2008 REED’s East Coast Edition - Navigation
can also customize the chart to only proffer for encoding the chart so that it could only
the information they need. be displayed and used with that company’s
Companies producing electronic charts software or display hardware. In the late
are introducing new products on an almost 1990s, the International Maritime Organiza-
weekly basis and keeping track of what’s tion (IMO), the marine branch of the United
available can be a full-time job. The major Nations, developed uniform standards for
sailing and boating magazines review new the creation of vector charts by international
equipment every month. You can also find chart agencies. In the U.S., two agencies
regular news and reports at www.panbo. produce official government charts to those
com, a marine electronics blog by magazine standards, NOAA (National Oceanic and
columnist Ben Ellison. Atmospheric Administration) and NGA
Types of Electronic Charts
(National Geospatial-intelligence Agency).
NOAA produces charts of the U.S. coastlines
There are essentially two types of electronic
for the public, while NGA charts the rest of
charts: raster and vector.
the world for the U.S. military. Many NGA
Raster charts are simply paper charts that
products are available to the public.
have been scanned into a computer. They are
NOAA charts are officially referred to as
generally less expensive than vector charts,
“Electronic Nautical Charts” or ENCs. While
maintain the appearance of paper charts and
ENCs are being produced for all the naviga-
can be easily viewed on any personal comput-
tional areas of the U.S., NOAA has also ap-
er. However, they have numerous drawbacks:
proved a form of raster chart (RNC), which
Because they are just scanned images, they
are now available online. For more informa-
are only as accurate as the resolution of the
tion on the availability of ENCs, RNCs and
scan, and can appear “blocky” when enlarged.
software to display them, see NOAA’s Web-
They are also difficult to update or alter. Fi-
site: http://chartmaker.ncd.noaa.gov/.
nally, file sizes for raster charts can be very
While the government has slowly moved
large, depending on the image’s resolution.
toward electronic charting, private compa-
Vector charts are computer generated. The
nies have flooded the market with a variety
elements of a vector chart are organized into
of both raster and vector charts. Most raster
layers. Each layer represents a specific type
charts can be displayed on personal comput-
of information—soundings, buoys, land
ers by a variety of software programs, but
features, lat/long lines, etc.—stored as geo-
many privately produced vector charts are
graphically referenced data in the chart file.
encoded so that they can only be accessed by
This design allows vector charts to be ma-
proprietary software or hardware. The qual-
nipulated in a huge variety of ways. They can
ity and features of private charting programs
be enlarged without losing their resolution;
vary widely, and there is no one best system
specific elements can be selected for display;
for all boats. Understand your needs and
they can be easily altered and updated; and
your boat’s electrical capacity before pur-
the file sizes are smaller. The disadvantages
chasing electronic charts.
are that they are substantially more expen-
sive, and because they must be created from
Displaying Electronic Charts
scratch, much of the globe is still not avail- Electronic charts can be displayed on
able, at least not from official government personal computers or on dedicated chart-
chart agencies. plotters. The format of the chart dictates the
Although many recreational boats use ras- type of hardware on which it can be used.
ter charts, vector charts are quickly becom- Dedicated chart-plotters usually use vector
ing the standard for electronic charting, and charts and tend to be more durable than the
have been adopted as the future format of average personal computer on a boat. Most
chart agencies worldwide. chart-plotters incorporate a GPS unit, and
Standards for
not surprisingly, GPS manufacturers are
Official Electronic Charts
some of the biggest producers of electronic
charts. The most sophisticated chart-plotters
Many companies began producing elec-
are designed to take input from other elec-
tronic charts over the last decade, and each
tronics such as depth sounders and radar,
of them used their own proprietary format
and can output information to an autopilot.
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