Research On Water Body Extraction Method In Karst Area Based On GF-2 Image

Water extraction research has always been the focus of scientific research.Especially with the development of remote sensing technology,people are increasingly inclined to use remote sensing images to extract water bodies.However,water extraction is easily affected by various factors,making it The precision of extraction is limited.In order to further improve the accuracy of water extraction,many scholars have proposed many solutions to various influencing factors to eliminate the interference factors in the water extraction process.Most methods are aimed at a single interference factor in the water extraction process,but shadows,clouds,bare soil,weathered rocks,dark buildings,floods,and pond water surfaces will all affect the accuracy of water extraction.Different influences,and in the current extraction of water bodies,methods that comprehensively consider the influence of multiple interference factors are still rarely studied.Especially in karst areas,in its complex topography,the influencing factors are more complex and diverse,and the relevant research on water extraction is even rarer.Therefore,this paper takes the karst area as the research area,uses the GF-2 image as the research data,comprehensively considers the various interference factors existing in the water body extraction,and conducts the water body extraction research.The main research contents and conclusions of this paper are as follows:There are various forms of water bodies,and there are differences in the spectrum of different bands of different water bodies.To extract water bodies comprehensively and accurately,it is necessary to solve the differences and commonalities between different water bodies.By analyzing the waveband spectrum law of GF-2 image water,this article proposes two methods of water extraction,spectral threshold analysis method and ultra-green water index method.Two methods are used to extract water bodies in four areas of severe rocky desertification,light rocky desertification,non-rocky desertification,and non-karst areas,and the results are compared and analyzed with three commonly used water body extraction methods.(1)The spectral threshold analysis method is divided into two steps.The first step is to construct the spectral range of each waveband of the water body.Since the spectral response functions of different water bodies in the same waveband are similar,by calculating the land within the water body threshold in each waveband.Object information,you can eliminate other ground objects except the water body threshold of each band,and then take the intersection of the extraction results of different bands,and the obtained water spectrum threshold result contains the water in each band,and also excludes the water in each band.Non-water bodies outside the threshold.The second step is to construct the spectral spatial ratio scatter points between the various bands of the water body,and make the fitting line of the water body scatter points.According to the point-to-line formula and the point-line threshold of the water body,the ground around the water body fitting line can be obtained.The results are obtained by intersecting the results obtained in the ratios of each band.The obtained water spectrum ratio results include the water bodies around the water body fitting line in the different band spectrum ratios,and exclude the non-water bodies other than the water body fitting line.Feature information.The water spectrum threshold value obtained in the two steps and the water spectrum ratio are intersected,and the spectrum threshold value analysis result obtained combines the water body extracted in the two-step operation process,and at the same time eliminates the non-water body in the two-step operation process.This method adopts a step-by-step refinement method to obtain the water body,which can take into account the commonalities between different water bodies in many aspects,and at the same time eliminate the non-water bodies that have great interference to the water body.(2)The ultra-green water index method is based on the GF-2 image,the spectral reflectance of different water bodies has a commonality,that is,the relationship between the spectral value of the green band and the other three bands,which satisfies the spectral value of the green band.Three times of,which is greater than the sum of the spectral values of the other three bands.According to the mean inequality,the gap between the two is enlarged,and then the formula is normalized to obtain the super-green water body index.Since different water bodies meet the characteristics of this equation,which is also a unique feature of water bodies,different types of water bodies can be extracted more comprehensively,and other ground features can be filtered out at the same time.(3)Through the two methods proposed in this paper,the four areas of Guizhou Province,including severe rocky desertification,light rocky desertification,non-rocky desertification,and non-karst areas,were studied for water extraction,and combined with the single-band threshold method,Comparison of single-band and shadow water index method and normalized water index water body extraction results show that the two methods proposed in this paper can effectively eliminate shadows,clouds,and rocky desertification rocks in karst mountainous areas.The interference of factors is more comprehensively extracted to pond water surface,flood water body,and water body under shadow.In the four areas of severe rocky desertification,light rocky desertification,non-rocky desertification,and non-karst,the extraction accuracy is higher than other areas.Several comparison methods.It provides new methods and technical support for water extraction in karst mountainous areas in Guizhou Province.