How To Handle GPS Failure at Sea (and why it’s absolutely crucial to be prepared)

“For thousands of years . . . sailors used the constellations, sun, and moon to navigate to distant shores. Today, all that’s needed is a device called a GPS receiver. GPS stands for Global Positioning System, and it lets us know where we are and where we are going anywhere on Earth.”

NOAA National Ocean Service

GPS is a godsend. Indeed, mariners, road-trippers, tourists and adventurers of all kinds depend on this device to get from point A to point B.

But as wonderful as GPS is, it’s crucial that we not lose the ability to find our way without it. Because GPS is not immune to failure. It can stop working for any number of reasons, from a dead battery to a lost signal—or even intentional jamming.

The odds of your GPS failing might be slim, but unless you’re well prepared, the consequences could be life threatening.

How to Handle a GPS Failure

  1. Always Carry a Backup: Sometimes the only “fix” you need is a backup GPS. That is, if the problem is with your device itself (a dead battery or other technical failing), then a having a second device on hand will quickly solve your problem. Here’s a great piece of advice from Steve Henkind in Sail Magazine:

I like to carry a spare that is similar or identical to the main unit; if I should have to activate the spare, there’s no learning curve involved. Also be aware that most units go through a cold start the first time you turn them on in a new area; this means it may take several minutes, or longer, to establish a fix while the unit is searching for the satellites. That’s why, if you are passing through navigationally tricky waters, it’s a good idea to start up the spare beforehand; once the spare unit has a fix, you can turn it off. Periodically turning on the spare also allows you to check that its batteries are strong and functional. 

  1. Navigate Manually: If your GPS fails due to a lost signal, you’ll need to use traditional methods and tools (e.g. paper chart, compass, parallel rulers) to verify your position and calculate course headings and distances to the closest port of call. Again, this is why it’s important to learn—and maintain—manual navigation skills.

There’s a great article in the Daily Boater on how to navigate to shore without a GPS, including these tips on how to verify your position:

  • If you can see land and can draw lines of position back from preferably 3 or more points on your paper charts, you have to be where they intersect.
  • If you can see only one landmark, you can calculate a “running fix.” Get a bearing from your … compass to the one point you can see. Draw the line of position from you to it – and write down the time. While maintaining course and speed, give yourself some time before taking another bearing to that landmark and draw the new line of position and mark the time. 

Don’t know how to do running fix? This article in Cruising World provides a step-by-step explanation.

  1. Call for Rescue: When you can’t navigate to land, for whatever reason, it’s time to call for help. If you have a standard VHF radio and are within radio range of the Coast Guard, send out a distress call. Using its Rescue-21 system, the USCG can pinpoint your location and quickly begin the search and rescue mission.

Learn more about Rescue-21 here.

TIP: Prepare, prepare, prepare! Many expert skippers recommend that you always keep a manual log of where you are and what course you should be steering to make your next waypoint—and update it every 15-30 minutes. If your GPS ever fails, the information in your log will provide a good starting point from which to navigate your way back to land (or in the worst-case scenario, the information may help expedite search and rescue efforts).

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