Previous

Part - V

GIS does its processing in several stages. In the initial stage it captures the data, and this can be done in several ways such as typing, scanning, or digitizing. Once the data has been captured it is stored, retrieved and managed. It is subsequently categorized as spatial data and attributes data as per the contents. Data manipulation and analysis is commonly thought of as the heart of the GIS. Overlaying, buffering, modeling, and analysis are some of the methods used in building a coverage or project. It also takes the users knowledge to recognize what is seen in the resulting map and data. Finally as per data output there is a map or graphic, which the user has generated after analyzing the data. Tabular data and reports can be generated as well to help explain the details seen in the map or graphic.

Geographic information systems work with two fundamentally different types of geographic models - the "vector" model and the "raster" model. In the vector model, information about points, lines, and polygons is encoded and stored as a collection of x, y coordinates. The location of a point feature, can be described by a single x, y coordinate. Linear features, such as roads and rivers, can be stored as a collection of point coordinates. Polygonal features, such as sales territories and river catchments, can be stored as a closed loop of coordinates.

The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type or accessibility costs for hospitals. The raster model has evolved to model such continuous features. A raster image comprises a collection of grid cells rather like a scanned map or picture. Both the vector and raster models for storing geographic data have unique advantages and disadvantages. Modern GIS are able to handle both models.

Applications of GIS are diverse. Some of which are: -

Next

* Contributed by -
Saurabh Singh,
MBA Global,
IMT Nagpur.