Remote Sensing application of current field on sea water surface layer and water quality on harbor and bay
Extraction of turbidity information
The turbidity is mainly determined by mud, sand and quantity of Chlorophyll, and represented as the seawater color. When there is a lot of sand, the water is yellow; when the quantity of chlorophyll is high, the water is green because they have different spectral characteristics for different TM bands. The first thing to extract turbidity information is to eliminate the watercolor differences caused by terrain changes and differences of surface current velocities. The method is to select different TM bands and time phases, and also to correct terrain influence by sea chart data. The second thing is to use band ratio (TMi / TMj) . The selection of i, j should be favorable for maing the ratio of mud and sand in water (TM2/TM1 ) , or for the ratio of chlorophyll (a) (TM1/TM3) . The third thing is to select the conditions to control the dynamics of the quantities of mud, sand and chlorophyll. For example, the water bodies with much sand are usually found in sediment areas, where the water is shallow and velocity is low. Once if it happens that strong current brings up sand, the sand contained in the water will increase. The area with a
large quantity of chlorphyl is the sea area, where the exchanging of water is bad. It means that the current field, current system, and terrain are control parameters of sea water turbidity. By the application of remote sensing image, sea chart, and related hydrometric information, we can make synthetic analysis. We can also use fuzzy membership functions
m (C1)
m(C2) to describe the control factors of sand quantity and chlorophyll quantity. At last the related membership functions of sand, chlorophyll ,and turbidity can be set up:
m(s) = F [TM2/TM1] Çm(C1)------------------(7)
m(ch) = F [TM 1 /TM3] Çm(C2) ----------------(8)
m(T) = m (S) + m(ch) --------------------------(9)
where
m(S) - sand membership function
m(ch) - chlorophyl quantity membership function
m(T) - synthetic related function of sand and cholorophy quantity
Ç-the "AND" logical operation of fuzzy function.
At last by practical sampling of membership functions and further relative analyzing we can transform (extrapolate) the related values to a distribution chart of sand, chorophyl quantity and turbidity
Extraction of tempera true information
As is well known, the remote sensing data about surface sea water temperatures can be obtained with TM7 or meteorological satellite sensors (NOAA10 AND NOAA 11)
Evaluation of Remote Sensing water quality environment
The water quality environment is composed of many factors. Different purposes of water quality requirements correspond to different water quality environment factors. For example, in the sea areas nearMiao island, an important seafood production place, the scallop is raised mainly. The water quality requirements are: appropriate temperatures, turbidities (especially alongshore current with various Nutritious salts and halliplankton), source transportation conditions, water exchange conditions, and seabed material and water depth conditions. Fig.4 is a cultivation condition chart after synthesizing various factors and related chart according to the scallop cultivation requirements. Relative classes of the conditions are shown on the chart. Class 1 is the best and Class 5 is the worst. The evolution results coincide with the field cultivation quantities. The remote sensing evaluation shows that the joining dam between North and South Changshan is - lands had destroyed the water exchange conditions for the water west to Changshan Island, Which results in low productivity of scallop in that area.
The water quality environment Remote Sensing evaluation has the advantages of global view, audiovisual, real-time, and synthesizing. It can be used as a complement or extension of routine survey. The practical profit of water resources survey in broad shallow seawater areas can be increased. It helps to make decisions about how to make better use of coastal zones.
References
- Arthur P. Cracknel < Remote Sensing
Applications in Marine Science and Technology > published in
cooperation with NATO Scientific Affairs Division 1982.
- Robert H. Stewart published uder the auspices of the Scripps
institution of oceanography UCSD 1985 P 108-113
- A.P. Cracknell< remote Sensing in
Meteorology Oceanography and Hydrology> published by ELLIS HORWOOD
LIMITED in 1981. P178-204
- yang yilong Vol.9, No.6, Nov., 1985
