Kokono Search: A Location Based Search Engine

Kokono Search: A Location Based Search Engine

3-9-11, Midori-cho, Musashino-shi, 180-8585, Tokyo, Japan
3-9-11, Midori-cho, Musashino-shi, 180-8585, Tokyo, Japan
Nobuyuki MIURA
3-5, Hikarino-oka, Yokosuka-shi,239-8536, Kanagawa, Japan


We have developed a location-based search system for web documents on the Internet. This system can find web documents based on the distance between locations that are described in web documents and a location specified by a user. It consists of three modules. (1) A robot that gathers documents from the Internet, (2) a parser that extracts address strings from web documents and associates latitude-longitude information to the original document and (3) a retrieval module. This system can retrieve location-related web documents overlooked by conventional keyword-based search engines. Keyword-based search engine overlooked more than 25% of location-related web documents compared with our search engine. We have served this location-based search as an experimental service named kokono search that is one of Mobile Info. Search [1],[2] services on the Internet.


Location-based search, Information extraction, Search engine, Selective gathering, Information integration, Information retrieval, Web robot


Recently, it has become possible to browse real world information, such as telephone directories, maps, town-guides, tourist-guides and shop-guides through an open-network like the Internet. Each of these sources is related to geographical locations and can be classified by using user location data such as the current location, user's destination and the user's residential address.

There are already many search engines [3] on the Internet, and most of them are keyword-based. Basically, when we attempt to search real world information about a specific geographical location, information about nearer locations from the specified location is more important. Unfortunately ,there are many cases that neighboring geographical regions have different addresses (i.e. keyword). Therefore, keyword-based search may overlook useful information about locations that are adjacent to the specified location.

To solve these problems, we developed location-based search engine. We define the location-based search as a search method based on the distance between a user-specified location and locations that are described in web documents. Locations are represented as address strings, telephone numbers, rail station name etc. in web documents. Our system converts them to latitude-longitude pairs or polygons consist of latitude-longitude pairs. Also a user-specified location is represented as a latitude-longitude pair. By using these latitude-longitude pairs to retrieve documents, our system finds documents about nearer locations from a specified location.


This system consists of following three components.
  1. The robot gathers web documents from the Internet. After a document was gathered, the robot prioritizes URLs that were included in it. For example, the priority is high when a link label contains location information (ex. Address etc.) Then the robot gathers web documents that have high priority.
  2. A parser extracts location information from web documents and converts them into latitude-longitude pairs or polygons.
  3. The retrieval module converts location information specified by user to a latitude-longitude pair and it creates a search circle whose center is this pair.
By judging overlaps of this circle and the latitude-longitude pairs or polygons, it picks up documents that are written about locations within this circle. The engine returns URLs of the documents as results of the search. The module calculates the radius of the circle automatically that the overlaps contain appropriate number of results.
Fig 1 An example of geographical regions searched by "location-based search" and "keyword-based search"
Figure 1 shows an example of geographical region searched by both search methods. The cross sign is the user-specified location. Keyword-based search engine retrieves documents about region enclosed by thick line. Although there are latitude-longitude pairs and polygons that are close to the cross sign and belong city 'B' or 'C', the documents about these locations cannot be found by the keyword-based search. On the contrary, location-based searchretrieves the documents about the region represented as meshed polygons. This region contains all latitude-longitude pairs and polygons that are close enough to the cross sign. As the result, we can also find location-related web documents overlooked by keyword-based search engine, when we use our location-based search engine.


  1. Katsumi Takahashi. A Mobile Portal Service to Provide Location Dependent Information. In Proc. from the Joint W3C-WAP Forum workshop on "Position dependent information services" (Feb, 2000)
  2. Mobile Info. Search. http://www.kokono.net/english/
  3. Google , http://www.google.com/