Multi-Resolution Geospatial Data in Mobile System
Résumé
Geographic Information Systems (GIS) have to support multi-resolution data in order to represent the real world at different scales. This need is also observed in the emerging field of mobile GIS. In this paper, we propose solutions for the management and visualization of multi-resolution vector data in a mobile spatial information visualization system. We first review the basic priciples of mobile GIS and management of multi-resolution data, and we mention various works that have already been conducted in the areas pertaining to our own research and development works. We then present the client-server architecture and the management approach adopted in the system. Our aim is to reduce the amount of data exchanged between the client and the server. Our solution is based on the use of increments in a multiscale database. In our database architecture, datasets for different predefined scales are precomputed and stored on the server side. Increments correspond to the difference between two datasets with different resolutions and are transmitted in order to increase or decrease the level of detail of information on the client upon request. They allow reusing data which are already present on the client side. They imply to take into consideration the different generalization operators, their mapping configurations and their modifications on objects representations. Finally, we describe our approach for presenting multi-resolution data: an adapted one relying on “intelligent zoom”. It consists in measuring the density of data at different resolutions and for different scales, and finding a balanced solution taking account of resolution and scale which respects the well-known “principle of constant density of data”. concerning date and localisation and might be enriched with meta-information. Data are used in various applications whose aim is to manage masses of spatio-temporal data either at real time or at time differed. The objective of this article is to present the problems, and to provide some elements of solution to the identified scientific bolts. After the presentation of relevant applications, a list of scientific problems is exposed and some solutions are then detailed. These reflexions and works result from members of teams of research collaborating within the pole "sensors" and within the working group "location-based services" of the French research group sponsored by CNRS, named GDR MAGIS.