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Old 26-07-2014, 16:01   #46
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Re: What will Happen to you when GPS goes Down

If everything(including compasses & some watches/most clocks)), stop.

In a rocking boat, those of us in the northern hemisphere can look for polaris for fairly accurate north and the sun at zenith(high noon) for fairly accurate south.

A sextant or astrolabe can give a fairly accurate latitude.

I'm not sure what to use for longitude.
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Old 26-07-2014, 16:05   #47
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Re: What will Happen to you when GPS goes Down

For longitude you need an accurate clock. You need to know how many hours you are behind or ahead of Greenwich, the prime meridian. Your accurate clock is set to Greenwich time. You know when it's noon there by that clock and you compare the time at the prime meridan to your local time to get longitude. Noon is used. So is dawn, ....

I think. I could be wrong. I'm old and that was a long time ago when we cooked that scheme up, me and my old Asian buddy Seiko...
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Old 26-07-2014, 16:15   #48
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Re: What will Happen to you when GPS goes Down

I think you're about 100% right.

Let's say accurate clocks are available ... no way to check accurate time.

I think I heard that the moons of Jupiter were often used(with tables), to determine a relatively accurate time.

Let's see what a 20 power scope on a relatively small boat in anything more than dead calm might show.

Maybe the transit of the moon or planets(with tables), through the stars might help with time.
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Old 26-07-2014, 16:42   #49
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Re: What will happen to you when gps goes down

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A GPS doesn't track you - you do understand that don't you, its not a transmitter, only a receiver. And the only information it receives is is the time signal from individual satellites.
The GPS signal jammer works by sending out its own signal on the same frequency as the GPS satellites, a noisy signal that prevents the GPS unit from receiving any useful information. There are a number of types of noise signals it can send; some call for a narrowband Gaussian signal, others for a simple continuous wave.

GPS signals are quite weak, being distributed out across the surface of the Earth by satellites high in orbit, so out of all the signals to jam, they're among the easiest to do so.

I cant say anything more since the NSA, GSCB and other spy organisations will put me on their terrorist list.
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Old 26-07-2014, 16:47   #50
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Re: What will Happen to you when GPS goes Down

Probably too late. Heck, I'm nervous just responding to you. You're gonna get on the cootie list.

You Kiwi's ain't been right since that Rainbow Warrior mess. The RNZN MCM and EOD folks were still talking about it the last few times I was over there training.
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Old 26-07-2014, 16:51   #51
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Re: What will Happen to you when GPS goes Down

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BTW- I bet an event that size will destroy our ability to use compasses, at least temporarily. That ought to get you to thinking. An extreme electromagnetic storm could do a lot more than disable our toys.
Guess I'm keeping my DR stuff around. Just the Luddite in me I guess.
Solar storm of 1859 - Wikipedia, the free encyclopedia
And at that point anarchy takes over on shore as well - I've watched enough zombie apocalypse movies to know...

"Excuse me you can steal my food and rape my women in 10 minutes. As soon as I get done taking a noonsight."

Head for the most remote location you can and wait it out. I guarantee you I will not be trying to find Los Angeles during the apocalypse.

Also for you Sextant guys I am sure you have a mechanical chronograph on board and that you keep the time accurate.

Finally - What is the term for someone who is making a logic argument but keeps pushing the boundary conditions to the point where their answer becomes valid? There is a precise term for it that escapes me.

So in the scenario of nuclear meltdown + solar flair + government conspiracy to shut down gps + the guy in the next boat has a gps jammer + I am so far away from land that I couldn't find a continent + I actually wanted to find a continent?

Yeah I guess in that scenario I should learn celestial navigation...

I'll put it on the priority list right after learn how to make whale blubber candles...
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Old 26-07-2014, 16:54   #52
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Re: What will Happen to you when GPS goes Down

I'm gonna go watch Costner's Water World, again. That's how you tell the goofies around here, ya know. If Captain Ron is their favorite sailing movie, look out.
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Old 26-07-2014, 17:42   #53
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Re: What will Happen to you when GPS goes Down

I don't understand why some of you aren't in underground bomb shelters wearing tin foil helmets.

