The multimedia data distribution system using map handling modules

Introduction
Recently, as the requirements have been emerging to use GIS systems on portable terminals, GIS application developers want mobile GIS components which enable them to integrate the systems easily. In addition, it is necessary for GIS to have a mechanism to manage the temporal and spatial information when users update data. with a distributed portable terminal. For example, the data management in time order is a critical need in areas such as disaster prevention and real estate systems. Against these backgrounds, we developed the map-handling module called GeoScope. It makes map processing simple and controls registered graphic data using temporal and spatial information. We paid attention to the real estate business because users with mobile terminals often transfer multimedia data: pictures, movies, and room arrangements. Accordingly, we developed a prototype GeoScope system that controls real estate data. This paper describes in detail the characteristics of GeoScope and the evaluation of the prototype system.

Problem Statement
There are several problems in controlling spatial and temporal data in the mobile GIS environment.

Problem of component based application development tools
It is necessary to isolate the developer from the need to code map-specific operations when they develop GIS applications. Such operations include [Basic function]
- Expansion, Reduction, Scroll
- Layer control
- Drawing polygon etc. [Navigation function]
- Route-guidance
- Display of deformed map [Fujii(Jan.1997)][Fujii(Apl.1997)] etc.
  GIS components with the navigation function did not exist.
Problem of data registration
When the users register data from each portable terminal, it is necessary to arrange those data in time order and to have a mechanism that permits uniform management on the server side. It is difllcult to manage data in time order when a mobile client is not always connected with the server.
Problem of data communication cost
It reduced data communication cost that frequency of client - server connection is decreased. But it is difficult to decrease its connection in the existing mechanism of data management. This problem is explained in detail in the paragraph 3.2.

This paper introduces GeoScope to solve these problems.

Map Handling Module: Geoscope
We developed GeoScope around two basic policies.

To conceal map-specific functions, we structured each function as a component. This allows the developer to access detailed map processing technology with needing detailed knowledge. The components were created using ActiveX controls (Microsoft component tools). Then, the components have navigation function. So our system solve problem (1) of section 2.
To allow the client to issue IDs to any polygon, the user can resister data on the map in the portable terminal without connecting to the server.

For instance, when the user uses the disaster prevention system, even if the client cannot communicate with the server, it is necessary to be able to register data on the portable terminal. Therefore, we created a mechanism by which unique IDs can be assigned to each polygon on each terminal. Its ID includes temporal information. So system solve both problem (2) and problem (3) of section 2.