Digital Chart of the World (DCW)

Spiral Development

The DCW program was an early adopter of a systems development methodology known as spiral development. The DCW was developed through four increasingly more complex spirals that resulted in four prototypes. These prototypes were used to develop VPF, VPFVIEW, and the DCW database. Prototypes 1 through 4 were published between December 1989 and December 1990. Through these prototypes (and associated review conferences), input was solicited from DMA and other project participants about the [Page 105]standard, the software, and the database. The conferences included participants from defense organizations in the United States, Canada, Australia, and the United Kingdom.

The VPF standard, developed concurrently with the database, was demonstrated in each of the prototypes and was published as a series of drafts. VPF development culminated in the publication of a military standard, MIL-STD-2407. (VPF has since been incorporated into the Digital Geographic Information Exchange Standard [DIGEST], where it is known as Vector Relational Format [VRF]; and DIGEST has been ratified as NATO Standardization Agreement 7074.) VPF is a georelational data structure that supports the direct use (storage, query, display, and modeling) of vector spatial geographic information. As such, it differed from other digital vector formats in the 1990s that supported only data exchange.

Data Sources and Database Production

After feedback from Prototype 4 was received, full database production was initiated. Data sources for automation included the entire ONC series (270 charts consisting of over 2,000 photographic separates) and the six JNCs. In addition, supplementary sources of data were incorporated, including vegetation data for North America derived from NASA's Advanced Very High Resolution Radiometer (AVHRR) satellite imagery. Data currency varies with the hard-copy source data and ranges from the 1960s to the 1980s.

The conversion of all the data to digital vector format was accomplished primarily by using a large-format raster scanner and then using a vectorization software product to convert the scanned data to vectors. Digital vector data was created and processed using ESRI's ARC/INFO software (Versions 5 and 6) and subsequently converted to VPF.

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