Abstract
Office of Management and the Budget Circular A-16 (revised 1990) defined the responsibilities of Federal agencies with respect to coordination of Federal surveying, mapping, and related spatial data activities and anticipated the eventual development of a “national digital spatial information resource.” Executive Order 12906, issued in April 1994, called for the development of that resource, to be referred to as the (U.S.) National Spatial Data Infrastructure (NSDI). The NSDI is defined as the technologies, policies, and people necessary to promote sharing of geospatial data throughout all levels of government, the private and non-profit sectors, and the academic community. This presentation provides history of the NSDI and the vision, goals, and objectives of the NSDI Strategic Plan. Particular emphasis will be paid to data standards, data documentation (metadata), data clearinghouse, and data access policy in the United States.

Introduction
The U.S. Federal government has recognised the need to coordinate Federal spatial data activities for nearly 50 years. The Bureau of the Budget issued Circular A-16 in January 1953 to coordinate Federal surveying and mapping activities, and reissued Circular A-16 in May 1967. The 1967 version identified leadership responsibilities for the Department of Interior, as pertaining to National Topographic Map Series and National Atlas of the United States, and for the Department of Commerce, as pertaining to National Networks of Geodetic Control.

Circular A-16 underwent a major revision and was reissued in October 1990 by the Office of Management and the Budget (OMB), the successor to the Bureau of the Budget [1]. The 1990 version of Circular A-16 took into consideration developments in digital geographic information systems and recognized activities pertaining to digital spatial data, in addition to traditional surveying and mapping activities. Its scope was expanded to include additional Executive Departments (comparable to ministries) and additional Federal spatial data programs. The objective of this circular was the “eventual development of a national digital spatial information resource, with the involvement of Federal, State, and local governments, and the private sector.” The 1990 version of OMB Circular A-16 called for establishment of an “interagency coordinating committee” to “promote the coordinated development, use, sharing, and dissemination of surveying, mapping, and related spatial data.”

Executive Order 12906, Coordinating Geographic Data Acquisition and Access: The National Spatial Data Infrastructure, signed by President Clinton and issued April 1994, named the national digital spatial information resource described in OMB Circular A-16 as the “National Spatial Data Infrastructure,” or NSDI [2]. It defined the NSDI as “the technology, policies, standards, and human resources necessary to acquire, process, store, distribute, and improve utilization of geospatial data.” Executive Order 12906 also provided for executive branch leadership by the Federal Geographic Data Committee as the interagency coordinating committee for the Federal government’s development of the NSDI. Executive Order 12906 called for

• Development of a National Geospatial Data Clearinghouse
• Standardized documentation of spatial data
• Development of spatial data standards
• Initial implementation of a national digital geospatial framework

The vision, goals, and supporting objectives of the National Spatial Data Infrastructure were articulated in the NSDI Strategic Plan released in 1997 [3]. The vision of the NSDI is that “Current and accurate geospatial data will be readily available to contribute locally, nationally, and globally to economic growth, environmental quality and stability, and social progress.” The goals and their supporting objectives built upon Executive Order 12906

Goal One:
Increase the awareness and understanding of the vision, concepts, and benefits of the NSDI through outreach and education.

Objectives

• Demonstrate the benefits of participation in the NSDI to existing and prospective participants.
• Promote principles and practices of the NSDI through formal and informal education and training.
• Identify and promote the attitudes and actions that help to develop the NSDI.

Goal Two:
Develop common solutions for discovery, access, and use of geospatial data in response to the needs of diverse communities.

Objectives

• Continue to develop a seamless National Geospatial Data Clearinghouse.
• Support the evolution of common means to describe geospatial data sets.
• Support the development of tools that allow for easy exchange of applications, information, and results.
• Research, develop, and implement architectures and technologies that enable data sharing.

Goal Three
Use community-based approaches to develop and maintain common collections of geospatial data for sound decision-making.

Objectives

• Continue to develop the National Geospatial Data Framework.
• Provide additional geospatial data that citizens, governments, and industry need.
• Promote common classification systems, content standards, data models, and other common models to facilitate data development, sharing, and use.
• Provide mechanisms and incentives to incorporate multi-resolution data from many organizations into the NSDI.

Goal Four:
Build relationships among organizations to support the continuing development of the NSDI.

