Do You Really Need A Chartplotter? A Navigator Explains!

Navigation at sea has been made both easier and safer with the continuing advances in technology.

A great example of this is the chartplotter. Each year, more and more people are fitting them to their boats, but that does not necessarily mean that you need to as well.

You do not need a chartplotter for navigation at sea, however, when used correctly they can make navigation much safer and simpler. If you do not use a chart plotter, you will instead need to use paper charts or another electronic system to be able to safely navigate.

Chartplotters are not required for any vessels at sea.

Small boats often do not have any requirements in terms of navigational or safety equipment, and those that do will probably be required to carry paper charts.

Larger boats and ships are required to carry either approved paper charts or a fully compliant ECDIS (Electronic Chart Display & Information System).

Chartplotters and ECDIS are similar in that they are both Electronic Chart Systems. The difference is that ECDIS is fully compliant with IMO performance standards, and carries an appropriate price tag to reflect that.

On a small boat, you would not consider an ECDIS, but you might consider a chartplotter.

The chartplotter will show you an electronic chart covering your passage, and automatically monitor your progress along your pre-determined route.

As chartplotters do not have international performance standards to meet, you will find that they are all slightly different to each other, with slightly different features.

If you choose to use one, you can select the chartplotter that meets your own requirements such as:

  • Screen size;
  • Features;
  • Mounting space;
  • Power consumption;
  • NMEA connectivity.

Unless you are legally required to carry a specific type of chart, you can choose to use a chartplotter for navigation if you wish.

On my own boat, I do not actually carry a chart plotter. I primarily use paper charts but also carry a chartplotter app on an iPad and mobile phone to aid my navigation.

What does a chartplotter do?

A chartplotter’s main function is to display an electronic chart and automatically plot your position on it using a GPS input.

Most have additional functionality which lets you plan your passage in advance by plotting the route that you intend to follow.

Chartplotters are one of the most convenient ways to display electronic charts on a small boat.

Most of them show vector charts, although there are some that will allow the display of raster charts too. Raster charts are scans of paper charts, and although they may look familiar, they are not well optimised for use on an electronic screen.

In fact, NOAA are in the process of sunsetting all raster charts as they no longer see them having a place in the digital future of navigation.

The future of digital charts, and chartplotters, is in the display of vector charts.

Vector charts contain a database of navigational information that a chartplotter can interpret and display to its user.

For example, a navigational buoy will have a position, characteristic, light, sound signal, name, and possibly extra notes. A chart plotter will interpret that data and show the buoy in the correct position when the screen is focused on the correct area.

Chartplotter users can “interrogate” the chart, and pull up all the data associated with the buoy, potentially getting far more information than is possible with paper, or raster charts.

Aside from the underlying chart data, a chartplotter also takes further data from a GPS.

It might be an internal GPS within the chartplotter, or it might be a separate GPS sending data through a NMEA network.

The chartplotter then plots your own boat onto the electronic chart, using the same reference system that it uses to display all the elements of the chart.

Your boat is continuously plotted onto the chart, enabling real-time monitoring of your position and passage.

What is the alternative to using a chartplotter?

A chartplotter is one of two main methods of displaying a chart to use on a small boat.

The other option is to use paper charts.

Traditional navigation has been conducted using paper charts for centuries, sometimes with very little apparent change in the charts over that time.

A lot of people prefer to use paper charts because there is no electronic element that could fail.

Paper charts have always been seen as the “default” option for all sorts of vessels, with governments around the world often insisting they are carried by large commercial vessels in addition to electronic charts.

As electronic charts are still relatively new, a lot of senior people in positions of authority have only experienced navigating with paper charts.

For this reason, you can still buy paper charts in most countries, giving you an alternative to using a chart plotter.

Over the next few years, however, this will be changing as the United States is in the process of phasing out all paper charts, including their raster equivalents.

You can use paper charts for navigation by drawing your passage plan on in pencil, then plotting your position at frequent intervals to monitor your progress.

The more frequent your plots, the better.

This is why so many people do prefer a chartplotter, however. Rather than manually plotting every 3 minutes, a chartplotter continuously plots your position. You can immediately see if you are heading off course.

Navigators will still need to have skills on paper charts, as it enables a better understanding of the fundamentals of navigation.

This always gives you the option of using a paper chart instead of a chartplotter, assuming paper charts are still being produced.

Can you use a tablet as a chartplotter?

You can use a tablet as a chartplotter by downloading an appropriate nautical charting app such as Navionics, C-Map or iNavX.

Modern tablets are very powerful computers, capable of a great deal of data analysis and interpretation.

