Geographic Information Systems as an Integrating Technology: Context, Concepts,
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1. Information Technologies in Geography
GIS is one of many information technologies that have transformed the ways
geographers conduct research and contribute to society. In the past two
decades, these information technologies have had tremendous effects on
research techniques specific to the discipline, as well as on the general
ways in which geographers communicate and collaborate.
Cartography and Computer-Assisted Drafting: Computers offer the
same advantages to cartographers that word-processing software offers writers.
Automated techniques are now the rule rather than the exception in cartographic
Photogrammetry and Remote Sensing: Aerial photogrammetry, a well-established
technique for cartographic production and geographic analysis, is now complemented
by the use of "remotely sensed" information gathered by satellites in outer
space. Information technologies have made both sorts of information far
more readily available and far easier to use.
Spatial Statistics: Statistical analysis and modeling of spatial
patterns and processes have long relied on computer technology. Advances
in information technology have made these techniques more widely accessible
and have allowed models to expand in complexity and scale to provide more
accurate depictions of real-world processes.
Geographic Information Systems (GIS): These systems allow geographers
to collate and analyze information far more readily than is possible with
traditional research techniques. As will be noted below, GIS can be viewed
as an integrating technology insofar as it draws upon and extends techniques
that geographers have long used to analyze natural and social systems.
Communication and Collaboration: Electronic mail, discussion lists,
and computer bulletin boards make it far easier for colleagues to communicate
ideas and share ideas, locally, nationally, and internationally. Distance-learning
techniques make it possible to hold interactive classes and workshops simultaneously
at distant locations.
Access to Library and Research Materials and Sources: Network access
to both primary and secondary research resources is expanding rapidly.
From their offices, scholars can now get information held by libraries,
government agencies, and research institutions all over the world.
Publication and Dissemination: Information technologies are reducing
substantially the cost of publishing and distributing information as well
as reducing the time required to circulate the latest news and research
2. The Course of Technological Innovation
These advances in the application of information technologies in geography
began several decades ago and will continue to expand their effects into
the foreseeable future. Scholars who have studied the spread of technological
innovations in society sometimes divide the process into four phases:
In geography, many innovations in the application of information technologies
began in the late 1950s, 1960s and early 1970s. Methods of sophisticated
mathematical and statistical modeling were developed and the first remote
sensing data became available. Researchers began also to envision the development
of geographic information systems. The mid-1970s to early 1990s was a period
of contagion. The first commercially available software for GIS became
available in the late 1970s and spurred many experiments, as did the development
of the first microcomputers in the early 1980s. This was an exciting time
in which the development of powerful software coupled with the availability
of inexpensive computers permitted many researchers to test new ideas and
applications for the first time. In the early 1990s, or perhaps just a
bit earlier, many innovations entered the coordination phase even as other
experimentation continued at a fast pace. The strengths and weaknesses
of many information technologies were by then apparent, and researchers
began to work together to cultivate the most promising applications on
a large scale. Arguably, the complete integration of information technologies
in geography has yet to be achieved except perhaps in a few relatively
specialized research areas. Complete integration across the discipline
may, in fact, be many years away.
Initiation: An innovation first becomes available.
Contagion: Far-ranging experimentation follows to see how the innovation
can be adapted to meet a wide variety of research and commercial needs.
Some, but not necessarily all of these experiments will work.
Coordination: The most promising applications of the innovation
gradually gain acceptance and are developed collaboratively. The coordination
of experimentation helps to distribute the potentially high costs of further
development and implementation.
Integration: A innovation is accepted and integrated into routine
3. GIS as an Integrating Technology
In the context of these innovations, geographic information systems have
served an important role as an integrating technology. Rather than being
completely new, GIS have evolved by linking a number of discrete technologies
into a whole that is greater than the sum of its parts. GIS have emerged
as very powerful technologies because they allow geographers to integrate
their data and methods in ways that support traditional forms of geographical
analysis, such as map overlay analysis as well as new types of analysis
and modeling that are beyond the capability of manual methods. With GIS
it is possible to map, model, query, and analyze large quantities of data
all held together within a single database.
