VPF Format

VPF uses a georelational data model that is designed to be used with any digital geographic data in vector format that can be represented using nodes (points), edges (lines), and faces (areas). VPF defines the format of data objects, while the georelational data model provides the method for organizing the data.

VPF organizes data into five hierarchical levels: Database, Library, Coverage, Feature, and Primitive.

Geometric primitives (i.e., nodes, edges, faces and text) describe spatial positions and topological relationships at the Primitive Level. Features (i.e., points, lines, areas, and text) are described using feature codes and attribute values at the Feature Level. Geometric primitives and feature data are "related" to each other via the georelational data model to provide a complete depiction and description of features. Features are grouped according to thematic relationships into feature classes (e.g., Roads) within coverages. Coverages group related feature classes (e.g. roads and railroads) into a common theme of data (e.g., transportation). A collection of coverages over the same geographic extent and using the same tiling scheme is called a library (i.e., data set). Libraries are grouped according to distribution and application factors into databases. A product specification, corresponding to a specific data base product, defines the precise contents of feature tables and implementation of the VPF standard. (Many parts of the standard are optional and are not always implemented.)