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|  MIL-D-89021
2.2 Non-government publications.
This section is not
applicable to this specification.
2.3 Order of precedence. In the event of a conflict
between the text of this document and the references cited
herein (except for related associated detail specifications,
specification sheets, or MS standards) the text of this document
takes precedence. Nothing in this document, however, supersedes
applicable laws and regulations unless a specific exemption has
been obtained.
3.
REQUIREMENTS
3.1 Source data limits. Digital Landmass Blanking (DLMB)
data is arranged into data files of 1 degree by 1 degree
geographic areas called cells. The reference origin for each
data file is the southwest corner of the cell. All cells with
western longitudes (i.e., longitude of reference origin of cell)
of 0 and 180 will be named 0E. and 180W, respectively. All
cells with a southern latitude of 0 (i.e., latitude of
reference origin of cell) will be named 0N. Multiple data
files are arranged onto magnetic tape in 1 degree bands of
latitude with a maximum of six 1 degree cells of longitude in
ascending order (180 west to 179 east). Cells both east and
west of 0 and 180 longitudes may be arranged on the same tape.
3.2 Format. DLMB data is a digital product. The format
for DLMB is the DMA standard format for Digital Terrain
Elevation Data (DTED). DLMB data consist of only two elevation
values generally spaced in a 3x3 arc-second interval (see TABLE
I, MIL-D-89000, MIL-D-89001): 0 for water and 200 meters (656
feet) for land. 1 X 1 arc-second DLMB data is not available.
DLMB data is referenced to the World Geodetic System datum.
3.3
Source material.
3.3.1 Primary sources. The DLMB data is derived from
cartographic sources having a preferred scale of 1:250,000 and
larger. Joint Operations Graphics (JOG) and nautical charts are
primary sources. The lineal data is processed by the E-3A
Maritime AWACS Land/Water Data generator which converts this
data into a land/water matrix (DLMB) format on World Geodetic
System (WGS) datum.
3.3.2 Secondary sources. All primary cartographic sources
are checked against the following secondary sources (listed in
order of preference) for island portrayal:
a.
Nautical Charts (1:250,000 scale)
4
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