The Research Of Enteromorpha Prolifera Monitoring In Qingdao Sea Area On The Basis Of Adaptive NDVI Threshold

Form 2008, the large-scale disaster of enteromorpha prolifera erupted in Qingdao sea area between May and August every year. It will consume too much oxygen when enteromorpha prolifera mass propagation, which pose a threat to other organisms in the bottom of the sea, and cause adverse effects to the offshore aquaculture. Large area of enteromorpha floated in the coast of Qingdao even drifted on the beach. Enteromorpha prolifera sent out a stench after decay, which influence the development of coastal tourism. In order to meet the needs of enteromorpha monitoring, the technology of Remote Sensing has become an important method of monitoring enteromorpha prolifera because it can provide macroscopic information and large scale information about earth surface quickly. Accurate data of enteromorpha remote sensing monitoring have important guiding significance for the salvage work. According to the enteromorpha schematic diagram of remote sensing monitoring and the area covered statistical figure, we can begin salvage operation be targeted. Then understand and control the development trend of enteromorpha disasters in the shortest possible time, which is good for the governance of enteromorpha. What’s more, monitoring enteromorpha by remote sensing has become an academic research hot spot in recent years.This article first gleaned MODIS image from Qingdao offshore area, as well as relevant historical data, such as the sea surface temperature data. It should be preprocessed to make preparation for extracting enteromorpha prolifera information. The process of pretreatment includes eliminate the Bowtie effect, geometric rectification, atmospheric correction and land masking. Then measured the actual spectrum curve of enteromorpha prolifera by wild spectrometer, and analyzed the spectral characteristics of the different enteromorpha spectral bands. The basic spectral characteristics of enteromorpha showed that it formed reflection valley in the blue band and red band and formed reflection peak in green band. The reflectance increased obviously and formed high reflection peak in the near infrared band, which laid the foundations for using remote sensing image to extract the enteromorpha information. After that, extracted the enteromorpha information through the methods image classification which included Minimum distance method, Normalized difference vegetation method, Spectral Angle Mapper based on the decomposition of mixed pixels. And extracted the enteromorpha information through the methods of image segmentation which included Minimum point threshold method, Iteration threshold method, Otsu method. On this basis, in order to easily analyze the situation of multi-temporal enteromorpha disaster, researched the threshold selection method on adaptive normalized difference vegetation index(NDVI). This method eliminated or reduced the influence of the cloud effectively, and extracted enteromorpha information on multiple images expediently. Finally, the paper extracted the multi-temporal enteromorpha disaster information of Qingdao sea area form 2008-2010. What’s more, it analyzed the space-time distribution characteristics and the factors which influenced large area gather of enteromorpha disasters on Qingdao sea area.In a word, the ultimate goal of this paper is to obtain an efficient enteromorpha information extraction method on the basis of remote sensing image, and then get space-time distribution characteristics of multi-temporal enteromorpha disaster on Qingdao sea area. Analyzing the influence factors of enteromorpha disaster outbreak, which may provide certain theoretical basis and technical reference about monitoring and management of enteromorpha prolifera in the future.