[MGI37-04] Preliminary Study of Water Quality Determination using Spectro-polarimetric Bidirectional Reflectance Factor
Keywords:Water Quality, Multispectral, BRDF
All living organisms require water as a foundation to support life and the development of human civilization. However, recent study shows that wetland sizes are decreasing in trend due to the increase in urbanization, climate change, and natural disaster. These lead to the degradation of water resource quality and quantity. The water quality is determined through the study of the biological, chemical, and physical features of the water bodies and currently, researchers have been using the Water Quality Index (WQI) through the in-situ measurements methods. However, the methodology has many shortcomings in large scales applications. While, spectral imaging equipped remote sensing can help in combating the problem, light reflecting on water surfaces that are usually roughened by small, wind-driven waves create a challenging measurement condition. As the incoming light arrives at the surface of the water, a portion of the light is reflected in the camera, while the pollutants inside the water reflect the other portion of it. At a particular angle, the light is reflected between the wave structures, due to the water wave, and creates a glittering effect. This produces specular reflection that blocks the actual reflection from the materials inside the water to the instruments. These reflections are in the polarized and unpolarized component of the light, which later can be separated by using a polarizer. These patterns also change shape depending on the water surface roughness and the solar elevation angle, therefore under very light-wind conditions the number of sun glints decreases. This can be better represented by using the bidirectional distribution function (BRDF) that visualize the relation of azimuth, zenith, incident, and camera angle. Combining different measurement angle, spectral, and polarization information reveals a comprehensive optical characteristic of an object in terms of the material compositions as well as surface characteristics, which may not be readily obtained using conventional imaging techniques.