GPS failure.Then what?

[Skipper]

If this topic has been analyzed, please direct me. I couldn't find anything in archives.

As most have discarded Loran and are GPS equipped in some form or another, what would the average sailor do if the GPS quit? IE: The satellite system goes down or is commandeered by the USG for national security, etc. Or, more likely, your GPS unit just fails or you lose electrical power.

Omitting backup units and other remedies for repairing the GPS situation, how would we navigate?

We have all sailed our patches long enough to dead reckon with the log and compass and\or use line of sight with good precision, even at night. However, what if we were near a foreign (different) port or enveloped in fog or at sea traveling to an island 80 miles offshore with a 2 knot (or so) windward current and THEN got into the fog etc etc.

Assuming most of us don't know how to use a sextant or the stars to navigate, at least not with reasonable accuracy, what would you do? What did they do in recent history prior to Loran and GPS?

 

[tommays]

Anchor

Well


I did get lost at night once way back before i could afford more than a compass and a bunch of stuff happened like the compass bulb burning OUT and a lack of enough spare flashlight batterys and the poor planing of youth got me stuck


I did what i could Anchor until i was able to tell were i was




Tommays

 

[Rick D]

Kinda Funny

When I have lost my GPS in the recent past, I get a bit queezy even tho I have two back ups. The truth is I have sailed most of my life without anything but a compass and AM radio. I no longer carry an AM radio that I could use to determine a null point, but if GPS was shut down for any serious time, it would be an option. I would have to figure out the antenna locations tho. I haven't looked in decades to see if they are still on the charts; I doubt if they are. Other than that, DR would be fine. For lengthy offshore work, I'd probably carry my old sextant and something with the tables on it, altho I'd have to figure out how to use it. Anyhow, as far an inshore work, a chart and depth tables work if you have a sounder. Just don't try a strange port at night or fog if you can avoid it. RD

 

[Don S/V ILLusion]

radar is good

in most any situation as a backup and serves as a redundant where-am-I source of info and in combination with a depth sounder to pinpoint a depth curve on the chart, can often verify a position quite precisely.

 

[MoonSailer]

Radio Direction Finder

I don't know if you can even find a RDF but it might work as a backup. I guess that I would observe what was observeable. Depth would be a good thing in a coastal area. Wave patterns might come in handy as a large island would change wave patterns. Birds...some birds are near shore only. Smells... Lights I have noticed a glow on the horizon over cities. Dead reckconing and reduced sailing speed at night if reefs are in the area. One thing I have noticed is that you have to see what is there and then match it to the chart. It is too easy to think that you are somewhere and then try to see what is on the chart. ALWAYS match what you see around you to the chart!!! Once you get visual references you can figure out your location. But if all else fails dropping the anchor is an option . I was told of a couple who tried to enter key west at night . They hit something and drowned!!!! If they had just dropped anchor and waited for daylight they might still be alive. So at night or in heavy fog reducing speed or stopping might be the best option. Actually if you fear tha tyou are too close to shore and might be driven ashore during periods of low visablity trying to reach open sea might be the best option.

 

[sailaway78]

Backups and backups

I am going to assume that you are referring to offshore, as mostly inshore there are bouys to guide you by, again making an assumption that you have paper charts so you can identify the bouys. First off in addition to the chartplotter, I carry a handheld GPS, which works on batteries. If all electrical on the boat goes down, the battery powered unit still works. And always have the necessary backup paper charts, which I will admit I seldom use. I would recommend practicing exactly the scenario you have described, using nothing but paper charts and a compass. Then even if the GPS system should go down, all is not lost. Always keep in your mind your approx. location and a compass course to (a) the nearest landfall and (b) your destination. I normally take notice of both at least once an hour. In addition to this a hand bearing compass can give you a pretty close location if you are within sight of any landmarks. Radar can be used for identifying a headland and sometimes a coast line. Depth finder can also be helpful at times. If I were crossing the gulf say from Tampa, to Port Isbell in S.Texas, I would have in mind an approx. compass course to Port Isbell at all times, and should all systems fail, I would then steer a few degrees north of that course. Thus assuring me that when I hit the beach I would know that I was north and not south of my destination, then turn south to reach it. Very good question, and I am looking forward to seeing what others have to say. Some pretty damn good sailors on this board.

 

[Mike B]

Water Depths & DR

I'd do what I did before I had a GPS and just plot a DR. Plus I use water depths as well. Having had my GPS quit on me I always carry a chart with me and frequently check water depths to validate my position. You can also use them to help guide you into a harbor. Take your time and study the chart before entering, know where the depths change and how gradual a change there is and you can make it in safely. Of course depending on conditions, amount of light, type of bottom, etc. I might choose to stand off until conditions improved.
Mike

 

[Buck2796]

Ummm...

Sat Nav has been discontinued,... but I believe Loran is still on.
Si Tex still sells a loran receiver... I'd be online ordering one...
Cause I'm not sure I like the implication of the first half of the phrase "Dead Reckoning".

