OF-99-386: Alabama Aquifer Vulnerability CD-ROM Project

Digital Mapping Techniques '99 -- Workshop Proceedings
U.S. Geological Survey Open-File Report 99-386

Alabama Aquifer Vulnerability CD-ROM Project: Digital Publication of GIS-Derived Map Products

By Berry H. Tew and Ruth T. Collier

Geological Survey of Alabama
420 Hackberry Lane
Tuscaloosa, AL 35486
Phone: (205) 349-2852
Fax: (205) 349-2861
e-mail: Ntew@gsa.state.al.us
Rcollier@gsa.state.al.us

INTRODUCTION

The Geological Survey of Alabama (GSA), in cooperation with and with funding from the Alabama Department of Environmental Management (ADEM), is producing a series of interactive CD-ROMs that provide an assessment of the vulnerability of ground-water aquifers in Alabama to potential contamination from surface sources. For the purposes of this project, the state has been divided into 13 areas and a CD-ROM will be developed for each. The CD-ROM for the first area to be studied, which includes the coastal counties of Alabama (Mobile and Baldwin), has been compiled as a prototype for the series. The CD-ROM for each area will contain an interpretive report, including text, tables, figures, and plates, developed in Adobe Acrobat format; a complete suite of the GIS data sets used for, or produced as part of, the project; and other pertinent and useful data layers (United States Geological Survey (USGS) Digital Raster Graphics (DRG) topographic maps for the area, roads, streams, etc.). All GIS data produced for this project are being developed as ESRI, Inc. ArcView shapefiles, using ArcView 3.1.

The Digital Geologic Map of Alabama (1:250,000-scale) is being used as a primary source of data for the aquifer vulnerability project, and the recharge areas for the major ground-water aquifers in each area are being derived from this GIS data set. A second derivative layer delineating the level of aquifer vulnerability to surface contamination will be produced for each area.

Along with the interpretive report and the GIS data, each CD-ROM will contain ESRI, Inc.'s free GIS tool, ArcExplorer, and the Adobe Acrobat Reader. Thus, users will be able to interact with the included data regardless of the availability of a commercial GIS software package.

A key element to the successful production of the CD-ROMs for this project is the conversion of map layouts, especially plate-size maps (24" x 36" and larger), created from the GIS data sets in ArcView, to high-quality, high-resolution Adobe Acrobat (.pdf) files for digital publication. This paper will detail some problems that were encountered during this conversion process and successful solutions that were employed to achieve the desired results.

PROJECT BACKGROUND

During the mid- and late-1980s, the USGS, in cooperation with ADEM, produced a series of reports that delineates the major aquifers in Alabama and characterizes their vulnerability to surface contamination. To prepare these reports, the state was divided into 13 geographic areas and each of these was addressed in a separate report (e.g., Mooty, 1988). These reports were widely disseminated and used by ground-water resource professionals in the state, as well as by the general public. Data for the reports were compiled at the 1:250,000-scale using the best available geologic maps to delineate aquifer recharge areas. For example, one source of data for the reports was the 1926 Geologic Map of Alabama (1:500,000 scale), which was at that time was the most up-to-date and detailed statewide geologic map available. Further, the USGS reports were compiled and published before the widespread usage of GIS technology and thus were developed as purely analog products with little consideration given to possible future digital conversion.

In 1988, the GSA published the first statewide geologic map of Alabama based on new mapping and compilation since the 1926 map. The publication of GSA Special Map (SM) 220, Geologic Map of Alabama (Szabo et al., 1988) was the culmination of decades of work by numerous geologists, including not only those affiliated with GSA, but a number of others involved in mapping the geology of Alabama for various purposes. SM 220, published at the scale of 1:250,000, comprises the largest scale and most accurate border-to-border depiction of Alabama's geology as presently understood. In 1996 and 1997, the GIS Group at GSA successfully undertook a digital conversion of the 1988 geologic map, thus providing a robust GIS data set of Alabama's surface geology (Tew et al., 1998).

