What Is a Chartplotter and What Is It Used for on a Boat?

A chartplotter is a boat navigation device that combines GPS positioning with an electronic nautical chart and shows the vessel's position in real time on a screen. The device enables safe navigation by showing the boat's exact position, its track, and the direction to your destination. It differs from a plain GPS unit in that the position data is displayed on a chart background showing channels, depth data, harbors, and other features critical to navigation. In Finland's fragmented archipelago, an electronic navigation device is a near-essential safety item for many boaters, making getting around safer and more comfortable in every season.

How does a chartplotter work in practice?

The device's operation is based on GPS satellite positioning and electronic charts. A built-in GPS receiver picks up signals from multiple satellites and uses them to calculate the boat's exact position. This position data is combined with nautical chart data stored on the chart card, so the vessel's position is drawn on the chart on the screen in real time.

Modern devices typically update position data 10 times per second, enabling accurate navigation even at higher speeds. GPS accuracy is typically about 3–5 meters in normal conditions, and with WAAS/EGNOS correction it can reach 1–2 meters. In the Finnish archipelago, this level of accuracy is sufficient for safe navigation along channels and into harbors.

Devices need a separate chart card containing the nautical chart data needed for navigation. The most popular chart options are Navionics, C-MAP, and Garmin BlueChart. Chart card choice depends on the brand of navigation device you use, since, for example, Garmin generally uses its own charts, while Raymarine, Lowrance, Simrad, and B&G are compatible with Navionics and C-MAP charts.

Installing a chart card is simple: the card is inserted into the device's memory card slot, after which the navigation device reads the chart data automatically. Most modern models use microSD cards, and older devices may have a standard SD card slot.

Basic chartplotter features and functions

Every chartplotter includes certain basic features that make navigation safe and convenient. The screen shows the boat's position, course over ground (COG), speed over ground (SOG), and track. The device also shows distance and direction to selected route and turn points, plus an estimated time of arrival (ETA).

Route planning is one of the most central functions. A boater can plan a route in advance by marking turn points on the chart, and the device guides toward the next point by providing clear navigation data. As the boat approaches a turn point, the navigation device signals with an audio alert and automatically switches to guiding toward the next leg. More advanced models include automatic route planning (Auto Routing), which accounts for the boat's draft and overhead clearances and makes use of official boating channels.

A typical chartplotter includes the following features:

• GPS positioning and track recording (Track)

• Creating and managing waypoints and routes

• Displaying depth data and channel markings on the chart

• Harbor information and service search function

• Instrument functions: speed, heading, distance, and time

• Anchor alarm and MOB (Man Overboard) function

AIS vessel traffic display is an add-on that's especially useful in busy waters and poor visibility. With an AIS receiver, nearby vessels, their heading, and speed are drawn on the screen, significantly improving situational awareness.

A multifunction display expands what you can do

Many modern chartplotters are multifunction displays (MFDs), where navigation functions can be combined with the boat's other systems. The NMEA 2000 network protocol allows different devices to be connected to the same system, so a single screen can control the chart, fishfinder, autopilot, engine data, and even the entertainment system.

A popular combination is a chartplotter and fishfinder in the same unit. The screen can then be split so that, for example, the nautical chart shows on the left and the sonar picture on the right. This is especially useful for anglers who want to track both their position on the chart and the underwater world at the same time. Raymarine, Garmin, Lowrance, and Simrad all offer a wide range of combo units for different uses and budgets.

Networking also opens up the possibility of controlling the autopilot directly from the navigation device's screen. Once the device and autopilot are connected to the same network, you can activate a route and let the autopilot steer the boat automatically from one turn point to the next. This frees your hands for other tasks and makes long passages more comfortable.

For most people, the plotter is the boat's most important electronic device and the heart of the whole system, so it's worth taking the time to choose it carefully. "Chartplotter" is somewhat of a misleading term nowadays, since most plotters on the market are actually multifunction displays that can be connected to all kinds of functions.

Chartplotter or smartphone – which suits boating?

Mobile apps such as Navionics Boating, Loisto, and Savvy Navvy have brought electronic navigation within reach of every boater via smartphone. Phone apps are affordable, easy to use, and always on hand – but they have clear limitations compared with a fixed navigation device.

The biggest advantage of a fixed navigation device is reliability. These devices are built to withstand sea spray, direct sunlight, temperature swings, and continuous use season after season. Screen brightness is typically 2–3 times better than on a regular smartphone, making it easy to read even in bright sunshine and with polarized sunglasses.

Another major advantage is that a fixed navigation device draws power from the boat's electrical system. A phone's battery can run out at a critical moment, while a chartplotter works as long as the boat has power. In addition, the phone is often needed for other things too – emergency calls and staying in touch – so reserving it solely for navigation isn't always practical.

Phone apps work well as a backup navigation system or for occasional day boating in familiar waters. For longer trips, unfamiliar waters, and more serious boating, a fixed navigation device is clearly the safer and more practical choice.

A phone is a good backup navigation system, but it doesn't replace a fixed chartplotter. Screen brightness, water resistance, and the ability to network with other devices make it superior, especially on long passages and in unfamiliar waters.

How do I choose the right chartplotter for my boat?

The most important criteria when choosing a navigation device are screen size, intended use, expandability, and budget. When thinking about screen size, keep in mind that too small a device makes reading the chart difficult, especially in sunshine, but too large a screen can be in the way in a cramped helm or block visibility.

