Chapter 4 - Using the Chart Screen
957 Operator’s Manual, Rev. B Page 35
Understanding nav aids
The nav aids on the CHART screen represent a variety of
standard “aids to navigation” used on coastal and inland
waterways throughout the United States. Nav aids are
displayed on the CHART screen as colored circles with white
letters. Most of these aids comprise buoys, lights, lighthouses,
and daybeacons, which typically are maintained by the U.S.
Coast Guard. Nav aids warn you of hidden dangers, such as
underwater hazards, and to help you to safely navigate specific
waterways and channels.
Buoys
Buoys are the most common type of nav aid. The 957 shows
green and red channel markers as green and red circles,
respectively.
Approach buoys are shown as circles with black on the upper
half and white on the lower half.
Sound buoys (featuring an audible signal, such as a bell, gong,
or whistle) are identified by a description in the INFO BAR
such as BELL, WHIS, GONG, or HORN).
Some nav aids have no chart symbol, and are shown on the
CHART screen as text only.
When you move the cursor onto a nav aid, the 957 displays a
description in the INFO BAR at the bottom of the screen, along
with the distance and bearing from your vessel to the nav aid.
CAUTION!
Nav aids have been converted from official paper charts into
the electronic format on your screen, and therefore aren’t
necessarily as accurate as the paper charts. You can expect
about a 95 percent accuracy rate. In some areas, only the most
important nav aids may be shown.
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