Challenge: GPS Stops Working !

[Chattcatdaddy]

Here is the challenge:

While on a long passage i.e. crossing the Pacific/Atlantic/etc... all your GPS equipment fails (including backups) halfway thru the passage. With what you currently have on your boat what would you do to plot your course? Do you carry a sextant? Paper Charts? SSB? Also if your GPS is tied to a chart plotter then you also lose that feature as well.

[daddle]

I'll worry about that when it happens. GPS, and sextants are but a flash in the pan in the history of crossing oceans. No sextant or paper charts here.

I'd probably sail on and hail passing ships for info. That's an old technique.

[gcaptain]

Originally Posted by daddle

I'll worry about that when it happens. GPS, and sextants are but a flash in the pan in the history of crossing oceans. No sextant or paper charts here.

I'd probably sail on and hail passing ships for info. That's an old technique.

Your right, sextants to calculate Longitude are just a flash in the pan but, unlike you, early ocean explorers didn't just set out in ignorant bliss. Charts, star charts and sextant like devices to calculate Latitude have been around for centuries.... and it doesn't take much skill or equipment to figure out the latitude (even a rough guess at the Long) on your boat either.

[bewitched]

I don't carry a sextant and even if I did, I don't know how to use one. So that's out

My first navigation aid would be the chartplotter - which would go to DR positions as soon as it looses GPS. I'd also fire up one of my laptops with charting software on it as a backup

I'd also record DR positions from the chart plotter to the paper chart and record my own DR observations in case everything electical were to go down - which would be on the cards if I had lost all GPS data (2 fixed antenna, one handheld and an iphone).

I'd then head for some land - the bigger the better.

Other ideas:
Radio for position from passing ships
AIS for position from passing ships
Borrow/ buy a GPS from nearby ships / sailing boats
Follow the planes
Run down the latitude

[gcaptain]

Follow the planes?? Sure if you want to take a great circle course through the arctic.


AIS for position from passing ships? Sure but if ships are in the area why not just call them on the VHF and ask your position.

DR positions? These are much less reliable than paper DR tracks.

Plus, assuming your electronics is working, you could fire up a star plotting program to estimate your position. You can get coordinates via you Sat Phone. Etc.

What hasn't been mentioned is a failure in the GPS constellation. This actually happened to me while sailing the Bay Of Bengal in 2003. That time I called the USAF GPS watchstander in Colorado but he was of little use... since then I've carried a GLONASS capable unit.

[boatman61]

This happened to me on my first solo Atlantic crossing in '01'.... about 500miles NNW of the Azores.... basicly I worked off my last known position 7hrs earlier the calculated currents (daily averages) from my Atlanitic/Med Pilot Charts and threw in a bit of leeway for wind as I went along.... I had no power at all on the boat apart from a 12v car battery hooked up to a 10w solar panel for my tiller pilot so VHF calls were not an option.
I continued with dead reckoning on course/speed/distance towards the Southern Approaches... the first ship I managed to attract to get a fix from turned out to be a new Customs Excise Vessel on sea trial who... after going all over the boat... told me if I maintained my course I'd be in Falmouth 23 miles away before sunset... the relief was enormous as by my calc's I should have been there 2 days earlier.... figure the 5 days of calms I'd experienced earlier had screwed me up and I'd drifted South further than I'd allowed for...
And.... I had not missed and headed up the Irish Sea... my big fear.
The hardest part was forcing myself to hold steady... the temptation to start 'hanging East' was enormous... so a 47 day passage nonstop from St Martin came to a close... I entered Salcombe the next day.

[jcapo]

Two sextants and chronometer on board from before the days of GPS. I
haven't worked a sight reduction by hand in years and I doubt I could do
it in a reasonable amount of time if I had to. So I opted for the Starpilot
software running on a high end TI calculator for sight reduction. Backup
for that would be by hand on paper.

John

[aychbawdy]

You can get a cheap plastic sextant for less than $ 100. Then you must learn some-
-things. If using one saved your skin ?? Well now, just remember to take many shots at a time and carry an accurate watch. Shoot the sun at 12:00 noon when sun is highest and there's one fix. Then take many for lats.

A piece of cake to an smart mariner.

[aychbawdy]

Another thought.......given man's penchant to destroy himself, The Sun will
certainly outlive the Sats.

[daddle]

Originally Posted by gcaptain

...unlike you, early ocean explorers didn't just set out in ignorant bliss.

Bliss I have in spades. Ignorant seems unfriendly.

The only place I worry about losing the GPS fix or the chart plotter is in foul reef strewn waters like my recent crossing of the Sulu Sea. Out in the open ocean there is far more time to solve the problem. A sextant would be useless in a place like the Sulu Sea unless somehow one got really disoriented. Accordingly, this ignoramus printed out a few charts before sailing thru the reefs.

[simonmd]

Always have one clock or even just an old wristwatch, set to GMT. Then you can always work out your Lat (roughly) by seeing how far ahead/behind your are at midday in your part of the world. Put together with a simple sextant and youve got a Long fix as well. You should always have paper charts as a backup anyway.

[MarkJ]

one does exactly the same as if the sextant threw a hissy fit and jumped overboard or it was cloudy. Pre GPS we have had whole long off shore races without one fix.

DR

Try it.

[Lodesman]

Originally Posted by simonmd

Then you can always work out your Lat (roughly) by seeing how far ahead/behind your are at midday in your part of the world. Put together with a simple sextant and youve got a Long fix as well.

I think it's the other way around.

[conachair]

Originally Posted by Chattcatdaddy

Here is the challenge:

While on a long passage i.e. crossing the Pacific/Atlantic/etc... all your GPS equipment fails (including backups) halfway thru the passage. With what you currently have on your boat what would you do to plot your course? Do you carry a sextant? Paper Charts? SSB? Also if your GPS is tied to a chart plotter then you also lose that feature as well.

Sextant first, if that falls overboard not sure. Probably DR/EP then look for plane contrails. I wouldn't trust EP too much though, certainly in the Atlantic if you compare log readings to gps the currents can be all over the place, for days they might be close to the pilot charts then they can reverse or push you in a random direction for half a day for no obvious reason.

Contrails mean you're getting close though. Especially somewhere like the Azores, Europe would be easier, keep heading east, it's really big, you'll get somewhere eventually then ask a fisherman and see what language he speaks

[MarkJ]

OK, now the sexytant has taken a swim and we are too stupid to use DR.

then we could just grab the hand bearing compass....

Look up the tide charts for where we have decided to make landfall... I am going to St Martin but theres no tide info for there. But there is for Road Bay, Anguilla.

Sun - standard transit (apparent rise and set of the upper limb)
Rises at 6:21 AM bearing 111°
Transit 11:58 AM altitude +052°
Sets at 5:34 PM bearing 249°

So just sail from the Canaries and each day at 6.21am see if the sun is just about to rise and on the correct bearing and drop anchor.