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MIL-D-89009
APPENDIX
40.
DATA QUALITY
The DCW database contains Data Quality (DQ) information at a
variety of levels, including:  (1) library, (2) coverage, (3)
feature, and (4) primitive.  In general, the information is
organized around concepts of spatial and thematic extent.
Consistent with the VPF standard, the available information
becomes increasingly more detailed at lower levels in the library
structure.  All DCW data quality information can be viewed through
the VPFVIEW software with the exception of the data quality
coverage Relate Attribute Tables (RATs), which can be viewed using
the VPFTBL command from the DOS operating system.
40.1  Data quality table.  The most general source of data
quality information within the DCW database is the VPF data
quality table (TABLE 9) resident at the library level.  This
standard VPF table is present in all DCW libraries.  The table
documents source data characteristics, date status, and general
data accuracy.  The DCW database also includes a narrative file
associated with the data quality table called "LINEAGE.DOC".  This
table contains data lineage information common to all DCW
coverages, including automation histories and standard processing
tolerances.
40.2  Data quality coverage.  Data quality information that
varies spatially across the library is described by the data
quality coverage.  The data quality coverage consists of the
effective data area borders of each ONC from which the data were
extracted.  The data quality coverage allows the user, through
visual display, to determine which DCW data were extracted from
which chart.  Implicit within this information is any date status
information, sheet specific positional accuracy characteristics,
and chart marginalia that may be available.  Existing source
marginalia is commonly augmented with additional comments based on
observations made during the automation process.  All of this
information is stored in data quality area feature tables and in
DQAREA relate attribute tables.  Attributes of borders between
sheets are maintained in data quality line feature tables and
DQLINE relate attribute tables.  Border attributes maintain
information on edgematch characteristics between adjacent
coverages.  There exists a one-to-many relationship between both
types of coverage feature tables and their respective RATs.
Finally, text features are used to document regional phenomena of
interest to the database user.  These are typically comments
describing localized problems, such as irreconcilable registration
offsets between data types.
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