When Your Chart Plotter Fails, Part 1 of 2

New Bern, NC

Are your piloting skills up to snuff? Have you become overly dependent on your GPS chart plotter? Those gadgets are so seductive, that it is hard to imagine being without them. Here are some common sense tips to avoid getting caught short.

Backups: We use a Lowrance chart plotter as my primary navigation device. I also have an Android smart phone with GPS and Navionics Chart Plotter software. I also kept my old smart phone that no longer receives cell phone signals, but the GPS and its chart plotter app still work. My wife’s iPad also has a GPS navigation app. In our ditch kit, we carry a Garmin 76 hand-held GPS, plus spare batteries. Five independent GPS units should be enough to assure that we never lose GPS function; right? Wrong; there are several ways to lose all backup GPS’ at once and some tips for what to do about it.

Lightning: In 2006 we were struck by lightning. It did a lot of predictable damage, but I was shocked to see that even some hand-held devices were fried by the EMP (electro-magnetic pulse). You could lose every single electronic device on board in a flash. The defense is to store electronic devices not in active use in a Faraday cage. The oven in your galley stove is a good place. Don’t do what I did though. I once forgot about the laptop and turned the oven on, resulting in laptop fondue. I also use cookie tins. They make good Faraday cages and come in many shapes and sizes.

Degredation: From 2005-2010 I used the anchor dragging alarm on our Lowrance chart plotter almost every night. But since then, hardly a night goes by without a false alarm. I learned that because of some launch failures and some budget problems, we have fewer than the full compliment of GPS satellites in the sky. They can’t cover every point in the globe every minute of the day. The practical effect is that my GPS sometimes calculates a position wrong by 300 feet or more, and that the error may persist for minutes before it snaps back. I’m told that the problem will get worse before it gets better again in future years. The more modern and the more expensive your GPS unit, the less vulnerable it is to degradation.

Malice: You may have heard that GPS signals can be easily jammed in a local area. You may even know that GPS signals can be spoofed giving inaccurate positions. It’s worse than that. Recent research shows that it is possible to attack GPS units via RF signals in ways that exploit bugs in particular makes and models. For example, there could be attacks specific to Garmin, or Raymarine, or any other brand. It is analogous to evil web sites that exploit bugs in the web browsers and the underlying operating system. We all know how unsuccessful all manufacturers of software have been in eliminating vulnerabilities. GPS units are no different. Still worse, hackers are closing in on ways to attack WAAS ground stations, and even the satellite uplink stations that support GPS. Also, need I mention cyberwar? The bottom line is that regional or even global GPS outages are not unthinkable in the near future.

But the prudent skipper doesn’t need a reason to plan for credible failures. So here are some ways to do that.

Always have paper charts for your cruising grounds on hand. Keep track of your current position on the chart or in your log. On the ICW, my wife notes the passage of every day marker, and moves a place marker on the chart to record that position.

On the ICW in normal daylight, you can always see the next day marker. You don’t need instruments at all as long as you keep your eye on the paper charts. If it is dark or foggy, drop your hook and wait. With our without GPS, it is too dangerous to navigate the ICW if you can’t

If you are inshore, or near shore where you can get a cell phone signal, your mobile devices will give a fair position estimate even without GPS. If you don’t have chart plotter software on your mobile device, you can still get raw lat/lon data. Google Maps or Apple maps will give you a pretty useful picture of your current position even without GPS. If you are near shore, learn to plot a bearing and distance to the nearest harbor entrance.

My phone tells me the time on shore, and the GPS tells me the time on board the boat, so who needs a watch any more? But in case of loss of GPS, an accurate watch becomes a critical part of your backup equipment. Carry one in the cookie tin.