A Multi-Dimensional View of GIS
Abstract
Geographic Information Systems has primarily revolved around two dimensions (2D) both for visual and spatial analysis, with the other dimentsion used sparingly for visualization or animation and time sequencing only. This paper will introduce the practical issue and will describe the development of a multi-dimensional visualization and spatial-analytical took for GIS.
Introduction
The use of three dimensional (3D) visualization techniques for both Remote Sensing and GIS integration has been widespread for quit some time now. This visualization method has been used primarily as an output medium to emphasize the multi-dimensional spatial relationships and temporal aspects of a process. In GIS, this usually takes the form of animation sequence corresponding to certain temporal processes such as growth, expansion and distribution. With remote sensing, this operation would entail draping(overlay) of graphic images corresponding to captured real world phenomena or image map derivatives over terrain models or surfaces. In general however, this visualization has been confined to the generation of fly-throughs, walk throughs in simple animation frame sequences, and limited model motion coupled with perspective viewing. The output is an end product by itself with no 'live' link either to the spatial-analytical process, the database, and the operator. Although some CAD systems have some capability in linking with external databases, most of them can only do so while in a CAD program environment.
GIS derives its power and popularity from its ability to do spatial object queries and attribution, to have links to structured databases, to do geographic analysis, and to generate colorful maps. This can be attributed to the functional and standardized design inherent in the data structure of conventional GIS's where a point can mean a stationary or non-stationary object or symbol such as houses, a line can represent linear features such as roads or rivers, and a region may represent administrative, soil and geologic boundaries. However, these GIS still do adhere to traditional cartographic methods of 2D and pseudo 3D representation, simplification, abstraction and generalization of reality. For most, this is sufficient enough.
The Pros and cons
Today, it is hard not to consider the advantages of three dimensional or even multi-dimensional systems of visualization and operation which afford us a higher level of representation and even more powerful viewing of spatial relationships among objects.
The disadvantages of having higher dimensions are its inherent compute-intensive(floating point) operations for rendering and visualization thereby requiring more expensive, faster and powerful hardware, software and operating systems. There is also the need of modifying the GIS model structure and topological representation to include this higher dimensionality in the data.
Recent advances in hardware integration, graphics software standardization, and the steady decline in costs for desktop computing technology have offered a more attractive medium for GIS visualization and Remotely Sensed Imaging. Video graphics capabilities including the most demanding rendering and imaging processes are being built-in to dedicated hardware thus freeing the (CPU) processor to do other more important tasks. RAM is increasing in capacity, getting smaller in size, and becoming cheaper. Storage devices are also faster, and larger capacities and lower costs per megabyte of storage space. These are encouraging development.
Current State of Technology
The "gaming" world has been keen in taking full advantage of these developments as can be seen in the fierce competition to provide the most "immersive" gaming experiences at the expense of achieving graphics realism and interactivity. In addition, most of these gaming technologies still use the most convenient and cheapest from of interaction and control via an on-screen output device and coupled with simple input devices such as mice and joysticks, to which most vides graphics hardware manufactures have responded with much enthusiasm.
