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Connecticut Geographic Information System, which is being developed by the NRC with support from the USGS and State agencies. The Connecticut Geographic Information System is already being used for statewide water-supply planning and, when fully operational, is expected to be one of the most powerful tools for groundwater protection programs (fig. 7).

The USGS cooperative program will continue to provide the science, data management concepts, and predictive tools for Connecticut to further develop and fully implement the ground-water management programs that are essential elements of the State strategy for ground-water protection. The ground-water strategy that has been such a productive Federal-State cooperative effort in Connecticut may be a model for other States; perhaps it will serve as a springboard to other similar programs elsewhere in protecting the Nation's vital ground-water resources.

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Geographic Information System Applications in the Earth Sciences

By John L. Place and David A. Nystrom

Introduction

A geographic information system (GIS) is a computer hardware and software system designed to collect, manage, analyze, and display spatially referenced data. In the simplest sense, a GIS automates the manual process of gathering and analyzing the wide variety of data needed to make land-use and resource-management decisions and solve earth-science problems.

Because GIS capabilities allow scientists to process and interrelate many more kinds of data than before, it is now possible to examine problems and to broaden scientific understanding in new ways. For example, scientists might combine and analyze data on vegetation, soils, surficial geology, rainfall, and runoff measurements within the same hydrologic drainage basin to study soil permeability or soil erosion.

The growing urban population has placed increased demands on the Nation's natural resources and the environment. Frequently, Federal and State agencies must respond quickly to complicated problems involving the assessment and management of natural resources or the monitoring or mitigation of natural and manmade hazards. The U.S. Geological Survey, for example, is often called upon to provide earth-science information quickly to aid in mitigating the effects of hazards such as earthquakes and landslides. A GIS is a valuable tool that helps USGS scientists to provide this information more rapidly, efficiently, and effectively.

Geographic Information Systems at the U.S. Geological Survey

The USGS and the State of Connecticut initiated a joint demonstration project in 1984 to evaluate the effectiveness of using a GIS in ongoing data collection, maintenance, and analytical programs of the Connecticut Natural Resources Cen

ter. The project solved several problems related to the quality of existing digital and mapped data, the mechanics of processing large natural-resource data bases, and the compatibility of digital data among different systems. The project successfully demonstrated GIS effectiveness for industrial site selection and determination of groundwater availability.

Encouraged by the results of the Connecticut demonstration project and other application studies, the Director of the USGS issued a bureauwide GIS policy statement to establish a sound GIS research base, to conduct cooperative application projects, to exchange digital data bases, and to provide a funding mechanism for encouraging the use of this new tool in USGS investigations.

Specific goals in the policy statement include:

• GIS research—Investigate advanced techniques to exchange digital spatial data; explore advanced computer-system architectures and techniques using improved data structures; apply knowledge-based inference models, expert systems, and natural query languages to multiple digital data bases and existing spatial datahandling techniques; and apply GIS technology to major missions of the Survey.

• Multidisciplinary demonstration projects—Develop projects that involve the USGS and local, State, and other Federal agencies, and provide those agencies with training and assistance in GIS technology and applications. Implement interdivisional application projects within the Survey to broaden GIS expertise and expand the existing network of shared resources (hardware, software, and data bases) and technique development.

• Federal government coordination— Encourage governmentwide GIS education, technology transfer, and definition of GIS research requirements through committees such as the Interior Digital Cartog

Facing page photograph by Mark A. Hardy, U.S. Geological Survey

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raphy Coordinating Committee and the Federal Interagency Committee on Digital Cartography.

• Exchange of earth-science and other spatial data—Develop automated interfaces among various earth-science data bases and GIS's and make it easier to access and exchange digital spatial data bases by developing standards for earthscience data.

In fiscal year 1987, the USGS established a GIS Research Laboratory in Reston, Virginia (fig. 1), to provide an interdivisional, multidisciplinary environment for research, development, and application of GIS technology. Additional GIS facilities are being established in Denver, Colorado, and Menlo Park, California, and capabilities are being increased in an existing facility in Sioux Falls, South Dakota. Future expansion of GIS capability is planned for Survey offices in Rolla, Missouri, and Anchorage, Alaska. This concentration of GIS technology and resources at key locations will make available a broader range of computer-based hardware and software than is now available at dispersed field locations.

