FEDERAL GEOGRAPHIC DATA COMMITTEE PHONE: 703-648-5514

U.S. GEOLOGICAL SURVEY, 590 NATIONAL CENTER FAX: 703-648-5755

RESTON, VIRGINIA 20192 HTTP://WWW.FGDC.GOV EMAIL: GDC@USGS.GOV

March 1997

The National Geospatial Data Clearinghouse

An estimated 4 billion dollars is spent annually by

the Federal government on the production,

management, and dissemination of geospatial data.

Many of these funds may be expended to collect

already existing data, but the ability to determine the

availability of data is almost non-existent. The

National Geospatial Data Clearinghouse is a means

of finding geospatial data, determining its fitness for

use, and obtaining or ordering it as economically as

possible.

WHAT IS THE CLEARINGHOUSE?

The Clearinghouse is a distributed, electronically

connected network of geospatial data producers,

managers and users. It is not a central repository

where data sets are stored. Through the

Clearinghouse, finding geospatial data will some day

be as easy as obtaining cash in a foreign country

through an automated teller machine.

Federal agencies are beginning to make information

about spatial data, called metadata, available on the

Internet as part of their participation in the National

Spatial Data Infrastructure (NSDI). Executive Order

12906, signed by President Clinton in 1994, requires

all Federal agencies that produce geospatial data to

document new data sets produced after January

1995 using the Content Standards for Digital

Geospatial Metadata adopted by the Federal

Geographic Data Committee. The Executive Order

also mandates that metadata be made available

through the Clearing-house so that the public can

determine what geospatial data exist, the condition

of these data, and how to access them. The

Executive Order applies only to Federal agencies,

but a wide variety of data producers and users

throughout the nation including State, local, and

tribal governments, academia, and the private sector

are participating in the Clearinghouse.

HOW DOES THE CLEARINGHOUSE WORK?

Rapid change is the hallmark of today's information

society. The Clearinghouse is evolving as quickly as

the technology that makes it possible. Each data

producer or maintainer is expected to describe

available data in electronic form and provide these

descriptions (the metadata) to the Internet using a

variety of software tools. Clearinghouse sites are

linked through the Internet.

Many current implementations make use of the World Wide Web technology that supports the use
of such client browsers as Mosaic and Netscape.

Text-based metadata descriptions can be accessed

by data users at remote sites and read using these

client programs. Based on the data descriptions, a

user can decide whether the data set meets their

needs. Frequently, a data producer will provide

direct on-line access to the data set, although this is

not a requirement of the Clearinghouse. Hypertext

technology allows linking to data sets that are not

stored on the same server as the metadata. If data

sets are not available on-line, the metadata will

contain information about how they can be ordered.

One of the essential requirements of the Clearinghouse is that it embody the ability to search for

geospatial data over the Internet. A communications

protocol known as Z39.50 is currently the focus of

research within the spatial data community as a

vehicle to allow remote searching for data. Metadata

can be indexed by servers running Z39.50 and users

can craft remote searches based on elements of the

metadata, for example geographic location, date of

creation, or source material. Browse software such

as Mosaic can provide gateways to these servers,

allowing graphic or forms-based queries for data.

BENEFITS

The abilities to search for data and to determine

their relevance are critical skills in a knowledgedriven economy. The use of geographic information

systems technology is spreading, and along with it

the demands for more and better geospatial data.

The Clearinghouse of the future will provide the

information to more economically find, share, and

use geospatial data.

HOW TO PARTICIPATE?

The Federal Geographic Data Committee is the

contact for prospective participants.

If you are a data producer:

!Learn and use the metadata standard.

!Establish a Clearinghouse node to provide

metadata on the Internet.

!Inform the FGDC of the existence of your

node.

!Participate in discussions of

Clearinghouse issues on the Internet

mailing list NSDI-L.

!Encourage vendors to provide tools

needed to participate in the Clearinghouse.

If you are a data user:

!Provide feedback to data producers on

what information about data is important to

you.

!Investigate the means to access the Internet.

!Participate in discussions of

Clearinghouse issues on the Internet

mailing list NSDI-L.

!Encourage vendors to provide the tools

needed to use the Clearinghouse as part of

their products.

ADDITIONAL INFORMATION

More information about the Clearinghouse can be

obtained at the address above. The World Wide

Web site <URL://http://www.fgdc.gov/> contains

links to Clearinghouse sites throughout the country.

Instructions for joining the NSDI-L mailing list are

also available from the FGDC. The following related

publications can be obtained from the FGDC:

FGDC Fact Sheet

NSDI Fact Sheet

Metadata Fact Sheet

The Value of Metadata

Metadata Workbook