The Vector Product Format (VPF) is a standard format, structure, and organization for large geographic databases that are based on a georelational data model and are intended for direct use. VPF is designed to be compatible with a wide variety of applications and products. VPF allows application software to read data directly from computer-readable media without prior conversion to an intermediate form. VPF uses tables and indexes that permit direct access by spatial location and thematic content and is designed to be used with any digital geographic data in vector format that can be represented using nodes, edges, and faces. VPF defines the format of data objects, and the georelational data model provides a data organization within which software can manipulate the VPF data objects. A Product Specification corresponding to a specific database product determines the precise contents of feature tables and their relationships in the database. In this context, each separate product or application is defined by a Product Specification implemented by using VPF structures.

VPF data is stored in a structure described in the Military Standard, Vector Product Format, MIL-STD-2407. The Standard specifies the structure for directories, tables, table columns, table join relationships, and media exchange conventions for all VPF data. The data structure itself can be thought of as a template or skeleton within which the geospatial features and metadata are stored. While the Standard describes the structure, it does not describe the contents of a set of VPF data; this is the role of "VPF Product Specifications."

Basic VPF Structure

VPF has three basic data structures. Namely "Directories", "Tables", and "Indices". All VPF data is defined in terms of one of these structures. There are several hierarchical directories in VPF which are described below. Tables are either ASCII or binary files which are stored within the directories. There are several types of tables, each of which has a specific structure of "columns" or fields for different kinds of information and many "rows" of records. Feature, attribution, location, geometry, and topology information is stored in various VPF tables. Indices are a special kind of table which have pointers between other tables and records.

A typical VPF Product has "VPF Databases" which contain "VPF Libraries" grouped by geographic area. A "VPF Library" contains "VPF Coverage" directories where "Feature Tables" store information about thematically similar geospatial features and their attributes over the geographic extent of the library. The location, geometry, and topology of the area, line, point, and text features that make up VPF data are stored in the lowest level VPF structure called a "Primitive Table". To facilitate faster access to primitive data, most VPF products are tiled. That is, the extent of the library is broken into tiles of equal size. Primitive tables are stored in "Tile Directories" within a VPF coverage. Topology among VPF features is only maintained within each coverage. Therefore VPF does not store topology between features which are in different coverages.

The VPF structure is known as a "relational" structure, because pointers and joins or "relationships" are used between the various tables to store the topology and attribution of the geospatial features. Without these "relational" structures the data would contain nothing more than simple geometry of the features not their topology. This makes VPF products attractive to developers and users of Geographic Information Systems (GIS) where spatial analysis is important.

A glossary of VPF related terms is available in the VPF Glossary

VPF Products

Just as there are several different types and scales of charts and maps that may be created for the same geographic area, each designed for different uses, there are also several types of VPF products of different levels of feature content and density. Military Standard, Vector Product Format, MIL-STD-2407 describes the structure and format conventions which must be met for a dataset to be considered a VPF data. The Standard does not, however, define the specific contents (coverages, features, and attributes) which make up a particular VPF product; that is the role of a "Product Specification".

Each VPF product is defined by a different Military Specification. Each Mil-Spec. describes the specific implementation of the general VPF structures that are defined in the VPF Military Standard. This includes which features, attributes, and attribute values will be allowed in the product as well as how the features will be grouped into coverages and what tiling scheme, if any, will be used. Several VPF products are being produced by NGA, commercial VPF providers, and mapping agencies in several other countries throughout the World. To find out more about the current suite of VPF products, visit the Geospatial Standards and Specifications web page where you will find a list of many NGA product specifications. You may also download a copy of many of the specifications. 

Symbolizing VPF Data

NGA has developed a standard set of digital symbology designed specifically for the display of VPF data. It is defined by the Military Specification, Geospatial Symbols for Digital Displays (GeoSym), MIL-DTL-89045. You can find information about the GeoSym development and download a copy of the symbology prototype at the GeoSym web page.