Components of a GIS

A GIS can be divided into five components: People, Data, Hardware, Software, and Procedures.  All of these components need to be in balance for the system to be successful. No one part can run without the other.


The people are the component who actually makes the GIS work.  They include a plethora of positions including GIS managers, database administrators, application specialists, systems analysts, and programmers. They are responsible for maintenance of the geographic database and provide technical support.  People also need to be educated to make decisions on what type of system to use.  People associated with a GIS can be categorized into: viewers, general users, and GIS specialists.

·        Viewers are the public at large whose only need is to browse a geographic database for referential material. These constitute the largest class of users.

·        General Users are people who use GIS to conducting business, performing professional services, and making decisions.  They include facility managers, resource managers, planners, scientists, engineers, lawyers, business entrepreneurs, etc.

·        GIS specialists are the people who make the GIS work. They include GIS managers, database administrators, application specialists, systems analysts, and programmers.  They are responsible for the maintenance of the geographic database and the provision of technical support to the other two classes of users. (Lo, 2002)



Procedures include how the data will be retrieved, input into the system, stored, managed, transformed, analyzed, and finally presented in a final output.  The procedures are the steps taken to answer the question needs to be resolved.  The ability of a GIS to perform spatial analysis and answer these questions is what differentiates this type of system from any other information systems. 

The transformation processes includes such tasks as adjusting the coordinate system, setting a projection, correcting any digitized errors in a data set, and converting data from vector to raster or raster to vector. (Carver, 1998)



Hardware consists of the technical equipment needed to run a GIS including a computer system with enough power to run the software, enough memory to store large amounts of data, and input and output devices such as scanners, digitizers, GPS data loggers, media disks, and printers. (Carver, 1998)



There are many different GIS software packages available today.  All packages must be capable of data input, storage, management, transformation, analysis, and output, but the appearance, methods, resources, and ease of use of the various systems may be very different. Today’s software packages are capable of allowing both graphical and descriptive data to be stored in a single database, known as the object-relational model.  Before this innovation, the geo-relational model was used. In this model, graphical and descriptive data sets were handled separately.  The modern packages usually come with a set of tools that can be customized to the users needs (Lo, 2002). 



Perhaps the most time consuming and costly aspect of initiating a GIS is creating a database.  There are several things to consider before acquiring geographic data.  It is crucial to check the quality of the data before obtaining it.  Errors in the data set can add many unpleasant and costly hours to implementing a GIS and the results and conclusions of the GIS analysis most likely will be wrong.  Several guidelines to look at include:

·        Lineage – This is a description of the source material from which the data were derived, and the methods of derivation, including all transformations involved in producing the final digital files.  This should include all dates of the source material and updates and changes made to it. (Guptill, 1995)

·        Positional Accuracy – This is the closeness of an entity in an appropriate coordinate system to that entity’s true position in the system.  The positional accuracy includes measures of the horizontal and vertical accuracy of the features in the data set. (Guptill, 1995)

·        Attribute Accuracy – An attribute is a fact about some location, set of locations, or features on the surface of the earth.  This information often includes measurements of some sort, such as temperature or elevation or a label of a place name.  The source of error usually lies within the collection of these facts.  It is vital to the analysis aspects of a GIS that this information be accurate.

·        Logical Consistency - Deals with the logical rules of structure and attribute rules for spatial data and describes the compatibility of a datum with other data in a data set.  There are several different mathematical theories and models used to test logical consistency such as metric and incidence tests, topological and order related tests.  These consistency checks should be run at different stages in the handling of spatial data. (Guptill, 1995)

·        Completeness – This is a check to see if relevant data is missing with regards to the features and the attributes.  This could deal with either omission errors or spatial rules such as minimum width or area that may limit the information. (Guptill, 1995) (Chrisman,1999)


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