20 seamanship secrets
THREE CHART FORMATS
Aft er fi nding your chart or charts, go to the columns headed Paper Date or
POD Date.
Paper Date. These are the common paper nautical charts issued by the
National Ocean Service (a department of NOAA) in the United States and by
corresponding agencies in other countries. Paper charts provide exceptional
accuracy and reliability.
POD (Print-on-Demand) Date. Print-on-demand charts are updated
versions of paper charts. When you place an order for a print-on-demand
chart, the vendor prints your chart on a machine linked to a chart correction
database. Your chart contains all updates to changes in aids to navigation,
shoals, and wrecks through the date of order. The cost is about 10% to 15%
more than a standard paper chart.
Raster Nautical Charts. A raster nautical chart, or RNC, is a scanned elec-
tronic version of a traditional chart. Because raster charts are scanned from a
traditional chart, their edition dates are the same as that shown in the DOLE
listing under the heading “PAPER DATE”. Dozens of RNCs can be scanned onto
a CD or DVD for use in a laptop or onboard computer, which displays the chart
and drives the associated navigation soft ware. Raster charts are too memory-
hungry to be compatible with most electronic chart plotters. RNCs have the
same level of precision as traditional charts—no less and no more. Th e electronic
alternative to RNCs is vector charts, which we’ll discuss in Chapter 2.
NOTICES TO MARINERS: VITAL DATA FOR KEEPING
CHARTS UPDATED
In the DOLE listing, in each column under the edition date you’ll fi nd dates
preceded by the designations NM or LNM. NM stands for Notices to Mariners
and LNM for Local Notices to Mariners. Both contain vital information on
new, revised, relocated, and removed aids to navigation, reports of wrecks,
dangerous shoaling, or bridge operation status.
Notices to Mariners cover waters worldwide. Local Notices to Mariners
cover only those waters within a U.S. Coast Guard District Boundary. The
Coast Guard issues both versions of notice to mariners once a week. As long
as you’re sailing in U.S. waters, you’ll only need the Local Notices to Mariners
to keep your charts up-to-date.
How to Download Free Weekly LNMs
- Type in the Coast Guard Navigation Center’s site address (http://www
.navcen.uscg.gov/lnm/default.htm). - Click on your area on the Coast Guard Districts map.