Estimating Rice Paddy Evapotranspiration using Field-based Remote Sensing
Date Issued
2012
Date
2012
Author(s)
Garcia Jimenez, Sergio
Abstract
Management of crop irrigation by using field-based remote sensing requires background data obtained from field experiments carried out under local conditions. In this study, spectral and evapotranspiration data were used to evaluate well-known vegetation indices (VI) and new spectral indicators for estimating current crop coefficient (Kc) in rice paddy under northern Taiwan climatic conditions. Estimated Kc values for the initial, development and late growth stages were very close to those suggested in previous research works, however, the Kc values at the mid-stage greatly differ from previous Kc values, possibly due to lysimeter method did not perfectly match the paddy soil heat conditions in the field. Spectral reflectance (Refl) values were smoothed and first-order derivative spectra (ρ) were calculated for each individual wavelength between 350 and 1050nm. Based on regression relationship analysis and principal component analysis (PCA) of grouped data, the most appropriate wavelengths were selected and new combinations were calculated by using rationing, differencing, normalized differencing and multiple regression. New indicators improve the degree of correlation between Kc and VI while no significant improvements were found for new wavelengths combinations derived from the first-order derivative.
Subjects
field-based remote sensing
crop evapotranspiration
rice paddy
vegetation index
soil water balance
Type
thesis
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