ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS", Bangkok, May 23-25, 2001
151
BUILDING OF B/S-BASED OBJECT ORIENTED ELECTRONIC CHART DATABASE
Guangru LI 1 Shaopeng SUN 2 Depeng ZHAO 3
1 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel:86-411-4729297
E-mail: creatlgr@sina.com
2 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel:86-411-4729297
E-mail: sun_sp@usa.net
3 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel: 86-411-4729297
KEY WORDS: Web-GIS Web-Chart, Electronic Chart Database (ECDB), Spatial Searching
ABSTRACT
This paper researches in system architecture of Internet-based Electronic Chart, and mainly discusses how to establish object-oriented
chart database, how to search useful spatial data from chart database.
1. INTRODUCTION
With the development of Internet, how to realize Electronic Chart
application through INTERNET makes more attention than before.
The rapid development of satellite communications provides an
unprecedented chance to the development of communications
between land and ship. Therefore, building IIS Electronic Chart
Server and the related technologies become pop technologies in
research of Electronic Chart. Web-Chart is the Electronic Chart
that based on Browser/Server structure, and Web-Chart realizes
the rapid display of vector graph and the seamless connection of
dynamic data. Browsers download this system from server into
client through INTERNET, and load graphic data, build database
link. When user uses data and graph, it produces dynamic SQL
language, and accesses database server through INTERNET,
then user can operate vector graph and dynamic data.
Database Server's realization is based on file system and
Database Management System (DBMS). It can satisfy request of
accessing database, especially accessing the structure data.
Application Server is commonly a server who can provide
universal or professional function based on all sorts of application
models or computing technology in professional field. It was built
based on basic data management function of file and database,
Web-chart, Site Server, WAP Gateway, and some other
applications are all members of this application server category.
They commonly need append function modules of different
professional fields. For example, the web application need user
to convey computing result to web server with HTTP protocol,
and make farther respond in web server. These functions
commonly were realized by systemfs Remote Procession Call
(RPC) or service progress. They provide functional modules to
interact with exterior and coordinate interior. Intelligent
information agent acts as this kind of functional module.
Web server is the core part of building of a web computing
platform. It provides many service functions supported by file
server, database server and application server. Ifs main aim is to
realize the connect interface of application service functions and
the call of HTTP.
Client is the front end to users access and process all sorts of
web service functions. It can realize many interactive functions to
users, and make these interactive functions to communicate with
HTTP protocol and web server. Commonly, client use directly
HTML language or Java ScriptA/B Script, but it will need ActiveX
control or Plug-in to deal with sophisticated computing to satisfy
the need of client function. In Web-GIS, we should satisfy the
distributed computing function. For this sophisticated function, we
use ActiveX or Plug-in to realize it.
Web-Chart can conveniently operate vector graph, such as zoom
out, zoom in, roam, pan and some other basic function.
Web-Chart also has some other merits:
1) The broader browse ability: Internet makes user can browse
the newest data from multi-server in different place
simultaneously. This feature facilitates the management of
Electronic Chart Data, makes management and combination
of distributed multi-data source become easier to achieve.
2) Platform independent: Don’t care what kind of machine the
server or client is, and what kind of chart software the
Web-chart server use, through Web browser, user can browse
Web-chart data transparently, dynamically assemble
distributed components and manage and analyze spatial data
cooperatively, to achieve the sharing of remote heterogeneous
data in spite of hardware and software. To achieve platform
independent, it is the key technology to build the
object-oriented ECDB.
2. BUILDING OF OBJECT ORIENTED ELECTRONIC
CHART DATABASE
Using object-oriented technology, we can extract information
from geographic object in Electronic Chart to create different
class, build the relations among them, and encapsulate attributes
and operations of classes. Using object-oriented data model, we
can define three-dimension spatial data model, spatial-temporal
data model and some other models and build the Internet-based
distributed spatial data model. Object-oriented technology is
based on object in concept. It combines the similar objects as
different classes. By generalizing the object class, we can create
hyper-class, these object classes were named sub-class.
Sub-class can inherit the method and attribute of hyper-class.
Object-oriented technology also provides the approach to extract
data, that is to say the generalization and aggregation of objects
or classes. We can build the hierarchy of objects by using
generalization and aggregation repeatedly to extract data. There
is the one-multi relation between every object and its member.
Object-oriented data extraction technology provides the
computing ability in lengthways spatial relations and realize the
object’s classing, unit, generalization, aggregation and class’s
