Department of Engineering, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558, Japan
The high costs of geographical information systems and geographical information were the key problem for some institutions that need to develop GIS. For this purpose, VENTEN that developed as Internet based GIS must be available at low costs. The Internet GIS or WebGIS system provides Geographical Information System (GIS) functions via the Internet-services for browsing and analyzing geographical information. In order to provide the GIS system with the heavy server-thin client method, the only choice available is the system, which performs GIS search and analysis by the web.
Keywords: Internet GIS; VENTEN: CGI; JICA
The Internet GIS or WebGIS system provides Geographical Information System
(GIS) functions via the Internet-services for browsing and analyzing
geographical information. The Internet was prototyped on the ARPANET (Advanced
Research Projects Agency Network of the Department of Defense) developed by the
United States Pentagon in 1970. As its name implies, it extends over various
networks, which are interconnected. Today, the Internet is indispensable.
However, the extensive use of the Internet by the general public in addition to
researchers and engineers spread explosively with the start of WWW (World Wide
Web) services using http (Hyper Text Transfer Protocol).
When WWW services were first started, most of the information provided was in text form pasted with images that had links. Shortly after, sites providing services with simple GIS functions using the http image distribution function and event-handling function emerged.
With htm (Hyper Text Markup Language), which is the format for describing the contents provided by WWW services, there is a term called image map, where multiple rectangular, circular and polygonal areas are set for an image. This enables different operations to be performed according to the position of the mouse pointer at the time the mouse was clicked. The designation of the polygonal areas allows the designation of any area. Therefore by linking to a page with different contents according to the clicked position, it is possible to enlarge and reduce images, as well as display the properties of objects at the position of the mouse pointer. This enables simple GIS functions (though browsing functions only) to be provided via the Internet (see Figure 1a).
However, with this method, it is necessary to compile all contents to be provided and link all of these pages, thus limiting to the static provision of contents. To overcome this limit, the CGI (Common Gateway Interface) method was adopted. CGI provides the user with the opportunity to execute programs for a process based on parameters from the client on the Web server. Texts and images output as a result of this process are returned to the user to allow dynamic provision of the contents compiled, which broadly expands the potential of contents provision (see Figure 1b).
However, systems based on this method also have their problems. Many of the programs executed in CGI are described by Perl (Practical Extraction and Report Language Pathologically Eclectic Rubbish Lister). If it can be executed on the Web server platform, principally programs can be described in any interpreter language, or any executable binary. But regardless of which programming language is used, the preparation of functions used by GIS requires the development of the whole GIS application, meaning considerable efforts for its development.
Currently, use of various GIS applications on the Web is being anticipated,
enabling requests to be received by http for processing. In addition, GIS
applications, which can be operated by, script such as GRASS (Geographic
Resources Analysis Support System) and GMT (The Generic Mapping Tools) can be
used on the Internet GIS system by incorporating them in the CGI. This method
allows the Internet GIS to be constructed by constructing only the interface
with the existing GIS application without the need to develop the whole GIS
I briefly outlined the history of the Internet GIS. Currently there are various types of sites providing such services according to the required purpose. B. Plewe attempted classification by heavy/light server and thick/thin client according to the balance in the appropriation of the server and client, as well as the classification of Internet GIS services into seven types according to the functions provided (1). According to his classification system, servers and clients can be proposed into heavy server-thin client, who concentrates the load at the server, and light server-thick client, which requires the client to bear most of the load. The merits and demerits of each are outlined below.
2.1. Heavy server-light client
- Maintenance is easy due to the central control of the data system
- Efficient use of the computer's capabilities
- Non PCs can be used for client machines
- Excessive concentration of load on the server
- Development of advanced server programs
- Increase in communication load
2.2. Light server-thick client
- Reduced communication load
- Need to incorporate plugin software and applets
2.3. The Classification of Internet GIS
Internet GIS services are classified as follows1)
- When acquiring raw data on the web
Only data services are provided. Processing is done by the independent GIS application of the client.
- Fixed map display
Geographical information pre-compiled is provided according to the requests of the user.
- Meta-data search
Provides search functions of geographical information meta-data. Data services are not necessary.
- Dynamic map browsing system
Returns generated geographical information based on user requests as the parameters.
- Data pre-processing system
Raw data is provided after converting to a format, which can be used by the user.
