A Study On Underwater Terrain Acquisition And Visualization Of Baiyangdian Lake

Baiyangdian Lake is an important part of the ecological pattern of water-city integration in Xiong’an New Area.The construction of its underwater topography not only helps to study the changes of flushing and siltation in each shallow lake area,but also provides an important basis for hydrogeological information analysis.With the development of the surveying and mapping national geographic information,China has put forward a higher demand for underwater topographic surveying and mapping.The traditional manual surveying and mapping methods will not only consume a lot of manpower and material resources,but also provide the weak visualization of underwater terrain.Therefore,the automation and intelligence of underwater topographic survey are urgently needed to be realized.This thesis takes part of Baiyangdian Lake as the research object to collect underwater topographic data by unmanned automatic cruise ship,and the underwater topographic visualization platform of Baiyangdian Lake is designed and built based on the secondary development of Map GIS.The main research contents are as follows:The unmanned automatic cruise ship equipped with side-scan sonar and single beam echo sounder was used to collect the underwater topographic data of Baiyangdian Lake,and in order to address the problem of errors in the bathymetry data,the baseline was first established based on the four quarters average method,and the measurement errors were subsequently corrected with a mathematical model to ensure the accuracy of the subsequent study.For the problem of poor quality and low efficiency of underwater topographic side scan sonar image stitching in lakes,an improved underwater sonar image stitching method based on spatial gradient Fuzzy C-Means was proposed.The traditional image stitching process was changed,and the underwater topographic sonar image was stitched after dividing the image into feature blocks.The spatial gradient information was introduced into the traditional FCM feature blocking algorithm to improve the accuracy of clustering.Experimental results show that the improved algorithm provides high image stitching quality and reduces implementation time compared with the traditional image stitching algorithm.In order to address the problems of poor quality of triangle mesh and unnatural transition of terrain undulation details in the process of topographic 3D modeling by the traditional Delaunay,an improved underwater 3D terrain optimization method based on Delaunay was proposed,which took aspect ratio and minimum tilt as the criteria for optimization selection and directly optimizes the triangle elements.Compared with the traditional Delaunay triangulation mesh,the improved underwater 3D topography optimization method can realize the 3D reconstruction of underwater terrain with high quality.The underwater topographic visualization platform for Baiyangdian Lake based on Map GIS was designed,which combined Map GIS 10 API for Java Script and other related technologies to visualize the 2D and 3D underwater topography of Baiyangdian Lake on a B/S architecture.