Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 19-11-2010, 00:56   #1
Registered User

Join Date: Dec 2008
Location: Chester, MD for now
Boat: Pearson Ariel 264
Posts: 124
Challenge: GPS Stops Working !

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.
__________________

__________________
Keith
International Man of Leisure
Chattcatdaddy is offline   Reply With Quote
Old 19-11-2010, 01:28   #2
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
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.
__________________

__________________
daddle is offline   Reply With Quote
Old 19-11-2010, 01:54   #3
Registered User
 
gcaptain's Avatar

Join Date: Oct 2010
Location: Morro Bay, CA
Boat: Tanton 43
Posts: 64
Quote:
Originally Posted by daddle View Post
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.
__________________
John Konrad
gcaptain is offline   Reply With Quote
Old 19-11-2010, 01:57   #4
Registered User
 
bewitched's Avatar

Join Date: Sep 2009
Posts: 885
Images: 3
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
__________________
bewitched is offline   Reply With Quote
Old 19-11-2010, 02:16   #5
Registered User
 
gcaptain's Avatar

Join Date: Oct 2010
Location: Morro Bay, CA
Boat: Tanton 43
Posts: 64
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.
__________________
John Konrad
gcaptain is offline   Reply With Quote
Old 19-11-2010, 03:02   #6
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: UK/Portugal
Posts: 20,210
Images: 2
Send a message via Skype™ to boatman61
pirate

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.
__________________


Born To Be Wild
boatman61 is offline   Reply With Quote
Old 19-11-2010, 04:10   #7
Registered User

Join Date: Mar 2007
Location: On the hook in Florida
Boat: Tayana V42 - Passages
Posts: 504
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
__________________
jcapo is offline   Reply With Quote
Old 19-11-2010, 06:53   #8
Registered User

Join Date: Nov 2010
Posts: 8
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 is offline   Reply With Quote
Old 19-11-2010, 06:55   #9
Registered User

Join Date: Nov 2010
Posts: 8
Another thought.......given man's penchant to destroy himself, The Sun will
certainly outlive the Sats.
__________________
aychbawdy is offline   Reply With Quote
Old 20-11-2010, 23:49   #10
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Quote:
Originally Posted by gcaptain View Post
...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.
__________________
daddle is offline   Reply With Quote
Old 21-11-2010, 03:04   #11
Registered User
 
simonmd's Avatar

Join Date: Nov 2010
Location: Sant Carles, S Spain
Boat: 30ft Catalac 900 "Rubessa"
Posts: 876
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.
__________________
simonmd is offline   Reply With Quote
Old 21-11-2010, 04:11   #12
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
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.
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 21-11-2010, 06:18   #13
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Out there doin' it
Boat: 47' Olympic Adventure
Posts: 2,635
Quote:
Originally Posted by simonmd View Post
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.
__________________
Lodesman is offline   Reply With Quote
Old 21-11-2010, 06:31   #14
Registered User

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 3,538
Quote:
Originally Posted by Chattcatdaddy View Post
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
__________________
conachair is offline   Reply With Quote
Old 21-11-2010, 06:40   #15
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
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.
__________________

__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Challenge: Wake Up The Mechanics - Outboard Challenge Ex-Calif Challenges 37 04-04-2016 09:55
Challenge: RTW, Shorthanded, with Minimal Stops and Fairly 'Quicklyish' David_Old_Jersey Challenges 37 19-03-2013 18:32
GPS NMEA output from the Sierra AirCard 881 working Athowhen OpenCPN 0 22-09-2010 12:47
Engine Stops - Then What? FraidNot General Sailing Forum 34 16-02-2010 15:04
Challenge: A Real Challenge Solved by a Forum Member Soft Air Challenges 10 27-03-2009 09:59



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 09:16.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.