The importance of GIS as an integrating technology is also evident
in its pedigree. The development of GIS has relied on innovations made
in many different disciplines: Geography, Cartography, Photogrammetry,
Remote Sensing, Surveying, Geodesy, Civil Engineering, Statistics, Computer
Science, Operations Research, Artificial Intelligence, Demography, and
many other branches of the social sciences, natural sciences, and engineering
have all contributed. Indeed, some of the most interesting applications
of GIS technology discussed below draw upon this interdisciplinary character
4. Geographic Information Systems: A Generic Definition
GIS is a special-purpose digital database in which a common spatial coordinate
system is the primary means of reference. Comprehensive GIS require a means of:
Data input, from maps, aerial photos, satellites, surveys, and other sources
Data storage, retrieval, and query
Data transformation, analysis, and modeling, including spatial statistics
Data reporting, such as maps, reports, and plans
Three observations should be made about this definition:
First, GIS are related to other database applications, but
with an important difference. All information in a GIS is linked to a spatial
reference. Other databases may contain locational information (such as
street addresses, or zip codes), but a GIS database uses geo-references
as the primary means of storing and accessing information.
Second, GIS integrates technology. Whereas other technologies might
be used only to analyze aerial photographs and satellite images, to create
statistical models, or to draft maps, these capabilities are all offered
together within a comprehensive GIS.
Third, GIS, with its array of functions, should be viewed as a process
rather than as merely software or hardware. GIS are for making decisions.
The way in which data is entered, stored, and analyzed within a GIS must
mirror the way information will be used for a specific research or decision-making
task. To see GIS as merely a software or hardware system is to miss the
crucial role it can play in a comprehensive decision-making process.
5. Other Definitions
Many people offer definitions of GIS. In the range of definitions presented
below, different emphases are placed on various aspects of GIS. Some miss
the true power of GIS, its ability to integrate information and to help
in making decisions, but all include the essential features of spatial
references and data analysis.
Click here to see the USGS's
definition of GIS (Scroll down to "What is a GIS?").
A definition quoted in William Huxhold's
Introduction to Urban Geographic Information Systems. (New York: Oxford
University Press, 1991), page 27, from some GIS/LIS '88 proceedings:
". . . The purpose of a traditional GIS is first and foremost spatial analysis.
Therefore, capabilities may have limited data capture and cartographic
output. Capabilities of analyses typically support decision making for
specific projects and/or limited geographic areas. The map data-base characteristics
(accuracy, continuity, completeness, etc) are typically appropriate for
small-scale map output. Vector and raster data interfaces may be available.
However, topology is usually the sole underlying data structure for spatial
C. Dana Tomlin's definition, from Geographic
Information Systems and Cartographic Modeling (Englewood Cliffs, NJ: Prentice-Hall,1990),
"A geographic information system is a facility for preparing, presenting,
and interpreting facts that pertain to the surface of the earth. This is
a broad definition . . . a considerably narrower definition, however, is
more often employed. In common parlance, a geographic information system
or GIS is a configuration of computer hardware and software specifically
designed for the acquisition, maintenance, and use of cartographic data."
From Jeffrey Star and John Estes, in Geographic
Information Systems: An Introduction (Englewood Cliffs, NJ: Prentice-Hall,
1990), page 2-3:
"A geographic information system (GIS) is 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-reference data, as well [as] a set of operations for working
with data . . . In a sense, a GIS may be thought of as a higher-order map."
And from Understanding GIS: The ARC/INFO Method
(Redlands, CA: Environmental System Research Institute, 1990), page 1.2:
A GIS is "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."
6. Related Terms: Acronyms, Synonyms, and
One reason why it can be difficult to agree on a single definition for
GIS is that various kinds of GIS exist, each made for different purposes
and for different types of decision making. A variety of names have been
applied to different types of GIS to distinguish their functions and roles.
One of the more common specialized systems, for instance, is usually referred
to as an AM/FM system. AM/FM is designed specifically for infrastructure
management. It is defined further below.
