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.
Highlights
The goniometer of the Rochester Institute of Technology-two (GRIT-T) is a second-generation goniometric system that was designed and built in the Chester F
The GRIT-T incorporates many features—some found in other systems and some that are new to the field—into one compact design that can measure the multiangular reflectance of a target in both a laboratory and field setting
The GRIT-T was tested in the laboratory at the Rochester Institute of Technology and tested in the field in the Nevada desert
Summary
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. In contrast in outdoor settings, where the light is from both a directional source (the Sun) and from a skylight, the term HCRF is used.[2,3,4,6] To accomplish these types of measurements, the GRIT-T incorporates many features into one compact design. While some of the features were leveraged from other systems, such as the dualview capability and the full automation, other features were added to satisfy the scientific requirements of our research group These new features include target-plane tracking, automated system leveling, minimized obscuration due to self-shading, digital elevation models (DEMs), and a number of other features to improve accuracy, mobility, and rigidity.
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