Hidden Dangers of Chartplotters Every Sailor Should Know

Chart Plotters are wonderful; perhaps the biggest step forward in navigation since the GPS was invented. But they do have some major issues that are dangerous that nobody seems to talk about. The biggest issue is that as you zoom in you lose perspective of where you are in the body of water; when you zoom out, you lose critical details that are required for safe navigation.

This means to navigate safely, you need to zoom in to see full details such as the depths soundings and proximity to dangers in the water close ahead. However, this close up view does not give you the overall situational awareness to determine if you are on course, so you need to zoom back out to see the surrounding area, resulting in constantly zooming in and out, yoyo effect. This is a limitation of the screens sizes and the compromises on the amount of details that can be shown at the various scales.

Even if you preplanned your route and check if for hazards, when you are sailing you will tend to tack off your course significant distances that will take you into areas that may have wrecks or rocks or other obstructions so it is important to double check the course ahead.

More than 15 years of navigating in coastal waters have taught me the simplest solution; multiple chart plotters at the helm completely mitigate the issue and provide redundancy. I use three to give me the simultaneous full understanding of all close approaching dangers, the depths and the overall situation from a short, medium and long range view all without ever touching a button.

This also gives you assurance that your fix shown on the plotter is correct; all three should always match; there are many parts of SF bay that seem to have reception problems although these areas seem to have shrank considerable the last few years as the technology improves. I typically add a new plotter every 5 years and retire the oldest of the 3; this gives me the latest technology with updated charts while maintaining redundancy.

Having multiple plotters allows me to work on one chart plotter to look at details, plan routes or change configuration while still having the other chart plotters showing were you are so you are not blind as you dive in to the menu system and lose your navigation view; always maintaining your situational awareness is critical operating in coastal areas.

As you can see in the video above the Gemini 105MC provides an excellent protected helm station to mount multiple units without interfering with your field of view; I really love having everything I need to safely operate the boat within my reach at the helm. It gives me the peace of mind to focus on sailing well; not playing with the plotter constantly.

As you get further offshore away from land, your attention to your position obviously is less critical, but most of us operate in coastal areas where you are constantly navigating through shallow water and narrow channels.

This issue of a single chart plotter zoomed in or out too far not showing small obstructions ahead has resulted in boats running aground both on SF bay and in high profile offshore races such as in the Volvo Ocean Race when team Vestas Wind ran aground in November of 2014 (see video below) so even with professional racing crews; so it can easily happen to the typical shorthanded cruiser.

To me, it critical to always have at least two chart plotters in clear view in front of the helmsman. There was a day when navigation was difficult and the units were fragile which forced navigation functions to be done below; but those days are long gone. A couple cheap Garmin GPS units mounted in front of the helmsman could have easily given the helmsman enough warning to avoid the grounding, on a million dollar yacht such as these, it seems incredible this could happen, but zooming in and out is tiring and unlikely to be done often when offshore, even when you have years of experience.

So please learn from these tragic mistakes, and avoid this issue; be safe out there.

Fair Winds

Volvo Ocean Race Vestas Wind Report: http://www.volvooceanrace.com/static/assets/content_v2/media/files/m36616_team-vestas-wind-inquiry-report-released-on-9-march-2015.pdf

SAVE the Schooner Aldebaran gofundme page: https://www.gofundme.com/3ifhhg

Inside Track - Leg 2 #8 | Volvo Team Vestas Wind Runs Aground in Nov 2014