Defining GIS

Basic definition of GIS:

An integrated set of hardware/software/humanware

Used to:

      Maintain (input, store, update)

      Manipulate (transform projections/datum, and cool analyses)

      Report on (map & tables, on screen or printed)

Spatial & attribute data.

There are 4 components to the definition of GIS:

1)     Computer – bits that make up the system (hardware, software)

2)     Processes – the “reason” for GIS (the ability of the software to combine data and conduct analyses)

3)     Data – geographic data is composed of 2 parts: spatial (where) and attribute (what)

4)     People - educated/trained staff to make it all happen

1.     Computer Hardware: The computer system (a.k.a. platform) consists of hardware (ranging from a pc to workstation to mini or mainframe) and an operating system (DOS, Windows 2000, UNIX, VMS, etc.).  I intentionally limit “computer system” to the platform and do not include the “GIS software” which is discussed below.  GIS started out on mainframes in early 1960’s.  It has since moved to work stations (UNIX based) and PC’s (DOS and now windows).  The most significant advance was the move to PC’s, as this made it available to “the masses”.  Additional hardware includes digitizers and scanners for input and plotters and printers for output.  Note that GPS data can also be downloaded into a GIS.  Although essential, I find this component the least interesting and seldom discuss it further.  But do note that most people who interact with GIS do so on a PC platform with Windows.

Computer Software: For any given platform there are many choices of GIS software.  For the PC there are many choices (ArcGIS, GeoMedia, Idrisi, GRASS, etc.).  Some were originally designed for municipal or natural resource or research/education purposes and had a specific application.  The method of data structure chosen was the one best suited for that application.  As software matures it tends to expand its utility.  A package originally designed for municipal applications can later be applied to natural resources and visa versa.  Thus, each of these software packages has a unique set of analytical procedures.  ArcGIS is the dominant GIS software package available.

 

2.     Processes: GIS processes are determined by the GIS software (as described above).  Some software is more comprehensive than others.  Functions common to all GIS software include the ability to:

1)     maintain data:

a)     capture (conversion of analog to digital, e.g. digitize “paper” map)

b)     import of previously captured data (e.g. Idrisi data -> to ArcView data)

c)     store data and

d)     retrieve data

2)     analyze data (especially spatial analysis)

a)     buffer features

b)     overlay map layers

c)     “911 routing”

d)     Catchment areas for schools

3)     output data

a)     maps and tables

b)     to screen and printer/plotter

 

3.     Data: To be captured and later analyzed in a GIS, features on (or in) the earth need to be described in 2 ways: where it is (defined by coordinates) and what it is (descriptive information).  If all we have is organized descriptive information we have a database.  However, if we have information about features that are descriptive AND spatially explicit (and we have software capable of conducting spatial analyses), then we have a GIS.  Critical to this is spatially explicit data.

 

4.     People: It is essential that the people involved in “doing GIS” be well educated (understand the theory and concepts) and trained (able to make the software do what it’s suppose to).  I think the education part of this is more critical now than 5 or 10 years ago.  Reason: the interface has become much simpler.  The technology has become much more accessible.  Thus, people can make the software do something without really understanding the geography/science behind it all – and the results could be misleading.

There are many definitions for GIS, some definitions for GIS include:

"An integrated package used for the input, storage, analysis and output of spatial information."

"A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public and private enterprises for explaining events, predicting outcomes, and planning strategies." (ESRI 1997)

"An Information System applied to geographical data or geographically distributed phenomena"

"An information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data." (Star and Estes 1990, p.2-3) 

"A system of hardware, software, data, people, organizations and institutional arrangements for collecting, storing, analyzing, and disseminating information about areas of the earth." (Dueker & Kjerne, 1989)

Geographic information system: an organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.   (ESRI Glossary).

A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.  (USGS).

Some definitions are more detailed than others.  A good definition will include the components and functions of GIS.