Research On Seamless Multi-Scale Electronic Navigation Charts Data Organization And Its Application

As the Electronic Chart Display and Information System (ECDIS) being installed on ship compulsively, implementation of IMO e-Navigation strategy and the development of marine and maritime Geographic Information System application in a deep-gonging way, the main achievements of electronic chart application by hydrographic shows a great social value. However, with the widely application of electronic chart technology, its inherent limitations are also revealed. The limitations lead to the difficulty in meeting the requirements for the transformation from the purpose of navigation to providing geographic information services. There for, IHO issued the S-100Universal Hydrographic Data Model formally in2010in other to adapt the new requirement for the maritime filed and the ocean research to the geographic information services and the next generation of ECDIS. On account of the coming huge transformation, this article presents the idea that the research and application of the electronic charts technology should transform the focus from charts to data, which can fundamentally remove the constraints from the S-57based electronic chart on the marine and ocean geographic information research. Aim at the data-centered, in the perspective of the data organization of global electronic chart, this article uses the entity-oriented thought, constructs a uniform organization schema based on the Spatial Information Multiple Grid(SIMG) in other to handle the seamless organization of electronic chart in a horizontal way and representation of multi-scale in a vertical way, which can implement the friendly user experience of electronic chart application system based on the electronic chart spatial database. The specific research Content as follows:1. Delve into the S-100and S-101. Especially analyze the contents which are directly to this research:frame structure, universal feature model, spatial mode, the application mode of electronic chart, feature catalogue, feature object identifier, geometry feature, scale and so on. S-100is developed based on the ISO19001geographic information serial standard, therefore, it can use the mature theory and technology of GIS field, and import more spatial information data sources to the hydrographic field. The following features of the S-100and S-101provide an important theory basis for this article:a. Object-relation oriented modeling method, which S-100uses UML to describe, defining the geographic spatial feature class and the relationship between the class objects, which are association, aggregation and composition, easy to describe the database which stores the feature objects. b. The classification of feature type, scale-dependent and scale-independent, which bring a big convenience for the spatial feature modeling based on the concept of scale-independent(the feature entity is only stored once in the database, but can be used for several scales).c. Replace the original concept of edit scale with display scale. Multiple scale presentation(the range of scale) can be divided by the requirement of application instead of data, and propose the concept of scale-dependent and scale-independent datasetod. There is no spatial database technology in the S-100and S-101electronic chart, which is still organized by the map sheet. Organizing the charts from map sheet to spatial database technology is one of the research contents in this article.2. Starting with the existing problems in the electronic chart, seeking the effective scheme based on the S-100data model and ENC data source. SIMG is applied successfully in the GIS global spatial data share, proposed by Li Deren academician, by which this article introduced into hydrographic field, build a uniform data organization frame and solve the problem of the electronic chart global share. This article carries out the research on analyzing the trait of electronic chart date firstly, based on the full understanding of SIMG theory system, solve the following three important question:the definition of grid, spatial feature gridding and spatial feature joint. Propose a cut algorithm which uses grid line to cut the complex polygon, which can implement the spatial geometry feature gridding and restoration effectively.3. Seamless electronic chart data organization is one of the most important content in the geographic spatial information uniform organization framework. Due to the reason why to produce electronic chart and the extreme bad performance of user experience in display, this article proposes a seamless organization theory based on the spatial data and uses spatial database technology to manage electronic chart data. Spatial database is the main way to implement the organization and display of the global wide spatial data. Making use of the SIMG technology, this article sets up a gridding seamless data organization of the spatial geographic feature entity, which ensure the high efficiency in data storage and speedability in data index in the physical layer, and in the logical layer, the technology makes the gridding division transparent to the user, that is to say, the searching result and feature display is seamless. Considering that the electronic chart data sources (S-57/S-101ENC) are based on the map sheet, this article gets down the research on the widely used electronic chart production system, and makes some principles on the edit of electronic chart, which ensure the data that can be used well in the database creation of the electronic chart spatial database.4. Another important content in the geographic spatial information uniform organization framework is the multi-scale data organization a presentation of electronic chart. Multi-scale presentation of the spatial data is one of the most popular researches and difficult point in the GIS field, because of the progress in the map generalization technology research. Comparing to the traditional GIS spatial data, there are some obvious differences in the electronic chart data:First, the electronic chart is divides freely by map sheet and not covers all the space, which is different from the map that is all-covered organization by the kilometer grid; Second, the number of the scales(6navigation usages,3to4scales in the same region to cover) of the electronic chart data is not enough to satisfy the requirement of the self-adaption and intelligent zoom(S-101has got15levels); Three, making use of the entity-oriented modeling method to model the spatial feature, which is adapt to the S-100data model based on the object-oriented characteristic and beneficial to build mapping in the object-relation database. The multi-scale data organization based on the entity-oriented non-scale thought divides the electronic chart data into6layer framework data by the usage, extracts the scale-independent feature to process alone, the geographic spatial feature are stored and presented in uniform(feature stored only once), uses entity to store the multi-scale geometry shape data of the feature, presents the geometry form in polymorphism by the behavior(external parameter), and establishes the spatial relationship between entity objects based on the feature entity in order to optimize the presentation of the feature entity. The organization method in this article overcomes the shortcomings of the modeling method which uses multiple databases to manage multiple data versions and multi-scale data, such as too much work to build database, data redundancy and difficulty in consistency preservation, and also solves the limitation from the auto map generation in "one database one version multi-scale" modeling method and the shortcoming in process efficiency and effect which is not enough to satisfy the actual application.Organization of seamless multi-scale electronic chart data can solve the horizontal and vertical problems in the global data management and display of the electronic chart application system, provides an extreme user experience in display. Specific to construct such an universal design framework of electronic chart application system and the key problems in extracting and outputting grid data fast, continuous roaming in longitude direction and self-adaption multi-scale presentation, this article provides the designation and implementation method, which is being applied in many projects and making the extreme user experience in display.