摘要
随着远洋海运事业的蓬勃发展,电子海图已经成为保证航行安全的重要工具。技术的进步和科技的发展使得电子海图以其存储方便,存储量大,易于修改等优点逐步取代了纸质海图。该系统不仅能够对雷达、声纳、罗经、GPS等信息进行综合处理,而且可以方便的实现航海人员的图上作业。电子海图显示系统涉及到诸多关键技术,如ENC文档的解析,系统电子航海图(SENC)的设计,海图数据检索,墨卡托投影和高斯投影的理论算法、海图的裁剪、显示等。
本课题研究侧重于ECDIS(电子海图显示与信息系统)的显示,主要研究了海图显示所涉及的一些关键技术,利用VC++开发了实现关键技术的系统。
首先介绍了海图的出现及发展,简要说明ECDIS的概念、组成、功能,分析了该系统的国内外发展现状。
本课题研究了S-57格式海图文档的理论模型、数据结构及封装标准,阐明了S-57格式海图数据的特点。并用示例说明了ENC的编码方式；深入分析了SENC设计的必要性,即ENC解析的必要,给出了SENC设计的基本原则和总体要求；在认真研究现有资料文献的基础上,提出了一种SENC格式设计方案；最后以实际编码为例对该方案进行了详细说明。
本课题还研究了墨卡托和高斯两种投影理论和算法,详细说明了地理坐标至投影坐标的转换方法,尤其是对于基准点的选取进行了特别讨论。最后对两种投影的优缺点和使用范围给予比较说明。
最后,本课题对海图显示信息按照要求进行分类处理,给出了信息分层的组织结构,给出了屏幕显示区域的计算方法。并以使用成熟的海图要素裁剪算法对海图进行了相应处理。最终将ENC文档简要显示在屏幕界面。
本课题来自大连海事大学导航研究所承担的吉林省交通厅的科技项目“船舶动态监控信息系统”,研究成果得到了应用。
With the rapid development of ocean shipping industry, electronic navigation charts have become an important tool to ensure the safety of navigation. The paper chart has been replaced by the ENC, because the ENC took the advantages that its convenient storage, larger capacity, and it was easy to modify. No only radar, sonar, compass, GPS and other information could be dealt conveniently by the system, but it also could facilitate the realization of the map for the seafarers. A lot of key technologies was involved in the ECDIS, such as the analysis of ENC document, the design of SENC, the data retrieval chart, the theory and algorithm of Mercator projection and Gauss projection, the cutting and display of electronic navigation chart.
By using VC++integrated programming environment to implement some core technology design for this system, much researches on the key technology of ENC displaying had been done by this paper, especially ECDIS displaying.
Firstly, the appearance and development of the ENC were introduced. In this part, some elements related with EDIS including concept, composing. function, etc. Besides, the development condition of this system internal and external the country had been analyzed, too.
The theoretical model, data structure and the packaging standards of S-57 format charts was researched by the study. And the characteristics of S-57 format chart data had also been clarified. Besides the coding style of ENC had been illustrated with examples. This research deeply analyzed the necessity of SENC design, which also included the necessity of ENC analysis. And the basic principle and total requirement was given by this paper. Based on existing documents, a SENC format design was provided. A detailed explanation with practical coding examples was given to this research at last.
The theory and algorithm of the Mercator and the Gaussian projection had been researched in this study, what's more a description for the method of the conversion of geographic coordinates to projection coordinates had also been given, it discussed the selection of reference points especially. Finally, the advantages and disadvantages and the use scope of two projectors to be given more notes.
Finally, the chart display information in accordance with the requirements of classification has been dealt in this subject, and it showed the hierarchical structure of information, given the calculation of the screen display area. Some sophisticated algorithms which was designed to cut the charts to be displayed had been taken to deal with the chart elements.. At last the ENC summary document will be appeared on the screen.
The research of this theme has been applied to the Jilin Communications Ministry's project which is undertaken by GNSS Institute in Dalian Maritime University. The project's name is "watercraft dynamic monitoring information system". The research result has had application in the project.
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