USGS Geologic Division Publications
Requirements for Digital Map Products

NOTE: this Policy was instituted May 24, 1999

Our scientific information supports the needs of a broad range of users. To increase its utility and to promote integration with related data sets produced by other organizations, our information should be readily available, well-documented, and well-structured. To support these goals, the Geologic Division Policy Manual (GDPM) chapter 6.1.3 requires that all Division map products be produced and distributed in electronic form, at a minimum. In addition, Geologic Division Memorandum No. 99-06 requires MF and I-maps to include a digital spatial database, where map content permits.

For maps, certain technical requirements for Director's Approval are described below. These requirements are addressed to map authors and members of the Division publications groups who, together, are responsible for producing maps for the public. The Geologic Division Information Council, composed of representatives of the scientific programs and the publications groups, drafted these requirements. The requirements are based on an October, 1996 interim guideline for submission of maps to the National Geologic Map Database.

In the transition from production of maps solely on paper to production of maps in digital format as well, the map's geographic, cartographic, and scientific information has been transformed from a strictly visual medium to one based on electronic files. "Digital" maps now commonly contain the coordinates for various map features, and a database of information about the features, which users may analyze. This document addresses the requirements for preparing a single digital map product for Director's Approval, and does not address the integration of data across maps of adjacent areas.

The Division policy and these requirements support, and are consistent with, Executive Order 12906 (which established the National Spatial Data Infrastructure) and Bureau requirements, especially SM 504.1. These policy statements are based on current (1999) technology and personnel structure, and may be modified as needed.

    Digital map database products (referred to as "products", below) will conform to guidelines for approval and publication as stated by the Division and Bureau, including the requirements of Executive Order 12906, USGS Manual chapter 504.1, GDPM chapter 6.1.3, and Geologic Division Memorandum No. 99-06.

    These requirements apply to products intended for release to the public in the formal and open-file series, and in external series as defined by Division policy. All products must be submitted through the Division publications groups for Director's approval. A product must conform to these requirements before Director's approval is granted. Conformance is the author's responsibility. The work needed to achieve conformance may be done by the author's submitting team or by the publications group, as defined in the product's publications plan.

    All vector map data (including point data) must be provided in: a) the Topological Vector Profile (TVP) of the Spatial Data Transfer Standard (SDTS), as required by Bureau policy, and b) Arc/Info format (Shape and/or Export), as required by GDPM chapter 6.1.3. All raster map data must be provided in: a) the SDTS Raster Profile, and b) Arc/Info Export format. Until vendor software is written to import and export SDTS files, authors may substitute a common, non-proprietary format (e.g., GEOTIFF). If the raster map data were not developed using Arc/Info Grid, then another common format may be substituted. Additional vector or raster formats, whether proprietary or not, may be included in the product. All data (both raster and vector) not appropriate to an SDTS transfer must be included in a non-proprietary format and also may be included in proprietary formats. If data are expressed in non-proprietary formats that are not supported by published documentation, those formats must be fully and clearly documented in the product.

    All associated files, tabular and otherwise, containing attribute data must accompany the map data files and, as much as is practical, be expressed in the non-proprietary data format used for the map. They also may be expressed in proprietary formats. Relevant data that is not compatible with the non-proprietary format must be included in some other format (e.g., summary data not associated with a spatial location could be provided in a plain text format). Lookup tables and color and line palettes (e.g., Arc/Info symbolsets and shadesets) also should be provided to permit users to display the map data interactively to a monitor.

    For the widest possible usage, file names must conform to the "8.3" convention. This convention requires that file names be limited to 8 characters or less, followed, if appropriate, by a period and a 3-character extension. An example would be the file name "readme.txt". The name and extension must be entirely composed of lower-case (not mixed-case) letters, numerals, underscore, and hyphen. The name must begin with a letter.

    Map data provided in geographic coordinates (latitude and longitude) is most generally useable. By definition, the vector map data in SDTS format is required to be in geographic coordinates. For other formats included in the product, the author may choose to provide the map data in geographic coordinates and/or in projected coordinates, in the map projection and ground units typically used for maps of that scale and location (e.g., the UTM projection for 30-minute by 60-minute,1:100,000-scale quadrangle maps, with ground units in meters). To avoid loss of data quality due to resampling during projection, raster thematic data should at least be provided in the original, unprojected form.

    Wherever possible, map products should be georeferenced to a digital base, preferably the one on which the map was compiled. As a service to users, the author may elect to include the base map with the product; this is required if the base is not published or is not commonly available. If a digital base was used, and if the base was revised to correct for spatial or attribution errors, it must be supplied (in vector or raster format) with the product. Revisions to published base maps must be supported with metadata that describes the data processing. However, not all geologic maps are compiled on a digital base, generally because one is not available. In such cases, it is suggested but not required that a) the base be scanned and georeferenced, b) the geologic map be geoferenced to the base, and c) the base be provided, in vector or raster format, with the product.

    All geologic and base map data must be documented with metadata conforming to the Content Standard for Digital Geospatial Metadata (CSDGM) of the Federal Geographic Data Committee (FGDC). Conformance of the metadata to the structure defined in the CSDGM will be determined using the USGS metadata parser "mp". Conformance of the content of the metadata to the CSDGM will be determined by technical reviews satisfactory to the publications groups.

    A brief, overall introduction and guide to the product must be included in a plain-text file named "readme.txt". This file must include, but is not limited to, the identity of the product, a brief product description, introductory instructions on how to extract information from the product, a table of contents describing how the product's directories and files are organized.

    A low-resolution "browse" graphics file that represents the finished map product must be provided in GIF, JPEG, TIFF, EPS or PDF format. This file is intended to be a relatively simple depiction of the data that enables the user to quickly visualize the map from the author's perspective. Typically, this graphics file is not a fully-detailed depiction of the map data; in such cases the graphic must contain, next to the map image, the following disclaimer: "NOTE: This image is not an authoritative representation of the data."

    The author is encouraged to also include a "plot file" (preferably EPS or PDF), intended to provide the user with the author's full interpretation of the map data. Commonly, these plot files are as detailed as published USGS maps. The decision to include a plot file might be based on the map content and complexity (is the product a complex, multi-purpose geologic map, or simply a derivative map showing areas of greater and lesser geologic hazard?) and the size of the file (will it, with the map product, fit on the intended media?). If a plot file is included, the author should note, in the metadata or readme.txt file, the plotter and the RIP software with which the map has successfully been plotted, and the dimensions of the plot image.

    The product must be contained in one or more files in a universal, cross-platform format. At present, the "tar" format best fits this description, and is required. The decision of whether to use one tar file or more should be based on the content and size of the product. Generally, one tar file is preferred because product integrity is more easily maintained. However, if the product is relatively large and contains an extensive base map and/or a large plot file, the author may choose to package the plot file or base map in a tar file separate from the geologic data. In that case, both tar files would contain the readme.txt file. If a tar file is large, it may be provided in a compressed format, using Unix compress or gzip; the definition of "large" will be based on the judgement of the author and publications group, and may depend on factors including the intended audience and method of distribution. The Division will maintain a Web site containing, for various operating systems, information on availability and use of these software. This product file requirement is intended to provide users with a simple means for copying the product to a local disk, which is especially helpful for products with many data files (such as SDTS transfers).

    Potential users of the data may want a brief overview of the product before deciding whether to acquire it. Therefore, authors will provide the following separate files to accompany the single-archive file containing the product (these are duplicates of files contained in the product): the readme.txt file, the browse graphic, and the metadata file in plain-text and, optionally, in HTML format.

This page is <>
Maintained by Dave Soller