Basics to gis concepts unit i

Editor's Notes

1. The history of using computers for mapping and spatial analysis shows that there have been parallel developments in automated data capture, data analysis and presentation in several broadly related fields. These fields are cadastral and topographical mapping, thematic cartography, civil engineering, geography ,mathematical studies of spatial cartography, utility network and remote sensing and image analysis. Military applications have overlapped and even dominated several of these monodisciplinary fields. Consequently there has been much duplication of efforts and multiplication of discipline specific jargon for different applications in different lands. This multiplicity effort from several fields is now resulting in the possibility of linking many kinds of spatial data processing together into general –purpose Geographical Information Systems.
2. Essentially all these fields are attempting the same sort of operations – namely to develop a powerful set of tools for collecting, storing, retrieving, transforming and displaying spatial data from the real world for a particular set of purposes. These set of tools together constitute a geographical information system.
3. GIS is an organized collection of hardware, software, geographic data and personnel designed to efficiently capture, store, update, manipulate and display all forms of geographically referenced information. In other words GIS is a system for capturing, storing, checking, integrating, manipulating, analysing and displaying data which are spatially referenced to the Earth. This is normally considered to involve a spatially referenced computer database and appropriate applications software.
4. GIS is a special – purpose digital database in which a common spatial coordinate system is the primary means of reference. Comprehensive GIS require a means of data input,storage,transformation and data reporting in the form of various output. GIS is desgined in such a way that it can effeciently capture data from source, can store in database, can perform analysis and modeling including spatial statistics and can clearly display the output in the form of maps, reports and plans.
5. GIS are related to other database applications, but with an important difference. All information in GIS is linked to a spatial reference. Other database may contain locational information (such as street address, zip codes), but a GIS database uses geo – references as the primary means of storing and accessing information. GIS integrates technology. Whereas other technologies might be used only to analyze aerial photographs and satellite images to create statistical models, or to draft maps, thee capabilities are all offered within comprehensive GIS. The importance of GIS an integrating technology is also evident in its pedigree. The development of GIS has relied on innovations made in many different disciplines : Geography, Cartography, Photogrammetry, Remote sensing, surveying etc have all contributed. Indeed, these efforts indicates its interdisciplinary character and heritage.
6. GIS with its array of functions, should be viewed as a process rather than as merely software or hardware. GIS for making decisions. The way data is entered, stored and analyzed within a GIS must mirror the way information will be used for a specific research or decision – making task. To see GIS as merely a software or hardware system is to miss the crucial role it can play in a comprehensive decision making process. Rather than being completely new, GIS have evolved by linking a number of discrete technologies into a whole that is greater than the sum of its parts. GIS has emerged as very powerful technologies because they allow geographers to integrate their data and methods in ways that support traditional forms of geographic analysis. With GIS it is possible to map, model, query and analyze large quantities of data all held together within a singal database.
7. Geographical Information Systems can be applied in different context and content of study and analysis. An area can be interpreted as a whole by studying the pattern of distribution of various phenomena , their linkages and trends of changes. Apart from this GIS is also considered for systematic management of places. Places can differ in concern with their size and functionality. It can be a watersheds, communities, neighborhoods or an ecosystems, for all these GIS is an opted management system.
8. Until very recently, most geographical information systems were set up for local applications, or for work on a limited project area. There are now strong indications that many users, particularly major government agencies are willing or have started to set up comprehensive countrywide systems. A good GIS system should be designed to answer these questions. Many of these questions are difficult to answer using conventional methods ( for example calculating the portion of different kinds of soil mapped requires either extensive work with planimeter or that map units drawn on the paper should be cut out and individually weighted. • A location can be described in many ways (place name, zip code, or a geographic reference) Instead of identifying what exists at a given location, you can find a location where certain conditions are satisfied Involves monitoring how things change over time Allows to describe and compare the distribution of phenomena and understand the processes which account for their distribution Allows different models of the world to be evaluated