"…The National Map contains blanket and quilt components. The blanket component [includes] proposed seamless national imagery coverage…and the proposed incorporation of the National Atlas into The National Map. The quilt component is evident in the proposed high-resolution patches of data where local or state partners link their higher-resolution data."

From Weaving a National Map: Review of the U.S. Geological Survey Concept of The National Map
(National Research Council, 2003)

The National Map Catalog is a database and associated Internet information service. In terms of the metaphor in the NRC report quoted above, the Catalog manages the "quilt" by tracking partners, services, data layers, and the relationships between them. It contributes to construction of the "blanket" by imposing some visual consistency, even when the displayed data are from multiple sources and have different characteristics.

The National Map Home Page

The National Map Viewer

Registering Web Map Services in The National Map Catalog (A working blueprint for adding data to The National Map. PDF)