Abstract
Lake Kasumigaura is polluted by massive growth of blue green algae during a typical summer. Measuring a quantity of chlorophyll-a in the phytoplankton is of importance in tackling with the lake water pollution problem. In this paper, a remote sensing method to estimate distribution of rich chlorophyll-a concentration in lakes or inland seas is proposed. In particular, relation between the quantity of chlorophyll-a and the spectral signature of water is investigated based on the observed data on the water surface.
To eliminate the influence of specular reflection from the water surface on the spectral signature of water, spectral reflectance below the water surface was measured. And the basic relationship between chlorophyll-a concentration and the spectral characteristics of water was analyzed. As a result, chlorophyll-a estimation model was derived using the ratio of spectral reflectance at two different wavelengths of 675 nm (red range) and 700 nm (near-infrared range). It was found that the spectral signature of near-infrared range is effective in remote sensing of rich chlorophyll water area like lakes or inland seas. Furthermore, in order to verify the appropriateness of the proposed model, theoretical analysis on the model was investigated based on the Kubelka-Munk theory.