Many of them are actually more powerful than the chartplotters that are fitted to most boats.

To turn your tablet into a chartplotter, you just download an app. My favourite is Navionics, but there are plenty of other alternatives.

Read my full comparison: Top 8 Apps For Marine Navigation.

With the app installed, you can then download a chart database covering the area you are intending to navigate.

It is the same vector information that is used by chartplotters. The app interprets it and displays it onto the screen so that you can view the full electronic chart.

Passage planning on a tablet is often easier than it is on a chartplotter because they are designed with excellent touch screens and the apps are optimised for touch screen use.

For monitoring, all tablets will be able to accept either an internal GPS feed, or use a Bluetooth GPS. Most apps will also be able to accept GPS data over WiFi if your boat has a NMEA to WiFi interface.

In summary, a tablet can be used as a chartplotter. It is actually my preferred plotter on my own boat. I like to use my iPad Mini as my chartplotter.

Tablets are not authorised by any administration as an acceptable form of navigation but when they are used as an aid, in conjunction with paper charts, it is fine.

For more detail about using a tablet as a chartplotter, check out my article with 9 tips for success: Can I Use A Tablet As A Chart Plotter: 9 Tips For Success

Can you use a mobile phone as a chartplotter

In the same way that you can use a tablet as a chartplotter, you can also use a mobile phone as a chartplotter.

They both run the same apps, so all you need is to download one of the chartplotter apps (Top 8 Apps), and purchase the charts you need.

The main disadvantage with a mobile phone is that the screen is often significantly smaller than it is on a tablet.

It is surprisingly easy to adapt to the smaller screen, but it does mean that you need to actively zoom in and out a bit more to be able to maintain a view of the bigger picture.

Mobile phones do hold one main advantage over tablets though. They usually have a cellular internet connection.

With an internet connection, you can download updates to your charts as soon as they are issued.

In summary, mobile phones can work as a chartplotter, but they are not ideal.

I like to use mine in addition to my tablet though, as a backup.

With Navionics, a single subscription gives me access to charts on my phone and my tablet.

Any routes that I plan are automatically pushed to all my devices, so I know that if my tablet stops working, and my paper charts get wet, I can still get home using my phone.

What is the difference between a GPS and a chartplotter?

The main difference between a GPS and a chartplotter is that a GPS gives your position as a latitude and longitude, and a chartplotter shows your position visually on an electronic chart.

A GPS provides the raw positional data that a chartplotter uses to plot your position, course, and speed, on its electronic chart.

You can use a GPS to navigate in conjunction with either a paper or electronic chart, but you cannot navigate with a GPS on its own.

It will tell you where you are, but without a map (or chart), you have no idea where you are in relation to other things.

A chartplotter contains the map that you need so that you can identify hazards and navigational features in order to find your way safely to your destination.

For a chartplotter to function effectively though, you need a GPS to give it positional data.

Most chartplotters have an integrated GPS, but you could also link it with a dedicated GPS through a marine network.

When you use a tablet or a mobile phone as a chartplotter, the GPS will either be provided by the device’s internal GPS, a Bluetooth GPS, or a GPS feed through your boat’s NMEA WiFi interface.

What is the difference between a fishfinder and a chartplotter?

A fishfinder is a sonar that shows the depths of various objects under your boat. It is used to find schools of fish.

A chartplotter is a navigational instrument that plots your position on an electronic chart. It is used for navigation.

Fishfinders are closely related to echo sounders, but they display depths on a screen rather than just displaying numbers.

When a sonar pulse leaves your boat, it travels through the water at the speed of sound. It bounces back off either the seabed or other objects that are in the water. By measuring the time it takes, the fishfinder calculates the depth under the transducer.

That depth is displayed visually on the screen. You will see a continuous line plotting the seabed if it is flat. 

Any school of fish will be visible as an image somewhere between the seabed and your boat.

Fishfinders are also great as a navigational tool because they can show you when you cross depth contours.

Although they can be used to help with navigation, fishfinders are primarily a depth detection tool.

Chartplotters, on the other hand, are purely a navigational tool. They take data that is already available in the form of an electronic chart, and they plot your position on it.

Sportfishing boats will often have a fishfinder and a chartplotter.

They will use the chartplotter to navigate to the general area that they want to fish, and then they will use the fishfinder to scan the water underneath the vessel to attempt to locate fish.

Interestingly, some nautical chart companies will allow you to upload fishfinder, or sonar, data to assist in creating more accurate charts.

Essentially, fishfinders are very similar to sonar systems that hydrographic vessels use, albeit far more basic. Nonetheless, they can still provide an additional source of data, particularly in areas that are surveyed infrequently.