By Lyn Stoesen

CONTENTS
Learning objectives
Overview
Definition and uses
Mapping and public

health

Accessing GIS
Current issues
References
Links



Learning objectives: After reading this article, users will be able to define geographic information systems (GIS), based on Web page materials.

After reading this article, users will be able to describe ways that GIS are used for public health, based on Web page materials.

After reading this article, users will be able to describe different kinds of GIS databases, programs, and tools, based on Web page materials.

Back to contents

Overview: This article will provide an introduction to GIS technology and its use in public health practice. The article offers a definition of GIS, a short history of the use of geographic information in public health, and examples of current research using GIS technology. It concludes with practical information on accessing GIS programs, GIS databases, and interactive online mapping tools.

Back to contents

Definition and uses: The term "GIS" can refer to geographic information systems or geographic information science. Most people think of GIS as a map-making tool, but GIS is about more than cartography -- it involves the ability to analyze spatial data in addition to simply representing it.

GIS are defined as computer-based systems for the integration and analysis of geographic data (Cromely & McLafferty, 2002). GIS technologies can show locations, quantities, densities, and proximities, can reveal patterns and relationships, and can be used to create maps, models, and graphs.

Cromley and McLafferty (2002) identify four functions that distinguish GIS technology: the ability to store and compute or display spatial relationships between objects; the ability to store many attributes of objects; the ability to analyze spatial and attribute data in addition to simply managing and retrieving data; and the ability to integrate spatial data from many sources. They further identify three broad categories of GIS functions: spatial database management; visualization and mapping; and spatial analysis.

Back to contents

Mapping and public health: While new technologies have revolutionized the use of geographic information for public health practice, maps have long been a part of disease research and surveillance. As early as the 1600s, plague maps were drawn to track epidemics (Koch, 2005). One of the most well-known maps in the field of public health was John Snow's map of the Soho neighborhood of London, which showed a relationship between cases of cholera and water supplies (Johnson, 2004).

Using maps to track socioeconomic data also has a long history. In the late 19th and early 20th centuries, Charles Booth created poverty maps of London (Spielman & Thill, 2008). The United States has conducted a decennial census since 1790; the census has grown to include detailed information on income, transportation patterns, occupations, and other data, based on geographic locations. These kinds of data are becoming increasingly important in studies of the social determinants of health.

The use of maps for public health research expanded dramatically in the 20th century as technology advanced and it continues to boom in the 21st. Public health researchers and practitioners use GIS in a number of ways. Epidemiologists and environmental scientists use mapping technologies for tracking disease outbreaks and examining the relationship of health outcomes to toxic sites. Other public health uses of GIS include tracking immunizations, health policy research, establishing service areas, health surveillance, emergency preparedness, needs assessments, monitoring and evaluation, and health impact assessments.

Behavioral health researchers also use GIS to establish correlations and explore relationships between environments and health outcomes. As researchers are moving beyond exploring individual risk factors and are increasingly focusing on the effects of social and physical environments on health, the importance of geospatial data is becoming clearer.

Geanuracos et al. (2007), for example, used GIS to plan HIV prevention interventions for high-risk youth. They found that "the maps produced with GIS software offer a unique method for visualizing an array of community characteristics, communicating them to nontechnical audiences, and incorporating them into a planning process." Maps produced during the project were used to support decision-making and spark community discussion about data collection.

Brower and Carroll (2007) used GIS mapping and 2003 crime data from the University of Wisconsin-Madison to address consequences of student drinking. They examined the time as well as location of crime reports and found that different categories of crime showed different temporal and spatial patterns. The results led directly to changes by city and university officials in addressing high-risk drinking.

In a third example, Owen et al. (2007) examined the physical attributes of residential neighborhoods, obtaining measures of connectedness and proximity using GIS databases, to examine walking behaviors. A "walkability index" was created using street centerline data, land use, zoning data, shopping center location data, and census data within a GIS application.

Back to contents

Accessing GIS: While computerized geographic data systems have been in use since the 1960s, for many years they were expensive and difficult to access. Today, however, there are many open source GIS applications, as well as commercial and proprietary applications. The most commonly used GIS application in the United States is ArcGIS, produced by ESRI (the Environmental Systems Research Institute).

ArcGIS systems include ArcReader, ArcView, ArcEditor, and ArcInfo. ArcReader is a free software product that allows users to view maps and data produced by ESRI programs, but it cannot be used to create maps. The licensed products include increasingly advanced editing tools.

