Proceedings of the 21st International Cartographic Conference (ICC) Durban, South Africa, 10 � 16 August 2003�Cartographic Renaissance� Hosted by The International Cartographic Association (ICA)ISBN: 0-958-46093-0 Produced by: Document Transformation Technologies

BROWSING THE TOPOGRAPHIC MAP OF GSITHROUGH THE INTERNET

Ando, A., Akeno, K., Saijo, Y., Matsumoto, T., Takakuwa, N. and Ohno, H.

Geographical Survey Institute, Ministry of Land, Infrastructure, and Transport,Kitasato-1, Tsukuba, Ibaraki, 305-0811, Japan. Tel: +81-29-864-1111 (7554). Fax: +81-29-864-1805.

E-mail: aando@gsi.go.jp

ABSTRACT

Geographical Survey Institute (GSI) has been started distributing the topographic map image data through the Internetsince 2000. All users can access and browse the map of Japan from the GSI�s Internet web site without charge. Thissystem had been accessed by many users since the publication, which amounts to 1,500,000 to 1,800,000 images in amonth. However, this system using the map image data has some problems. To solve the problems, a new system calledas �Denshi Kokudo Web System (Web System of Digital Japan)� with the vector map data was designed and completedin this spring. This presentation is an introduction of these old and new topographic map browsing systems.

1. BACKGROUND AND INTRODUCTION OF OLD-TYPE BROWSING SYSTEM

Geographical Survey Institute (GSI), who is national mapping organization of Japan, has been promoting anddistributing a variety of topographical information of Japan. The service includes not only to create and distribute papermaps, but also to distribute the digital map products, such as color raster graphics, vector data and DEM, on CD-ROM.Recently GSI has been started distributing the topographical map data through the Internet (Figure 1).

Figure 1. Index map of the topographic map image data browsing system of GSI.�http://www.mapbrowse.gsi.go.jp/� (Japanese Only)

The above-mentioned browsing service has been provided since July 2000. All users can access and browse the mapfrom the GSI�s Internet web site without charge. The map data stored in this system is image (raster) data created fromtopographic paper map at a scale of 1 to 25,000 covering the whole Japan. Format of the image file is PNG, and thecolor is black and white with 125 micrometers resolution (Figure 2). The image file is divided into many tiles that havethe same extent as paper maps.

Figure 2. Map browsing system of GSI. Format of the map image is PNG, and the color is black and white.Unlike general map web services, the map is displayed in a full size.

In this browsing system, users can search themap by using index maps. They are also able tosearch the specified point on the map by placename, the name of community facilities, andcoordinates (search service). This system givesthe approximate coordinate value of click pointon the browsing map (coordinate valueindication service).

The system is accessible from any computersconnected to the Internet. All users can browsethe maps of the whole Japan freely, so that thissystem acquires a good reputation from manyusers. It had been accessed by many users sincethe publication, which amounts to 1,500,000 to1,800,000 images in a month (Figure 3). Itindicates that about 50,000 images aredistributed per day.

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Figure 3. The total number of accessed map images of eachmonth in the browsing system of GSI.

2. RESULT OF ACCESS LOG ANALYSIS

As a result of access log analysis on the Internet web page, some interesting trends of user preference were obtained.The most popular maps in this system are of big city area. On the other hand, according to the result of sales of papermaps, the maps of mountain areas and tourist spots top the list. This fact shows that the purpose of the users of the papermaps and this Internet browsing system varies, and this system creates and stimulates the demand of new map users.

3. PROBLEMS OF THE OLD SYSTEM AND INTRODUCTION OF NEW SYSTEM

However, this system has some problems. Firstly, it is difficult to change the scale of the browsing image freely becauseof the resolution of the image itself. To display the next map image in a seamless manner is another problem, becausethe map image files are divided into tiles of a fixed size.

To help solve these problems, a new system called as �Denshi Kokudo Web System (Web System of Digital Japan)�was designed and finally completed in this spring. The following is an introduction of the new system.

The map data stored in this new system is vector data that covers the whole Japan. The basic scale of its source data is 1to 25,000, but the users can change the scale of browsing image freely without distorting the image because of thenature of the vector data (Figures 4 and 5). Compared with the former system with black and white image, the newsystem provides the users with color map images. It indicates that all users can browse the topographical map in theircomputers, that is, the map image completely same as the published paper map. In addition, this new system renderseamless image so that user can scroll the map image of whole Japan.

This new system provides both search and coordinate value indication services as the former system did. Users canobtain the attribute information of community facilities such as name and address. If users change the image scale, thisnew system provides the appropriate map data in accordance with its scale.

Figure 4. New map browsing system. The source map data stored in this system is vector data witha scale of 1 to 25,000.

Figure 5. Zoom-up image of the new system. Users can change the scale of browsing image freelywithout distorting the image.

As the vector map data of this system is stored in an Internet server of GSI, users can browse the map image byaccessing our web site through the Internet. GSI manages a whole map data as one seamless vector formed database.Database is updated day by day. Though paper maps are produced using the database periodically, the map from theweb is always the latest one.

4. FUTURE PLAN OF THE NEW SYSTEM

Some tools for constructing web sitesincluding our new map browsingsystem is being designed by GSIbecause there is a demand from a lot ofcentral and local governments toprovide the citizens with publicinformation that should be overlaid onthe base map data. GSI will providethem with the base map data and thesetools without charge. Our tools will behighly effective for these organizationsto easily construct their own web sitesto provide such information. To thisend, GSI is customizing our service inaccordance with ISO and otherstandards. When this effort iscompleted, users will be able toconstruct a web sites with the newsystem in which their standardizeddata is overlaid on the map datadistributed from GSI. We are alsotrying to develop Open GISConsortium (OGC) Web Map Server(WMS). This server is also an effectivetool for users to browse and usedistributed geographical images thatare shared using the OGC WMSspecification. We will continue toprovide users with the good service in distr

Figure 6. Sample image of overlaying the other data on base map of GSI.In this image, the map data of existing vegetation data is overlaid on thebase map distributed from GSI. Users will be able to construct a web siteand provide citizens with a lot of information easily by using our tools.

ibuting the data as a basis of the spatial data infrastructure of Japan.