How to Buy Marine Electronics
GPS Chart Plotters
A typical chart plotter consists of a display unit,
which is mounted at the helm of the vessel, and an antenna mounted on
top of the boat to track the GPS signals. The latitude and longitude
from the antenna are sent down to the display unit and then shown graphically
on the chart screen by precisely overlaying the vessel position on the
chart. An icon resembling the shape of a boat will appear on the screen,
and all chart information surrounding the vessel including buoys, water
depth, obstructions, and land masses will be displayed. Functions such
as navigating, zooming in and out on the chart, and creating waypoints
and routes are typical operations of most modern chart plotters. Here
are some common questions a consumer might ask while researching a chart
plotter to purchase for their boat.
What is the price range of the most popular chart
Units range from $500 for a small, basic, low-end unit
up to $18,000 for a large, sophisticated, high-end plotter.
What will be the primary operations
of the chart plotter?
A chart plotter will let you easily navigate with the aid
of an electronic chart. Most units have a “point and shoot” feature
that allows a user to move the screen cursor to a designated location,
and navigate to that point with the press of a button. You can easily
add waypoints onto the chart, or manually enter waypoints from a
logbook. A plotter with a built-in keypad is always best because
it easily allows you to enter names and numbers associated with waypoints
Most modern units have the capability to be connected
to a home PC or laptop. This feature allows a user to enter waypoints
and routes at home using some type of navigation software, and then
they can bring a laptop to the boat and download all of the created
waypoints into the GPS.
What is the difference between WAAS and DGPS?
and Beacon DGPS are two forms of differential signals that a chart
plotter can accept to make the unit more accurate. Beacon DGPS (also
called Coast Guard Differential) and WAAS operate on the same theory.
Basically, the correction is provided when a monitoring station calculates
the difference between where it knows it is and the place the GPS says
it is. In Beacon DGPS, this correction is broadcast on low frequencies
from the land-based Coast Guard beacon station itself. With WAAS, the
correction is sent from the master stations to the satellites for broadcast
over the same high frequency as the GPS signal. Because WAAS is satellite
based, this eliminates severe weather Beacon DGPS outages, which can
happen in a thunderstorm.
Most manufacturers offer GPS, DGPS, and WAAS
versions of their chart plotters. Although most people today are
buying WAAS plotters, for the ultimate in accuracy and reliability
some manufacturers offer a WAAS and DGPS combination versions of
Are most chart plotters easy to use?
Many chart plotter manufacturers
pride themselves on having the most user-friendly unit on the market.
A hands-on demo will tell the tale if a unit is easy to use or not.
Chances are if you can easily operate the unit in a showroom, you
shouldn’t have a problem operating
it on the boat. Having a chart plotter that is not user friendly or
intuitive is a bad idea. You do not want to have to break out the
manual every time you leave the dock. Boating is supposed to be fun;
reading an operator’s manual every time you go out is no one’s
idea of fun.
What level of performance should I look for?
The performance of a chart
plotter will greatly vary with price. A lower end unit will generally
perform slower than a higher end unit. Things to look for are zooming
speed, screen redraw while scrolling across the chart, and how fast
a unit responds to a button press. A good thing to remember is, you
don’t want to be waiting for
a unit to execute a command if you are in a critical situation such
as at night, in fog, or in a tight channel with a lot of current.
You want to press a button, and have the information displayed almost
instantly in front of you.
Are there different types of charts?
One major feature of a chart
plotter is the ability to read small micro cartridges called vector
chart cards. These chart cards will contain buoy data, water depth,
bottom contours, obstructions, land masses, and port information.
Vector chart cards are typically sold in regions and will contain
all of the particular chart data for a specific region. (Example:
Typically the East Coast of Florida is on one chart card; however,
regions vary by manufacturer.) The way the actual chart appears on
the screen differs by manufacturer as well.
Raster charts are CD-ROM
based charts to use on PC-based charting systems. These are scanned
in paper charts and are used in larger chart plotters with a screen
size greater than 8 inches.
Can chart plotters communicate with other
electronics on the boat?
Most GPS units can communicate with other
electronics via NMEA data sentences. This data communication is also
called interfacing. Plotters can be connected to drive an autopilot,
send GPS data to a radar or fish finder, send distress signals to
a VHF radio, and can also connect to a PC navigation program. An
authorized installer will know best how to interface different pieces
of gear so they can communicate with each other.
What display features
Choosing a display size for a chart plotter basically
depends on the amount of dash space you will have to mount your electronics.
Chart plotter displays are typically between 5 and 12 inches. This
is not the physical dimensions of the unit, but the diagonal dimension
of the screen’s
viewing area. There are basically two versions of screens available
today: color and black & white (monochrome). The monochrome versions
are typically lower priced than the color models. Most buyers today
are purchasing color units because of the rich and vivid colors that
appear on the screen. It is also easier to pick out buoys, land masses,
and channels on a color screen.
Choosing a waterproof display is
also important if the unit will be exposed to any weather or spray.
Most chart plotters are waterproof or splashproof, but be sure to
check the manufacturer’s specifications.
Is sunlight an issue?
Most color displays on the market now are readable
in direct sunlight. Manufacturers will use sunlight readability as
one of their main advertising points to the customer. If there is
no mention of sunlight readability in the product literature, the
unit is designed to be in an enclosed area, with minimal sun. Asking
a sales person to power up the unit on a sunny day is a good idea.
Some color displays can look bright in a showroom and not so bright
outside in the sun. Monochrome displays are also traditionally easy
to read in direct sun.
What about reliability and warranty?
Chart plotters will be one of
the most important pieces of electronic equipment on the vessel,
and should be viewed as an investment, and not just a purchase. After
all, you’ll have to rely on it if you’re
ever stuck in the fog, boating in unfamiliar waters, or trying to find
that secret fishing hole.
Most boating magazines run a special issue
on electronics annually. Reading the reviews on what the experts
have to say can help influence your decision. One of the best sources
of information is the marina where the boat is kept. Most marinas
are tight-knit communities. Ask around. Talk to people who have run
boats for quite some time. Ask them what they like to use. Word of
mouth says a lot about a product.
As for warranties, most manufacturers
offer one to two years. The warranty typically covers parts and labor
and will vary by manufacturer. A quality chart plotter and installation
should typically last five years or more.
Before making your purchase,
ask for a hands-on demo of the chart plotter. Touching buttons, looking
at the screen, and seeing the actual dimension of the unit can sway
your buying decision. You can also do side-by-side comparisons of
different units if you can’t
quite make up your mind.
Message from Scuba Steve:
After your hands on demo be sure to visit
http://www.scubasteve.biz to make your purchase.