Geographic Information Systems as an Integrating Technology: Context, Concepts, and Definitions
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 geography, as well as on the general ways in which scientists and scholars communicate and collaborate.
General Communication, Research, and Publication Technologies
- 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 production.
- 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 results.
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 research tasks.
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 and heritage.
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:
Three observations should be made about this definition:
- 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
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.
- 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 analyses."
- C. Dana Tomlin's definition, from Geographic Information Systems and Cartographic Modeling (Englewood Cliffs, NJ: Prentice-Hall,1990), page xi:
- "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 More
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 terms:
- 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)
- Computerized GIS
- Environmental Information System
- GIS (Geographic Information System)
- Geographically Referenced Information System
- Geo-Information System
- Image-Based Information System
- LIS (Land Information System)
- Land Management System
- Land Record System
- Land Resources Information System
- Multipurpose Cadastre:
- 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 Database
- 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 processes.
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 tools.
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
- wildlife habitat,
- wild and scenic rivers,
- recreation resources,
- agricultural lands,
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 useful in
- zoning and subdivision planning,
- land acquisition,
- environmental impact policy,
- water quality management,
- maintenance of ownership.
- address matching,
- location analysis or site selection,
- development of evacuation plans.
10. Many Software Systems Support GIS Decision Making
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 or ArcGIS (produced by the Environmental Systems Research Institute) 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 MapInfo 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.