyperspectralmentioning

confidence: 99%

Modeling and intercomparison of field and laboratory hyperspectral goniometer measurements with G-LiHT imagery of the Algodones Dunes

Eon

Ambeau

et al. 2017

Self Cite

“…In the previous goniometer design of GRIT, a broad azimuthal swath of AE15 deg from the backscatter region of the principal plane was completely shadowed by the arc of the goniometer. 1 In contrast, the GRIT-T is designed so that only regions within phase angles of ∼5 deg from the illumination source orientation are partially shadowed by the instrument profile. In addition to an increased achievable range for directional reflectance measurements, this design allows the system to consecutively measure the forward and backward segments of the solar principal plane with minimal time in between traversals.…”

Section: System Designmentioning

confidence: 99%

“…The first-generation system, GRIT, was a prototype developed by our research group to measure BCRF in the laboratory and HCRF in the field and to further our research in the theory and application of radiative transfer models. 1 The lessons learned from operating the GRIT for two years greatly impacted the design and engineering of the second-generation system. Since the GRIT had been operated in countless laboratory experiments and multiple field experiments, our research group was able to identify the improvements necessary to achieve both better accuracy and precision as well as improved mobility.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to the first-generation system, the goniometer of the Rochester Institute of Technology (GRIT), 1 the GRIT-T collects reflected radiance on a spherical grid in both laboratory and field settings. However, in a field setting, the GRIT-T collects simultaneous incoming and reflected radiance.…”

Section: Introductionmentioning

confidence: 99%

“…These insights quickly became the tenets of the GRIT-T design and were combined with attractive features that were found in other published systems, e.g., the dual field-of-view (FoV) FIGOS, the GOPHER, the automated spectrogoniometer, the FIGIFIGO, and the University of Twente goniometer. 6,[10][11][12][13] These systems, and the GRIT, 1 provided inspiration for the GRIT-T design and had a dramatic impact on the overall capabilities and features implemented in the GRIT-T.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Fully automated laboratory and field-portable goniometer used for performing accurate and precise multiangular reflectance measurements

Harms

Ambeau

et al. 2017

Self Cite

, "Fully automated laboratory and field-portable goniometer used for performing accurate and precise multiangular reflectance measurements," J. Appl. Remote Sens. 11(4), 046014 (2017), doi: 10.1117/1.JRS.11.046014. Abstract. Field-portable goniometers are created for a wide variety of applications. Many of these applications require specific types of instruments and measurement schemes and must operate in challenging environments. Therefore, designs are based on the requirements that are specific to the application. We present a field-portable goniometer that was designed for measuring the hemispherical-conical reflectance factor (HCRF) of various soils and low-growing vegetation in austere coastal and desert environments and biconical reflectance factors in laboratory settings. Unlike some goniometers, this system features a requirement for "target-plane tracking" to ensure that measurements can be collected on sloped surfaces, without compromising angular accuracy. The system also features a second upward-looking spectrometer to measure the spatially dependent incoming illumination, an integrated software package to provide full automation, an automated leveling system to ensure a standard frame of reference, a design that minimizes the obscuration due to self-shading to measure the opposition effect, and the ability to record a digital elevation model of the target region. This fully automated and highly mobile system obtains accurate and precise measurements of HCRF in a wide variety of terrain and in less time than most other systems while not sacrificing consistency or repeatability in laboratory environments.

Flexible field goniometer system: the Goniometer for Outdoor Portable Hyperspectral Earth Reflectance

Abelev

Montes

et al. 2016

Self Cite

, "Fully automated laboratory and field-portable goniometer used for performing accurate and precise multiangular reflectance measurements," Abstract. Field-portable goniometers are created for a wide variety of applications. Many of these applications require specific types of instruments and measurement schemes and must operate in challenging environments. Therefore, designs are based on the requirements that are specific to the application. We present a field-portable goniometer that was designed for measuring the hemispherical-conical reflectance factor (HCRF) of various soils and low-growing vegetation in austere coastal and desert environments and biconical reflectance factors in laboratory settings. Unlike some goniometers, this system features a requirement for "target-plane tracking" to ensure that measurements can be collected on sloped surfaces, without compromising angular accuracy. The system also features a second upward-looking spectrometer to measure the spatially dependent incoming illumination, an integrated software package to provide full automation, an automated leveling system to ensure a standard frame of reference, a design that minimizes the obscuration due to self-shading to measure the opposition effect, and the ability to record a digital elevation model of the target region. This fully automated and highly mobile system obtains accurate and precise measurements of HCRF in a wide variety of terrain and in less time than most other systems while not sacrificing consistency or repeatability in laboratory environments.