Holes In The Wall
CHART VERSUS CHART
Before heading for the Holes in the Wall of Southeast
Alaska, some consideration should be given to the
differences between Canadian Hydrographic Service
(CHS) charts covering Canadian waters and National
Oceanic and Atmospheric Administration (NOAA) charts
of U.S. waters.
First and foremost, the means of establishing chart datum
and the markings for rocks (which may or may not be
exposed) differ. Also, all NOAA charting is in fathoms and
feet. As an example, a rock that uncovers 8 feet at zero tide
on a CHS chart will have an underlined depth (i.e., 8 on
fathom and feet charts and 2. 5 on metric charts), while the
NOAA chart will show only an asterisk or a cross with a
dotted circle around it. There are no drying heights for
rocks, although there may be a comment such as “breaker”
or “bares at half tide” for significant rocks.
The blue tint on NOAA coastal charts is used “to
accentuate shoal areas,” and the depths of this shaded
area often differ from chart to chart. United States Coast
Pilot recommends that boaters proceeding into the blue
shaded regions on the NOAA charts exercise caution. On
the CHS coastal charts, there is a standard for contour
depths based on the use of two distinct blue tints. However,
care must be taken when moving from one chart to the next;
newer charts are metric, with horizontal datum based on
NAD 83 (North American Datum of 1983), while older
charts show depths in fathoms and feet and may be using
NAD 27 (North American Datum of 1927).
Although the tidal ranges in the United States and
Canada are identical in the respective tide tables, minus
tides are common in Alaska, since datums are set to the
mean of the lower low water rather than the lower low
water used in CHS charting and tide tables. This means that
on low tides, controlling depths may be several feet less
than the depths indicated on NOAA charts. Be cautious:
we have heard Maydays from both pleasure craft and
cruise ships during our Alaskan travels.
approach to this anchorage that is usually kelp covered
and can easily be seen. From reading United States Coast
Pilot, you might expect this shallow area to be in the
entry, but it is in fact well outside and clearly marked on
the chart. Enter down the middle of the passage and
favor the north shore at the inside of the narrows, as
there is a reef that extends a short distance into the bay.
Most of the channel is about 6-1/2 fathoms; the depth
decreases to about 4 fathoms at the inner end of the
channel before dropping back to 6. In settled conditions
you can anchor anywhere, but a residual swell does
enter, and you can take shelter from this and the
afternoon breeze just to the south of the entrance.
Although this Hole in the Wall is on the open coast
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