Research On Spaceborne GNSS-R Water Detection Method Based On CYGNSS Data

Water is the source of human life.Hydrological research and water resource management are very important to human beings.The rational use of water resource is conducive to human life and production,and the detection of water distribution is helpful for human to monitor the ecological environment and protect water resources.Scholars at home and abroad have carried out extensive research on water detection methods,but there are still many challenges.Global navigation satellite system reflectometry(GNSS-R)is a new type of remote sensing technology,which has the advantages of low cost,all-weather,high spatial-temporal resolution and large coverage.Using GPS L-band as signal,it has strong penetration of cloud,rain and fog,and has a bright future in the field of water detection.The purpose of this paper is to explore the spaceborne GNSS-R water body detection,the main research contents and achievements include the following three aspects:(1)Based on the CYGNSS satellite data,this paper analyzes the correction effect of coherent scattering and diffuse scattering on the surface reflectance value,obtains the surface reflectance model,and extracts the water characteristic parameters based on the surface reflectance model for subsequent research.(2)Aiming at the problem of flood detection,a spaceborne GNSS-R flood detection method based on CYGNSS data is proposed.Firstly,the original data are obtained,and the outliers are removed for data calibration.Then,the flood inundation area is detected based on the surface reflectance value,and the grid is interpolated by the natural neighbor interpolation method.Finally,the regional flood inundation is analyzed by using MODIS Image and surface reflectance value map.The results show that satellite GNSS-R technology has the ability to detect flood,and because of its relatively short revisit time,satellite GNSS-R technology will be able to detect flood disaster in near real time,which has important application value and scientific significance.(3)Aiming at the problem of water distribution detection,a spaceborne GNSS-R water distribution detection algorithm based on CYGNSS data is proposed.Firstly,the original data are obtained,the research area is divided into grids.After removing the outliers and invalid values,the regional mean algorithm is used to recalculate the reflectivity of each grid.Then,the grid sample variance and standard deviation are used as the measurement index,and the random walk image segmentation algorithm is used to detect the water distribution Finally,the distribution of water body in Congo Basin is analyzed by the proposed method,and the results are evaluated by MODIS data.The results show that the spaceborne GNSS-R technology has a strong ability to detect water distribution,which further expands the application scenarios of GNSS-R.