The Defence Geospatial Information Working Group (DGIWG)
was established in 1985 to foster the exchange of digital geospatial
information (DGI). Initially, DGIWG was concerned only with the
exchange of geographic data between independent national systems,
hence, the DIgital Geographic Exchange STandard (DIGEST)
was developed to enable this exchange to occur in a compatible manner.
This standard went through several editions with the latest edition
being published in September, 2000.
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 main body
of DIGEST (Part 2 of the DIGEST document) defined a data model
that applied to all digital geographic information, and several
annexes described the encoding of this data in different forms.
These forms were:
- A - Bulk interchange using the ISO 8211 data descriptive file
- B - Transaction and update using the ISO 8824/8825 telecommunication
- C - Vector products using the Vector Relational Format corresponding
to US MIL STD 2407
- D - Imagery using the NATO Secondary Imagery Format corresponding
to ISO 12087-5 BIIF
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.