Differences in vegetation index values using measurements from two azimuth and multiple zenith viewing angles
Yuna Cho 1,2
Euni Jo 1,2
Jaeil Cho 1,2
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Department of Applied Plant Science, Chonnam National University, Gwangju 61186, Republic of Korea
BK21 FOUR Center for IT-Bio Convergence System Agriculture, Chonnam National University, Gwangju 61186, Republic of Korea
National Institute of Crop Sciences, Rural Development Administration, Wanju 55365, Republic of Korea
National Institute of Agricultural Sciences, Rural Development Administration, Wanju 55365, Republic of Korea
Department of Spatial Information Engineering, Pukyong National University, Busan 48513, Republic of Korea
Final revision date: 2023-12-17
Acceptance date: 2023-12-27
Publication date: 2024-01-31
Corresponding author
Jaeil Cho   

Applied Plant Science, Chonnam National University, Korea (South)
Int. Agrophys. 2024, 38(1): 77-86
  • To investigate how crop surface reflectance and vegetation indices varied according to the direction of the light source and sensor viewing, a hyper-spectrometer of visible to near-infrared wavelengths mounted on a field goniometer was used at four growth stages in rice paddies. The NDVI was less sensitive to the directions of sensor viewing than the EVI.
Vegetation indices based on selected wavelength reflectance measurements are used to represent crop growth and physiological conditions. However, it has been determined that the anisotropic properties of the crop canopy surface can govern both the spectral reflectance and vegetation indices. In this study, in order to investigate how crop surface reflectance and vegetation indices varied according to the direction of the light source and sensor viewing, a hyper-spectrometer of visible to near-infrared wavelengths mounted on a field goniometer was used at vegetative and reproductive growth stages in rice paddy. It was found that most of the wavelength reflectance measurements produced by the sparse vegetation cover fraction were not sensitive to solar-illumination and sensor-viewing angles. In addition, the reflectance of visible wavelengths was found to be less sensitive to the solar and sensor angles than the red-edge and near-infrared wavelengths. The lowest normalized difference vegetation index value in a day occurred at the nadir sensor-viewing angle before rice heading, but after heading, when ripened grains began to bow, the lowest value was recorded at the sensor zenith angle of 25°. Enhanced vegetation index measurements were found to be more sensitive to the direction of sensor viewing and less affected by sun glint than normalized difference vegetation index measurements. Additional field observation measurements should increase our level of understanding of how vegetation indices change on anisotropic crop surfaces.
This work was carried out with the support of "Cooperative Research Program for Agriculture Science and Technology Development (Project No. RS-2021-RD009991)" by the Rural Development Administration.
The authors declare no conflict of interest.
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