We are presently positioned at the beginning of the twenty first century with the fast growing trends in computer technology information systems and virtual world to obtain data about the physical and cultural worlds, and to use these data to do research or to solve practical problems. The current digital and analog electronic devices facilitate the inventory of resources and the rapid execution of arithmetic or logical operations. These Information Systems are undergoing much improvement and they are able to create, manipulate, store and use spatial data much faster and at a rapid rate as compared to conventional methods.

An Information System, a collection of data and tools for working with those data, contains data in analog form or digital form about the phenomena in the real world. Our perception of the world through selection, generalization and synthesis give us information and the representation of this information that is, the data constitute a model of those phenomena. So the collection of

Satellite Remote Sensing and GIS Applications in Agricultural Meteorology pp. 103120

data, the database is a physical repository of varied views of the real world representing our knowledge at one point in time. Information is derived from the individual data elements in a database, the information directly apparent i.e. information is produced from data by our thought processes, intuition or what ever based on our knowledge. Therefore in a database context the terms data, information and knowledge are differentiated. It can be summarized that the data are very important and add value as we progress from data to information, to knowledge. The data, which has many origins and forms, may be any of the following:

• Real, for example the terrain conditions etc.

• Captured, i.e. recorded digital data from remote sensing satellites or aerial photographs of any area.

• Interpreted, i.e. land use from remote sensing data.

• Encoded, i.e. recordings of rain-gauge data, depth of well data etc.

• Structured or organized such as tables about conditions of particular watershed.

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