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Digital Mapping Techniques '00 -- Workshop Proceedings
U.S. Geological Survey Open-File Report 00-325

Digital Geologic Map Production at the North Carolina Geological Survey

By Jeffrey C. Reid, Michael A. Medina and Mark W. Carter

Division of Land Resources
North Carolina Geological Survey
1612 Mail Service Center
Raleigh, NC 27699-1612
Telephone: (919) 733-2423
Fax: (919) 733-0900


Geologic map production at the North Carolina Geological Survey (NCGS) increasingly uses MapInfo Professional 5.5 for digital geologic map preparation and layout. Field sheets are digitized using GSMCAD (Williams, 1999). Files are imported into MapInfo as .dxf files. Digital raster graphic (DRG) 7.5-minute topographic maps provide the base; DRGs are projected to state plane coordinates or UTM coordinates in NAD27 or NAD83 projection. Paint Shop Pro (ver. 5.01) is used to remove the green overprint and to greyscale the DRGs. On-screen digitizing is becoming more commonly used.

Several 7.5-minute geologic maps in the Raleigh 1:100,000-scale sheet (a STATEMAP project area under the National Geologic Mapping Act) were created using MapInfo and released this year as NCGS Open-File Reports. Additional 1:100,000-scale county maps were created with MapInfo depicting active and inactive mine subsidence issues. These maps, also to be released as Open-File Reports, were designed to be used by county and city planning departments.

Digital orthophoto quarter quadrangles (DOQs) are used as a base in some projects. DRGs and DOQs are registered using WorldReg software. Geologic map symbols come from either GSMCAD (Williams, 1999) or in some cases from Geosymbol -- a MapInfo add-on from Data Directions. Both programs are fully compatible with MapInfo software. Shape files are produced as needed for users of ArcView. Files in other formats are produced as needed for clients.

Experiments in Geologic Map Production
The NCGS continues to experiment with several means of geologic map production. These experiments include: 1) using Mr. Sid technology on a map server to access the raster version of the state geologic map (NCGS, 1985) and generalized geologic map (NCGS, 1991) at the NCDOT's Travel and Tourism's Internet site (\Geologic_Maps/) and, 2) use of PDF files to produce camera-ready color printing pre-press and printer's color separations (Clark, 1999). Map production is limited to paper. No digital geologic maps, other than the 1985 state geologic map (NCGS, 1985), are contained in the state's corporate database.

Issues in Geologic Map Production in North Carolina
Key issues in geologic map production in North Carolina are: 1) an estimated five-year production backlog of 7.5-minute geologic maps produced from 1968 to the present under the auspices of several cooperative mapping agreements with the Tennessee Valley Authority (TVA) and the USGS, including, most recently, STATEMAP, 2) geologic map production funding, and 3) metadata requirements. Additional resources will also be needed to digitally update the state geologic map (NCGS, 1985) which will soon go out-of-print. A related concern is the need for statewide vector hypsography.

Innovative techniques are being considered to relieve the backlog of TVA-era manuscript maps. These techniques have scanning and production of raster images as a common theme. Production may include CD-ROM venues using MapInfo Proviewer and PDF file formats.

North Carolina now requires that all digital maps, including geologic maps, be accompanied by metadata. In addition, complete metadata is required for a map to be included in the state's corporate database. Since many geologic maps consist of diverse base materials and, in many cases, the author is deceased or cannot be contacted, documentation of these maps is difficult. Thus, digital map production is slowed. Writing full FGDC compliant metadata may take almost as long as cartographic map production. Image files (e.g. PDF, GIF and TIFF) formats are a temporary solution for dissemination on the Internet. However, these do not result in the digital geologic map data being collected, stored, and maintained in the state's corporate database. Provisional vector digital map layers, such as the 1985 state geologic map, are available on a mapping application site hosted by the Information Technology Services group of the Department of Environment and Natural Resources, and at the NC Center for Geographic Information and Analysis.

In North Carolina, the Freedom of Information Act requires that digital geologic information also be available in hard-copy format. Over the past several years, the North Carolina Geological Survey has explored methods to construct and publish geologic maps "in-house", yet retain the data in GIS-compatible formats. Our primary goals for map production are to reduce (1) the cost of printing highest-quality "traditional" maps, and (2) space (and cost)-consuming inventory.

One method employs GSMCAD 1.3, Adobe Illustrator 8, and MAPublisher 3.5. MAPublisher 3.5 is a suite of Plug-in GIS filters for Illustrator which was developed by Avenza Software (Muleme, 1999). This map production method is nearly identical to that currently in use by the USGS, Central Publications Group of the Geologic Division (Lane and others, 1999).

The procedure includes: (1) digitizing field-collected point and line data using a CalComp DrawingBoard III digitizing tablet and GSMCAD; (2) exporting the GSMCAD files as ArcView shapefiles (the ArcView shapefiles form the basis for both the final hard-copy map and the digital geologic dataset); (3) importing the shapefiles in Adobe Illustrator via MAPublisher to construct the traditional paper-printed map; and (4) printing the map in Illustrator format using either in-house equipment or a local blueprint shop. This process was used to reproduce a limited number of copies.

The high-end graphics capabilities of Illustrator allow for further cartographic editing of the geologic data, which is then merged with a 7.5-minute DRG topographic base (Adobe Photoshop 5.5 is used to convert the DRG to a grayscale bitmap or TIFF image) (Carter and Weiner, 1999). For smaller-scale maps such as county geologic maps (Carter and Merschat, in prep), a wholly vector-based base map can be constructed in Illustrator from hydrography and cultural (roadway and railroad networks) vector files available from the NCDOT or USGS. Ancillary geologic information, including cross sections, detailed rock unit descriptions, stratigraphic correlation diagrams, tabulated whole-rock geochemical data, references, etc. are constructed in Illustrator and incorporated into the map layout, which is limited only by the dimensions of the print media (typically 34" x 44").

In a small agency such as the NCGS, the field geologist is also typically the cartographer. This is advantageous because the map author is given tighter control over cartographic decision-making. It also allows for editing and interpretation of the geologic data throughout the map-making process--from field collection to final printing.


Carter, M. W., and Merschat, C. E., in preparation, The geology of Avery County: North Carolina Geological Survey Geonotes.

Carter, M. W., and Weiner, L. S., 1999, Bedrock geologic map of the Fines Creek 7.5-minute quadrangle, North Carolina: North Carolina Geological Survey, Geologic Map Series 8.

Clark, Timothy W., 1999, America's First State Geologic Map (175th anniversary poster), NC Geological Survey Geologic Map 7, in color.

Lane, D. E., Donatich, A., Bruinstein, F. G., and Shock, N. A., 1999, Digital geologic map production and database development in the Central Publications Group of the Geologic Division, U.S. Geological Survey, in D.R. Soller, ed., Digital Mapping Techniques '99 - Workshop Proceedings: U.S. Geological Survey Open-File Report 99-386, p. 11-15,

Muleme, S., 1999, Avenza's MAPublisher, in D.R. Soller, ed., Digital Mapping Techniques '99 - Workshop Proceedings: U.S.Geological Survey Open-File Report 99-386, p. 17-18,

NCGS, 1985, 1985 State Geologic Map of North Carolina: North Carolina Geological Survey, Raleigh, scale 1:500,000, in color.

NCGS, 1991, Generalized Geologic Map of North Carolina: North Carolina Geological Survey, Raleigh, 11 inches by 17 inches, in color.

Williams, V.S., Selnar, G.I., and Taylor, R.B., 1999, GSMCAD, version 1.3: U.S. Geological Survey Open-File Report 96-007,

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