 

[kloudie1]

NAVIGATION STUFF

Familiarization with the places you’ll be travelling through is a big one..Google Earth is great for doing this as is http://demo.geogarage.com/noaa/.. Then I have my first chartplotter, only installed about 6 months ago, then a hand held GPS, and finally an old but still very functional Raytheon (pre Raymarine) LORAN unit. The GovMint decided to keep that system on for several more years. Of course, the LORAN and my handheld only give position (yes speed and COG to waypoint but no charts) so I always have current charts of my route, both in paper and the most current ones on laptop.. WHEW.. Failing all of that, in the Gulf of Mexico, if you go north, pretty soon you'll find land.. then the only problem is figuring where!
DR is easier when ya remember that 60 kts is 1 mile/min , 6 kts is 1 mile in 10 minutes and 3 kts is one mile in 20 minutes

 

[Ross]

I have given this question a lot of thought. The first thing

I need is the ability to keep time. Without that I would be truly lost. I carry a copy of Reed's Nautical Almanac with tide and current tables. I carry an up to date Old Farmers Almanac. It gives daily declinations of the sun. I have a Davis mk 3 sextant. Thus I could find latitude and if I tried real hard I could get longitude within a degree.
Given the fog, night time, poor visibility given in the question I would proceed very cautiously even heaving-to if necessary.
I carry paper charts and a lead line and have a good compass. I own a taffrail log but I don't carry it.

 

[Rick Webb]

Pull in Somwheres and Ask

Just like Capt Ron

 

[George H260]

No charts?

My first navigation lesson involved following the depth contour on a chart.

Before any electronics, sailors worked hard to have the most current charts for the area, and kept detailed records of in-shore depths. The sounding lead was a sailors best friend.

Using the sun/moon/stars and depth contours sailors could navigate the most difficult seas and harbors.

The navigation skills of our ancestors are amazing; Capt William Bligh and Joshua Slocum are only two examples...

That said, there are thousands of wrecks that are testimony to how dangerous the sea can be and not all of our predecessors were really very good (or lucky) at finding their way...

 

[Ross]

A lee shore is a terrible place to be!!! especially if you aren't

sure where you are. If I were somewhere off the east coast of the USA at night I would head east until morning.

 

[David10790]

Compass, Watch, Dividers, Rulers and Chart

Assuming you know where you were when you started and what time it was, these basic tools can get you almost anywhere. I took an Offshore Sailing School course and sailed overnight from Tortola to St. Maarten, about 110 nm of open ocean, using only the above. We got there. No advanced math or tables needed. Even if your GPS fails you will likely still have your depth, speed and log; even without these dead reckoning with attention to detail will get you through.

 

[william24424]

Dead reckoning...

Other back-ups mentioned, and a healthy fear/respect for the ocean. Your problem excludes the noon shot/star positioning because of fog, however, if clear, a few of us might find the latitude from the sextant, I've yet to get an accurate longitude (haven't given up yet) New England weather changes quickly, my list of equipment for coastal cruising is as follows: handheld gps, loran, radar, charts, back-up batteries, sextant, compass, knot meter, dividers, spare charts, handheld compass, vhf radio, back-up handheld vhf, calculator, depth meter, 2 timepieces, and a cigar just in case I need to smoke.

 

[Mike B]

No need to head East

Ross no need to head East, just keep an eye on your depths and the chart. Stay off a couple of miles and unless you're in an area know for shoaling you'd be fine just to heave to.
Mike

 

[JoshGray]

I may have missed this in the previous

responses, but the very first thing you would do if the GPS failed was immediately record your position, or last known position, on your chart. From there, use your compass and DR to get where you want to go. If you had a sextant, tables, and the knowledge necessary to use it... well, you're no too worried. You're also probably not worried b/c you could always teleport back to the past where those things belong. I kid, I kid. I say this b/c I'm jealous that I don't have one. And yes, you should always have a chart, and the prudent sailor will record positions on the paper chart at specified intervals (when appropriate, of course... I don't bother if I can see familiar land). All the previous responses seem to be pretty much dead-on though.

By the way, I got to navigate my way back in from the ocean after dark for the first time a couple of weeks ago. It was very, very challenging even with a chart, even having sailed those waters in the daylight for several days prior, and even having made notes on compass courses from particular ATONs. As soon as the big light went out, it was like someone lit up a christmas tree. Yeah, I could see the 'green one'... and that other green one, and those fifty-six red ones, and a dozen or so blinking white ones... you get the picture. The lights on the shore, towers, stoplights, etc. made it a real challenge. I'm pleased to have gotten that experience though.

 

[Ross]

Last weekend Nancy and I stayed in the slip and

messed about with the boat and watched the lights. We watched boats at anchor that didn't display an anchor light. (we knew they were there because we watched them drop the hook)some used solar walk-way lights, almost invisible.) We watched a tug come up river with barely visible lights on the barge. I would not consider making a night passage if the water way was narrow and there was traffic. The risk is just too great.

 

[Ross]

Mike, The thought of a lee shore scares me

so I want a lot of sea room.

 

[Joe]

if you're offshore...

you take your last known position and figure a dead reckoning course from that point the best you can. To learn the principles of dead reckoning, pick up a copy of John Rousemaniere's "Annapolis Book of Seamanship" which devotes a siginficant amount to piloting and dr. Anyway, you DR until you can fix your position using navigational aids, celestial navigation, another boat, etc.... make your adjustments and continue DR until the next opportunity to fix your position. To DR you'll need a compass, chart, time piece and a speed log.

Before the advent of reliable chronometers sailors used the noon fix to establish their lattitude and used DR to estimate their longitude. The sailing master, masters mates and quartermasters were charged with the task of recording the DR information at the turn of each 1/2 hour glass. They would measure speed by casting the log off the stern and then count the knots in the line as if reeled off while someone marked the time. Course direction was steered by the quartermasters and logged by the watch officer or mates.