Keywords: LBS, hyperlayering, svg, goSVG, poi, map
He has participated in the goSVG Working Group since 2003.
He has participated in the goSVG Working Group since 2003.
My research theme is web applications and spatial information systems. Our controlling company KDDI is a communication career which offers an international phone call, a long-distance call, a cellular phone, etc. I developed the mapping system for the underwater robot for submarine commnunication cable construction. From 1995, I applied web technology to this system. From such circumstances, the development of spatial information service platform based on web technology is one of the main research themes of mine. I developed SVG (Scalable Vector Graphics) browsers for embedded computers. One of the concrete target is a cellular phone. I have standardization activities about the spatial information systems in Japan. Moreover, KDDI R&D Laboratories Inc. is the member of W3C, and we are cooperating in the standardization of SVG.
In Location Based Service (LBS), it is essential that a system provides up-to-date data to users. Hyperlayering is an architecture, which makes it possible to divide and maintain the base map and POI data, and it is incorporated in the SVG and goSVG specifications. In this paper, we present an implementation of hyperlayering, which aims to validate hyperlayering by developing a browser that conforms to the goSVG specification, and a server as an application of hyperlayering that dynamically converts POI information on TAB Separated Value into goSVG.
1. goSVG Specification for LBS
2. Hyperlayering Architecture
2.1 Outline of Hyperlayering Architecture
2.2 Implementation of Hyperlayering
2.2.1 Map Request Protocol
2.2.2 Container File
2.2.3 Coordinate Reference System
3. POI Server
3.1 Attributes of POI
3.2 Automatic Creation of Container File
In these days, car navigation systems and mobile phones with high-resolution screens and GPS are widely used in Japan. LBS (Location Based Service) has, therefore, become familiar and the importance of LBS has been emphasized. Under such circumstances, KDDI has been working to specify the enhancement of SVG required for LBS and standardize it in the goSVG WG [g conents exchange promotion association] , which is supported by the Ministry of Economy, Trade and Industry (METI) of Japan. This specification is called goSVG and some specifications in it are the enhancement of SVG Mobile. This section lists up some features of goSVG enhanced for LBS as shown below.
Hyperlayering architecture is based on the following background fact involvingGeographic Information System (GIS). The interoperability of GIS has been a critical issue since the data is relevant only at a certain location and can not be shared between various GIS.
For this reason, users have to access to a certain service provider to obtain information. This means that users are forced to download POI with the map, even if they only desire up-to-date POI data. This is not desirable for users of mobile terminals in terms of the amount of the data transmitted, and processing time.
We came up with an idea to realize the interoperability of LBS with WWW on the Internet similar to GIS. This architecture is called "Hyperlayering." The mechanism of hyperlayering is shown in Figure 1 . It is assumed that contents representing geographic information are delivered on WWW. Then, search engines will search for the map and POI overlaid on the map required by users. Search engines then provide the information used for overlaying multiple layers as search results. Browsers access these multiple information, overlay them and display them as a content.
This protocol specifies the request format from clients to servers, in order to obtain the map required by users. A GET request on HTTP is used. Figure 2 shows an example of the request made. In this request the descriptions of position, coordinate system, range, aspect ratio and display size follow after '?' and are separated by '&'.
HTTP GET japan.svg?position=+35.6023+135.254/&datum=wgs83&r=200&aspect=0.75&w=640
As shown in Figure 1 , search engines provide information used for overlaying multiple layers. This file with multiple layers is called the "container file." Figure 3 shows an example of the container file. In this figure, 3 multiple layers are defined as hyper links in image tags. Browsers access to the URLs described in "xlink:href=" and overlay and display them as contents.
<?xml version="1.0" encoding="utf-8" ?> <svg viewBox="0 0 640.00 480.00" xmlns="http://www.w3.org/2000/svg" xmlns:gxml="http://www.dpc.or.jp/gxml"> <metadata> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns" xmlns:crs="http://www.w3.org/crs" xmlns:svg="http://www.w3.org/svg"> <rdf:Description> <crs:CoordinateReferenceSystem rdf:resource="http://www.svg.ne.jp/wgs84" svg:transform="matrix(21606.73, 0, 0, -26666.67, -3014212, 957024)"/> </rdf:Description> </rdf:RDF> </metadata> <defs> <polygon id="poi00" points="0 -6 2 -2 6 -2 3 1 4 6 0 4 -4 6 -3 1 -6 -2 -2 -2" fill="#ef017e" stroke="none"/> <circle id="poi1" r="5" fill="#00ff00"/> <circle id="poi01" r="5" fill="#0000ff"/> </defs> <image width="640.00" height="480.00" xlink:href="http://jamaps3.kddlabs.co.jp/jamaps/japan/japan.svg?position=%2B35.879399%2B139.518220%2F&r=1000&datum=wgs84&aspect=0.75&w=640"/> <image width="640.00" height="480.00" xlink:href="http://www.jamaps.org/cgi-bin/POI/poi_plot.cgi?position=%2B35.879399%2B139.518220%2F&r=1000&datum=wgs84&aspect=0.75&w=640"/> </svg>
Figure 3: Example of Container File
Multiple layers should be manipulated in the same coordinate system to make sure that they are accurately overlaid. This is realized by transforming each layer into SVG coordinates from geographical coordinates by using transformation parameters described in the crs:CoordinateReferenceSystem tag. These transformation parameters are defined in the svg:transform attribute in the crs:CoordinateReferenceSystem tag. Figure 4 shows the relationship between geographical and SVG coordinates.
As shown in Figure 4 , the transformation can be performed easily from geographical coordinates to SVG coordinates, and vice versa. Not much computational power is needed to compute this matrix.
POI overlaid on the map is very important to make LBS attractive. A straightforward creation of the POI server is desired to realize LBS. For this reason, we developed the POI server based on goSVG. Features of this server are as follows.
More details are described below.
The attributes of POI are defined in the goSVG specification.
Here, a symbol should be described in a file and the file name should be the same as the value of ID attribute. The value of ID is used to relate POI and the symbol.
The POI server dynamically creates a container file by the following request. Each content to be overlaid is described in a sequence delimited by '&'
Making the above request leads the server to provide the container file shown in Figure 3 . The crs:CoordinateReferenceSystem tag is automatically inserted and image tags are described as multiple layers.
This means that users can select the map according to each application by setting appropriate parameters.
In this paper, an implementation of the hyperlayering architecture is described. We have developed a browser according to this architecture, called the goSVG browser. We have also developed the POI server, which has features to dynamically create a POI database and a container file by requests made by users. Using this system, application of LBS will be provided easily.
This system will be available for a field trial conducted by METI to validate LBS based on the hyperlayering architecture.
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