Design And Integration Of The Core Modules Of Island WebGIS Based On Cesium

As an important part of national territorial security and marine economy,island-based research and development has been paid more and more attention.The geographical location of islands is special.At present,the research on islands is mostly in the basic stage.The development platform mostly applies the traditional GIS technology,which is insufficient in the analysis efficiency and accuracy.There is no more intuitive understanding,analysis and expression of the three-dimensional spatial topography and landform of islands.As an emerging technology,WebGIS has gradually become one of the research hotspots in the GIS field.Its advantages of cross-platform,plug-in free and efficient visualization analysis make it widely used in the development of geographic information system.Cesium,as a typical representative of WebGIS technology,has many excellent features and superior performance,which is the preferred development platform for island spatial analysis and development.Based on the preliminary research and development of the research group,this thesis continues to excavate the topographic and spatial characteristics of the island,and conducts in-depth research and improvement on the core key technologies.On this basis,Cesium framework is used to extend,optimize and integrate the key technologies of the island GIS system.The purpose is to make the improved island system has higher overall efficiency,more functions and better user experience,providing technical support and analysis reference for island development,exploration and protection.The main research results of this thesis are as follows:(1)Visibility analysis algorithm based on the viewshed and curve reachability research.Based on different application scenarios of island spatial visual analysis,this thesis realizes the research of visibility analysis from two perspectives.Firstly,based on the basic principle of traditional LOS(Line of Sight)visual analysis,a local extremum shadow detection method based on terrain curve of single LOS is proposed in combination with the occlusion relationship between island terrain features and LOS.In this method,the continuous shaded area of terrain curve is detected by the key points,critical slope and extremum interval of terrain curve,and the unnecessary terrain grid calculation is reduced.Then,the method of circular LOS model,variable step sampling and visual radius self-adaptation is proposed to expand the dimension of single-line of sight and realize viewshed analysis.The accuracy and efficiency of analysis are improved comprehensively through algorithm improvement and optimization.Then,on the basis and inspiration of straight LOS viewshed analysis,the principle of curved reachability is analyzed and expounded,and the expansion research of island curve visibility is carried out.Based on the analysis of the relationship between trajectory cluster,envelope of multiview curve and terrain,an algorithm of curve reachable region is proposed,which provides a reference for judging the reachable range of curve projection.Finally,the algorithm module is integrated and verified by Cesium framework.Experimental results show that the proposed visual analysis algorithm can be applied to different visibility analysis scenes,and the analysis efficiency is greatly improved under the premise of guaranteeing certain accuracy.(2)Dynamic inundation analysis algorithm based on scale adaptive hierarchical and segmental seed spread.Based on the traditional inundation analysis,the relationship between active inundation algorithm and topography and data organization is analyzed in combination with seed spread inundation algorithm in this thesis.The iterative depth of inundation algorithm in large area and high precision terrain is greatly reduced by hierarchical block processing of terrain data,and the problem of low analysis efficiency is effectively solved.In addition,the dynamic inundation evolution simulation is realized by combining hydrodynamics knowledge,which makes the analysis process diachronic and dynamic.Finally,the algorithm module is integrated and verified by Cesium framework.Experiments show that the proposed algorithm can efficiently analyze and simulate flood dynamic inundation in large area scenarios while ensuring certain accuracy.(3)Improved PSO-ACO fusion path planning algorithm combined with multi-factor terrain fitness.In this thesis,an island surface fitness model is constructed based on the special island terrain environment and the influence of terrain factors and surface attributes on path planning is further considered.Then,after analyzing the principle and advantages of PSO and ACO path planning algorithms,a PSO-ACO population fusion path planning algorithm based on multi-factor terrain fitness was proposed by improving and optimizing the two algorithms and integrating them organically with the surface fitness model.This algorithm gives full play to the global searching ability of PSO algorithm and the local optimization ability of ACO algorithm,which effectively improves the feasibility of path planning results and the iterative efficiency of analysis.In addition,the curvature of the final planned path is reduced as much as possible through the proposed path smoothing mechanism.Finally,the algorithm module is integrated and verified by Cesium framework.Experiments results show that the proposed algorithm improves the accuracy,efficiency and feasibility of the path planning,and the path is smoother.(4)Realization and integration of key technologies of island WebGIS based on Cesium.Based on WebGIS architecture and Cesium development framework,the overall structural framework and functional framework of the system are further improved and expanded on the basis of the system development in the early stage of the research group.Combined with the spatial analysis algorithm in this thesis,the integrated development of island map browsing module,terrain and space analysis core module and auxiliary function module is realized.Finally,through the release and test of the designed system,it shows that each functional module can run efficiently and correctly,and the overall performance of the system is improved.Finally,the thesis summarizes the above work and prospects the future research direction.