Through the remainder of this chapter and the next, we'll investigate the particular data products that comprise the framework themes of the U.S. National Spatial Data Infrastructure (NSDI). The format I'll use to discuss these data products reflects the Federal Geographic Data Committee's Metadata standard (FGDC, 1998c). Metadata is data about data. It is used to document the content, quality, format, ownership, and lineage of individual data sets. As the FGDC likes to point out, the most familiar example of metadata is the "Nutrition Facts" panel printed on food and drink labels in the United States. Metadata also provides the keywords needed to search for available data in specialized clearinghouses and in the World Wide Web.
Some of the key headings included in the FGDC metadata standard include:
- Identification Information: Who created the data, a brief description of its content, form, and purpose; its status, spatial extent, and use restrictions;
- Data Quality Information: Accuracy and completeness of attributes, horizontal and vertical positions, sources, and procedures used to create the data;
- Spatial Reference Information: Projection and/or coordinate system; datum and ellipsoid;
- Entity and Attribute Information: Feature and attribute categories used; and
- Distribution Information: Availability, and how to acquire the data.
FGDC's Content Standard for Digital Geospatial Metadata is published here. Geospatial professionals understand the value of metadata and know how to find it and how to interpret it.