What will Happen to you when GPS goes Down

[denverd0n]

Saw an interesting comment today in the "Good Old Boat" online newsletter. Mentioned how lots of folks talk about the possibility of GPS going down, so they insist that it is still important to know how to use a sextant. Of course, to use a sextant you need an extremely accurate reading of the time. And what do almost all of these folks use to accurately set their clocks? Radio-transmitted "ticks," that are generated by an atomic clock, broadcast on various frequencies by government agencies.

As Arsenio Hall used to say, "Things that make you go, hmmmm."

[barnakiel]

This is in line with my observations too.

Most sailors, as well as any other consumers of technology, will fall into one of two categories:

- those who know how to use a sextant, and will also tend to have an in-depth understanding of gps and higher than average gps/radar, etc. skills,

- those who say sextants and compasses are useless, and will also tend to be hardly able to use a plotter, not actually understanding, neither willing to understand, how a plotter works and what its limitations (as well as extra uses) are.

How many plotter potatoes know how to get a celestial fix out of a plotter that lost its gps signal?

It was not a question.

Few.

b.

[colemj]

Originally Posted by barnakiel

This is in line with my observations too.

Most sailors, as well as any other consumers of technology, will fall into one of two categories:

- those who know how to use a sextant, and will also tend to have an in-depth understanding of gps and higher than average gps/radar, etc. skills,

- those who say sextants and compasses are useless, and will also tend to be hardly able to use a plotter, not actually understanding, neither willing to understand, how a plotter works and what its limitations (as well as extra uses) are.

How many plotter potatoes know how to get a celestial fix out of a plotter that lost its gps signal?

It was not a question.

Few.

b.

Nice black and white world you live in there!

I bet the majority of people here fall into a category of those who say sextants are useless (and even don't know how to use one), as well as being very proficient with plotters, plotting, DR, etc. And know how to point the boat at dry land no matter where they are in the world without any electronic help.

I will wager that those who are most tied to "traditional" navigation techniques are the least able to use electronics to their fullest. Where do you think the Pardeys would fall here?

And the answer to your question is none. It is not possible to get a celestial fix out of a plotter short of cutting it into a protractor and modifying it to take an angle from the horizon. I bet you could not do it!

Mark

[Canibul]

Originally Posted by Pirate999

I've seen you. Message received.. Beer on the way.

Thanks, I knew a fellow Texian would come through.

I did get a few strange replies to my smoke signals, from Colorado, but they were disjointed and confusing. Like someone was eating Cheetos and giggling.


Hey, on this GPS going out thing....how about if we modify the question slightly and say that an EMP burst takes EVERYthing out. Except for those of you who store stuff in Faraday cages, of course. So now you have NO electronics.

[robert sailor]

I'm with Mark on this one...just don't see it ever happening and I'm one of the older farts that used to use celestial navigation years ago. Its about akin to those that prepare themselves for the 2nd coming...one of those don't hold your breath moments!

If you got a bit unlucky you could get hit with lightning but that in itself is a long shot and in many cases you can protect a hand held that would see you through. The world has changed very quickly and its hard to keep up.

[Auspicious]

Originally Posted by muttnik

It's not unknown for me to devote large chunks of time to writing software to do interesting things with navigational data.

Cool. I'll look them up.

Have you found or developed the spherical trig to avoid needing to use HO tables for celestial nav? I would think one would need some awful almanac data for the stars being used. It might not result in any savings in stuff to carry around, but the idea is interesting to me.

Originally Posted by denverd0n

Of course, to use a sextant you need an extremely accurate reading of the time. And what do almost all of these folks use to accurately set their clocks? Radio-transmitted "ticks," that are generated by an atomic clock, broadcast on various frequencies by government agencies.

There are other approaches. One is to carry a reliable time standard. Battery operated quartz watches are inexpensive and startlingly accurate. As an alternative a good mechanical watch can be tracked over time. Mine runs fast but is consistent. I can make reasonable adjustments (on paper - don't touch the watch) for several weeks. Once you make landfall where you know your location you can reset your adjustment factor by working backwards.

Four seconds error in the time standard is about a nautical mile. Taking the time and the sight together is really hard. A stop watch helps - you can compare the delta time to the time standard below and it is easier to hit the button on a stop watch than get all the numbers straight at once on a moving boat deck. Errors from taking the sight can be significant. I know I do a much better job from the bridge wing of a ship than I do with my arm hooked around a shroud on a small boat.

The biggest deal is having enough paper to do all the arithmetic by hand if you don't have a working calculator. PITA.

Originally Posted by barnakiel

How many plotter potatoes know how to get a celestial fix out of a plotter that lost its gps signal?

Pardon? What are you talking about? Some model plotters I can force a position IN based on a fix but I can't think of any way that any plotter I have touched supports a celestial fix. Educate me.

[konakoma]

Every cruiser should have paper charts and use them in conjunction with GPS. We have a Garmin 4210 with Caribbean charts and have sailed right through islands, according to the track line, so they cannot be trusted. Pencil dots on charts always work with TOM (thumb on map). Visual piloting skills are critical.

[barnakiel]

Originally Posted by Auspicious

(...)

Pardon? What are you talking about? Some model plotters I can force a position IN based on a fix but I can't think of any way that any plotter I have touched supports a celestial fix. Educate me.

A plotter that loses its GPS capability will still deliver all other functions, e.g. route calculations.

Now imagine you enter one WPT1 at your EP.

Now imagine you enter the other WPT2 at alt+GHA.

Now what are your dist and dir if you look up such a rte on your now ex-gps plotter?

Any plainest GPS handheld will do the same.

