DYNAMIC INFORMATION IN GIS SYSTEMS

Time can be characterized as the fourth dimension of the physical space-time continuum. Time is either a particular instant at which a structure or a process exists or occurs, or a period over which a structure endures or a process continues. From the human point of view, a concrete system can move in any direction on the spatial dimension, but only forward on the temporal dimension. GIS systems generally deal with static information. Static objects can be defined as objects that do not change in a short time period. In many situations, the information in GIS applications does change dynamically. Environmental problems, for example, have a significant dynamic component, which means that the conditions of the real system, at the time the decision is made, are the results of all the past history of the system and influence its subsequent behavior. Dynamicallity in a process may be possible to measure. The measure should include components such as Size of change, frequencies of change, and time interval. The dynamicallity of a system should, in addition, include the need of change in representation (for example, how often must the screen be updated) and how time-critical decisions are. Time can be represented by a series of snapshots, and the shorter time periods between the snapshots, the more it imitates a continuous course of events. The time lapse is represented by a minimum of two pictures, up to complete animation. Real time and presentation time are not necessarily the same, as it is desirable to shorten very long time lapses (for example geological changes), and lengthen (prolong) rapid time lapses (such as explosions). We define presentation time as a relation between observation interval (time interval between observations) and picture rate (the rate of changing pictures on the screen). In this paper some functions for handling dynamic information in GIS systems are presented.