Key Technologies For Visualization Of Multi-beam Data

The multi-beam sounding system can transmit dozens of hundreds of beams in the direction perpendicular to the route,and a survey line can get a fully covered strip,so as to express the seafloor topography accurately,quickly and intuitively.Visual expression technology can make use of the full covered discrete data obtained by the multi-beam sounding system to generate the digital elevation model of the seafloor,and create a realistic three-dimensional sea floor scene by superposing color rendering and lighting effects.Visual expression technology is a real and intuitive description of the seabed terrain.It is an important way for human beings to understand the marine environment.It has important application value and practical significance in many areas such as national economy,national defense and safety.But high efficiency operation also determines the mass characteristics of multi-beam bathymetric data And the measurement area of multi-beam measurement project is usually large.If we directly use the massive multi-beam raw data to analyze and express the seabed terrain,it will cost a lot of time and computer resources.So the fast and effective algorithm for simplifying the multi beam data is beneficial to the fast processing of data analysis and mapping.The first,in this paper,the traditional method of data simplification based on TIN is studied.In view of the shortcoming of exponential increase in the number of query times when judging whether a point needs to be simplified,the process of data simplification based on TIN is improved,and the number of times of search and calculation in simplification is reduced.Secondly,a simplified method of partition multi-threshold data is proposed.The multi-beam data in the measured area is partitioned by regular grid.In order to avoid redundancy and oversimplify,the best simplified threshold is selected for each partition.Finally,the evaluation method of data quality of multibcam bathymetric data is presented.The experimental results show that the time of the improved TIN based data simplification is greatly reduced,and the partition multi-threshold method improves the data simplification.The quality of the simplified algorithm is equivalent to a single thresholdIn this paper,the simplified multi-beam bathymetric data is used for visual expression research.First of all,the types,advantages and disadvantages of seabed digital elevation models are analyzed.Second,we propose a color rendering algorithm based on RGB and HSL color models,and a color matching method for DEM rendering.Third,we analyze the related factors that affect the illumination effect of the seabed terrain.The principle of Phone lighting model and Gouraud shading model based on OpenGL is expounded.Finally,the visualization expression of seafloor terrain based on OpenGL 3D graphics library is implementedEven in the same survey area,the seabed terrain features of different plots will be different.If the same simplified threshold is adopted in the same survey area,the simplified result of the flat seabed will still have data redundancy,or when the threshold is too large,it will cause the lack of topographic feature points in the large terrain,and the data simplification is oversimplified.In addition,the traditional method of TIN based data simplification needs to traverse all measurement points in the test area when judging whether a point needs to be simplified.As the amount of data increases,the number of traversal queries increases exponentially,which puts forward higher requirements for data processing time and computer performance.The results show that the visual expression of this paper is smooth,rich in color,and increases the stereoscopic character of the topographic map with the light effect.