Simple and elegant.

And completely out of range of skills of an average plotter potato. But probably well within range of skills of a sextant dodo.

Love,
b.

[muttnik]

Originally Posted by Auspicious

Have you found or developed the spherical trig to avoid needing to use HO tables for celestial nav?

My party trick is mostly getting nmea data from A to B in useful ways. I've always done celestial stuff on paper and haven't even investigated sean's celestial nav plugin for openCPN.

Originally Posted by Auspicious

Taking the time and the sight together is really hard. A stop watch helps - you can compare the delta time to the time standard below and it is easier to hit the button on a stop watch than get all the numbers straight at once on a moving boat deck.

I always wondered why not one of the "sailing watches" you can buy has the facility to record multiple deltas to facilitate star sights. People have suggested (on this forum) using a voice recorder, saying "mark" for a known base time then on taking each sight so that you can subsequently work out the time. Lack of a voice recorder and possible inhibition about talking to myself on night watch always deterred me.

...but we're getting off topic. I still dispute the OP's contention that an interest in marine electronics implies a lack of familiarity with more "traditional" navigation :-)

[barnakiel]

And the time does not have to be all that accurate. We use a plain Casio that I set exact on departure, then update from gps signal once a week. I know how much ahead or late it gets per week then.

Celestial fix is not to enter a narrow channel, it is to find the other side then go ahead piloting from your landfall.

I would not be writing this but sure this touches upon "how much faith do you place in your watch" theme. A Casio is an electronic watch, hence it adresses the issue discussed.

b.

[colemj]

Originally Posted by konakoma

Every cruiser should have paper charts and use them in conjunction with GPS. We have a Garmin 4210 with Caribbean charts and have sailed right through islands, according to the track line, so they cannot be trusted. Pencil dots on charts always work with TOM (thumb on map). Visual piloting skills are critical.

That is a function of the charts and not the chart plotter. If your plotter is using the same charts as you have on paper, then there will be no difference and you will sail right across land with your paper charts also.

If you are arguing that your paper charts are more accurate than those on your plotter, then the problem lies in how you chose your plotter and/or charts loaded into your plotter.

Mark

[barnakiel]

Originally Posted by colemj

(...)

I will wager that those who are most tied to "traditional" navigation techniques are the least able to use electronics to their fullest. Where do you think the Pardeys would fall here?

(...)

And the answer to your question is none. It is not possible to get a celestial fix out of a plotter short of cutting it into a protractor and modifying it to take an angle from the horizon. I bet you could not do it!

Mark

This is not what I have seen on our route. We met plenty of sailors and I noticed they were either very proficient with everything (sextant or gps or diesel engines) or else they were pretty ignorant of anything. Surprisingly, they all seemed to be doing just fine!

YMMV. I am much into sailing far or not at all, hence my vision.

As for getting a celestial fix from a plotter that lost its gps capacity read into my other post above.

b.

[Auspicious]

Originally Posted by barnakiel

A plotter that loses its GPS capability will still deliver all other functions, e.g. route calculations.

Now imagine you enter one WPT1 at your EP.

Now imagine you enter the other WPT2 at alt+GHA.

Now what are your dist and dir if you look up such a rte on your now ex-gps plotter?

That isn't what you said. You said "How many plotter potatoes know how to get a celestial fix out of a plotter that lost its gps signal?" Using an electronic plotter as a plotting aid (like a plotting board) has nothing to do with getting a fix out of the plotter.

If English is not your native language you deserve some understanding, but what you said is not what you seem to have meant.

For myself, a notepad and a plotting sheet are easier to use than a plotter for DR and tracking fixes but hey, if you like sticking your head in the plotter have a great time.

Originally Posted by muttnik

I always wondered why not one of the "sailing watches" you can buy has the facility to record multiple deltas to facilitate star sights.

Multiple deltas would be great.

I'm not big on the voice recorder idea although I'm not sure why.

Originally Posted by muttnik

...but we're getting off topic. I still dispute the OP's contention that an interest in marine electronics implies a lack of familiarity with more "traditional" navigation :-)

I definitely agree with you.

Originally Posted by barnakiel

And the time does not have to be all that accurate. We use a plain Casio that I set exact on departure, then update from gps signal once a week. I know how much ahead or late it gets per week then.

*grin* My mechanical watch probably drifts more per day than your Casio does per month.

Originally Posted by colemj

That is a function of the charts and not the chart plotter. If your plotter is using the same charts as you have on paper, then there will be no difference and you will sail right across land with your paper charts also.

If you are arguing that your paper charts are more accurate than those on your plotter, then the problem lies in how you chose your plotter and/or charts loaded into your plotter.

Agree. Ultimately the basis is all the same. Is the GPS datum on your plotter set correctly to agree with the chart data?

[Reiziger]

Originally Posted by s/v Jedi

Nah, those all support GLONASS already

In an unprecedented total disruption of a fully operational GNSS constellation, all satellites in the Russian GLONASS broadcast corrupt information for 11 hours, from just past midnight until noon Russian time (UTC+4), on April 2, 2014 (or 5 p.m. on April 1, 2014 to 4 a.m. April 2, 2014, U.S. Eastern time). This rendered the system completely unusable to all worldwide GLONASS receivers. Full and correct service has now been restored.

[Stumble]

I still can't see any situation in which all navigation satellites go out that every onboard piece of electronics doesn't also go out. So a battery operated watch becomes as useless as a chart plotter. In a large CME even a mounted compass is likely to go out.

Frankly I just don't see the point in worrying about it. Down this road leads becoming a guest on Doomsday Preppers