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2: GIS Database:
After image interpretation a relational database is created. A GIS stores a representation of the world in the form of layers connected by a common geographical frame of reference. Each of the features on a layer as shown in fig2. has a unique identifier, which distinguishes it from the rest of the features on the layer, and allow us to relate it to relevant information stored in external databases, etc. This allows us to capture only those elements of the world that are of interest to us, like catchment area, under forestation, covered under snow etc.



3: Knowledge based expert system:
Expert system contains knowledge and experience gleaned from human experts of the domain. The program asks users series of questions about their problem and gives them advice based on its store of knowledge and responses received from user against the queries made. The system developed here is rule based system and has following four functional modules like other rule based systems:

(i) Knowledge base (ii) Inference Engine (ii) Explanation facilities (iv) user Interface. The functional flow and organization of these modules is shown in fig.3. The development of ES requires creation of this entire module. The overall development process of rule-based expert system is shown in the Fig.4 In the present work the knowledge-based system has been developed in Turbo-Prolog environment. This AI language provides almost all facilities for the development of rule-based expert system. Turbo-Prolog works as an inference engine in backward chaining mechanism and supports logic based knowledge representation. Thus the development of ES in the turbo-Prolog requires only creation of knowledge base and suitable users interface.

The explanation of the reasoning of the system can be seen by tracing the sequence of rules framed in the system while executing the program for which turbo-Prolog provides in-built trace facilities. It can be activated at any particular point of the trace window. However, for more complex system the more user-friendly explanatory system can be designed. We have adopted the top down design approach. As shown in Fig.5. To develop the system, which emphasizes the division of a main goal of image interpretation into simpler sub goals. These simpler goals create opportunity to gear up the questions related to knowledge base of the system to simpler level, which make the system useful even for the very beginner in the photo interpretation.



Expert System Development:



4: Knowledge base development:
The knowledge base of the system has been organized in the two parts, the static database and the dynamic database. The facts and rules related to the visual interpretation of the satellite imagery have been placed in the static database. The steps involved are, Knowledge Acquisition, Knowledge representation, User representation.

5: Sources of Spatial Data:
Accurate and current information is vital for maintaining and improving customer service. Through the computerized environment, a GIS can keep information accurate and current. There are number of other sources of Spatial Data,

• Census and Survey data
• Arial photographs
• Satellite Images and Global positioning systems
• LIDAR (Light detection and ranging)
• ALTM (Air born laser Terrain Mapping)

Census and Survey data are collections of related informations. Aerial photography is the first method of remote sensing, it is capturing of images from a position above the Earth's surface. Wide availability, relatively low cost, wide area views, time freezing ability, high spectral and spatial resolution, three dimensional perspective, of aerial photographs make immense value as a data source for GIS. Satellite images are collected by sensors on board a satellite and then relayed to earth as a series of electronic signals, which are processed by computer to produce an image. Most of the GPS receivers will store collected co-ordinates and associated attribute information in their internal memory so they can be downloaded directly into a GIS database.

Light detection and ranging (LIDAR) and Air borne Laser Terrain Mapping (ALTM ), are the latest sources in the transmission sector. Laser mapping produces equivalent data that are produced by GPS and land surveys at a faster rate. For GIS remotely sensed data offers many advantages. First images are always available in digital form, so that transfer to a computer is not a problem. However some processing like reduction of volume, adjust resolution, change pixel shape or alter the projection of data. There is opportunity to process images or use different wavebands for the collection of data to highlight particular feature.

Proposed Methodology:
In major hydel projects data collection is a very difficult job, due to the inhospitable environment in most of the construction sites. Hence taking into account such hazards or any unforeseen circumstances, GPS and remote sensing technologies will provide not only fast and accurate but also reliable geomorphologic and geological data, which can be very successfully analyzed by GIS in knowledge base environment to give complete picture about the stability and durability of the structure, which in turn helps to get alternative solution to take optimal decision. Following are the important steps for developments of hydropower project.

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