GRASS, the Geographic Resources Analysis Support System, is used in academic, government and commercial settings for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization.

EpiInfo is a free public domain statistical software program developed by the Centers for Disease Control. It allows data entry and analysis and includes a mapping function. The Census Bureau offers a free Census and Survey Processing System (CPSPro) which allows users to enter, tabulate, and map census and survey data.

GIS technology relies on data. There are many data sources available at the local, state and national levels. The National Center for Health Statistics offers many sources for health-related geospatial data and provides links to maps it has created using GIS. The CDC provides links to many data sources, including state sources, as well as downloads for EpiInfo.

While analysis is an integral aspect of GIS technologies, there are also resources that allow users to simply create maps using available data. The National Atlas site, produced by the U.S. Department of the Interior, allows users to produce customized maps through its Map Maker page; users can access health data (under the "People" tab) to create and print maps using vital statistics. The Census Bureau's American FactFinder page also offers tools for map creation and printing.

Back to contents

Current issues: Healthy People 2010 identifies GIS as a growing and important area for public health practice. Among the public health infrastructure goals it identifies is the aim of "increas[ing] the proportion of all major national, state, and local health data systems that use geocoding to promote nationwide use of geographic information systems (GIS) at all levels."

Despite the many advances made in GIS technology, there are limitations to what these systems can do. First, GIS is necessarily limited by the data available. Data collection remains a challenge for many subjects, particularly those related to behavioral health. GIS is only as good as the information available.

An additional concern, particularly related to GIS and health data, is privacy and the use of electronic medical records in GIS analyses. Further, access to many data sets below the county level is restricted due to confidentiality concerns. While Kwan and Schuurman (2004) argue that "the social implications of GIS can be addressed in the technical realm," communities under study must become increasingly involved and informed about data acquisition and use.

As the public health workforce grows and technologies advance, the availability of GIS applications and data will also increase. All public health practitioners should be familiar with GIS technologies and capabilities in order to stay informed about current research, conduct their own studies, and advance the profession.

Back to contents

References:

Brower, A.M., & Carroll, L. (2007). Spatial and temporal aspects of alcohol-related crime in a college town. Journal of American College Health, 55(5), 267-275.

Cromely, E. & McLafferty, S. (2002). GIS and public health. New York: Guilford Press.

Geanuracos, C.G., Cunningham, S.D., Weiss, G., Forte, D., Reid, L. M. H., & Ellen, J. M. (2007) Use of geographic information systems for planning HIV prevention interventions for high-risk youths. American Journal of Public Health, 97(11), 1974-1981.

Johnson, S. (2006). The ghost map. New York: Riverhead Books.

Koch, T. (2005). Cartographies of disease: Maps, mapping, and medicine. Redlands, Calif.: ESRI Press.

Kwan, M. & Schuurman, N. (2004). Introduction: Issues of privacy protection and analysis of public health data. Cartographica, 39(2), 1-4.

Maantay, J. & Ziegler, J. (2006). GIS for the urban environment. ESRI Press: Redlands, Calif.

Maheswaren, R. & Craglia, M. (eds.) (2005). GIS in public health practice. Boca Raton, Fla.: CRC Press.

Melnick, A. (2002). Introduction to geographic information systems in public health. Gaithersburg, Md.: Aspen Publishers.

Owen, N., Cerin, E., Leslie, E., duToit, L., Coffee, N, Frank, L.D., et al. (2007). Neighborhood walkability and the walking behavior of Australian adults. American Journal of Preventive Medicine, 33(5), 387-395.

Spielman, S.E. & Thill, J. (2008). Social area analysis, data mining, and GIS. Computers, Environment and Urban Systems, 32, 110-122.

Talen, E., & Shah, S. (2007). Neighborhood evaluation using GIS: An exploratory study. Environment and Behavior, 39(5), 583-615.

Back to contents

Links:
General GIS information:
GIS Lounge information portal
National Center for Health Statistics GIS page
International Journal of Health Geographics
World Health Organization Public Health Mapping and GIS Programme

GIS tools and downloads:
Epi Info download page
Maptitude (GIS software)
ArcGIS (GIS software)
ArcReader (free map viewing software)
Healthmapper (World Health Organization tool)
Centers for Disease Control Resources for Creating Public Health Maps
National Atlas Map Maker
Census Bureau American FactFinder

GIS data sources:
National Center for Health Statistics
Epi Info data
GIS data Web sites
Geospatial and attribute data sources
Statewide data

Back to contents