The amount of energy one would spend planning for, and mitigating, events like solar flares that will melt all wiring and Russia and China taking aim at GPS satellites would be much better off spent elsewhere planning for real problems.

How many of you think the chances are real high that:
1. you would be out to sea when Russia starts shooting down our satellites
AND
2. you would want to return to land?

Frankly, I think the planning for such remote and far-flung catastrophes is poor seamanship. It instills fear and irrationality where it doesn't belong.

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Old 26-07-2014, 17:45   #54
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Re: What will Happen to you when GPS goes Down

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Finally - What is the term for someone who is making a logic argument but keeps pushing the boundary conditions to the point where their answer becomes valid? There is a precise term for it that escapes me.
Loonies.

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Old 26-07-2014, 17:58   #55
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Re: What will Happen to you when GPS goes Down

Canibul had it right in his first post
For a historical perspective Nav USED to be the defining thing is Attack Aviation, we had to hit the FLOT at +30 seconds and -0.
Turn the clock forward and Nav is no longer an issue, it's taken for granted.
There are two GPS signals at totally different freqs, one for civilian use, one for military, military requires a secure "fill" to receive plus it's higher power and penetrates foliage etc much better, Military can turn the civilian one off with no military effect. Plus GPS can be denied for specific arreas, it's not on or off for the world.Then there is SA, selected availability, only thing Bill Clinton did that I agree with was to turn off SA, SA amounts to a time signal "lie" that keeps your GPS from being very accurate. Russia was going to launch their version of GPS that was going to be more accurate than ours with SA turned on, so Bill turned it off, then of course there is WAAS that makes GPS almost as accurate as it is with differential ground station.
GPS is incredibly easy to jam, but it's very localized depending on the jammers power output, you can cause real problems at the local airport, but not for a cruising boat out in the middle of the ocean.

Bottom line, I believe it's prudent to have a real good understanding which way land is and not be a GPS slave, Canibul's tips are I believe pretty good.
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Old 26-07-2014, 17:59   #56
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Re: What will happen to you when gps goes down

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Guess I will fire up the VLF / Omega long range nav unit and plot the fix on paper. This should keep working until the big boys stop talking to submarines .

Sorry, they shut those down in 1997. We did use them as a backup right up to the end.
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Old 26-07-2014, 18:01   #57
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Re: What will Happen to you when GPS goes Down

There are two very unlikely reasons the military will shut down the civilian (C/A signal) GPS or severely degrade its accuracy.

Thousands of civilian agencies use it for law enforcement and emergency purposes. Commercial aircraft use it now, although not dependent on it at this point in time.

It would be pointless to deny GPS to any enemies which also have access to GLONAST.


I do believe that mariners should have multiple ways of obtaining a fix and be proficient at it.
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Old 26-07-2014, 18:03   #58
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Re: What will Happen to you when GPS goes Down

This is a funny thread.

Can it merged into the Joke Thread
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Old 26-07-2014, 18:11   #59
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Re: What will happen to you when gps goes down

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Sorry, they shut those down in 1997. We did use them as a backup right up to the end.
Hmm... please correct me if I'm wrong but wasn't it only the Omega transmitters that were shut down - thus limiting the full time availability of the system. I thought the VLF transmitters stayed on line, maybe not 24/7 but at least every time someone wanted to ask a sub to surface for a more intense chat via satellite - so grab a "quick" fix when ya can

However for the purposes of this crazy thread, my VLF / Omega long range nav unit will suit me very well as I do all the other stuff mentioned in order to hunt down Mark J and raid his home brew while the rest of the world destroys it's self
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Old 26-07-2014, 18:16   #60
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Re: What will Happen to you when GPS goes Down

Subs don't have to surface to obtain a fix, They only need to be right under the surface with an antenna sticking up above the surface. This dramatically reduces their ability to be detected. Use your own imagination on how they would communicate via satellite and stay undetected.
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