Catamarans & Sailing | Sailing Tips & Tricks

The Cruiser’s Chartplotter

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One of the most important pieces of equipment on a cruising boat, chartplotters aren’t often used to their full potential.

What is a Chartplotter?

It sounds simple enough – something that plots charts – but a chartplotter is a complicated and extremely valuable piece of equipment on the boat.

In fact, the manufacturers would like you to start calling them MultiFunction Displays (MFDs), as they do so much more than just plotting charts.

For the purpose of this post, I’m going to continue to refer to them as chartplotters.

What Chartplotter Do We Have?

We have a Raymarine e120 MFD. The e120 is now a legacy model, replaced by the Axiom Pro 12 S + Navionics. Read why we chose Raymarine and the specifics about our electronics system.

While I will try to address some of the features of Garmin, my screenshots and experiences are with Raymarine.

There is also a difference in the actual charts used with the software. Raymarine has its own chart software – called Lighthouse – but we, and many cruisers we know, use Navionics. Some of the features mentioned in this post are through Navionics.

Useful Chartplotter Features

There are so many under-appreciated features hidden inside your chartplotter.

NMEA

NMEA (National Marine Electronics Association) is a not-for-profit organization that has organized an electrical standard for the multiple components of marine electronics to use. Our electronics system has a NMEA backbone that provides one network to plug devices into.

What this means is that once your system is set up, new devices are “plug and play”. For example, we have added sensors to our engines that can read engine temperature. This data is added to the options available on any of our NMEA displays, meaning we can modify any of our display screens to show engine temperature. Pretty cool!

Garmin devices are also compatible to NMEA.

Basic schematics for our electrical system installed in La Rochelle.

MicroSD Card

The microSD card is where much of the information is stored – the charts themselves, files, tracks, waypoints, etc. The microSD card is removable and there are two slots on our chartplotter.

When you buy charts, you are actually buying a microSD card with the charts on it.

User Manual

The User Manual for your chartplotter is available to view on your chartplotter. There is a user manual icon on the home page.

Other PDFs can also be saved and viewed on your chartplotter, like the owner’s manual for your boat.

Buddy Tracking

If you have AIS, you can mark an AIS target as a “Buddy”. This boat will now show up on your chartplotter with a special icon. When a buddy pops into your AIS range, your AIS will beep. This isn’t super useful, but fun!

Tide Stations

Select any point on the chart, go to Find Nearest, and select Tide Stations. The chartplotter will present you with a list of the nearest tide stations, which you can then view the local tide charts.

Man Overboard Mode

Our chartplotter has a Man Overboard (MOB) function available. MOB has two modes: Dead Reckoning or Position mode. Dead Reckoning mode calculates position using wind and tides and should be more accurate.

Measure

The Measure feature can help you determine the distance between any two points on your chart. You can measure the distance between two points or distance to your boat.

Garmin offers a similar measure feature.

Touchlock

On the home screen, you can engage the Touchlock feature. This is why I think the HybridTouch system is so critical. A time or two, with heavy rains and salty screens, the touch sensor has misbehaved. You can easily navigate to turn Touchlock on, which disables the touchscreen feature and leaves you with the buttons and knobs to navigate.

Waypoints, Routes, and Tracks

Waypoints

Waypoints are a single position on your chartplotter. You can name and organize your waypoints into folders. By touching the waypoint, you can see the latitude & longitude, range (distance from the waypoint to you) and the bearing (compass heading from you to the waypoint).

You can set a waypoint by touching anywhere on your chartplotter, or by pressing the WPT button, which will give you the option of setting a waypoint at the vessel, at the cursor, or at a specific latitude & longitude.

Routes

A route is a series of waypoints set in a specific order. You can build a route on your chartplotter or in a program like SAS Planet or on your chartplotter you can build a route from your track.

You can then use your autopilot to follow the route.

Imported Route

Tracks

Tracks are the record of where your boat has been. They are automatically created with three setting choices: auto (minimizing track points whilst maintaining the correlation between the track and the actual path followed), time, and distance. We have ours set for auto.

Unfortunately, each track can contain 10,000 track points and you can only have 16 tracks. We blaze through that and have to export our older tracks to save them and then delete them from our chartplotter.

Our track around the Seychelles.

Data Displays

A view of the charts has several locations where information can be displayed.

Databar
Extended Databar
Databoxes
Status Bar

The information displayed here can be modified by going to Homescreen > Customize > Databar Set-up menu.

Display Orientation

The chartplotter allows you to change the orientation of the chart that is showing. You have three choices: North-Up, Course-Up, or Head-Up.

