Chapter 4.2 – Perspective: Geographical Information Systems

Publisher Summary The geographical information system (GIS) is the digital information system whose records are somehow geographically referenced. This chapter discusses some of the distinctions between the brain and geographical atlases, and describes the approaches to tackle various challenges resulting from these differences. Georeferenced data consist of data elements whose locations are spatially referenced to earth. The data types managed by GIS are conventional record-based data consisting of alphanumeric attributes, images, and spatial data. For spatial data, spatial relationships are categorized into three types: topological relationships, direction relationships, and metric relationships. Raster data are simply a bitmap that, if displayed, illustrate the image of an area. They are tightly related to field view or space view. The database is managed by Informix Universal server v9.2, which is an Object-Relational-Database Management System (OR-DBMS). The levels are stored as binary large objects (BLOBs) within the relations. The Java applet that serves as the graphical user interface (GUI) retrieves the entire image corresponding to an atlas level in one shot and immediately displays it to the user. This chapter demonstrates how these features are supported through a spatial database management system, and mentions several commercial products and the ways they support these features.