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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 plotters?
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 and routes.

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?
WAAS 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 their plotters.

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 operator’s 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 are important?
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.

Author: ME

Message from Scuba Steve:
After your hands on demo be sure to visit to make your purchase.