Objectives

• Develop a process that allows stakeholder groups to define logical and complementary roles in support of the NSDI.
• Build a network of organizations linked through commitment to common interests within the context of the NSDI.
• Remove regulatory and administrative barriers to agreement formation.
• Find new resources for data production, integration, and maintenance.
• Identify and support the personal, institutional, and economic behaviors; technologies; policies and legal frameworks that promote the development of the NSDI.
• Participate with the international geospatial data information community in the development of a global geospatial data infrastructure.

The major successes of the National Spatial Data Infrastructure to promote data sharing have been an active standards program, standardised documentation of spatial data, and development of the National Geospatial Data Clearinghouse. The major part of this paper will cover these topics, which are interrelated, and Federal data access policy in the United States.

Standards
The Federal Geographic Data Committee initiated a program to develop data standards to promote sharing of data among Federal agencies and other segments of the geospatial data community in the United States [4]. The FGDC standards process is modeled after the standards processes used by ISO and the American National Standards Institute (ANSI). It has five major stages

• Proposal stage
• Project stage
• Draft stage
• Review stage
• Endorsement stage

Since 1995, sixteen data standards have completed all stages of the FGDC standards process and have been endorsed by the FGDC. The first standard endorsed by the FGDC was the Content Standard for Digital Geospatial Metadata for documenting spatial data. This standard will be discussed more at length in the next section of this paper. Other standards endorsed include the Spatial Data Transfer Standard and its profiles and data content and classification standards for spatial data themes such as soils, wetlands, and vegetation, and for utilities.

OMB Circular A-119 calls for Federal agencies to use voluntary consensus standards in lieu of government-specific activities [5]. In this context, “consensus” is characterized by general agreement, but not necessarily unanimity. These standards are developed and endorsed through an open process that provides due process for criticism and redress. Standards developed through ISO and ANSI-accredited standards development organisations meet these criteria. The FGDC and individual Federal agencies support voluntary consensus activities as members of the ANSI-accredited National Committee for Information Technology Standards Technical Committee L1 on Geographic Information Systems. Many FGDC members are also nominated U.S. technical experts to ISO Technical Committee 211, Geographic information/Geomatics [6], which is developing standards on topics such as spatial referencing, quality evaluation and reporting, metadata, and imagery and gridded data.

Metadata
EO 12906 called for Federal agencies to document all new data by January 1995 and to develop a schedule for documenting previously acquired spatial data by April 1995. This documentation is referred to as Metadata [7], or “data about data.” Metadata may be used to

• Organise and maintain an organization’s investment in data
• Provide information to data catalogues and clearinghouses
• Provide information to aid data transfer.

Metadata is documented using the aforementioned FGDC Content Standard for Digital Geospatial Metadata. It has undergone revision since its endorsement by the FGDC in 1995, and the FGDC endorsed Version 2.0 in 1998. Version 2.0 provides guidelines to geospatial data communities to restrict domains and conditionalities of existing Metadata elements and to develop new Metadata elements for their communities’ needs for documentation. Theme-specific metadata that builds on the FGDC Content Standard for Digital Geospatial Metadata, Version 2.0, are referred to as profiles.

Various communities are using the FGDC Content Standard for Digital Geospatial Metadata, Version 2.0 as the basis for developing theme-specific profiles. In 1999, the FGDC endorsed the Biological Data Profile of the Metadata standard, which contains additional metadata elements for taxonomic classifications and for documentation of laboratory studies. The Shoreline Data Profile is pending endorsement, while Metadata Extensions for Remote Sensing Swath Data is pending public review.

The FGDC Content Standard for Digital Geospatial Metadata was the basis for developing ISO 19115, Geographic information/Geomatics – Metadata, which has been recently submitted for registration as a Draft International Standard. The FGDC is implementing a strategy to convert existing Metadata formatted according to the FGDC standard to Metadata that complies with ISO 19115, when ISO 19115 is adopted as an International Standard (currently projected for July 2001).

Metadata is divided into ten sections. Seven sections (see Figure 1) document different aspects about the data set. Only two sections – Section 1, Identification Information, and Section 7, Metadata Reference Information – are absolutely mandatory for data documentation. However, it behooves data producers to document their spatial data sets as completely as possible to maintain the value of their spatial data assets. Section 6, Distribution information, may provide a URL to spatial data set itself, if it is available via the Internet.


FGDC Metadata Structure

Metadata documents spatial data by means of logical groupings of elements. Data elements are logical primitive items of information for entry. Compound elements contain data elements and even embed other compound elements. Compound elements describe the relationships among other elements. Figures 2 and 3 are graphical representations of the metadata structures for Section 1, Identification Information and Section 1.5, Spatial domain, and show how compound elements can embed both data elements and other compound elements.

