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Integrating GIS and modelbase
V. K. Panchal, Lokesh K. Sinha, Vinay kanwar and S. D. Mehta
Abstract
The geographical applications deals with objects whose not only position in space matter but temporal changes also have to be studied for gaining insight into the futuristic trends. This is achieved through modelling and simulation of the geoprocess. Spatial data management and analysis is handled by Geographic Information system technology efficiently. In spite of this the integration of GIS with modelling system remains a very active research area. In this paper, a loosely coupled system is proposed in this direction. GIS is the best example of information technology, which captures, manipulates, process and display multisource and voluminous geo-referenced data. With in the last 25 years this technology has encompassed the science and technology of remote sensing, cartography, surveying, geodesy, photogrammetry and of course the 'mother' science to GIS, geography. Geometric and thematic data about terrain objects stored in a GIS can be kept up to data by using remotely sensed data. Geometric and thematic information can be extracted from RS data by segmentation and classification techniques respectively. As the terrain objects change in time, their representation in GIS should be updated. But, in the situation when simulation of the geo-referenced activities are required for decision making then it is expected the GIS be linked to a modelbase management system. The models for river flood plain landscape combines a purely spatial process, the stochastic pyramid with analytical description on each landform of fluvial landscape or for the rainfall model, which may have submodels like the throughfall, the surface flow, overland flow, stream flow, sub-watershed and sub-surface model Not only in environmental problems, in scientific and engineering, military domain, assessment also involves forecasting and analysing WHAT_IF scenario, which is an inherently difficult problem in any domain. (Agarwala, 1992; Colombo,1992). The management of natural resources requires the integration of very large volumes of information from numerous sources. The information technology, and in particular, the integration of database management system, GIS, remote sensing & image processing, simulation & multicriteria optimisation models, expert systems and computer graphics provide effective tools for decision making. Most environmental and resource management problems like movement potential, natural & manmade hazard zonation, flooding potential, environmental studies, disaster management etc., have an obvious spatial component. Within the domain of environmental modeling this is addressed by spatially distributed models. The integration of complex & powerful software tools in problem oriented systems provide direct & easy access to gigantic bytes of data. it supports their interactive analysis and helps to display & interpret results in a common graphic user interface. The multifaceted nature of many terrain problems needs access to a range of models, data and other information. Modeling allows prediction of an expected future state. Modeling and simulation provide a rapid means of investigating the expected response of a system to possible future changes by undertaking the necessary computation which are commonly complex and data intensive. The necessity to integrate simulation models of these kind of spatial process with GIS technology is well recognised (burrough et. Al. 1988, Densham 1993). These integrated system offer a virtual environment where user can assess the scenario and evaluate various strategies. The available software for modeling and simulation are very advanced & some of the desired features such as representation of spatial data and provision of expert help, can not be easily delivered using such S/W (young). Just how simulation S/W is to be integrated with GIS software is a subject. Nyerges & goodchild identify S/W integration strategies that range from loosely coupled to full integrated system. Loosely coupled system: In a loosely coupled system GIS software is used to construct input files that a simulation program can read. The result of the simulation is then read back into the GIS S/W for display and analysis. The loosely coupled system may be developed using existing technologies, but this integration is lacks in providing.
GIS user, in this system has access to simulation models through software hooks and or built in macro languages. These integration strategies can provide access to a consistent user interface and data structure, but currently available S/W does not support model development or user interaction during a simulated event. (figure) 
Ideally, in a fully integrated system, simulation models, GIS capabilities are part of the same geo-processing S/W. Such a software system should support the construction, execution & manipulation of geographical simulation model in seamless, user friendly environment. In this paper we have shown how this problem can be tackled using existing technologies till the time a modelbased GIS is available commercially House
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