Study On Automatic Extraction Of Coastline In Yellow River Delta Based On Multi-spectral Data Over The Past 50 Years

The Yellow River delta lies in the south of Bohai sea, projecting into the area between Bohai Gulf and Laizhou bay, it also experienced the rapid economic, social development and human reconstruction on coastal landforms in the past 50 years. The weak tidal deltas continental deposition is famous for the rapid silting and erosion of Yellow River. Compared with the general coast the difference is obvious which includes coastline change rate and change direction, because of the dynamic action of ocean and river emptying into the sea. The Yellow River Delta National Efficient Ecological Economic Zone was listed in national strategic planning, however geomorphic evolution is very frequent over the past 50 years in the Yellow River delta, the resource-environment and town planning all demand that the prediction to the evolution of future trend of coastal landform erosion and deposition be more accurate and precise. Based on its evolution mechanism and process of coastline changes in the more than years from the perspective of scale, so as to reveal the relationships among the coastline changes of Yellow River delta, changes of the Yellow River estuary, sediment discharge and coastal zone land use in recent 50 years, through Digital Shoreline Analysis System and the fractal dimension analysis(FA) of coastline.Studies based on the Yellow River Delta, through comprehensive analysis of the observed spectra and spectral remote sensing image data, research for nearly 50 years the evolution of Yellow River Delta coastal dynamic geomorphology. This article used the data source including mapping data sources to different times of large scale charts, topographic maps, remote sensing images. Methods are as follows:1. Comparing measured spectrums with the remote sensing image then classifying and extracting the coastline of Yellow River delta. Meanwhile, using visual interpretation for extracting the coastline of experiment part, based on revision of Shandong’s coastline of 908 special projects. Secondly, use the ROC(Receiver Operating Characteristic) curve to evaluate the accuracy of the extraction result by 0.5 pixels and 1 pixel, which is found on the matching of two lines based on Matlab2012.2. Automatic extracting coastline from 14 remote sensing images in 50 years, based on automatic extraction methods, vector quantization, the definition and geomet-ric correction for 15 bathymetric chart, followed by shoreline digital analysis system(DSAS) quantitative analysis of extraction of coastline change process. Based on Matlab language period depending on the box-counting dimension to calculate the one-dimensional curve of coastline fractal dimension and complex twists and turns and leads the coast changes of expression.3. Preprocessing 14 remote sensing image from 1973 to 2015, 5 imagines were selected to map thematic map of coastal zone land use, combining the transfer matrix of land use, change of estuary and sediment discharge into the sea, analysis of the Yellow River delta coastline change characteristics of the mechanism. Based on the above method, the comprehensive study shows that:1. Coastline automatic extraction: the experimental result of vector-based coastline was directly applied in the subsequent GIS analysis. On the whole, through this new method, we can extract the coastline of Yellow River delta quickly with an accuracy of one pixel and an extraction confidence level of higher than 90%.2. Coastline changes of the Yellow River Delta: nearly 50 years as the main research foundation, the dimensions as reference background in one hundred. 1855-2015, the coastline showed increasing trend, but some sudden increase events interrupted during 1980-1984, 1996-1998 and 2000-2002, coastline length and forward coast showed increasing trend in 1855-1959, during 1959-2015 the minimum value in 1984, maximum in 2002 and forward coast shrinking on the whole, 1974-1980, 1980-1988 on peak. From 1959 to 1984, the length of the coastline decreased, retreat rate increased, and the morphology became smooth and simple; from 1984 to 2015, the length of the coastline increased, retreat rate decreased, and the morphology became complex and tortuous; among them, during 1984-1988, 1988-1992, 1996-1998, 1998-2000, coastline moved slowly, only moved in the estuary and coastal rarely influenced by human disturbance there were times almost imbalances in 1968-1974, 1992-1994,1994-1996, 2006-2015. To sum up we know, the dynamic change of the coastline in the Yellow River Delta area had a regional and transitional features. Finally, that could accelerate it into balance under the effect of artificial, shoreline length increases, morphology tend to be simple and smooth.3. Coastal zone land use: Land use changes of the Yellow River delta show obvious periodic,natural type continues to decline and artificial types increase gradually, eventually, salt pan and culture pond separate accumulation plain and tidal flats,characterized by a zonal distribution. Advance to the sea as a whole artificial type and natural type on the delta coastal zone. During 1974-2015 the Yellow River delta land use change and the change in estuaries, concentration of the sediment and water into sea and sea power, wave, tidal changes and combination of human factors influenced the mechanism of the evolution of coastal zone in the region, especially man-made factors over the past 20 years.