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movement and fate of hazardous substances in hydrologic systems. The effects of high selenium levels associated with irrigation return waters in the southwestern San Joaquin Valley of California became an issue of intense concern in 1984. Our scientists are working closely with colleagues in the Bureau of Reclamation, the Fish and Wildlife Service, and State agencies to identify geochemical pathways of the selenium in waters of the agricultural systems and wildlife lands of that area.

The worldwide availability of strategic minerals is another concern of critical national interest. In recent years, as the United States began to rely more on imports to satisfy mineral needs, the Geological Survey responded with new programs of basic research and evaluation of mineral resources. These programs have included the Conterminous United States Mineral Appraisal Program, a similar appraisal program of Alaska, and assessments of approximately 50 million acres of Federal wilderness lands throughout the country. The publication in 1984 of Professional Paper 1300, Wilderness Mineral Potential, was a significant milestone in our long-term efforts to thoroughly characterize the mineral wealth of the Nation. This comprehensive volume summarizes 20 years of cooperative studies with the Bureau of Mines and the Forest Service.

The establishment in 1983 of the U.S. Exclusive Economic Zone (EEZ) 200 nautical miles seaward from the Nation's coastline tremendously increased the area within which mineral and energy resources must be assessed. In 1984, the Geological Survey completed detailed geophysical surveys of the Juan de Fuca and Gorda Ridges in the Pacific in cooperation with the Hawaii Institute of Geophysics, completed sonar mapping of 250,000 square miles of the west coast EEZ, and conducted a major scientific cruise to identify likely areas of potential seafloor minerals in the zone surrounding United States island territories in the Pacific. In addition to exploration of the EEZ, Geological Survey crews on the Research Vessel Samuel P. Lee accomplished the first comprehensive geophysical survey of the Antarctic continental

margin to be made by an American expedition. An intensive multidisciplinary resource appraisal program for the EEZ, begun in 1984, will be continued, concentrating on specific geologic provinces within the zone. The Nation must establish a solid scientific framework for the exploration and development of this new frontier, because the beginning of resource development by industry in the EEZ will depend on there being sufficient evidence that a substantial potential exists for energy and mineral resources.

By far the most pervasive technological change affecting us in recent years has been the greatly expanded use of computers. The automation of spatial data has made it possible to create digital models of the Earth's surface, for both natural and manmade features. These basic spatial data can be manipulated and combined in any desired format in the computer. Products designed and prepared on the computer have become part of our routine mapping processes. Together, the various types of digital cartographic data that are being assembled constitute the National Digital Cartographic Data Base. We continue to compile and manage large volumes of resource data, including data on water, coal, petroleum, and mineral resources, in digital data bases. Not only have we developed the means to acquire and store these diverse data, but we also have developed innovative new programs to manipulate and effectively use these large volumes of data; for example, our water simulation models mathematically evaluate the effects on water quantity and quality from such complex and interrelated causes as changes in rainfall and irrigation pumping rates.

An essential part of the Geological Survey mission has always been the dissemination of the results of scientific data collection and research. During this year, we published more than 4,900 technical reports and 6,600 new maps, which are still our primary channels of information dissemination. Our dissemination function has been enhanced by the use of digital data and direct computer access to make information more readily available to the public. The National Cartographic Information

Center provides access points across the country for machine-readable tapes of cartographic and geographic data. The National Water Data Exchange functions as a clearinghouse for locating and facilitating access to water resource data. New procedures for managing information in the National Digital Cartographic Data Base will result in significant overall savings to the Federal Government. In cooperation with the Bureau of the Census, we are preparing digital l:100,000-scale map data for the entire conterminous United States that will provide essential support to the 1990 Decennial Census.

An important new publication that deserves special mention is the National Water Summary, an annual overview of water conditions and concerns throughout the Nation. In 1984, we issued the first summary, and the second edition is now in the advanced stages of preparation. The information in each Summary is obtained through research and investigations supported by many of the 800 State and local agencies that are cooperators in our Federal-State Cooperative Program and by other Federal agencies.

Finally, on a more personal note, but one that I am certain is shared by all my colleagues: The high point of the year for me was the opportunity in

September to honor two of the finest leaders of the Geological Survey family, Dr. Thomas B. Nolan and Dr. Vincent E. McKelvey. Tom was presented with a 60-year pin and a letter from the President congratulating him for his long service to the Nation. We surprised Vince by dedicating our new annual forum on energy and mineral resources as the McKelvey Forum. These two men have between them more than 100 years of service as geologists, public servants, and Directors of the U.S. Geological Survey. We could ask for no finer examples to guide us as we pursue our second century of providing "earth science in the public service."