Three sections - Citation Information, Time Period Information, and Contact Information – contain information required by the other seven sections and are always embedded in the other sections, as they cannot stand alone.


Graphic Representation of MetadataStructure Section 1, Identification Information

The smallest identifiable data product (e.g. file) for which Metadata are customarily collected may equate to a specific satellite image or vector data set. Collections of data sets (e.g. flight lines, satellite “paths”, map or data series) may also have generalized Metadata inherited by individual data sets.


Graphical Representation of Metadata Structure Section 1.5, Spatial Domain

The National Geospatial Data Clearinghouse
The National Geospatial Data Clearinghouse is a distributed service to locate geospatial data based on characteristics identified in Metadata [8]. It may be likened to a spatial Internet Search engine, but NSDI Clearinghouse enables the user to search by geographic area as well as by words and phrases (see Figure 4). The Clearinghouse also allows users to query all or part of the community of registered clearinghouse sites, or nodes, in a single session (see Figure 5).


Clearinghouse Query by Geographic Location - India


Clearinghouse Query by Registred Node - CARTERRA IRS Imagery


Results of Clearinghouse Query - CARTERRA IRS

To be registered as a clearinghouse node, a web site shall have in place:

• Metadata provided in formatted text or marked-up in Standard Generalised Markup Language (SGML).
• Computer hardware to store the indexed Metadata in various forms connected to the Internet.
• Search and retrieve protocol known as ANSI Z39.50-1995 (ISO 10163-1995) that supports access to Metadata.

Some users regard Clearinghouse to resemble a card catalog, rather than a library, as a Metadata record provides information about the data set and how to locate and access it, but usually not the data itself. Clearinghouse sites are encouraged to provide hypertext linkages within their Metadata entries to enable users to directly download the digital data set. Where digital data are too large to be made available through the Internet or the data products are for sale, linkage to an order form can be provided in lieu of a data set.

When a delegation from India visited the United States in September 2000, the author noted that India does not have a registered Clearinghouse node. It is to India’s advantage to join the Clearinghouse, as the Clearinghouse provides a low-cost means to promote available spatial data sets. The search facility on the web site for India’s National Remote Sensing Agency provides no interactive way to “draw” windows for a geographic area of interest for IRS imagery, but requires that the user know and enter values for latitude and longitude. However, metadata about IRS imagery, which is marketed through Space Imaging, is searchable on the registered CARTERRA node, down to the image scene level (see Figures 6 and 7). Other global spatial data collections searchable through Clearinghouse provide coverage over India.

Federal Data Access Policy in the U.S.
Access to spatial data sets produced for and by the U.S. government is characterized by “free and fair,” “full and open” access to all citizens for taxpayer purchased data, information, and interpretative products. The Federal government does not copyright its data. Unlike other countries (including Australia and Canada), it does not collect royalties for its data. Federal agencies are to set use charges for data products sufficient to recover the cost of dissemination, but to exclude costs associated with the original collection and processing of the data.


Metadata for IRS Image Scene with browse image

Another public value is the protection of the privacy, security, and accuracy of personal information. Information privacy is a citizen’s claim to control the terms under which personal information is acquired, disclosed, and used. The Federal Geographic Data Committee issued a policy statement on access to public information and the protection of personal information privacy in April 1998 [9]. The policy recognized that federal geospatial databases are being built with increasing levels of geographic specificity and often include personal information, either retrievable by name or another identifier specific to a person. It stated that federal geospatial databases are subject to the Privacy Act of 1974 and may contain personal information prohibited from disclosure by law.

A policy statement issued by the FGDC in 1992 [10] stated that Federal agencies shall maintain an information dissemination management system for geographic data that include easily accessible information about the data holdings, including quality assessments, supporting information, and guidance and aids for locating and obtaining the data – concepts that evolved into Metadata and the National Geospatial Data Clearinghouse. In addition, Federal agencies are to take advantage of all dissemination channels, Federal and non-Federal, including State and local governments and private sector entities, in discharging agency data dissemination responsibilities.

At the same time, the Federal government is relying more on acquiring data from external sources. A recent article in the Washington Post newspaper reported about the Federal government approving the sale of high-resolution imagery from Space Imaging to the public [11]. Even the intelligence community itself is relying more on purchase of high-resolution imagery. In this context, free and fair, full and open access is to be balanced against protection of proprietary interests of licensed information and data – and national security requirements.

