U.S. Geological Survey Manual

OPR: Director's Office

1. Purpose. This chapter establishes policy on the minimum standards for USGS digital spatial data intended for release to the public.

2. References.

A. Office of Management and Budget Circular A-16 (Revised)

B. Federal Information Processing Standard (FIPS): No. 173 Spatial Data Transfer Standard

C. Executive Order 12906

3. Definitions.

A. Attribute. A defined characteristic of an entity (e.g., composition).

B. Entity. A real-world phenomenon that is not subdivided into phenomena of the same kind (e.g., bridge).

C. FIPS. Federal Information Processing Standard

D. Metadata. Descriptive information about a collection of data that enables end-user evaluation of its fitness for use.

E. Profile. A clearly defined and limited subset of the Spatial Data Transfer Standard (SDTS) designed for use with a specific type of data.

F. Raster. A digital representation of a graphic image composed of an array of pixels (picture elements) arranged in rows and columns.

G. Spatial Data. Geographically referenced features that are described by geographic positions and attributes in an analog and/or computer-readable (digital) form.

H. Spatial Data Transfer Standard (SDTS). FIPS 173. Provides an exchange mechanism for the transfer to spatial data between dissimilar computer systems. SDTS specifies exchange constructs, addressing formats, structure, and content for spatially referenced vector and raster (including gridded) data.

I. Vector. A digital representation of a graphic image composed of points and line segments to represent point, line, and area features.

4. Policy. The USGS can make major advances in improving spatial data exchange by providing digital spatial data products to the public in conformance with the following standards:

A. For Data Georeference. The geographic location system as described in FIPS 70-1.

B. For Data Transfer. The Spatial Data Transfer Standard (SDTS-FIPS 173), at a minimum.

C. For Data Documentation. The Content Standards for Digital Geospatial Metadata.

5. Procedures and Responsibilities.

A. Use of Standard Coordinate Systems. Geographic location is the use of a coordinate system to define the position of a point or cell that may be on, above, or below the Earth's surface. The USGS has accepted the standard described in Federal Information Processing Standard (FIPS) 70-1, "Specifications for Representation of Geographic Point Locations for Information Interchange." This standard is applicable to the three most widely used location conventions in the United States: latitude and longitude, Universal Transverse Mercator System, and the State Plane Coordinate System. All future USGS geospatial data bases will use one of these three coordinate systems or support the conversion of coordinate data to one of these three coordinate systems.

B. Use of the Spatial Data Transfer Standard. Digital spatial data sets produced by the USGS include information stored in both vector and raster data structures. The Topological Vector Profile of the SDTS has been approved and available since February 1994 for use in exchange of vector-based spatial data and their attributes. Given the robust nature of the SDTS and its standing as a FIPS, USGS will provide digital spatial data to the public in the appropriate SDTS Profile, as a minimum. This will ensure that formats of spatial data products from the USGS are more consistent and users of major GIS systems will be able to import most USGS data with a minimum of translator software. Data sets that are not amenable to formatting with the existing profiles of SDTS should be made available in a non-proprietary format commonly used within the discipline so as to serve the widest possible user audience. The appropriate formats should be dictated by the target user community (e.g. oil and gas, facilities mapping) and by the native format of the digital spatial data set.

The development of new SDTS profiles for earth science information is encouraged by the USGS. Where possible, the USGS should strive to develop support software to interpret and convert these new profiles.

C. Use of the Content Standard for Digital Geospatial Metadata. The Federal Geographic Data Committee (FGDC) has developed a comprehensive set of descriptive elements for digital spatial data sets. These descriptors, known as metadata, allow for the characterization of the digital data set. Metadata includes quality declarations, spatial accuracy and coordinate system definition, references to browse graphics, a data dictionary, and lineage, among other elements. When placed in an on-line searchable form, metadata can allow a potential user to determine a data set's fitness for a specific application prior to the acquisition of a data set.

Executive Order 12906 mandates the use of the FGDC metadata content standard and requires that all federal agencies document all new digital spatial data sets using the standard elements. All new USGS digital spatial data sets must have such compliant documentation. In addition, compliant documentation should be developed for digital spatial data sets developed prior to January 11, 1995. The documentation must be made available to support browsing at USGS National Geospatial Data Clearinghouse nodes and must also accompany the data set in transfer.