GIS or Geospatial Information System is a computer based approach to collecting, analyzing, visualizing and maintaining data about location, that is, spatial data. GIS has a broad area of application including: Biology, City and Regional Planning, Earth and Environmental Sciences, Anthropology and Archaeology, Criminal Justice, Political Science, Sociology, Public Health and Transportation Systems, History, Literature, Civil Engineering, ad much more.
Despite the broad range of applications, there are two basic question that researchers ask when using GIS : where and what. Where is something located and what area its characteristics. To answer the Where researchers use spatial data and to answer the what researchers use attribute data. From these basic question we can derive higher -level question like what is nearby and how do these things interact with each other.
As we saw before GIS is used for "collecting, analyzing, visualizing and maintaining data about location." This definition also traces the history and antecedents of GIS starting with Cartography in the ancient world. One of the earliest maps yet discovered dates from circa 6,500 BC and shows a town that was once situated at Çatalhöyük in Turkey, with a volcano erupting over it. In the thousands of years since then maps have been used to show the features and locations on the Earth and help people understand where they are and where they are going.
An important story in the origins of GIS is the development of spatial analysis in the 1850s, when Dr. John Snow developed a map of Cholera incidences in London. By mapping the locations of Cholera incidences and by studying the behavior of people who drank water from a nearby well, Dr. Snow was able to infer that contaminated water supplied by the well was the source of the Cholera outbreak and made a convincing case for turning the well off. Dr. Snow's research represent foundational contributions to Spatial Analysis, Epidemiology and the Germ Theory of disease transmission.
Developments leading to GIS accelerated in the years after World War II, and most notably include what is known in Geography and the Social Sciences as the "Quantitative Revolution" which changed the perspectives of these disciplines away from idiographic or static, descriptive, narrative-based approaches toward the nomothetic perspective, which focuses on generalizing laws about processes that are derived from rigorous scientific methods and explain the way things change over time, such as when researchers develop a model of a process.
A parallel development was the invention of digital computers which provided a means for automating the collection, processing and analysis of these data.
Although there are early examples of computer-based spatial analysis and visualization like the Federal Census Bureau which used punch card computers to tabulate population data since 1890 , the Canada Geographic Information System developed by Roger Tomlinson in the 1960s is generally accepted as the first GIS . Canada's vast territory and extensive natural resources, and the need top manage them at close scale, motivated the development of this system, and included among its processes the digitizing of aerial images and identifying land-uses.
Nearly contemporary with this development was the Synagraphic Mapping System or SYMAP developed by Howard Fisher in 1964 at Harvard University. Two succeeding developments were ODYSSEY in 1979 which more closely resembles the GIS software that is popular today, but its proprietor went bankrupt before the software could be widely distributed; and GRID developed by Environmental System Research Institute (ESRI) which used satellite and aerial images to represent spatial data, and later developed program called Planning Information Overlay System. The advent of micro-computing in the late 1970s and early 1980s introduced more opportunities to develop GIS software for a greater range of applications and for people with a variety of background and research interests. ESRI took advantage of this development and produced ARCINFO which became very popular and ESRI became an industry leader.
Other widely used GIS platforms include Maptitude by the Caliper Corporation which is used widely in transportation analysis, and QGIS formerly Quantum GIS, which is likely the most widely used open source GIS platform.