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Charts are constructed on many different
scales, ranging from about 1:2,500 to 1:14,000,000 (and even smaller for
some world charts). Small-scale charts are used for voyage planning and
offshore navigation. Charts of larger scale are
used as the vessel approaches land. Several methods of classifying charts
according to scale are in use in various nations. The following classifications
of nautical charts are those used by the National Ocean Survey: Sailing
charts are the smallest scale charts used for planning, fixing position
at sea, and for plotting while proceeding on a long voyage. The scale
is generally smaller than 1:600,000.
The shoreline and topography are generalized and only offshore soundings,
the principal navigational lights, outer buoys, and landmarks visible
at considerable distances are shown. General charts are intended for coastwise
navigation outside of outlying reefs and shoals. The scales range from
about 1:150,000 to 1:600,000. Coast (coastal) charts are intended for
inshore coastwise navigation where the course may lie inside outlying
reefs and shoals, for entering or leaving bays and harbors of considerable
width, and for navigating large inland waterways. The scales range from
about 1:50,000 to 1:150,000. Harbor charts are intended for navigation
and anchorage in harbors and small waterways. The scale is generally larger
than 1:50,000. |
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