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Analysis of High-Resolution Aerial Images
Published in Rangachar Kasturi, Mohan M. Trivedi, Image Analysis Applications, 2020
where the integration is performed over the hemisphere and fr(Θi, Φi, Θr, Φr; λ) is the bidirectional reflectance distribution function (BRDF) of the object surface (Nicodemus et al., 1977; Woodham and Gray, 1987; Slater, 1985). The BRDF specifies the reflectance properties of a surface. Both the incident beam geometry (i.e., Θi, Φi) and reflected beam geometry (i.e., Θr, Φr) are considered in the evaluation of the BRDF as shown in Fig. 8.3. It also depends on the wavelength A. The BRDF of an object surface can be defined by fr(θi,φi;θr,φγ;λ)=dLr(λ)dI(λ)
Multi-View, Deep Learning, and Contextual Analysis: Promising Approaches for sUAS Land Cover Classification
Published in J.B. Sharma, Applications of Small Unmanned Aircraft Systems, 2019
Several researchers explored the use of multi-view spectral reflectance data to model semi-empirical BRDF models (Koukal et al. 2014; Pacifici et al. 2014; Su et al. 2007) and used the parameters of the modeled BRDF in image classification. Using multi-view spectral data of automatically segmented objects to model the BRDF and extracting BRDF parameters from high-resolution images captured by sUAS for classification purposes have rarely been studied. sUAS provides a unique opportunity to model BRDF since a typical flight mission involves many overlapping pictures, where the same object can be seen from different viewing angles within a relatively short acquisition time (small variation in sun angle). Both physical and statistical models (Liang and Strahler 1994) have been used to model BRDF. Physical modeling requires information about the land cover such as leaf biophysical parameters and canopy structure, while statistical modeling tends to characterize the shape of the BRDF. Statistical models can be divided into empirical models that mathematically fit the BRDF shape and semi-empirical models that integrate some of the physical characteristics when describing the BRDF form.
Understanding Data Sources
Published in Praveen Kumar, Jay Alameda, Peter Bajcsy, Mike Folk, Momcilo Markus, Hydroinformatics: Data Integrative Approaches in Computation, Analysis, and Modeling, 2005
The BRDF modeling problem poses several challenges due to (1) complex geometric and photometric properties of scene/object materials, (2) outdoor environment, and (3) seasonal changes. The complexity of geometric and photometric properties of scene/object materials can be demonstrated by inspecting specular surfaces (artificial grass), diffuse surfaces (concrete), isotropic surfaces (leather), anisotropic surfaces (straw), surfaces with large height variations (pebbles), surfaces with small height variations (sandpaper), pastel surfaces (cotton), colored surfaces (velvet), natural surfaces (lettuce), and man-made surfaces (sponge). These example surfaces are presented in Figure 15.2. One has to understand all variations and formulate adequate models to predict variations of these kinds. Additional modeling challenges are related to the dynamic outdoor environment with a complex 3D structure. For example, researchers at the University of Nebraska are modeling solar radiation interactions at the earth surface (see URL: http://snrs.unl.edu/agmet/908/wheat_canopy.htm). The appearances of wheat canopy (1) on one day (e.g., see the images of May 8, 1999, 55° Solar Zenith Angle, [36.77 N; 97.13 W] near Ponca City, Oklahoma at the URL) and (2) on three different days during the wheat growing season clearly illustrate the complexity of scene modeling.
Research on elaborate image simulation method for close-range space target
Published in Journal of Modern Optics, 2023
Hongyuan Wang, Qianhao Ning, Zhiqiang Yan, Xiang Liu, Yinxi Lu
The bidirectional reflectance distribution function (BRDF) is used to express the variation of the relationship between incident irradiance and reflected radiance on a specific material surface. At a certain point p on the material surface, given a set of incident direction and outgoing direction , BRDF is defined as the following calculation formula: where represents the radiance reflected along the direction at point p, represents the radiance incident along the direction at point p, and is the angle between the incident direction and the normal direction of the panel.
Satellite remote sensing of aerosol optical depth: advances, challenges, and perspectives
Published in Critical Reviews in Environmental Science and Technology, 2020
Xiaoli Wei, Ni-Bin Chang, Kaixu Bai, Wei Gao
From the theoretical side, in 2005, the BRDF was considered by the AOD retrieval algorithm over land (Luo, Trishchenko, Latifovic, & Li, 2005). BRDF is a dependent that is sensitive to satellite geometry and is used to describe the reflection of incoming direct and diffuse solar light from land or ocean surfaces. In the peer-research, the anisotropic effect of land surface such as that determined via the DB and DT AOD retrieval algorithms follows the assumption that BRDF may usually be neglected because it assumes the land surface as a Lambertian reflectivity. However, such an assumption is invalid and does not represent the inherent surface reflectance character (Tian, Liu, Song, et al., 2018). Yang, Xue, and Guang (2012) compared the MODIS AOD data by considering the cases with or without BRDF, and their results show that accuracy in AOD retrieval has been improved by accounting for the BRDF effect in AOD retrieval practices. In addition, the BRDF effect is included in the 6S model to improve the atmosphere (Vermote, Tanré, Deuzé, & Herman, 2006; Franch, Vermote, Sobrino, & Fédèle, 2013). Nevertheless, the BRDF correction only considered the mean values of anisotropy shape factors while ignoring the variation of BRDF shape within different land surface categories (Tian, Liu, Song, et al., 2018). Therefore, estimation of the BRDF accuracy and/or development of a new model of the BRDF function to reduce the bias of AOD retrieval will still be a challenge in the future (Guang et al., 2012; Montes & Ureña, 2012; Kalantari & Molan, 2016).
A BRDF study on the visual appearance properties of titanium in the heating process
Published in Journal of Modern Optics, 2018
Yanlei Liu, Kun Yu, Longfei Li, Yuejin Zhao, Zilong Liu, Yufang Liu
For a stabilized and parallel incident illumination, the radiance determined by the light source is the function of wavelength and can be measured before the sample is installed. The BRDF can be obtained by measuring the reflected radiance .