The NSDI in Year 2001
While there have been notable successes in the realization of the NSDI in the United States, much more can be done to realize the NSDI vision that “current and accurate geospatial data will be readily available to contribute locally, nationally, and globally to economic growth, environmental quality and stability, and social progress.”

EO 12906 called for the initial implementation of a national digital geospatial framework to support the 2000 Census. At the time of this writing, Framework is more a concept than a reality. Framework comprises those data themes needed by a variety of data applications [12]. Seven themes were identified through requirements analysis of different data applications. These seven data themes are

• Geodetic control
• Cadastral data
• Elevation data
• Hydrographic Data
• Transportation Data
• Government Boundaries
• Orthoimagery

The obstacles to implementing Framework are primarily organizational. Various Federal agencies have leadership for data programs for Framework themes, and there is no common organizational model for developing consensus among stakeholders in the various segments of the U.S. geospatial data community. Similarly, the role of the Federal Geographic Data Committee in coordinating the Framework needs to be clarified.

As geographic information standards developed through ISO become international standards, the U.S. must vote to adopt the ISO standards as national standards. As OMB Circular A-119 requires Federal agencies to use voluntary consensus standards in lieu of government standards, whenever possible, FGDC standards must be evaluated for consistency with the ISO standards and revised accordingly. As noted previously, an implementation strategy is being developed to convert data structured according to the existing FGDC metadata standard to the structure used by the ISO metadata standard.

The national geospatial data clearinghouse has facilitated data discovery. Its capability to query multiple clearinghouse nodes for data covering a common geographic area of interest enables integration of Web mapping capabilities developed through the Open GIS Consortium to portray and overlay data from different sources on varying projections, datums, and coordinate systems.

Conclusions
This paper has highlighted components of the National Spatial Data Infrastructure in the U.S. and provided an overview of the NSDI in the year 2001. The author hopes that the content has provided India with inspiration for developing and expanding its own National Geospatial Data Infrastructure. India is a world leader in Information Technology and Remote Sensing. The author challenges India to leverage its expertise not only nationally, but also internationally. The author puts forward two specific recommendations to increase India’s visibility

• Produce Metadata to document spatial data sets and qualify geospatial data web sites for registration as Clearinghouse nodes.
• Upgrade India’s membership on ISO Technical Committee 211, Geographic information/Geomatics, from observer (O-) status to participant (P-) status to actively participate on new work items on imagery and gridded data.
• In closing, development of a National Geospatial Data Infrastructure is work in progress. It not merely involves technology and data standards, but also people, organizations, and policies.

References

• Office of Management and the Budget Circular A-016 (Revised), October 19, 1990, Coordination of Surveying, Mapping, and Related Spatial Data Activities ( http://www.whitehouse.gov/omb/circulars/a016/a016.html ) [1]
• Executive Order 12906, Coordinating Geographic Data Acquisition And Access: The National Spatial Data Infrastructure, April 11, 1994 ( http://www.fgdc.gov/publications/documents/geninfo/execord.html )[2]
• Goals and Objectives of the NSDI Strategy ( http://www.fgdc.gov/nsdi/strategy/goals.html )[3]
• FGDC standards ( http://www.fgdc.gov/standards/standards.html )[4]
• OMB Circular A-119 (Revised), February 10, 1998, Federal Participation in the Development and Use of Voluntary Consensus Standards and in Conformity Assessment Activities ( http://www.whitehouse.gov/omb/circulars/a119/a119.html )[5]
• ISO Technical Committee 211, Geographic information/Geomatics,(http://www.statkart.no/isotc211/welcome.html)[6]
• Metadata ( http://www.fgdc.gov/metadata/metadata.html )[7]
• Clearinghouse ( http://www.fgdc.gov/clearinghouse/clearinghouse.html )[8]
• FGDC Policy on FGDC Policy on Access to Public Information and the Protection of Personal Information Privacy in Federal Geospatial Databases, April 1998 ( http://www.fgdc.gov/fgdc/policies/privacypolicy.pdf  )[9]
• Policy Statements for Federal Geographic Data Sharing, June 1992 ( http://www.fgdc.gov/fgdc/policies/datashare.pdf )[10]
• Washington Post, December 16, 2000, U.S. Is Relaxing Rules on Sale of Satellite Photos [11]
• Framework( http://www.fgdc.gov/framework/framework.html )[12]