| The 21 st century is the century of the ocean.Since the 18 th National Congress of the Communist Party of China,my country has put forward the maritime power strategy for the first time,which has important practical and strategic significance in the current complicated domestic and international situation.China is a large maritime country with 18,000 kilometers of coastline(excluding island sea boundaries),more than 3million square kilometers of sea area,and rich marine resources,of which marine fishery resources are one of the most precious marine resources for mankind.The marine fishery geographic information system(GIS)is the guarantee for the rational development and utilization of marine fishery resources.Because the geographic characteristics of the ocean and the land are very different,such as the flexibility,dynamics,data indirectness,ambiguity,and multi-scale characteristics of the ocean,traditional terrestrial GIS is difficult to apply to the research of marine fisheries.At the same time,my country’s satellite remote sensing technology has developed rapidly: So far,my country has launched 55 Beidou navigation satellites,completed the global network of Beidou satellites,and provided services to the world.It has been widely used in transportation,agriculture,forestry and fishery.Based on the analysis of the spatial characteristics of marine fishery vessel position data,multi-dimensional data query,and the stacking division of fishing area grid structure at different resolutions,this paper studies and explores the respective advantages of geographic grid models in the field of marine fishery.The importance of grid model to marine fishery data analysis and model exploration is analyzed,and the idea that the development of marine fishery GIS should be based on geographic grid model is put forward.This paper is based on the geographic grid model to establish a grid of marine fishery ship position data index and the development of Base4 coding for China’s sea area(Bohai,Yellow,East,South China Sea)two aspects of research concretely based on the geographic grid model marine fishery GIS Connotation: Based on the correlation theory of observational data,the global structure detection and local correlation measurement of spatial features of the geographic grid model are studied;the spatial expression of ocean elements under the grid model is studied.Including:direct correspondence of ocean elements in geographic space,distribution characteristics of spatial objects,data index expression,data spatial proximity relationship expression,and comprehensive expression of attributes that vary with spatial scale.It also provides the idea of gridding under the geographic grid model and the spatial division method of cascading architecture.The main contents of this paper are as follows:(1)Combining the characteristics of ship position data,design the organizational structure of ship position data under the geographic grid modelIn view of the large amount of historical data of VMS or AIS on the ocean and its continuous real-time data,in the case of a large number of ships,it is easy to form a large-scale data.Therefore,in order to solve the problem of unified organization and efficient management of massive ship position data,this paper is based on the organizational structure of ship position data under the geographic grid model,and obtains the longitude and latitude information of ship position through the global navigation satellite positioning system.Based on Geohash’s geocoding format and the principle of space division and space curve filling,a unified organizational coding structure is established,and the obtained ship position information is coded to generate longitude and latitude respectively,and cross-combined to generate a unified binary code.As a result,a one-dimensional string is generated,which provides data preparation for neighborhood search and spatial query of data.(2)Based on the organization code and index structure of ship position data under the geographic grid model,research on the query method for ship position dataBased on the grid data organization coding mode under the established geographic grid model,the neighborhood or nearest neighbor query method of ship position spatial data is studied.In terms of query,it can be divided into the query of ship position data that meets the preset distance condition and the query of the nearest ship.The query under preset conditions is to set different effective distances to meet actual needs according to the actual query range.For example,in rescue,you can search the database for neighboring ships that meet the effective rescue conditions based on this,and accurately locate the space range of the query.To speed up data reading speed and efficiency,the land command center then dispatches ships to perform corresponding management;in the nearest neighbor query,combined with the eight-direction neighborhood search method,and then based on finding whether the characters in the eight neighborhoods are located on the boundary,two situations are discussed.Finally,the problem of coding mutations in the same grid is solved.Finally,based on the grid coding of spatial division,a method of searching the neighborhood based on the effective rescue distance and the location of the wrecked ship is proposed to find the ship that is adjacent to and closest to the wrecked ship for rescue.The effective rescue distance is set by the type and speed of the rescue ship,and different code search lengths can be set according to the effective rescue distance.In terms of time efficiency and memory occupancy,the experimental results show that compared with the traditional method of calculating the distance between ships,the coded ship position occupies less memory and has higher computational efficiency.Further improve efficiency when inquiring about and processing rescue ships in the vicinity of ships in distress.(3)Experimental scheme design and algorithm efficiency testIn order to verify the performance of this research method,this research uses R software to implement a search and rescue method based on the gridded neighborhood ship position data.The experimental data takes the East China Sea as the spatial scope,and 10,000 floating-point ship position data are simulated and 4 bits are reserved for effective digits.The experimental environment is Windows 10 operating system,2.40 GHz Intel Core(TM)i5 CPU,4G RAM,and 500 G 7200 RPM hard drive.Specifically,from the comparison of memory usage and time efficiency,it is concluded that grid coding reduces the consumption of memory resources and makes more efficient use of memory resources.It also verifies that the encoding is performed by calculating the user’s running time,system running time,and elapsed time.The query time is shorter than the calculation time before encoding.(4)A Regional Division Method for Establishing China’s Seas Stacking FrameworkIn order to solve the problem that the direct correspondence between the division and numbering of my country’s fishing areas and geographic space is relatively weak,this article provides a method of area division based on a cascading framework,so that the coding of fishing areas not only reflects geographic spatial information,but also based on different codes.The length can determine the level of the division of the fishing area. |
PDF Full Text Request