The Experts below are selected from a list of 102102 Experts worldwide ranked by ideXlab platform
John V Martonchik - One of the best experts on this subject based on the ideXlab platform.
-
exploration of a polarized Surface bidirectional reflectance model using the ground based multiangle spectropolarimetric imager
Atmosphere, 2012Co-Authors: David J Diner, John V Martonchik, B E Rheingans, S Geier, Veljko M Jovanovic, A B Davis, Russell A Chipman, Stephen C McclainAbstract:Accurate characterization of Surface Reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to evaluate a Surface polarized bidirectional reflectance distribution function (PBRDF) model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument’s bands (470, 660, and 865 nm). A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the Surface model, which is comprised of a volumetric Reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular Reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized Reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof), possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized Surface Reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.
-
determination of aerosol optical depth and land Surface directional reflectances using multiangle imagery
Journal of Geophysical Research, 1997Co-Authors: John V MartonchikAbstract:Spectral aerosol optical depths, Surface hemispherical-directional reflectance factors, and bihemispherical reflectances (albedos) are retrieved for an area of Glacier National Park using spectral, multiangle imagery obtained with the airborne advanced solid state array spectroradiometer (ASAS). The retrieval algorithms are described and are identical in principle to those being devised for use by the multiangle imaging spectroradiometer (MISR) which will fly on the EOS-AM1 spacecraft in 1998. As part of its science mission, MISR will produce global coverage of both aerosol amounts and land Surface Reflection properties. The results in this paper represent the initial effort in applying the MISR algorithms to real data. These algorithms will undergo additional testing and validation as more multiangle data become available.
A. P. Annan - One of the best experts on this subject based on the ideXlab platform.
-
Measuring Soil Water Content with Ground Penetrating Radar
Vadose Zone Journal, 2013Co-Authors: J A Huisman, S.s. Hubbard, John D. Redman, A. P. AnnanAbstract:We present a comprehensive review of methods to measure soil water content with ground penetrating radar (GPR). We distinguish four methodologies: soil water content determined from reflected wave velocity, soil water content determined from ground wave velocity, soil water content determined from transmitted wave velocity between boreholes, and soil water content determined from the Surface Reflection coefficient. For each of these four methodologies, we discuss the basic principles, illustrate the quality of the data with field examples, discuss the possibilities and limitations, and identify areas where future research is required.We hope that this review will further stimulate the community to consider ground penetrating radar as one of the possible tools to measure soil water content.
-
measuring soil water content with ground penetrating radar a review
Vadose Zone Journal, 2003Co-Authors: J A Huisman, S.s. Hubbard, John D. Redman, A. P. AnnanAbstract:We present a comprehensive review of methods to measure soil water content with ground penetrating radar (GPR). We distinguish four methodologies: soil water content determined from reflected wave velocity, soil water content determined from ground wave velocity, soil water content determined from transmitted wave velocity between boreholes, and soil water content determined from the Surface Reflection coefficient. For each of these four methodologies, we discuss the basic principles, illustrate the quality of the data with field examples, discuss the possibilities and limitations, and identify areas where future research is required. We hope that this review will further stimulate the community to consider ground penetrating radar as one of the possible tools to measure soil water content.
Oleg Dubovik - One of the best experts on this subject based on the ideXlab platform.
-
coupled retrieval of aerosol properties and land Surface Reflection using the airborne multiangle spectropolarimetric imager
Journal of Geophysical Research, 2017Co-Authors: Gerard Van Harten, David J Diner, Olga V Kalashnikova, Felix C Seidel, Carol J Bruegge, Oleg DubovikAbstract:The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) has been flying aboard the NASA ER-2 high altitude aircraft since October 2010. In step-and-stare operation mode, AirMSPI acquires radiance and polarization data in bands centered at 355, 380, 445, 470*, 555, 660*, 865*, and 935 nm (* denotes polarimetric bands). The imaged area covers about 10 km by 11 km and is typically observed from 9 viewing angles between ±66° off nadir. For a simultaneous retrieval of aerosol properties and Surface Reflection using AirMSPI, an efficient and flexible retrieval algorithm has been developed. It imposes multiple types of physical constraints on spectral and spatial variations of aerosol properties as well as spectral and temporal variations of Surface Reflection. Retrieval uncertainty is formulated by accounting for both instrumental errors and physical constraints. A hybrid Markov-chain/adding-doubling radiative transfer (RT) model is developed to combine the computational strengths of these two methods in modeling polarized RT in vertically inhomogeneous and homogeneous media, respectively. Our retrieval approach is tested using 27 AirMSPI datasets with low to moderately high aerosol loadings, acquired during four NASA field campaigns plus one AirMSPI pre-engineering test flight. The retrieval results including aerosol optical depth, single scattering albedo, aerosol size and refractive index are compared with AERONET aerosol reference data. We identify the best angular combinations for 2-, 3-, 5-, 7-angle observations from the retrieval quality assessment of various angular combinations. We also explore the benefits of polarimetric and multiangular measurements, and target revisits in constraining aerosol property and Surface Reflection retrieval.
Simo Saarakkala - One of the best experts on this subject based on the ideXlab platform.
-
quantification of the optical Surface Reflection and Surface roughness of articular cartilage using optical coherence tomography
Physics in Medicine and Biology, 2009Co-Authors: Simo Saarakkala, Shuzhe Wang, Yanping Huang, Yongping ZhengAbstract:Optical coherence tomography (OCT) is a promising new technique for characterizing the structural changes of articular cartilage in osteoarthritis (OA). The calculation of quantitative parameters from the OCT signal is an important step to develop OCT as an effective diagnostic technique. In this study, two novel parameters for the quantification of optical Surface Reflection and Surface roughness from OCT measurements are introduced: optical Surface Reflection coefficient (ORC), describing the amount of a ratio of the optical Reflection from cartilage Surface with respect to that from a reference material, and OCT roughness index (ORI) indicating the smoothness of the cartilage Surface. The sensitivity of ORC and ORI to detect changes in bovine articular cartilage samples after enzymatic degradations of collagen and proteoglycans using collagenase and trypsin enzymes, respectively, was tested in vitro. A significant decrease (p < 0.001) in ORC as well as a significant increase (p < 0.001) in ORI was observed after collagenase digestion. After trypsin digestion, no significant changes in ORC or ORI were observed. To conclude, the new parameters introduced were demonstrated to be feasible and sensitive to detect typical OA-like degenerative changes in the collagen network. From the clinical point of view, the quantification of OCT measurements is of great interest since OCT probes have been already miniaturized and applied in patient studies during arthroscopy or open knee surgery in vivo. Further studies are still necessary to demonstrate the clinical capability of the introduced parameters for naturally occurring early OA changes in the cartilage.
H Suzuki - One of the best experts on this subject based on the ideXlab platform.
-
1 tb s 16 b all optical serial to parallel conversion using a Surface Reflection optical switch
IEEE Photonics Technology Letters, 2003Co-Authors: R Takahashi, H SuzukiAbstract:A novel scheme for all-optical serial-to-parallel conversion is proposed for label recognition of ultrafast burst optical packets. A compact 18-ch serial-to-parallel converter module was developed using a spin-polarized Surface-Reflection all-optical switch made of low-temperature grown Be-doped strained InGaAs-InAlAs multiple quantum wells. A 1-Tb/s 16-b optical packet was converted into 16 parallel slow (82-MHz rate) electrical pulses with a contrast ratio of more than 6 dB.