In addition, some systems that are similar in both function and
name to GIS, nevertheless are not really geographic information systems
as defined above. Broadly, these similar systems do not share GIS's ability
to perform complex analysis. CAD systems, for example, are sometimes confused
with GIS. Not long ago, a major distinction existed between GIS and CAD,
but the their differences are beginning to disappear. CAD systems, used
mainly for the precise drafting required by engineers and architects, are
capable of producing maps though not designed for that purpose. However,
CAD originally lacked coordinate systems and did not provide for map projections.
Nor were CAD systems linked to data bases, an essential feature of GIS.
These features have been added to recent CAD systems, but geographic information
systems still offer a richer array of geographic functions.
The use of so many acronyms, synonyms, and terms with related
meaning can cause some confusion. Consider a few of the most widely used
AGIS (Automated Geographic Information System)
AM/FM (Automated Mapping and Facilities Management):
Automated mapping by itself allows storage and manipulation of map information.
AM/FM systems add the ability to link stores of information about the features
mapped. However, AM/FM is not used for spatial analysis, and it lacks the
topological data structures of GIS.
CAD (Computer-Assisted Drafting): These systems
were designed for drafting and design. They handle spatial data as graphics
rather than as information. While they can produce high-quality maps, generally
they are less able to perform complex spatial analyses.
CAM (Computer-Assisted Mapping, or Manufacturing)
Environmental Information System
GIS (Geographic Information System)
Geographically Referenced Information System
Image-Based Information System
LIS (Land Information System)
Land Management System
Land Record System
Land Resources Information System
Multipurpose Cadastre: These systems store information
about parcels of land. They are used in urban geographic information systems
in order to collect and maintain data associated with property. Identifiers
assigned to each parcel link information to each plot of land. All information
is carefully stored with a geodetic reference frame because a high degree
of accuracy is necessary in maintaining information about parcel boundaries
and ownership. Because information in multipurpose cadastres is also linked
to street addresses, these systems can be used for keeping track of such
things as emergency response, crime, delivery of municipal services, and
tax assessments. All such information can then be integrated and analyzed
Multipurpose Geographic Data System
Multipurpose Land Record System
Natural Resources Inventory System
Natural Resources Management Information System
Planning Information System
Resource Information System
Spatial Data Handling System
Spatial Information System
7. The GIS View of the World
GIS provide powerful tools for addressing geographical and environmental
issues. Consider the schematic diagram below. Imagine that the GIS allows
us to arrange information about a given region or city as a set of maps
with each map displaying information about one characteristic of the region.
In the case below, a set of maps that will be helpful for urban transportation
planning have been gathered. Each of these separate thematic maps is referred
to as a layer, coverage, or level. And each layer has been carefully
overlaid on the others so that every location is precisely matched to its
corresponding locations on all the other maps. The bottom layer of this
diagram is the most important, for it represents the grid of a locational
reference system (such as latitude and longitude) to which all the maps
have been precisely registered.
Once these maps have been registered carefully within a common locational
reference system, information displayed on the different layers can be
compared and analyzed in combination. Transit routes can be compared to
the location of shopping malls, population density to centers of employment.
In addition. single locations or areas can be separated from surrounding
locations, as in the diagram below, by simply cutting all the layers of
the desired location from the larger map. Whether for one location or the
entire region, GIS offers a means of searching for spatial patterns and
Not all analyses will require using all of the map layers simultaneously.
In some cases, a researcher will use information selectively to consider
relationships between specific layers. Furthermore, information from two
or more layers might be combined and then transformed into a new layer
for use in subsequent analyses. This process of combining and transforming
information from different layers is sometimes called map "algebra" insofar
as it involves adding and subtracting information. If, for example, we
wanted to consider the effects of widening a road, we could begin with
the road layer, widen a road to its new width to produce a new map, and
overlay this new map on layers representing land use.
8. The Appeal and Potential of GIS
The great appeal of GIS stems from their ability to integrate great quantities
of information about the environment and to provide a powerful repertoire
of analytical tools to explore this data. The example above displayed only
a few map layers pertaining to urban transportation planning. The layers
included would be very different if the application involved modeling the
habitat of an endangered species or the environmental consequences of leakage
from a hazardous materials site.
