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The Nautical Chart Numbering System
Background
Information
DMA assigns a number to every nautical chart used by the U.S. Navy,
regardless of the organization producing the chart. Charts produced by
the NOS, and charts of foreign governments are also assigned numbers
by DMA so that they may be filed in sequence with the
DMAHTC-produced charts. DMA charts have numbers consisting of
one to five digits. The number of digits generally indicates the scale
range, and the number itself indicates the geographical area covered by
the chart. The chart numbering system is as follows:
Number of Digits
Scale
Description
1 (1-9)
None
Symbol and flag charts.
2 (10-99)
1:9,000,000
These charts depict a major
and smaller
portion of an ocean basin or a
large area, with the first digit
identifying the ocean basin.
3 (100-999)
Between
These are general charts whose
1:2,000,000
numbers are based on the nine
and
ocean basins.
1:9,000,000.
4 (5000-9999)
Various
This category includes great circle
tracking charts, electronic
navigation system plotting charts,
and special-purpose non-
navigational charts and diagrams.
Four-digit charts with a letter
prefix (EOIOI-E8614) are bottom
contour charts.
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