The foresight of the Geological Survey's past leaders in encouraging the highest standards in our work and in the hiring of highly professional people at all levels has enabled us to build on their foundation and make a real contribution to the needs and progress of the Nation. As we face new challenges in future years, we must continue to maintain our historic standards of excellence and to strive for the highest levels of accomplishment. Our success will depend on the awareness, enthusiasm, and commitment of our people for their strong tradition of serving the Nation as its principal source of earth science information.

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Perspectives

l:100,000-Scale Digital Cartographic Data Base For Federal Requirements

By Stephen C. Guptill

Background

The increasing demand of the Nation's natural resource managers for the manipulation, analysis, and display of large quantities of earth science data has necessitated the use of computers and the building of geographic information systems. Traditional data formats and manipulation techniques are inadequate to meet the demands of today's scientists and information analysts. In the past, most data were presented as maps, tables, and textual reports. Each organization collected data in a different way and produced their output in various formats. The scales of such graphics as maps are different, the data codes used to identify certain elements differ from agency to agency, and the data formats are difficult to correlate; for example, geologic data in map form are difficult to correlate with census tabulations in computer-readable form. Such data formats are difficult to change, thus slowing the evaluation process. Usually, data prepared and presented in a form to address specific problems do not lend themselves to the consideration of alternatives, and it is time consuming to incorporate new data into out-of-date graphic materials. To help overcome these problems, computers and geographic information systems can provide a common language. These systems require, in digital form, the spatial data on map products. Only recently has it become technologically feasible and cost-effective to assemble and use data bases containing large amounts of digital spatial data.

For a number of years, the U.S. Geological Survey has been pursuing the development of a Digital Cartographic Data Base. The initial plans were for the data base to consist of boundaries, public land net, streams and water bodies, and transportation features shown on l:24,000-scale maps; elevation

data largely obtained concurrently with the orthophotoquad program; planimetric features from the l:2,000,000-scale sectional maps of the National Atlas of the United States of America; elevation data obtained from the l:250,000-scale map series; land use and land cover and associated map data; and geographic names. Because of a number of technological developments and programmatic opportunities, the scope of the data base has been increased to include digital cartographic data collected from l:100,000-scale base maps. These data will provide complete coverage of such transportation features as roads, railroads, powerlines, and pipelines and such hydrographic features as streams, rivers, and water bodies. This major new effort will attempt to achieve nationwide coverage by the end of the decade.

The decision to create this data base was reached, in part, through the combination of two forces: the maturing of efficient and economical data capture technology and the requirements expressed for a major use of the data. The l:100.000-scale map series was designed to facilitate automated data capture; for example, by raster scanners. The methodologies and procedures used in the data capture process have developed enough so that we can take advantage of the design features of the l:100,000-scale maps and rapidly build a digital cartographic data base. Once these data are produced, the U.S. Bureau of the Census intends to use them as the cartographic framework of their geographic support system for the 1990 Decennial Census. The collaboration of a major data producer with a major data user at the inception of this project augurs well for the successful creation of an intermediate-scale digital cartographic data base that will meet national needs.

Data Base Description

l:100,000-Scale Maps

In the mid-1970's, the Geological Survey began its program of l:100,000scale mapping. The level of content was determined mainly by evaluating the content of the l:24,000-scale maps. Each feature shown at l:24,000 was evaluated and designated "include" or "exclude" at l:100,000. The drawing (feature separate) on which the feature would be shown also was determined. The colorseparation system of map production, in which a separate drawing is prepared for each color to be printed, was expanded to a feature-separation system. In the new system, such major components of the map as roads and hydrography are subdivided into classes, and separate master scribed drawings are prepared for each class (fig. 1).

Tho frnmnwork and content of tho l:100,000-scale base maps are derived primarily from l:24,000-scale maps, with updates during the production process. This production process generally has the following phases: (1) reducing larger scale maps to l:100,000 scale and mosaicking on the Universal Transverse Mercator projection, (2) updating the mosaicked base, (3) scribing the planimetric feature separate manuscripts, (4) scribing the contour manuscript, and (5) printing the complete metric topographic edition. If the base map material is less than 3 years old, only major features are updated. Material older than 3 years often requires more extensive planimetric updating. High-altitude aerial photographs are frequently used as the source of the update (figs. 2, 3).

A number of design characteristics of the l:100,000-scale maps were chosen for compatibility with automated digitizing techniques. These

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