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,
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,
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,
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
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,
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.
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)