Information networks straddle the world. Nothing remains concealed. But the sheer volume of information dissolves the information. We are unable to take it all in." said Gunther Grass in his interview to
New Statesman & Society in 1990.
The power of information
lies in the exactness and usability of processed data and the speed and cost at
which it is available. This case study from Japan is about the technology used
to process and share the sheer volume of geographic data acquired by a corporate
giant over a period of years.
The Client and their requirement
Our client is a Japanese geo-technical consultant specialized in the field of soil engineering and primarily involved in construction projects all over Japan since 1954. In the recent years it has started automating the task of processing its geographic data and sharing the information processed. We at
RMSI developed desktop and client server geographic information systems for the client to manage river, highway and dam projects in Japan. These desktop and client server systems which used ESRI MapObjects and MapInfo technology helped the client to process their data to a great extent, but were not available to all the users in the organization which has 70 offices all over Japan. It was not economical for the client to install these individual mapping systems in all its offices and for its clients. This also lead to problems in data sharing, maintenance, manipulation and resulted in redundant data storage. There was need to develop a larger system that could serve many users without data redundancy.
A solution emerges
Enterprise wide GIS was the
answer to the problem. Unlike the traditional desktop GIS, this requires
building of methodologies to make the data available to all the users. Web
became the ideal medium to share information among the users through web
browsers. The existing Local-Net connecting its offices served as Intranet for
the client’s engineers and the Internet to serve the client’s
customers. To start with, a prototype of the Enterprise GIS was planned. It
consists of a wide range of features from map navigation tools to querying
databases, searching and identifying features, preparing thematic and cosmetic
maps, generating 3D images and contour maps, associating user information to
features, printing map plots and creating map documents for reports, exporting
maps into various data formats… etc. In addition to the above features
available for every user, administrators must be able to create and manage
projects and other users.
Design objectives
Some of the key design objectives were
interactivity, which has to be at par with a desktop system,
high response time, which should be acceptable to the users,
simplicity, to help the client’s geo-technical engineers who are not used to such advanced information systems. And, above all an effective way to maintain the state of each browser accessing the server.
Selecting the software
The software to support the
mapping part of the web-based Enterprise GIS was to be chosen, considering the
client’s financial and time constraints. Also the possibility of reusing
the components developed for desktop and client server GIS was kept in mind.
Many web-based GIS software products were evaluated. ESRI MapObjects Internet
Map Server (IMS) emerged as one solution to the problem, a state-of-the-art
technology to build mapping applications for the Internet and Intranet. The
product consists of a CGI application in the form of a DLL (called esrimap.dll)
and an ActiveX control (called weblink.ocx). The product enables application
developer to build server applications that serve web client requests for maps
by creating them on the fly. ESRI shape file was chosen as the data format to
store the spatial data. MapObjects 1.1 and MS Visual Basic 5.0 were selected to
prepare the maps at the server. MS Access was chosen to store the tabular
information of all GIS projects.
Having decided the mapping engine and
database at the server, the selection of software to present the maps and
tabular information at the browser remained. Java 1.1 was chosen to provide
interactive mapping tools through applets at the client browser. The non-mapping
part, which included the tabular information of all GIS projects were handled by
HTML forms, Java/VB scripts at the client side and by MS Active Server Pages and
ActiveX DLLs at the server side. The whole system rested on MS Internet
Information Server accessed by a normal web browser such as Internet Explorer or
Netscape Navigator.
Architecture
The web-based
GIS Software primarily consists of two components: the
server and
web client, which runs in the browser.
The server is aset of applications that serve the requests made by a client. It is divided into two sections: the
Map Server which prepares maps from the spatial database based on requests and sends them back to client; the
Data Server which is responsible for managing tabular
data at the server and sending tabular information to clients.
The web client is partitioned into two separate frames, the main
map frame and the side
information frame. Primarily, it
makes request for map images and HTML pages. The main map frame is a Java applet
that displays the map. The information frame displays HTML pages in response to
the user inputs in the map frame or in the information frame itself.
The
data server component consists of Active Server Pages (ASP) which
provide all the user interfaces required to access the database from the client
browser. All the business logic that did not require map generation is packaged
in the form of ActiveX components that are invoked by these ASPs.
