Development and testing of an ear-leaf model for rice canopy reflectance

作者:Zhao, Liyun; Xu, Xiaoqing; Zhang, Min; Cheng, Tao; Zhu, Yan; Cao, Weixing; Tian, Yongchao*
来源:Journal of Applied Remote Sensing, 2018, 12(01): 016016.
DOI:10.1117/1.JRS.12.016016

摘要

Existing vegetation radiative transfer models seldom consider the effects of rice panicles on canopy spectrum. An ear-leaf model was established by adding a rice ear module to 4SAIL-RowCrop model. The geometrical optical model of the rice panicle was developed by assuming that the rice panicle is an upright cylinder. The rice panicle component was considered to be part of the canopy, and seven rice canopy scene components were defined including canopy without ear, the first and second kind of sunlit soil, the first and second kind of shaded soil, sunlit ear, and shaded ear. Thus, the directional radiation of the spike layer was described using the geometrical optical model. Reflectance and transmittance of the rice canopy were calculated using the 4SAIL model. The reflection and radiation characteristics of the soil layer were modeled using 4SAIL-RowCrop. Then, the row-sowed rice canopy scene reflectance was simulated by iterating reflectivity of the seven components in proportion. The ear-leaf model has good simulation accuracy for forward and backward reflectance with the mean R-2, relative root mean square error, and RE values between the simulated and measured spectra of typical bands of 0.91, 19%, and 10%, respectively. Thus, the ear-leaf model provides a more technical support for the simulation of canopy reflectance and retrieval of growth parameters in rice.