Low-altitude hyperspectral observation of paddy using radio-controlled helicopter

To monitor the chlorophyll content of rice leaves, transparent leave-color monitoring device SPAD; named for the Soil & Plant Analyzer Development, is widely used in Japan. For wide area of paddy, however, it requires lots of elaboration to measure the SPAD values by hand. The objective of this study is to solve this problem by estimating the SPAD values through remote sensing. In rainy season, it is difficult to make use of airborne or satellite image sensors to observe paddy fields. Thus, we made use of a hyperspectral sensor mounted on a low-altitude radio-controlled helicopter, and calculated new indices LVI_pure (Leave-color Verified Index) and LVI_mix using the obtained data to estimate the SPAD values. As a result, the relations between the SPAD value and the estimation index exhibit high correlation: R² = 0.885 for LVI_pure and R² = 0.927 for LVI_mix, which facilitated to obtain "the estimated SPAD value image" from the hyperspectral data.