Location Related Information Retrieval in Digital City Kyoto

Kaoru Hiramatsu <hiramatu@cslab.kecl.ntt.co.jp>
NTT Communication Science Laboratories
Japan

Yuji Nagato <nagato@digitalcity.gr.jp>
NTT Comware Corporation
Japan

Jun-ichi Akahani <akahani@cslab.kecl.ntt.co.jp>
NTT Communication Science Laboratories
Japan

Kiyoshi Kogure <kogure@cslab.kecl.ntt.co.jp>
NTT Communication Science Laboratories
Japan

Abstract

Information services focused on a specified area are becoming popular not only on the Internet but also on cellular phone networks. One of the key contents of these services is online digital maps that contain links to Web pages about the objects located within each map area. Although many services using online digital maps have been launched, basic problems still remain including readability of the map contents and usability of the system through small-sized terminals such as personal data assistants (PDAs) and cellular phones. To resolve these problems, we have implemented Mobile InfoMap (MIM), which is an information retrieval system based on InfoMap and GeoLink. MIM is tailored to be accessed from small-sized terminals via cellular-phone networks. Using a small-sized terminal with a positioning system, MIM enables users to get geographical maps on which the users' current position is centered automatically and that include useful information related to the users' current position. In this paper, we describe the system architecture and the results of a preliminary experiment.

Contents

• Introduction
• Mobile InfoMap
• Current Implementation
• Client
• Server
• Experiments
• Conclusion

Introduction

Information services focused on a specified area are becoming popular both on the Internet and on cellular phone networks, e.g., the i-mode and WAP-based service. One of the key contents of these services is an online digital map that includes useful links to Web pages about the objects located within the specified area. Some information portal sites have begun to provide such contents. Since 1999, we have supplied the digital map service InfoMap[2] on an experimental information portal site, Digital City Kyoto[3]. InfoMap is a digital map service that provides useful search functions enabling users to choose links to Web pages in various manners. InfoMap is based on the GeoLink[1] system which enables users to search for Web pages with constraints on logical and geographical relationships.

The superimposition of online data on digital maps is convenient because it enables users to get specified area information with geographical relationships at a glance. Such an approach seems natural and it is expected to handle information not only to relatively static Web pages but also to much more dynamic data such as the human voice in online communication tools and physical sensory data in specified areas. However, the size of a digital map for placing information is limited and this causes overlaps of icons (or other types of representation) of information within the specified area. These overlaps decrease readability and usability and make the service unsustainable over the long term under on explosive increase of information. The overlap gets more serious if users receive the map service through small-sized terminals such as personal data assistants (PDAs) and cellular phones via wireless networks such as the NTT DoCoMo i-mode network[4]. In Japan, some digital map services for cellular phone networks are available, but these problems have not been cured.

To resolve these problems, we extended InfoMap[2], which requires a large size Web browser for displaying search results. The extended system is called Mobile InfoMap (MIM) which enables users to receive a geographical map with retrieved information from the small-sized terminals. To improve usability of the geographical map with retrieved information on the small-sized terminals, MIM also provides two search functions, such as category search and keyword search. The search functions also improve readability of the result. Moreover, by using a PDA that is equipped with a positioning system, MIM enables users to automatically retrieve location-related information surrounding the user's current position.

In the following sections, we describe more details of MIM and a preliminary experiment result using a prototype system of MIM that includes practical data in Kyoto city and utilizes a PDA equipped with a global positioning system (GPS).

Mobile InfoMap

Figure 1 shows the access methods and typical screen images of MIM. MIM has two access methods. One is from a PDA with GPS and the other is from a desktop PC.

If MIM is invoked from a PDA with GPS, the search will proceed as follows.

1. The PDA measures the user's position data, such as latitude and longitude, and transmits it to the MIM server.
2. The MIM server returns a geographical map that includes useful links to Web pages about objects within the surrounding area, such as Web pages of restaurant menus and bus timetables.
3. After getting the main map, the user can perform actions from the following options:
• browse Web pages listed within the main map page,
• search additional information using a detailed search page,
• browse a wide area map, and
• use communication tools such as a bulletin board system (BBS) and mail that are enabled to include the user's current position.

If MIM is invoked from a desktop PC, the user can use the same functions as from a PDA with GPS. In this case, the user should designate a favorite geographical position by filling out a form including latitude and longitude.

Fig.1 Mobile InfoMap overview

Current Implementation

The MIM system consists of client PDAs, a location information center, and a MIM server on a Web server (Fig.2). The connection between them is established through the wireless dial-up networking of the PDAs. The connection speed of wireless dial-up is 9600 bps. The system components behave as follows.

1. The client measures his/her current position using GPS and the location information center.
2. The client sends a search request to the MIM server via the cellular-phone network and the Internet.
3. After receiving the request, the MIM server searches Web pages related to the position using GeoLink.
4. The retrieved Web pages are superimposed onto the geographical map as icons and returned to the client as the search result.

