Geographical Information System (GIS) is a technology that provides the means to collect and use geographic data to assist in the development of Agriculture. A digital map is generally of much greater value than the same map printed on a paper as the digital version can be combined with other sources of data for analyzing information with a graphical presentation. The GIS software makes it possible to synthesize large amounts of different data, combining different layers of information to manage and retrieve the data in a more useful manner. GIS provides a powerful means for agricultural scientists to better service to the farmers and farming community in answering their query and helping in a better decision making to implement planning activities for the development of agriculture.
overview of Geographic Information System (GIS)
A Geographical Information System (GIS) is a system for capturing, storing, analyzing and managing data and associated attributes, which are spatially referenced to the Earth. The geographical information system is also called as a geographic information system or geospatial information system. It is an information system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically referenced information. In a more generic sense, GIS is a software tool that allows users to create interactive queries, analyze the spatial information, edit data, maps, and present the results of all these operations. GIS technology is becoming essential tool to combine various maps and remote sensing information to generate various models, which are used in real time environment. Geographical information system is the science utilizing the geographic concepts, applications and systems.
GIS technology is a crucial part of spatial data infrastructure, which the White House defines as “the technology, policies, standards, human resources, and related activities necessary to acquire, process, distribute, use, maintain, and preserve spatial data.” GIS can use any information that includes location. The location can be expressed in many different ways, such as latitude and longitude, address, or ZIP code.
Figure 1: Geographical Information System
Definition of Geographical Information System (GIS)
With few places, it’s fairly easy to keep track of the connections between place and information. But with a lot of information, and a lot of places, we can no longer keep track of it all. And this task become more complicated if we added changes over time, say, changes in locations, names, or what you find there. There is a limit to how large a scale to which one can increase this. At some point, the amount of information is overwhelming. It’s not very “scalable.” To manage this overload of information, the scientists invented a very special tool. That is THE MAP. One perfect solution is to automate the link between the map and the information. In order to process and track much larger quantities of geographic information, and this what Geographical Information System (GIS) software do. We can define GIS by following definition:
“Geographic Information Systems is a computer-based tool that analyzes, stores, manipulates and visualizes geographic information, usually in a map”.
Concept of Geographical Information System (GIS)
GIS stands for Geographic Information System. Geographic refers to earth science, which studies regions, resources, people, etc. Earth has a spatial component. The land extends in all directions, within which all things or attributes exist. Anything happening or existing in space is spatial or spatially distributed. It must have a geographic reference that is, be geo-referenced. Also, there must be definable boundaries or limits in space. Information is simply any facts or data about a given space on Earth. Examples include slope, rainfall amounts, population, road networks, and vegetation. These may collectively be referred to as attributes, factors, or variables within a defined space on Earth, e.g., the location, country, drainage basin, etc. Systems are a structured set of objects or parts that are related to one another or which operate together as one whole unit following a defined pattern.
Figure 2: Components of computer-based GIS
A geographic information system is therefore a system dealing with geographic information about a particular space with a defined boundary. It combines technical and human resources with a set of organizing procedures to produce information in support of decision making, as shown in Figure 2.
Functionality of GIS
GIS functionality refers to the set of functions that a GIS can perform. The GIS provides the following set of capabilities for spatially referenced land related data and information: data input, data storage and retrieval, data manipulation and analysis, and data output and reporting
- Data Input: This function involves the identification and collection of data necessary for processing in the GIS as obtained from the various sources.
- Keyboard: Attributes data are commonly entered by keyboard during manual digitizing or as a separate operation in which the attributes are entered with a code to indicate the spatial element they describe.
- Manual Digitizing: In manual digitizing, the map is affixed to a digitizing table and a pointing device is used to trace the map features. To digitize, data are registered on the digitizing table, then input into the GIS, transformed to standardized world coordinates, and finally, the various features are assigned attributes.
- Scanning: A scan of a digital image of the map is produced by moving an electronic detector across the map surface.
- Import of Existing Digital Files: This involves converting information using a computer text editor to create flat files that list a series of data coordinates.
- Data Storage and Retrieval: The purpose of data storage and retrieval is to organize the data in a topographically structured form so that it can easily be retrieved for subsequent manipulation, analysis, and display.
- Data Manipulation and Analysis: This functional component performs a number of tasks, mainly geometric calculations, map-overlay computations, network analysis, and production of estimates of parameters for transfer to external analytical models; all through user-defined rules
- Data Output and Reporting: Output for all or selected portions of the spatial database are displayed using standard or cartographic formats. Various hardware devices, such as plotters, displays, and printers, may be used for output presentation of maps, tables, and figures. Information is thus presented in a form suitable to the user, usually in hard copy, “softcopy,” or using electronic files or format.
 “Geographical Information Systems (GIS)”, available online at: http://www.manage.gov.in/studymaterial/GIS.pdf
 “Chapter Two: GIS Geographical Information Systems”, available online at: http://shodhganga.inflibnet.ac.in/bitstream/10603/126331/12/12_chapter%202.pdf
 C. M. Ondieki and S.K. Murimi, “Applications of Geographic Information Systems”, Environmental Monitoring – Volume II, Encyclopedia of Life Support Systems (EOLSS).