By the mid-1990s, it was widely recognized that the original aquifer vulnerability reports, although having served their purpose well, were badly in need of revision and update in order to remain useful. In addition to the availability of a new geologic map for the state, numerous new data related to aquifers and ground water in Alabama had been collected in the ensuing years due to drilling of new water wells and various monitoring programs and research efforts. For example, the early 1990s saw the development of numerous wellhead protection programs around the state designed to meet the requirements of amendments to the Safe Drinking Water Act originally enacted by Congress in 1974. The 1986 amendments directed the U.S. Environmental Protection Agency to oversee the states' development of plans and programs to protect areas providing ground water to public water supply wells or springs. ADEM administers Alabama's Wellhead Protection Program (WHPP) which requires a geologic and hydrologic evaluation, delineation of wellhead protection area boundaries, and a potential contaminant source inventory for public drinking water supply wells and springs. Thus, development of the WHPP resulted in an abundance of new ground-water-related data for many parts of the state.

In 1997, personnel in the Ground Water Branch at ADEM contacted GSA relative to development of a project to update and revise the original thirteen aquifer vulnerability reports. During the course of discussions regarding the project, several desirable outcomes were enumerated. First, it was decided that the 13 geographic areas of the original reports were familiar to the user base and should be retained as the basic format for preparation of the new reports. Second, it was determined that data for the reports should be compiled at the 1:100,000 scale, where possible, rather than at the 1:250,000 scale of the original reports. Third, it was agreed that all data for the project should be developed digitally in a GIS environment, should result in useful, comprehensive GIS databases for ground water resources in Alabama, and should be fully documented with Federal Geographic Data Committee (FGDC)-compliant metadata. Fourth, it was deemed necessary that data in individual data layers should be consistent and seamless from area to area so that each layer would eventually constitute border-to-border coverage for Alabama at project completion. Fifth, it was decided that the resulting interpretive reports, GIS data, and metadata should be compiled and distributed in CD-ROM format and that the CD-ROMs should provide interactivity between the data and the user. Sixth and finally, a determination was made that the CD-ROM should include a GIS data browser so that the user would not be required to have access to commercial GIS software to interact with the included data.

To facilitate the desired project outcomes, a project plan was developed by GSA and presented to ADEM. The primary elements of the plan included the following: evaluate, revise, and recompile data from the original reports as appropriate; compile new data; develop necessary GIS data layers, including incorporation of existing digital geospatial data where appropriate; develop interpretive reports on the basis of spatial analysis and hydrogeologic research; and, publish the reports and geospatial data on an interactive CD-ROM. This project plan was approved and the project was initiated in the fall of 1997.

DIGITAL PUBLICATION OF GIS-DERIVED MAP PRODUCTS

As indicated above, GIS data layers associated with the aquifer vulnerability CD-ROM project are being developed as ESRI, Inc. ArcView( shapefiles owing to the fact that ArcView( GIS software is in widespread use among ground-water professionals and many others in Alabama. Thus, developing data in shapefile format alleviates many issues associated with data transfer and ease of use. Consequently, the majority of illustrations for the interpretive aquifer vulnerability reports, primarily consisting of maps, are being developed using the page layout tools in ArcView. These maps range from rather simple, page size (8.5" x 11") illustrations depicting one or two data themes to complex, plate size (24" x 36") maps that illustrate multiple data themes and the results of various spatial analyses and contain large areas of color and pattern fill. Although the data used to generate the maps are being provided on the CD-ROM, allowing the user to interact with the data for their own applications and visualizations, providing a high quality, high resolution, static version of each map generated by the research hydrogeologists at GSA as part of the Adobe Acrobat-formatted interpretive report for screen viewing and printing is desirable. Thus, it is necessary to convert ArcView layouts into Adobe Acrobat documents for integration in the reports. As we prototyped the project, we discovered that this conversion process is not entirely straightforward.

The most direct method to create an Acrobat .pdf file from ArcView is to print from the ArcView layout to the Adobe Acrobat PDFwriter, a virtual Postscript printer that is included with the Adobe Acrobat distribution. Using this method, print resolution is user-selectable up to 600 dpi. Basically, ArcView creates a Postscript file from the layout and sends it to the PDFwriter. The next-most direct method is to export a Postscript file from ArcView and then use Acrobat Distiller, a .pdf creation utility included in the Acrobat distribution, to "distill" the Postscript file into an Acrobat file. Again, resolution is user-selectable up to 600 dpi. Both of these methods result in beautiful, high-resolution .pdf versions of the original ArcView layouts and either method is excellent for the creation of Acrobat documents from small, relative simple layouts. However, owing to the manner in which ArcView writes Postscript, large and complex layouts such as the plate-size maps from our project take an inordinate amount of time to draw (and redraw after zooming, resizing, etc.) on the screen. An Acrobat .pdf file created from a typical plate in the aquifer vulnerability project can take two minutes or longer to fully redraw. We explored taking the ArcView generated Postscript files through a "middleware" procedure, such as opening the file in Corel Draw or other software packages and printing to the PDFwriter, as well as using the Save As command and "distilling" the resulting file through Acrobat Distiller, but these procedures did nothing to eliminate the problems with screen draws and redraws. The lengthy draw times associated with Acrobat files created from ArcView-generated Postscript were deemed unacceptable for our purposes and we set about trying to develop a workaround procedure that provided a reasonable compromise between file resolution and drawing time.