Imagine the potential of a system in which dozens or hundreds
of maps layers are arrayed to display information about transportation
networks, hydrography, population characteristics, economic activity, political
jurisdictions, and other characteristics of the natural and social environments.
Such a system would be valuable in a wide range of situations--for urban
planning, environmental resource management, hazards management, emergency
planning, or transportation forecasting, and so on. The ability to separate
information in layers, and then combine it with other layers of information
is the reason why GIS hold such great potential as research and decision-making
9. Application Areas
GIS are now used extensively in government, business, and research for
a wide range of applications including environmental resource analysis,
landuse planning, locational analysis, tax appraisal, utility and infrastructure
planning, real estate analysis, marketing and demographic analysis, habitat
studies, and archaeological analysis.
One of the first major areas of application
was in natural resources management, including management of
One of the largest areas of application has been
in facilities management. Uses for GIS in this area have included
wild and scenic rivers,
Local, state, and federal governments have found
GIS particularly useful in land management. GIS has been commonly
applied in areas like
locating underground pipes and cables,
balancing loads in electrical networks,
planning facility maintenance,
tracking energy use.
More recent and innovative uses of GIS have used
information based on street-networks. GIS has been found to be particularly
zoning and subdivision planning,
environmental impact policy,
water quality management,
maintenance of ownership.
The range of applications for GIS is growing as systems become
more efficient, more common, and less expensive. Some of the newest applications
have taken GIS to unexpected areas. The USGS and
the city of Boulder, Colorado have come up with some innovative uses for
location analysis or site selection,
development of evacuation plans.
10. Many Software Systems Support GIS Decision
These days, dozens of software systems offer GIS decision-making capabilities.
The range and number available sometimes make it difficult to discern the
differences among systems and the strengths and limitations of each. The
important point to remember is that there are as many different types of
GIS software systems as there are decision-making processes. Particular
GIS software systems are often specialized to fit certain types of decision
making. That is, they are customized to meet needs specific to demographic
forecasting, transportation planning, environmental resource analysis,
urban planning, and so on. These systems may respond well to individual
problems, but they are also limiting. Special- purpose GIS designed for
airport planning and maintenance, for instance, will not be well suited
to demographic modeling.
Other software systems are not so specialized. The Intergraph Corporation's
MGE/MGA system, Arc/INFO (produced by the Environmental Systems Research
Institute), or Tydac's SPANS software have become well-known because they
can be used in a wide number of applications. These general purpose systems
also offer features that can be customized to meet various individual needs.
Other systems such as Atlas*GIS, MapInfo, and ArcView attempt
to provide functions that will be of value in one or more of the broad
application domains, for instance in demographic analysis or marketing
research. Yet quite apart from these more general systems, there are dozens
of very specialized software systems that are best suited to one task,
one application, or even to just one part of a broader decision- making
process, for example for storing maintenance records of a highway system
or for planning the expansion of an electric distribution network.
Antenucci, John C.; Brown, Kay; Croswell, Peter L.; Kevany, Michael
J.; and Archer, Hugh N. 1991. "Introduction," "Evolution of the Technology,"
and "Applications." Chaps. 1-3 in Geographic Information Systems: A Guide
to the Technology. New York: Van Nostrand Reinhold.
Krol, Ed. 1992. The Whole Internet: User's Guide and Catalog.
Sebastopol, CA: O'Reilly and Associates. Chapters 5 and 6.
Burrough, P.A. 1986. "Geographic Information Systems." Chap. 1
in Principles of Geographic Information Systems for Land Resources Assessment.
Oxford: Oxford University Press.
Huxhold, William E. 1991. "Information in the Organization" and
"Applications of Urban Geographic Information Systems." Chaps. 1 and 3
in An Introduction to Urban Geographic Information Systems. New York: Oxford
Star, Jeffrey and John Estes. 1990. "Introduction" and "Background
and History." Chaps. 1 and 2 in Geographic Information Systems: An Introduction.
Englewood Cliffs, NJ: Prentice- Hall.
Tobler, W.R. 1959. "Automation and Cartography." Geographical
Review 49: 526-534.
Last revised 25 September 1997. RRR.