Studying On Extracting Weak Information Of Rice Under Pb Pollution Stress From Remotely Sensed Data Based On Fractal-Wavelet Model

Pb is a potential hazardous pollution in farmland soil. Pb pollution has significant impacts on the growth of rice, and it may cause reduction of rice yield. The concentrations of pollutants will increasing as toxins are passed up the food chain and ultimately threatening the health of human beings. So studying of rice under Pb pollution stress and analysis of hyperspectral change of rice under Pb pollution stress are important for avoiding rice polluted and protecting agricultural environment and human being heath.The goal of this research is to derive a new model named fractal- wavelet model for extraction from remotely sensed information of rice under Pb pollution stress. According to analysis and compare and summarize of wavelet and fractal theory, this paper proposes the method of extracting hyperspectral weak change of rice under Pb pollution stress by using fractal dimension, which was performed by wavelet transform. First, singularity analysis were carried out between healthy rice and rice under Pb pollution respectively, and then for healthy rice and rice under Pb pollution respectively, the fractal dimensions of hyperspectral curves (450nm-700nm) and second derivative curves were calculated at the tillering stage and the heading stage. Results showed that the fractal dimensions of hyperspectral curves of the rice under Pb pollution decrease, compared with these of the healthy rice. The fractal dimensions of second derivative curves also decreased, and the difference in the fractal dimension between tillering stage and heading stage of the rice under Pb pollution is larger than that of healthy rice, according to which we regard that the fractal dimensions of second derivative curves in judging whether the rice was polluted is better. Meanwhile, it can be concluded that it is the best time to monitor the rice under Pb pollution at the tillering stage. Finally, the paper establishes a predict model for chlorophyll concentration based on fractal dimension, which we achieve a nice accuracy.There are five chapters in this paper. Chapter one is an overview of previous research work on the usage of remote sensing technology in vegetation health monitoring area. Chapter two introduces the biochemical reaction mechanism of rice under Pb pollution stress, and the vegetation indexes which are used in this field. Then it points the disadvantages of these indexes. Chapter three introduces the sample plot and data collection and the choice of range of band, and then how to enhance and extract spectral weak information with fractal and wavelet. Chapter four specifies the result of enhancing and extracting spectral weak information with fractal and wavelet, and then analysis the effect of the model. This paper establish a predict model for chlorophyll concentration based on fractal dimension at last. Chapter five is the conclusion of this research work and the plan of next work.