What Types of Data Can Be Used in a GIS?

Any variable that can be located spatially can be entered into a GIS. For example, an area feature of the earth (e.g., a lake shoreline) can be linked to the attributes associated with the feature (e.g., salinity or depth of the lake). The primary requirement for the source data is that the locations of the variables be known. Location may be annotated by x, y, and z coordinates of longitude, latitude, and elevation or by systems such as zip codes or census geography (e.g., census tracts). A GIS can also convert existing digital information that is not in map form into recognizable and usable forms. For example, digital satellite images can be analyzed to produce a map-like layer of digital information (e.g., vegetative cover). A steadily growing source of data suitable for GIS applications is readily accessible on the Internet.

How Does a GIS Work? 

A critical component of a GIS is its capability to conduct complex spatial analyses and produce visual images (i.e., on a computer screen or paper) that convey the results of such analyses to assist in decision-making. Maps and other graphics are generated, enabling the viewer to visualize, and thereby more readily comprehend, the analytic results or simulations of potential events. For example, ATSDR used data on population, roads, streams, and land elevation—as well as information gathered from interviews with residents—to track the progress of a chlorine gas spill from a train derailment near Alberton, Montana. Through the use of GIS, the local terrain was modeled, the movement of the spill was mapped, and estimates of the size of the potentially exposed population were made. This simulation enabled ATSDR to respond quickly to the public health issues related to the spill. (For additional information on ATSDR's involvement in the Alberton spill, see "Tracking the plumes" in GIS for Health Organizations (1). 

References

1. Lang L. GIS for health organizations. Redlands (CA): ESRI Press; 2000.

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ATSDR Plays Leadership Role in Use of GIS in Public Health

C. Virginia Lee, MD, MPH, MA, ATSDR 

ATSDR was among the first public health agencies to recognize the tremendous potential geographical  information system (GIS) technology held for environmental public health activities and research. The agency foresaw many applications for GIS technology that would assist in fulfilling its mission, which is to prevent or minimize adverse human health effects resulting from environmental exposures to toxic chemicals at hazardous waste sites and accidental spills of toxic chemicals. In 1989, ATSDR established a GIS program within the agency to assist in its broad range of public health activities and research (e.g., exposure assessment and mitigation, surveillance, health studies, health intervention and prevention, and community characterization). 

GIS came of age at ATSDR and in the public health field during the 1990s, as public health researchers used GIS technology for mapping and spatial analyses of data on diseases and environmental  contaminants. During the decade, ATSDR sponsored, with institutional cosponsors and partnerships, the first national conferences held in the United States on the use of GIS in public health. These conferences, conducted in Atlanta, Tampa, and San Diego, were attended by state and local public health and environmental officials, academic researchers, and  representatives of other federal agencies using GIS technology. The proceedings of the 1998 conference are available on the ATSDR Web site at  /gis/conference98. 

GIS at ATSDR: 2000 and Beyond

During its initial development, the primary focus of the geographic information system (GIS) program at ATSDR was in support of the public health assessment and health consultation program in the Division of Health Assessment and Consultation (DHAC). GIS maps help health assessors identify geographic areas of particular health concern and susceptible subpopulations (e.g., children, childbearing-aged women, the elderly, and minority populations). 

In ensuing years, epidemiologists in the Division of Health Studies used it to characterize sites for studies, and the Division of Health Education and Promotion used it to plan and conduct education programs in communities near hazardous waste sites. ATSDR also uses GIS to determine past and future exposure potential, to analyze health data, and to investigate potential exposure to hazardous substances at the local, regional, and national levels. 

Moreover, GIS data provide the basis of the population information used in many ATSDR publications. Because GIS maps greatly enhance the ability to integrate and graphically display a wide array of data, GIS maps are used in many agency reports (e.g., public health assessments, health consultations, health studies, educational materials, and agency reports to Congress). 

