Remote Sensing application of current field on sea water surface layer and water quality on harbor and bay
Li Yinxi
Remote Sensing Satellite ground Station of Chinese
Academy of sciences, Beijing, China
ChiYaobin
Beijing Research Institute for information of Remote
Sensing, Beijing, China
Li Teifang
Center for Remote Sensing, Zhongshan University
Guangzhou,China
Abstract
The remote sensing sea water current field is an instantaneous status data surface current which is recorded during satellite pass it shows the directions and speeds of the surface layer currents, interactions between different current systems and water patches, and relationships between sea water, land and island. Because the surface layer current field is certainly related to the situation under seawater, it can be well used to analyze water bodies, under seawater dynamics, and water exchange in bodies. Besides, the remotely sensed information about water temperatures, transparencies tells how the natural environmental factors influence harbor water quality, so that it is useful for evaluation of cultivation in sea water, city and harbor sewage disposal engineering, and self-cleaning capability. The advantage of remote sensing technology is the provision of global, cheap, direct information about how the environment influences water quality, its diffusion and exchange, so that we can have a better understanding of the wide sea areas. In this paper we discuss characteristics of the remote sensing current field and extractions of various sea water surface current field information based on images processing and fuzzy criteria method so as to evaluate the preset status of the sea water resources of sea areas around the Miao Islands, Bohai sea , China.
Characteristics of the Remote Sensing current field
There are two features for the spectral reflectance of surface current: the movement of seawater surface in vertical or horizontal directions causes irregular distribution of the roughness of water surface. The ratio of incident and reflected sunlight changes. For example, if velocity is high, the water surface vibrates more strongly, the ratio of diffused and reflected light increases, while the ratio of entering part decreases, which results in the increase of the brightness value of the pixels. On the contrary, if the water surface is quiet and smooth, the entering part increases, the brightness
value of the pixels decreases, the second feature is the dependence of quality, chemical, physical characteristics of suspended matter and dissolved substances, which result in the water color changes, and in turn the forms of currents, current tracks. That is, the suspended matter and dissolved substances play the role of tracking items. For example, the alongshore currents carry a lot of mud and sand from the land, they are mostly yellow color; the currents from deep seas are blue. These two color differences are big, which shows the relationships between their interactions.
The above-mentioned current information is represented as spectral information and sensed by sensors. Total signal L can be shown as follows:
L= Lsg + Lhg + Lp+ Lw ----------------(1)
where : Lsg - information about the change of water surface rough-ness
Lw-radiation signal of water bodies, providing the color information of different current system and wate patches
