觀測角度對植被反射光譜及光譜特徵之影響－以水稻為例

Changes of Canopy Reflectance Spectrum and Spectral Characteristics to Viewing Angles of Spectroradiometer: A Case Study in Rice

李裕娟(Yuh-Jyuan Lee) ； 楊純明(Chwen-Ming Yang)

《中華農業研究》 52卷4期 (2003/12) Pp. 297-310

https://doi.org/10.29951/JARC.200312.0005

摘要

Field experiments were conducted in the experimental farm of Taiwan Agricultural Research Institute at Wufeng, Taiwan to study changes of canopy reflectance spectrum and spectral characteristics to viewing angles of spectroradiometer for rice plants grown in the first and the second cropping seasons of 2002. By analysis of the ground-based remotely sensed hyperspectral reflectance data, it was found that curves of reflectance spectrum were affected by the viewing angles in both maximum tillering and dough stages in both crops. In general, reflectance was lower at nadir viewing and was increased with the increasing viewing angles. When further divided the measured spectral domain (350-2500nm) into 10 broad bands, i.e., UV(350-400nm), V(400-425nm), B(425-490nm), G(490-560nm), Y(560-585nm), 0(585-640nm), R(640-740nm), NIR(740-l300nm), SWIR(1300-l800nm), and MIR(1800-2400nm), it was shown a quadratic function for the relationships between waveband mean reflectance and viewing angles. Again, generally reflectance was elevated with the increase of viewing angle, either face to or back to the sun. By calculating the simulated wavebands(G, R, NIR and SWIR)mean reflectance of SPOT satellite and comparing to the corresponded broad-band and narrow-band values, it indicated that usually reflectances of narrow bands were greater than values of SPOT and broad bands and were all exhibited a curvilinear trend to the viewing angles.

關鍵字

水稻 ； 太陽方位角 ； 觀測角 ； 窄波段 ； 寬波段

並列摘要

Field experiments were conducted in the experimental farm of Taiwan Agricultural Research Institute at Wufeng, Taiwan to study changes of canopy reflectance spectrum and spectral characteristics to viewing angles of spectroradiometer for rice plants grown in the first and the second cropping seasons of 2002. By analysis of the ground-based remotely sensed hyperspectral reflectance data, it was found that curves of reflectance spectrum were affected by the viewing angles in both maximum tillering and dough stages in both crops. In general, reflectance was lower at nadir viewing and was increased with the increasing viewing angles. When further divided the measured spectral domain (350-2500nm) into 10 broad bands, i.e., UV(350-400nm), V(400-425nm), B(425-490nm), G(490-560nm), Y(560-585nm), 0(585-640nm), R(640-740nm), NIR(740-l300nm), SWIR(1300-l800nm), and MIR(1800-2400nm), it was shown a quadratic function for the relationships between waveband mean reflectance and viewing angles. Again, generally reflectance was elevated with the increase of viewing angle, either face to or back to the sun. By calculating the simulated wavebands(G, R, NIR and SWIR)mean reflectance of SPOT satellite and comparing to the corresponded broad-band and narrow-band values, it indicated that usually reflectances of narrow bands were greater than values of SPOT and broad bands and were all exhibited a curvilinear trend to the viewing angles.

並列關鍵字

Oryza sativa L ； Solar zenith angle ； Viewing zenith angle ； Narrow band ； Broad band