We put the chartplotter in North-Up mode when we are planning, but keep it in Head-Up mode otherwise.

Vessel Position

This is the latitude and longitude of where your vessel is currently located.

Speed

Calculated through the paddlewheel on your transducer, Speed is actually Speed Through the Water. It is a measurement of how fast the water is running past your keel. If this is zero, your paddlewheel is clogged. Pull and clean your transducer.

SOG

Speed Over Ground (SOG) is calculated from your GPS coordinates. This is the speed with which you are moving over the earth’s surface.

Speed Versus SOG

By comparing your SOG and Speed Through the Water, you can determine the currents acting on your boat. If your speed through the water is higher than your speed over ground, you have an opposing current. If your speed through the water is lower than your speed over ground, then the current is working with you.

Heading

The heading is which direction you are facing as read by the compass. We do have a physical compass installed at our helm station, which is showing us magnetic heading. The chartplotter can be configured to show true heading or magnetic heading.

Read more about true versus magnetic headings.

COG

Course Over Ground is what direction you are traveling, calculated on your GPS position. COG would vary from heading due to wind and currents. Just like with headings, the chartplotter can be configured to show true course over ground or magnetic course over ground.

Cursor Position

This is the latitude and longitude where your cursor is on the chart.

AWA

Apparent Wind Angle is read from your wind indicator at the top of your mast. This is the wind angle information that you need to trim your sails.

AWS

Apparent Wind Speed is also read from your wind indicator at the top of your mast. For catamarans, AWS is closely tied to reefing; we have a chart that tells us when to reef based on the wind angle and wind speed. In monohulls, many people will reef by feel, as monohulls heel over the higher the wind speed is relative to the sail area.

TWS

True Wind Speed is calculated from your AWS and Heading.

Apparent Wind Speed versus True Wind Speed

Settle in for a physics lesson!

If your boat is stationary, your apparent wind speed equals the true wind speed.

In a physics equation, the apparent wind speed is a combination of the vector of the wind and the vector of the speed of the object.

If the true wind speed is 10 knots, and your boat is moving directly into the wind at 5 knots, your apparent wind speed is 15 knots.

If the true wind speed is 10 knots, and your boat is moving directly downwind at 5 knots, your apparent wind speed is 5 knots.

True wind speed is great for being able to compare the winds around you to the predicted forecast, but most cruising boats sail to the apparent wind speed, as that is what is exerting forces on your boat.

VMG to Waypoint

Velocity Made Good tells you how fast you are moving towards your waypoint, calculated using your bearing to waypoint and speed over ground.

Let’s say you are motoring directly into the wind and traveling at 5 knots, but you decide to raise the sails and tack your way upwind. Now you are sailing 60 degrees to the wind at 7 knots. VMG will calculate your speed towards your waypoint, which will decrease the further away you get from the direct line.

DTW

Distance to Waypoint is the direct line between you and your destination.

Time

The time as set by you. Vessel time is not tied to any connection, so you have no way of knowing when you cross a time zone out at sea. You make your own time and decide when to adjust the clocks.

Gnd Log Trip

Your mileage. Twice during our cruising life, we woke up to find that our boat had been magically transported some great distance for a moment overnight, such as deep into the interior of England.

When this happens, the data point can be removed from your track, thus cleaning your track up. However, we have been told that it can not be removed from the Ground Log Trip. This makes the Gnd Log Trip pretty worthless because we have to know how far off our Ground Log Trip actually is.

Rudder

The rudder angle, indicating the direction your rudder is set to steer to course. The more your boat is getting pushed by wind and waves perpendicular to your course, the higher your rudder will be turned.

The rudder angle is read from a sensor in our Raymarine autopilot.

Depth

The distance from your transducer to the seabed. This should be calibrated according to how far your transducer is from the waterline.

Pilot Status

This displays what mode your autopilot is currently running.

BTW

Bearing to Waypoint is the angle between your current course and your waypoint.

TWD

True Wind Direction is calculated from your AWA and your COG. This is helpful to compare the conditions to the forecast.

What feature do you find helpful?

I’m sure there are plenty more features in chartplotters I don’t know or use. Do you have one I should check out? Let me know!

6 Comments

  1. Perfect… I thought my E series had to go to Raymarine for touch screen repair as I had read they often fail as mine seemed to have. But after reading your article I just checked the Touchlock function and sure enough, it was somehow in the lock mode.
    Touch screen function restored and embarrassing return to Raymarine avoided!

    mick

  2. Another incredible blog post. The attention to detail is magnificent! This should help lots of people better understand the underlying functions of many different chart plotters. I love what you two make together!

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