In early 2000, ATSDR expanded its outreach efforts with a satellite broadcast, "Geographical Information Systems in Public Health: Using Mapping and Spatial Analysis Technologies for Health  Protection." This program provided information on (a) GIS concepts, terminology, and data; (b) spatial statistics and analysis functions; and (c) applications of GIS in public health practice and surveillance. The broadcast was directed toward state health and environmental agencies, colleges and universities, and hospitals throughout the United States. Copies of the video of the broadcast are available.* 

ATSDR also expanded the availability of GIS products through the agency's new Internet map server, GATHER. The map server is an important first step in making the agency's GIS products publicly available for all interested individuals and groups. 

The increasing availability of health, demographic, and environmental databases containing local, regional, national, and international information—combined with major advances in computerized spatial imagery and spatial statistical analyses—hold tremendous promise for mitigation of environmental exposures and adverse health effects. ATSDR's GIS program will continue to seek innovative applications to use GIS technology in accomplishing its environmental public health mission. 

GIS Products and Services Available to ATSDR and Health Departments in Participating States 

ATSDR provides a variety of GIS-based products and services to support site-specific activities conducted by ATSDR staff and the employees of health departments in the 28 states that have cooperative agreements with ATSDR. (Figure 2.) GIS products and services also are available to other local, state, and federal governmental agencies.  Spatial analysis services offered by the Spatial Analysis Activity Group (SAAG) at ATSDR include digitizing maps and other data, database creation and analysis, and map production. SAAG also provides consultation and special support for site-specific projects (e.g., making		Figure 2. ATSDR Has Cooperative Agreements with Health Departments in 28 States (in green) for Site-Specific Activities
specialized GIS queries, conducting complex spatial analyses, and identifying, selecting, and obtaining new data files). In addition, SAAG also conducts introductory classes in the use of GIS at ATSDR and provides training workshops in the use of GIS software. Presentations on GIS applications and research are given to a variety of audiences at meetings, workshops, and conferences.  SAAG has produced introductory demographic GIS maps for most Superfund sites and for other hazardous waste sites ATSDR has investigated. The SAAG extracted block-level demographic data from the 1990 census and used GIS to complete basic spatial analyses to generate site-specific demographic estimates. Each resulting GIS map contains the site location, the area within a 1-mile radius of the site, and population statistics (e.g., the size and distribution of subpopulations that have potentially greater susceptibility because of race/ethnicity, sex, and age). For many sites, information on environmental contaminants and health outcomes has been incorporated into the GIS to visually depict geographic  areas of particular public health concern.  Employees of state public health agencies can place requests for site-specific projects in their respective states. Information on requesting GIS services is available from the ATSDR/DHAC technical project officers assigned to state agencies. Others interested in collaborating with ATSDR on GIS projects are invited  to contact C. Virginia Lee, SAIDS Section Chief, at (404) 639-6056 (e-mail: cvlee@cdc.gov).

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ATSDR's New Map Server, GATHER, Provides Internet Access to GIS Data and Products

The Geographic Analysis Tool for Health and Environmental Research (GATHER) is a Web site application recently launched by ATSDR's GIS staff. The GATHER map server can be accessed at http://gis.cdc.gov/atsdr. GATHER enables all Internet users to access GIS data in a variety of formats; modify a map view through the display, zoom, and pan functions; query the data; and perform desktop spatial analysis. GATHER users can view, print from their local printer, and e-mail site-specific demographic maps in a format developed by the GIS staff. Each map contains the site location, the area within a 1-mile radius of the site, and relevant demographic data (e.g., number of children aged 6 years or less and the distribution of adults aged 65 years or more).

GATHER accesses a variety of data layers (e.g., census population and housing data, roads, hydrography, schools, and graphic images) to display, at several geographic scales, GIS maps of most Superfund hazardous waste sites (including U.S. Department of Energy and U.S. Department of Defense facilities) and other sites where ATSDR conducts public health activities and research. If the data are available, the site-specific maps contain information on the chemicals of concern. Once a site has been mapped, relevant documents can be accessed by clicking on the icon "ATSDR DOCS for this site," which is a link to all ATSDR-published documents for that site.

GATHER is an initial step in making ATSDR's GIS data and GIS products widely available to individuals in affected communities; private-sector groups; and local, state, and federal governmental agencies. The next release of GATHER will enable users to create buffer zones around a map feature, and ATSDR plans for future versions of GATHER to include a linking feature that will enable users to view a wider range of site-related materials.