- GIS search and analysis by the web
GIS functions are provided in the server or client according to user requests.
- Net-oriented GIS software
GIS applications operating on the client machine and server data services are linked seamlessly.
Let us consider the ideals of VENTEN taking into account these classifications. As described earlier, in the meeting of disaster management officers from various countries held prior to the development of VENTEN, the high costs of geographical information systems and geographical information were pointed out, and therefore VENTEN must be available at low costs for both. Regarding the system, though methods using plugins and applets are also feasible, considering the differences in the performance of computers available in Asia and small capacity of networks inevitably, the heavy server-thin client method was adopted. Though not pointed out by B Plewe, to leave most of the processing to the client machine, the client machine must receive the geographical information in a state close to the raw data. Considering the existence of pessimistic data providers in the distribution of original data, leaving processing to the server and distributing only the processed final product should be advantageous for resolving copyright problems.
Next, let us consider the positioning of the seven groups of Internet GIS systems. In order to provide the GIS system with the heavy server-thin client method, the only choice available is the system, which performs GIS search and analysis by the web. Though the method of preparing all the conceivable analysis results may be possible for the fixed map display type system, this fixed map display system is not realistic when taking into account the need to cover the extensive area of 22 countries in Asia, and the possible enhancement of disaster management information in the future. Having considered these points, we decided to develop the heavy server-thin client method and system, which performs, GIS search and analysis by the web in the construction of the VENTEN system, and selected the required platform.
In this development of VENTEN, with the aim to provide geographical
information of the same density in all 22 countries in Asia, development is
carried out on one system. In reality, the density of the geographical
information obtained differs by country and region, as are the distribution
conditions of the geographical information. In the future, we hope to study ways
of providing the appropriate system when required, including the coexistence of
multiple systems. For this, we must listen to the comments of users targeting
VENTEN, and continue to make further improvements. For the four basic elements
composing GIS, D J MAGUIRE gave computer hardware, computer software, data, and
lifeware (2). He also described lifeware as follows.
"Finally, the most important GIS element is lifeware; the people responsible for designing, mounting, and using GIS. Without appropriately trained manpower with the visions and responsibilities towards their projects, nothing can be achieved."
Like computers, systems, and data, the engineers designing and developing the system are said to be important, as are the users. Systems and data services, which do not match user needs, have no meaning whatsoever. The ADRC is therefore calling the disaster management officers of member countries to use VENTEN and report on the results. We also organize a lecture called Basic GIS and Remote Sensing for Disaster Management and training 2) within the Seminar on Disaster Management training course for disaster management officers, held jointly with the Japan International Cooperation Agency, to have the trainees actually operate VENTEN and collect their opinions. As the trainees were given only a short time of about one hour to use VENTEN, most of their comments were about data inadequacies (data is not the most recent, data is missing), required data (hospitals, military facilities, etc.), and the need to collect disaster management geographical information of not only ADRC member countries but of the whole world. Data inadequacy is a problem requiring immediate solutions, and currently we are calling counterparts in member countries to provide the latest data. In the future, we hope to hold longer courses to seek opinions and comments on the functions and interface of the system, and implement improvements so that the system fully incorporates the opinions of users.
1) The names "heavy server/light server" and "thick
client/thin client" and the seven Internet GIS types were quoted precisely
from reference (1), and their descriptions were the edited version of the
contents described in reference (1).
2) Seminar on Disaster Management organized by Asian Disaster Reduction Center and Japan International Cooperation Agency, 1/11/2001-2/9/2001. Attended by 14 trainees from 13 countries. Basic GIS and Remote Sensing for Disaster Management was carried out on 1/13/2001.
Brandon Plewe, "GIS ONLINE Information retrieval, Mapping, and the Internet", Delmar publishing, 1997, Translated into Japanese by Atsuyuki OKABE, Sakura SHINOAKI and Mitsuru NASU, KOKINSHOIN, 2001 Edited by David J Maguire, Michael F Goodchild and David W Rhind, "GEOGRAPHICAL INFORMATION SYSTEMS Principles and Applications", Longman Group UK Limited, 1991,Translated into Japanese by Noboru OGATA, Kazuyuki KONAGAYA, Teruko USUI and Takamasa SAKAI, KOKINSHOIN, 1998