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Data inputs and its accuracy levels
Imagery Analysis
The satellite images were geo-referenced. This mapping procedure removes geometric distortions of the image and changes the c o-ordinate system of the image to spatial database coordinate system. Maximum possible Ground Control Points [GCPs] were selected, uniformly over the total area for better interpolation.

• Geo-referencing of satellite image, image processing and generation of classified information from (False Color Composite) FCC. (LISS-III)
• Digital data integration, warping, edge matching updating and sketching of data base system modification and access capability.
• Image Classification using various techniques including Visual Interpretation

Digital enhancement techniques were used as they help to improve the feature sharpness and contrast for simple interpretation along with visual interpretation techniques. The training sites were selected based on limited field checks and visual interpretation of imagery for areas that represent known features. Based on these identified sites classification techniques were applied to generate the required thematic maps. Certain mathematical models and filters were used as well to enhance certain features like water resources to help in easy interpretation and mapping the same.

Various thematic layers generated using remote sensing data like, land use/cover etc, was integrated with slope, drainage density and other collateral data in a Geographic Information system (GIS) framework and analysed.

Software components
Arc Hydro has been designed to represent data from hydrography and hydrology, thereby creating a basis for obtaining a deeper understanding of surface water systems. The description, study and charting of bodies of water, such as rivers, lakes and seas, is called hydrography. The natural partner of the hydrographic description of water bodies is the study of water movement through them. This is the domain of hydrology, the science dealing with the properties, distribution and circulation of water on the surface of the land, in the soil and underlying rocks, and in the atmosphere.

The Arc Hydro tools are a set of utilities developed on top of the Arc Hydro data model. They operate in the ArcGIS environment. Some of the functions require the Spatial and 3D Analyst extensions. Two major functions, which have been used in the creation of database for watershed analysis purpose, are ‘Terrain Pre-processing’ and ‘Watershed Processing’.

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