Estimation Of Tidal Characteristic Lines Based On Remote Sensing Waterside Lines

Silt tidal flat is located in the sensitive zone of the land and the sea,along with the tidal rises and falls,the tidal flat is periodically inundated by seawater,which is of sensitivity,variety,complexity and is the key area of dynamic monitoring in coastal zone.The characteristic curve of tide level is the most basic data of the dynamic monitoring in the coastal zone,since the conventional topographic survey is restricted by the factors of terrain,climate,hydrology and manpower,people can not aquire the large-scale characteristics line of the tide level.Remote sensing technology has many advantages:it covers wide areas and has a great amount of information,it is all-weather and is not restricted by the natural conditions ect.There are greater superiority in the research of extracting large-scale characteritics curve of the tide level than in the conventional method.The research takes the typical representative silt tidal flat in Dafeng as the research area,chooses the Landsat5,8 remote sensing images as the main remote sensing data resource,combines the wild topographic survey data.Based on the analysis of the topographic feature of the silt tidal flat,it does research on a variety of methods to extract the water edge and make an accurate and quick extraction of the water edge of the silt tidal flat;by building the water edge elevation calculation model and combining the tide level in the tide station when the satellite form a image,it estimates the water line elevation;two methods have been put forward that calculate the characteristics curve of the tide level indirectly based on the remote sensing water lines,which provide effective technical means for large-scale muddy tidal flat topographic observation and provide basic data for the research of muddy tidal flats and beach evolution.The main research contents and conclusions in this thesis are as follows:First,the analyzation of the silt tidal flat topographic characteristics and the extraction of the water line.By utilizing the wild topographic survey data,it systematically analyze the topographic characteristics of the muddy tidal flat and obtain the average grade through the measured height computation.Based on Landsat remote sensing image data,combining the topographic feature of the silt tidal flat,it extracts and does research on the tidal flat water line by using single-band threshold method and supervised classification method respectively.It turns out that the average offset distance and root-mean-square deviation of the water line extracted by supervised classification method is relatively small and the method is accurate in the extraction of the muddy tidal flat water edge.Second,the elevation calculation of the beach face water line.According to the principle of water level correction with zoning method,establish water edge elevation calculation model and do segmentation discretization processing on it;in order to obtain more accurate satellite imaging time tide level,we make a harmonic analysis by choosing the tide level data of different length.It turns out that the longer the water level data length is and the higher the accuration of the harmonic constant calculation is,the more accurate tide level prediction is;according to the satellite imaging time tide level in the tide station,we calculate the elevation of the water line by utilizing the water line elevation calculation model and make a correlation and verification between the wild measured elevation data with the calculated elevation.The result shows that the main absolute error is 0.1m and the overall accuracy is 81%.Third,the calculation of the characteristics line of the tide level.To obtain the local eigenvalue of the tide level by making statistics on the tide level data in the tidal station;converting the calculation of the tide level characteristics line into the calculation of the tide level characteristic points,calculating the tide level characteristics points respectively based on the mono-temporal and multi-temporal water lines.And then connecting them in turn to form the tide level characteristics line and make a accuracy verification on the high water line of the mean springs by utilizing the measured points in the wild topographic survey.It turns out that the tide level characteristics line calculated based on the mono-temporal water line deviated from the average distance of 15.65m,the measured points by 23.1m,which is close to the actual tide level characteristics line.Fourth,in order to obtain the spatial distribution of tidal flat erosion variation,the endpoint method is utilized to make an analysis on the erosion variation of the tidal flats nearby the mean springs' high-water level and low-water level.Generally speaking,the trend of the erosion variation in the high and the low tidal flat in Dafeng remains fairly consistent.