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At present, GIS activities in the Survey represent a broad-based, bureauwide approach to developing GIS technology in support of national earth-science information needs. The Information Systems Division is assessing GIS hardware capabilities and microcomputer applications, developing the Earth Science Information' Network and the Earth Science Data Directory, and studying the merging of artificial intelligence and GIS technologies. The Geologic Division is using GIS software capabilities such as gridding, contouring, feature extraction, overlay, and display to manipulate and analyze geologic data. The Water Resources Division, the largest user, has GIS facilities in 40 of its State locations and has linked them with a distributed information system called GEONET. The National Mapping Division is developing advanced techniques for spatial data manipulation, analysis, and display.

Cooperative Projects Using Geographic Information Systems

In addition to the GIS projects underway within the Survey, the bureau is also working with other Federal and State agencies on a number of cooperative GIS projects (fig. 2). The projects are geographically dispersed and the objectives are varied, ranging from the study of pollution in the Elizabeth River, Virginia, to the determination of potential landslide areas in California. The foiiowing descriptions of several of the projects illustrate how GIS technology can be used to combine, analyze, and display a variety of digital data to suit a broad range of objectives.

In the Elizabeth River Project, more than 30 earth-science and natural-resource data bases are being integrated in a GIS to study pollution problems in and near Norfolk, Virginia, in cooperation with the U.S. Environmental Protection Agency. The Elizabeth River basin, in southeastern Virginia, drains approximately 205 square miles of some of the most heavily industrialized and developed areas on the Chesapeake Bay watershed. A GIS will be used to study and analyze the interaction between the ground-water system and the river, including the relationship of groundwater flow to the potential movement of toxic chemicals.

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Pothole locations Drainage basin bounds Overflow points

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Figure 3. Analysis of test site 3 from the lames River Hydrology Project. Above, Computerdelineated potholes are shown in red draped on a shaded-relief presentation of elevation data. Below, Potholes that were selected for runoff modeling are shown with their watersheds and pour points and sample tabular information.

Figure 4. Bedrock geologic map of test area in western Maine near Kingfield. Map was digitized from the Maine Geological Survey's 7985 Bedrock Geologic Map of Maine.

Figure 5. Color composite image of same area with digitized geologic contacts and faults superimposed. The image, centered on the Lexington batholith, combines magnetic and gravity data to show subsurface details. Coincident magnetic and gravity lows produce blue or black areas, such as over the Lexington batholith. The batholith is probably thickest beneath the blue area. Coincident highs produce yellow or white areas and commonly indicate mafic rocks. Coincident magnetic highs and gravity lows produce magenta areas and commonly indicate pyrrhotite-rich metamorphic rocks. The image represents one of many combinations of geophysical and geologic data of the area.

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gon is the development of a prototype GIS for use by State agencies in the management of water resources. A central repository of spatial information about the river basin will provide query, analysis, and display capabilities for developing watersupply and water-management alternatives. In a second phase, the GIS will be used to prepare a management document that will describe existing conditions of natural resources, predict future conditions, and suggest management alternatives for achieving various levels of development in the basin.

The Quebec-Maine-Gulf of Maine Global Geoscience Transect Project will use a number of different GIS's to integrate geologic, topographic, magnetic, gravity, and seismic reflection and refraction data to create three-dimensional models of the Earth's crust. The transect is approximately 880 km (500 miles) long, 100 km (60 miles) wide, and as much as 50 km (30 miles) deep, beginning in southeastern Quebec, crossing Maine to Penobscot Bay, and continuing from Penobscot Bay across the Gulf of Maine to Georges Bank and the continental edge. Digital data for a test area approximately 50 by 75 km (30 by 45 miles) near Kingfield, Maine, have been used to evaluate the models and processes that will be applied to the larger study area (figs. 4, 5).

GIS for the Future

In addition to the projects mentioned, numerous other projects are underway, including the application of GIS technology to resource management in the greater Yellowstone area in Wyoming, Montana, and Idaho; the assessment of irrigationdrainage quality near Dakes, North Dakota; and the geochemical interpretation of soil, shallow aquifer material, and ground water in the Carson River basin, Nevada-California.

The powerful capabilities of GIS's offer new possibilities for integrating, analyzing, combining, and comparing earth-science data obtained from a variety of sources. The USGS will continue to investigate new ways to apply this tool in mission-oriented studies and in the generation of digital and graphic products to fulfill earth-science information needs.

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