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The page includes following topics:

• Definition of GISystem.

• Definition of GIScience and GIService.

• Brief history of GISystem.

• Data sources of GISystem.

• Characteristics of data model in GISysem.

• Software of GISystem.

What is a GISystem?

Many definitions of GIS have been suggested over the years, such as "a container of maps in digital form", "a computerized tool for solving geographic problems", "a tool for performing operations on geographic data that are too tedious or expensive or inaccurate if performed by hand" (Longley, et al, Geographic Information Systems and Science, 2001). Let's look at some of the definitions given by the professional institutes:

USGS (United States Geological Survey): In the strictest sense, a GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations.

ESRI (Earth Science Research Institute): GIS is a system of computer software, hardware and data, and personal to help manipulate, analyze and present information that is tided to spatial data.

INHS (Illinois Natural History Survey): A Geographic Information System (GIS) is an organized collection of computer hardware, software, geographic data, and personnel designed to capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. This System allows users to perform very difficult, time consuming, or otherwise impractical spatial analyses.

In general, we could derive the practical definition of GIS as a computerized system designed to dealing with the collection, storage, manipulation, analysis, visualization and displaying geographic information. GIS is a tool to perform the spatial analysis which will put insight to the activities and phenomena carrying out everyday.

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What is GIScience?

Geographic Information Science (GIScience) is advocated to address are a set of intellectual and scientific questions which go well beyond the technical capabilities of GIS.  The concept was first advocated by Michael Goodchild. 

 "...There is a pressing need to recognize and develop the role of science in GIS.This is meant in two senses. The first has to do with the extent to which GIS as a field contains a legitimate set of scientific questions, the extent to which these can be expressed, and the extent to which they are generic, rather than specific to particular fields of application. ... The second sense has to do with the role of GIS as a toolbox in science generally -with GIS for science rather than the science of GIS." (Goodchild, Spatial Information Science, 1990)

Thinking about the uniqueness of the spatial data, their location based characteristics, their spatial dependence, Goodchild proposed the contents for GIScience, such as data collection and measurement, spatial statistics, theories of spatial data, data structures, algorithms and processes, display and analytical tools. (Spatial Information Science, 1990)

It is known that the information science studies the fundamental issues arising from the creation, handling, storage, and use of  information. So, similarly, we could infer that GIScience should also study the fundamental issues specifically arising from the special set, geographic information. 

GIsystem is part of the Geographic Information whole, which also includes the fundamental issues of GIsicence. (Longley, Geographic Information System and Science, 2001) 

What is GIService?

GIService is the kind of services dealing with the geographic information, such as the design and development of the GIS, geographic information retrieval, analysis, etc. For example, MapQuest (www.mapquest.com) provides a routing service for people to find the best driving route between two points.

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How is GISystem developed?

The first GIS, Canada Geographic Information System was developed in mid-1960s to identify the nation's land  resources and their existing, and potential uses. 

In the late 1960s, US Bureau of the Census created the DIME program (Dual Independent Map Encoding) for all US streets to support automatic referencing and aggregation of census data. 

In late 1970s, Harvard University's Laboratory for Computer Graphics and Spatial Analysis developed a general-purpose GIS (ODYSSEY GIS).

The first automated cartography developments occured in the 1960s, and by the late 1970s most major cartographic agencies were already partly computerized.

GIS began to take off in the early 1980s, when the price of computing hardware had fallen to a level that could sustain a significant software industry and cost-effective applications. 

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What are the major components of GISystem?

According to the ESRI, the major components of GIS is hardware, software, data, people, procedure and network.

• Hardware, is the devices that the user interacts directly in carrying out GIS operations, such as the computer, digitizer, plotter, etc.

• Software, normally runs locally in the user's machine, also supports user to carry out multiple spatial analysis and management.

• Data, which is quite critical to GIS, contains either an explicit geographic reference, such as a latitude and longitude coordinate, or an implicit reference such as an address, postal code, census tract name, forest stand identifier, or road name.

• People is most active components dealing with the design, programming, operation and management of GIS.

• Procedure, more related to the management aspect of GIS, is referred to lines of reporting, control points, and other mechanism for ensuring the high quality of GIS.

• Network allows rapid communication and sharing digital information. The internet has proven very popular as a vehicle for delivering GIS applications.   

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What are data sources of GISystem?

• Digitizing and scanning of maps
  Use the digitizer to transform the information from analog format, such as a paper map, to digital format, so that it can be stored and displayed with a computer . Or use scanner to convert the analog paper map to computer-readable form automatically. 
  

• Input image data
  Image data includes satellite images, aerial photographs and other remotely sensed or scanned data, which are in the raster form. Remote sensing has become a more and more important data source for GISystem
  

• Direct data entry including Global Position System (GPS)
  Surveying field data which measure the distance and angle to decide the location of other points could also be transferred into the GISystem. GPS is a set of hardware and software designed to determine accurate locations on the earth using signals received from selected satellites. Location data and associated attribute data can be transferred to mapping and GISystem.
  

• Transfer data from existing sources
  data are obtained already in digital format from Government Agencies such as Australian Geological Survey Organisation http://www.agso.gov.au , the Australian Survey and Land Information Group (AUSLIG) http://www.auslig.gov.au , and other sources. (Please refer to the WebResource page for available online data provider.)

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What's Basic Data Model in GISystem?

• Vector data model
  Vector data represents the locations of the discrete objectives by points, lines and areas.
  

• Raster data model
  Continuous numeric values, such as elevation, and continuous categories, such as vegetation types, are represented using the raster model.  Raster model divides the entire study area into a regular grid of cells in specific sequence, each cell has a unique value representing different types.

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What is Different Kinds of GISystem Software?

A modern GIS software system comprises an integrated suite of software components, including end user applications, geographic tools and data access components. GIS software packages could be classified as six groups based on the functionality and type. (Longley, Goodchild, et al, Geographic Information Systems and Science, 2001).

• Professional GIS
  The distinctive features of professional GIS include data collection and editing, database administration, advanced geoprocessing and analysis, and other specialist tools, such as ESRI ArcInfo, Samllworld GIS.
  

• Desktop GIS
  Desktop GIS focus on data use, rather than data creation, and provide excellent tools for making maps, reports, and charts. Well-know examples include ESRI ArcView, Intergraph GeoMedia, MapInfor professional, Clark Lab's Idrisi, etc.
  

• Hand-held GIS
  Hand-held GIS are lightweight systems designed for mobile and field use, such as Autodesk Onsite, ESRI ArcPad, and Smallworld Scout.
  

• Component GIS
  Component GIS are tool kits and used by knowledgeable programmers to create focused applications. Examples include Blue Marble Geographic GeoObjects, and MapInfo MapX.
  

• GIS viewer
  GIS viewer are able to display and query popular file formats, such as ESRI ArcExplorer, Intergraph's GeoMedia, and MapInfo's ProViewer.
  

• Internet GIS
  Internet GIS focus on display and query applications, as well as maping. Examples include Autodestk MapGuide, ESRI ArcIMS, Intergraph GeoMedia Web Map, and MapInfo MapXtreme.

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