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Cartographic considerations for DCW database. |
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|  MIL-D-89009
3.9
Cartographic considerations for DCW database.
a. Source.
The DMA's 1:1,000,000 ONC series of
aeronautical charts provides the fundamental source data
set as of September, 1989. The JNC series of DMA
products at 1:2,000,000 scale supplements the ONC data.
Six JNCs have been utilized as the source for the
Antarctic region, where there is'nt any ONC coverage.
b. Compilation scale.
The compilation scale of the DCW is
1:1,000,000.
c. Minimum polygon size. Where polygons on ONCs were below
the minimum capturable size of <3.05 millimeters
(0.12 inch) in circumference, and consist of a single
edge, they are represented as point features.
d. Connection rules. Connection rules apply for linear
road and railroad features in the DCW database. Where
roads and railroads are broken by text on an ONC, gaps
wider than 0.1 inch (2.54 millimeters) in the network
are coded as special connectors with TYPE attribute code
of 8, and STATUS attribute code of 4, 6, or 9. Smaller
gaps along a road or railroad are coded with the TYPE
attribute code 1 or 2, and STATUS attribute code 1, 2,
3, or 5. Connectivity rules do not apply in situations
where gaps are clearly due to natural obstructions.
Gaps created due to a road or railroad not being shown
in the urban area of the ONC source were connected
either with accurate delineation compiled from
collateral source material (for 359 major cities) or
with straight lines forming a "wagon wheel" (for the
remaining cities). These gaps in the city areas of the
ONCs are coded as special connectors with a TYPE
attribute code of 8 and a STATUS attribute code of 4.
3.10 Source map projections. The projection parameters for
the ONCs vary with map sheet and the producing agency. Data
capture was principally in the Lambert Conformal projection from
the ONCs, and Transverse Mercator projection for the JNCs.
3.11 DCW projection. Regardless of the original map
projection, all data captured from ONC and JNC sheets were
converted to geographic coordinates in decimal degrees for storage
in the DCW database. Projection parameters were developed
specifically for each map sheet.
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