Quantitative Inversion Model of Water Chlorophyll-a Based on Spectral Analysis

Water quality has direct impact on national production and people's daily water use, so accurate, and efficient water quality monitoring is particularly important. Taking BaiYangdian as the study area, the spectral characteristics of water is analyzed, and then the concentration inversion model of chlorophyll-a is studied in order to establish a proper inversion model of chlorophyll-a concentration for BaiYangdian.In this paper, semi-empirical method was taken to establish quantitative model of chlorophyll-a based on ground measured spectrum. The results show that: (1) the original water reflectance has little correlation with chlorophyll-a concentration, while that of the normalized water reflectance is much higher. Wavelengths of 557 nm and 665 nm have high negative correlation, while that of 722 nm and 717 nm have high positive correlation. (2) Chlorophyll-a concentration is taken as variable; and with the normalized reflectance of the water, the band ratio of its maximum positive and negative correlation band are taken as the dependent variable. And then, the regression analysis of exponential, logarithmic, power, linear and quadratic models was made, and the linear model and a quadratic model are much better. Through verification: using linear model of R717/R557 to calculate the concentration of chlorophyll- a has the minimum relative error. The model is y = 83.248x - 45.239.