The Researches Of Electronic Chart Database And Its Indexing Techonoly

With the development of the electronic computer, image-processing technology and navigation technology, electronic chart system has been brought out to describe the ocean geographic condition and navigation information in digital form. For its vividness, directness, flexibility and other matchless advantages in comparison with the paper chart, ENC has led to a profound technology revolution in the fields of navigation and plotting. Most countries of the world have paid highly attention to electronic charts and its application system. They have developed various products related to electronic navigation chart and made a big progress in type, function and technical performance of the charts.As the basic of electronic chart application system, ECDB decides the function and performance of the system. Only through making use of highly efficient index technology can we realize the accurately and quickly searching for the suited chart data in large amount of data. Taking the chart data of format S-57 as the source data, in this paper we utilize the database management system Oracle 9i to build up electronic chart database, and also accomplish quick searching for the SENC data through R-tree spatial index technology.In the first chapter of this paper, it is mainly to introduce the development of technologies in relevant fields to electronic chart and the background of building up the electronic chart database. And also the content, goal and realistic meaning of the research are pointed out in this chapter.The content of chapter 2 is the foundation of building up electronic chart database. This chapter focuses on relevant the data structure of electronic navigation chart and the international standards. It gives a comparison between raster chart and vector chart, thus selecting the vector chart data which meets the Standard IHO S-57 (V3.0) to be the source of ECDB. In this chapter it is also to make a further introduction on the mathematics model, data structure and the procedure of making ENC.In chapter 3, by analyzing the data structure and algorithm of several spatial index technologies in common use, like binary-tree, B-tree, Quad-tree, R-tree, it comes to the conclusion that R-tree should be the most suitable spatial index for setting up ECDB. And then it gives a specific introduction on the data structure and basic algorithm of R-tree, including searching, deleting, inserting, splitting, etc.Chapter 4 is the core of this paper. In this part, through the study of database management skills that are currently applied, we determine to build up ECDB in Oracle 9i, and then the whole process of database building has been explained. The first step, according to the requirement of S-57, is to design the table name and field attribute of the database. The second step, considering the need of practical navigation, is to set the limits of data. The third step is to input the actual data into the ECDB, create R-tree index and build up ECDB. The last step is to implement the management of ECDB, by using SQL language.The conclusion part of this paper has concluded the research of the subject and then put forward further imagination and expectation on the future's research work.