Fig.2 Mobile InfoMap architecture

Client

A prototype of an MIM client has been implemented using Naviewn (Fig.3). Naviewn is a WindowsCE-based PDA produced by NTT DoCoMo[4]. It is 82 mm x 153 mm x 18 mm in size, 220 g in weight, and equipped with a 240 x 320 dots LCD touch screen and Web browser (HTML 3.2 base). Naviewn is also equipped with a modem to provide wireless communication via the cellular phone and an Enhanced GPS[5] to obtain self position data.

The client sends a search request to the MIM server via a cellular phone network that is based on a dial up connection. The request includes the client's current position measured by GPS with the location information center. A margin of the position data error is less than approximately 50 meters and the measurement takes about 30 seconds. After a few seconds, the server sends back a surrounding area map image that includes Web page links as a search result. The client then displays it on the Web browser.

Fig.3 Naviewn

Server

The MIM server is based on a back-end system of the InfoMap[2] and tuned to accessing from small-sized screen terminals. The MIM server has databases of geographical maps and point of interests (POI), and is accessible via common gateway interface (CGI) programs on a Web server (Fig.4). Receiving a request from a user's client, the MIM server searches neighborhood information Web pages close to the user's position, composes a geographical map image on which the user's position is centered, and then superimposes icons on the map and returns it to the client. The icons represent geographical positions of information of the Web pages.

Fig.4 Server architecture

According to client specifications, the size of the map image is adjustable by the MIM server. In the case of Naviewn, the size of the map image is 100 x 100 dots (about 4 KB).

Experiments

We set up a prototype of the MIM service using practical information in Kyoto city. The databases of MIM include about 5000 Web pages and cover an area of approximately 200 square kilo meters of Kyoto city. In this section, we provide detailed explanation of a screen image and communication sequence between the MIM client and server as preliminary experiment results on MIM.

Figure 5 shows an example result from a user utilizing the Naviewn in the central area of Kyoto. The left side map of Fig.5 illustrates the rough position of the user in the city. As shown in this figure, the user's position was N35°00'11.0", E135°46'14.0". The right side image of Fig.5 is a browser image that was displayed on the Naviewn as the search result. The area of the image is 100 x 100 meters, and includes five round icons of Web page links. Table 1 provides the details of the superimposed information listed in the middle of the browser window.

Fig.5 Screen image of a search result

While in the above search, the client communicated with the server as shown in Fig.6. The communication can be divided into three parts, position measurement, system processing, and information retrieval. In the first part, the user selected the service on a Web browser of a PDA. Then, the PDA dialed up to a location information center, measured the user's position with the center, and downloaded the position data. This part took about 23 seconds. Next, the PDA started post-processing of the position data and task switching on the PDA. The time of this task switching of WindowsCE deeply depends on the processing power of the PDA. This second section took approximately 41 seconds. The third part was the connection for information retrieval. The PDA established a connection to an information service provider and sent a search request to the MIM server. The search request consisted of a uniform resource locator (URL) of a CGI program that included the user's position. Finally, after processing, a search result was returned to the client. The third part took about 36 seconds for a total search time of approximately 100 seconds. The search result consisted of an HTML file (about 1 KB) and a geographical map image that included five icons.

In this result, time for the position measurement only takes 12 seconds. The GPS satellite positions seems good enough to measure the PDA position, but the time for measurement depends on the GPS satellite positions, a PDA location, and weather conditions.

Fig.6 Communication sequence

Conclusion

In this paper, we described MIM, which is an information retrieval system based on InfoMap and GeoLink. MIM is accessible from a PDA which is equipped with a positioning system via a cellular-phone network, enabling users to get geographical maps automatically centered on the users' current position. Although the prototype of the MIM service was set up using practical data in Kyoto city, the MIM service is able to be applied to not only outdoor services but also indoor use if appropriate databases and a positioning system are available.

Throughout the implementing and testing of MIM, it has become clear that MIM still has some problems when put into practical use. One of the larger problems is system usability due to hardware design and system performance. As described in the previous section, the search requires two connections and take approximately 100 seconds. This waiting time is caused by the system performance of the PDA and is too long for mobile users to use on a street corner. Furthermore, we have made ad hoc prototype client so that the client consists of a PDA and a cellular phone which are connected by thin cable. This hardware design spoils portability for the client. However, hardware devices are innovated year by year, so these problems will be resolved by fully integrated PDAs in the near future. For network services like MIM to become popular, it is obvious that a standard hardware of PDAs and cellular phones which are suitable for MIM and a typical service architecture for providing geographical maps with useful information will be required.

Acknowledgments

This paper owes much to the thoughtful and helpful comments of Prof. Toru Ishida of Kyoto University and members of the Digital City Kyoto Experimental Forum. We also wish to thank contents holders for permission to use Web pages concerned with Kyoto.

References

1. Hiramatsu, K., and Ishida, T., An Augmented Web Space for Digital Cities, The 2001 Symposium on Applications and the Internet (SAINT2001), pp.105-112 (2001)
2. Hiramatsu, K., Kobayashi, K., Benjamin, B., Ishida, T., and Akahani, J., Map-based User Interface for Digital City Kyoto, INET2000 The Internet Global Summit, CD-ROM (2000)
3. Digital City Kyoto, http://www.digitalcity.gr.jp/
4. NTT DoCoMo, http://www.nttdocomo.co.jp/
5. SnapTrack, Inc., http://www.snaptrack.com/