When choosing screen size, the following recommendations can help:

• 5–7 inches: Small boats, jet skis, dinghy sailing, backup navigator

• 9 inches: The most common choice for day boats and fishing boats – a good compromise between size and usability

• 12–16 inches: Larger motorboats, sailboats, and professional use

Intended use significantly affects model choice. Anglers benefit from a combo unit with both navigation functions and a fishfinder – this lets you see both your position on the chart and the underwater world on the same screen. Sailors, meanwhile, appreciate models that display sailing data, such as B&G devices with built-in wind angle, VMG, and other data important for sailing. For cruising boaters, good chart support and the ability to connect an autopilot to the system matter most.

Networking is an important feature if you're planning to expand the system later. An NMEA 2000-compatible device allows an autopilot, VHF radio, wind instruments, radar, and other devices to be connected to the same network. Stand-alone devices, on the other hand, suit those who want a simple, affordable basic solution.

Tips for beginners

It's worth starting to use a new chartplotter by getting to know it calmly at home or at the dock before heading out on the water. Most navigation devices have built-in tutorials, quick guides, and simulator modes that let you learn the basic functions quickly without the boat needing to be moving.

Here are the six most important tips for a beginner user:

1. Mark your home harbor and important places as waypoints. Once your frequently used locations are saved, navigating between them is quick and easy. You can also group waypoints into folders, for example "Home waters," "Fishing spots," or "Places to visit."

2. Always record your track. The Track function automatically saves your route to the device's memory. The track lets you safely retrace your route if visibility drops due to fog or darkness.

3. Check your chart's update status regularly. Navionics and other chart manufacturers continually update their charts, and an up-to-date chart is the foundation of safety. Channels, harbors, and depth data can change over the years.

4. Don't blindly trust automatic routing. Automatic route planning is a useful aid, but you should always check the final route yourself. In Finland's rocky waters, the algorithm doesn't always account for every special feature.

5. Keep a paper chart and compass on board. Electronics can fail unexpectedly, for example due to a lightning strike or an electrical fault. A paper chart and compass are still important equipment on every boat.

6. Practice emergency functions in advance. It's worth practicing the MOB (Man Overboard) function before you actually need it. Most devices have a quick MOB button that immediately records the position.

Maintenance and updates

A chartplotter requires little maintenance, but regular upkeep extends the device's lifespan and ensures reliable operation. Wipe the screen with a soft microfiber cloth and fresh water after every outing, especially in salt water. Don't use alcohol-based cleaners, as they can damage the screen coating.

Chart updates should be done at least once a year before the boating season starts. Most chart manufacturers offer an annual update entitlement that includes the latest channel changes, depth data, and harbor information. Navionics charts can be updated with the Chart Installer program on a computer or via the ActiveCaptain app on a mobile device.

Software updates are also worth keeping current. Manufacturers regularly release updates that improve performance, fix software bugs, and add new features. Update instructions are available on the manufacturer's website or in the device's manual.

Frequently asked questions about chartplotters

Does a chartplotter need an internet connection to work?

No. The device works entirely independently, without a network connection, using GPS satellites and the chart card installed in the device. An internet connection is only useful for chart updates and weather services.

What's the difference between a chartplotter and a fishfinder?

A chartplotter shows the boat's position on a nautical chart using GPS, while a fishfinder uses reflected sound waves to show what's under the boat. Many combo units include both functions in the same device.

Can the device be used without a chart card?

Technically yes, but the practical benefit is negligible. Without a chart card, the device only shows the boat's position on a blank background, with no nautical chart data available. Some devices include a built-in basic map, but it's usually too coarse for precise navigation.

How long does a chartplotter last in use?

Quality devices typically last 8–15 years. Electronics aging and the end of chart update support are usually the reasons a device gets replaced before it actually breaks.

How much does a chartplotter cost?

A simple device costs around €300–500. Mid-range combo units with a fishfinder cost €600–1,500, and top-tier models can exceed €3,000. In addition, a chart card typically costs €100–250.

Which brand is the best?

There's no single "best" brand – the choice depends on intended use and preference. Garmin is known for ease of use, Lowrance and Simrad are popular among anglers, B&G is the sailor's choice, and Raymarine offers versatile options for every use.

Chartplotters from Marinekauppa

A chartplotter is today's boater's most important navigation device, combining GPS positioning with an electronic nautical chart. It significantly improves navigational safety and comfort, especially in Finland's rocky waters. While phone apps offer an affordable option for occasional use, a fixed navigation device is superior in reliability, screen quality, and expandability on long passages and in demanding conditions.

In Marinekauppa's extensive range you'll find chartplotters from leading manufacturers: Raymarine, Garmin, Lowrance, Simrad, B&G, and Humminbird. The range includes both stand-alone navigation devices and combo units with a built-in fishfinder. Remember to get a suitable chart card covering the waters you need – for Finnish sea areas, the most popular choice is Navionics EU644L!

Sources

GPS.gov – Official GPS system information and technical specifications

Navionics – Electronic nautical chart manufacturer

Raymarine – Marine electronics manufacturer

Disclaimer

This guide provides general guidance only and does not replace the product manufacturer's operating, installation, or service instructions. Marinekauppa is not responsible for actions taken based on this guide or their consequences. Always check product-specific instructions and consult a qualified professional if needed.