The Digital Geographic Information Exchange Standard (DIGEST) was developed by the DGIWG (previously known as the Digital Geographic Information Working Group) to support efficient exchange of Digital Geographic Information among nations, data producers, and data users. It was designed as a “family of standards” capable of supporting the exchange of multiple data types (e.g. vector). DIGEST was first published in June 1991 with the release of Edition 1.0. It underwent a number of revisions and was last issued in September 2000 with the release of Edition 2.1.
While the exchange of data sets between national systems was sufficient at first, the requirement to distribute data products directly to military end users became more important over time. DGIWG set out to develop data product specifications that were compliant with DIGEST by addressing various types of data. Imagery (raster data), elevation data (matrix data), and boundary data (vector data) were addressed in different parts of the DIGEST standard. The capability to handle different encoding for the same data content was also introduced in DIGEST.
The DIGEST standard is divided into 4 parts:
- Part 1 is a brief General Description of the standard.
- Part 2 consist of Theoretical Model, Exchange Structure, Encapsulation Specifications (Annexes A through D) and a Standard ASCII Table of Contents (Annex E). The Part 2 encapsulations include: Annex A – Bulk interchange using the ISO 8211 data descriptive file format; Annex B – Transaction and update using the ISO 8824/8825 telecommunication standard; Annex C – Vector products using the Vector Relational Format corresponding to U.S. MIL-STD-2407; Annex D – Imagery using the NATO Secondary Imagery Format corresponding to ISO 12087-5, Basic Imagery Interchange format (BIIF)
- Part 3 consists of Codes and Parameters
- Part 4 is a Feature and Attribute Coding Catalogue (FACC) Data Dictionary
Recent developments in geospatial services have made obsolete the approach of defining data products in terms of an exchange format. Any portion of a broad suite of geospatial data needs to be dynamically accessible through a network. This situation has changed the approach taken by DGIWG. DIGEST is still retained for backward compatibility, but now information is defined in terms of an information content model, which can be expressed through an exchange format or through an application interface.
DIGEST is no longer maintained by DGIWG but is provided here because legacy systems are still operating that are based on this standard.