Mobile information community develops quickly, as mobile telecommunication technology matches to the third generation. XML-based GIS becomes a global standard and the foundation. Recent developed Geography Markup Language (GML) allows integration of GIS location-based services, telematics, and intelligent transportation systems. In this paper, we propose a tourism information system for supporting the location based service of GIS applications. The system implements thin-client/server technology for mobile Web mapping service. The system includes traditional GIS system for navigation service and location finder POI services. The system for location and POI determination with design concerns are presented. An experimental user interface of PDA within the system is illustrated for the system procedures.