The first procedure that we explored involved using an export option from ArcView other than Postscript. The idea was to export in a format (such as JPEG) that could be read by an intermediate software package (such as Adobe PhotoShop) that could then, in turn, be used to produce the Acrobat documents using the PDFwriter. This method produced less than desirable results due to the ArcView's limitations for export resolution in most file formats. For most formats, such as JPEG and Windows Metafile, the maximum resolution for export from ArcView is 144 dpi. At this resolution, plate-size maps are entirely too "jaggy" in appearance and, for the most part, barely legible. However, drawing times for the resulting .pdf files are extremely rapid.

On the basis of the experiences with the above procedures, it was determined that the most likely chance of success lay in identifying a software application with the capability to directly open a high-resolution ArcView Postscript file and save this file in an image format, such as JPEG, at a relatively high resolution, which could then be opened and printed to Acrobat format using the PDFwriter. We were aware that Aladdin GhostScript, a free software package (<http://www.cs.wisc.edu/~ghost/aladdin/get550.html>), had the ability to work with, and convert between, a number of file types and so we decided to experiment with GhostScript to determine if its capabilities suited our needs. We acquired a copy of GhostScript 5.50 for Windows NT and its graphical interface module, GSView 2.70, and immediately determined that the package could open an ArcView PostScript file. Further, GhostScript has the capability to "print" the open file to a 300 dpi JPEG file. We worked through this procedure with one of the large, complex maps from the aquifer vulnerability project and opened the resulting file in Adobe PhotoShop LE. The quality of the JPEG image was excellent. However, file size was rather large owing to the fact that the GhostScript JPEG file contained red/green/blue (RGB) color. To reduce file size, the RGB file was changed to Indexed Color within PhotoShop LE. We then printed the file to the PDFwriter and opened the resulting Acrobat file with Acrobat Reader to test legibility and resolution, as well as drawing time. The file opened quickly, redrew quickly, and the overall quality was quite good. Thus, the experiment using GhostScript as a "middleware" application was successful. Subsequently, we have used this procedure to produce Adobe Acrobat files from ArcView layouts with excellent results.

SUMMARY

The joint GSA/ADEM aquifer vulnerability CD-ROM project required the digital publication of map products generated from layouts in the ArcView 3.1 GIS software package as Adobe Acrobat .pdf format files. Direct conversion of ArcView layouts to Acrobat files, especially when dealing with large, complex map compositions, proved to result in Acrobat files that were unacceptable due to inordinately long draw and redraw times. Several procedures were explored in attempts to address this problem, but most resulted in quick file draw time, but unacceptable maps due to low resolution. One procedure, however, employing Aladdin GhostScript 5.50 for Windows NT and Adobe PhotoShop LE as "middleware" applications, resulted in Acrobat format files that opened and redrew quickly and were of high quality in terms of resolution. Thus, a successful methodology for digital publication of large, complex ArcView map layouts in Adobe Acrobat format was developed.

REFERENCES CITED

Mooty, W.S., 1988, Geohydrology and susceptibility of major aquifers to surface contamination in Alabama; Area 13: U.S. Geological Survey Water-Resources Investigations Report 88-4080, 29 p.

Szabo, M.W., Osborne, W.E., Copeland, C.W., and Neathery, T.L., 1988, Geologic Map of Alabama: Geological Survey of Alabama, SM 220.

Tew, B.H., Taylor, D.T., and Osborne, W.E., 1998, Production of the 1:250,000-Scale Digital Geologic Map of Alabama, in Soller, D.R., ed., Digital Mapping Techniques '98--Workshop Proceedings: U.S. Geological Survey Open-File Report 98-487, p. 5-7, https://pubs.usgs.gov/openfile/of98-487/tew.html.

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