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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #1  
Old 02-10-2010
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A Plug for Celestial Navigation

After so many years of scorn from so many, especially my stink pot fishing "friends" I offer this:
Dick


BBC News - Sat-nav devices face big errors as solar activity rises
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  #2  
Old 02-10-2010
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Dick,

From the linked article: "If we project those [error components] forward, it varies quite a lot across the Earth; looking at the UK it will be about 10-metre errors in the positioning."

My own celestial navigation skill is just a bit over that spec; do you mean to say yours are better than 10-M ?

I think your stink pot friends will still not be persuaded!

Wayne
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Old 02-10-2010
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Quote:
Originally Posted by wwilson View Post
Dick,

From the linked article: "If we project those [error components] forward, it varies quite a lot across the Earth; looking at the UK it will be about 10-metre errors in the positioning."

My own celestial navigation skill is just a bit over that spec; do you mean to say yours are better than 10-M ?

I think your stink pot friends will still not be persuaded!

Wayne
Wayne,
I don't know the answer to your question. Am usually between 1/4 and 1/2 mile when my little deep full keeled sloop isn't being tossed about.
No gps aboard.
Dick
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Old 02-10-2010
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In the case of the quote, the M stood for meters I'm afraid. So GPS will have that added to its currently speced. uncertainty.

In an old Practical Sailor test of sextants some years ago - the accuracy of the average fix of the 6 testers was slightly less than one nautical mile, dismal by the standards of GPS - even degraded with sun spot interference.

I certainly respect your celestial navigation ethic (and skill), but sadly the "scorn" of your stinkpot friends will likely remain.

Wayne
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Old 02-11-2010
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Yeah I've heard these arguments before. If your sailboat has no electricity or just basic lights then "proper" navigation is important but I prefer GPS. Sure I've been asked what happens if it fails.

Well if my charplotter fails I guess I could rely on the laptop system that we always use. If that fails as well I guess we could use the back up laptop, if that fails the old laptop might work if I could get the TV to work as a monitor, if that fails I guess the old Gecko would have to do as we always have paper charts.

If the GPS system fails......well then I'll just stay out because clearly that would be the best place to be when that happens.
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Old 02-11-2010
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Originally Posted by Flybyknight View Post
Wayne,

No gps aboard.
Dick
I started sailing before GPS was available, but to not have GPS data available today is IMHO madness.
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Old 02-11-2010
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Originally Posted by noelex77 View Post
I started sailing before GPS was available, but to not have GPS data available today is IMHO madness.
Well - as I said, I do respect Dick's ethic and skill. noelx77, "Madness", is maybe hyperbole? Intentionally Luddite I think, but put myself into that same (Luddite) category with respect to some modern technology - cellular phones and Twitter and Face Book come to mind.

Architeuthis, I share your snicker wrt the "What if" skeptics. It could just as well be asked What if you make an arithmetic error in the sight reduction, or the calculator you use fails, or what if you drop and misalign the sextant or drop it overboard, or... well there are as many what if on the celestial side of the ledger as the GPS. The answer I suppose is have a backup for either.

At any rate it is an admirable skill and I respect it. I used to do arithmetic with a slide rule - can't remember how it works anymore, always had trouble keeping track of the decimal.

Under 3-ft of snow in VA with too much time on my hands

Wayne
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Old 02-11-2010
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If anything, the solar flare problem is more an argument in favor of ensuring mariners are adequately trained in coastal piloting, not CN. According to the article, GPS is used by ships entering harbors, in which an error of tens of meters can mean the difference between safe passage and grounding, and also in which CN is never used.
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Old 02-11-2010
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Personally I think the most important fact with both systems is understanding that they are not 100% accurate all the time. Use it for a reference, but look around as well. I have seem so many people blast by an unmarked under water rock with just feet to spare because the GPS "says" they won't hit it. If you KNOW your CN is 1/2 mile off, you will look out for visual signs of where you actually are, slow down if needed, and give yourself plenty of extra room. Same for GPS in my opinion. If you understand that a GPS can be off for various reasons (Solar flares, obstructed antenna, typical variance, charts not quite aligned with GPS data exactly, etc) and actually watch where you are and allow for variances, you will be much better off.

In this technical age, it is so easy to rely heavily on things that we believe are precise to the point of doing really dangerous things. 10M could get some people I know in HUGE trouble, but the CN navigator knows his readings are not precise, and takes measures to compensate.

Personally I use a basic GPS with latt long only, and paper charts 'cause it's what I have. Only thing wrong withchart plotters in my opinion is the price tag (to many other projects ahead of that) and people who stare at the screen only and never look up to see if it is correct.

We sail inland mostly at this point, so I use a lot of visual references from land and markers. We have a sextant and are learning to use it, mostly because it's intriguing and somewhat as a backup to electrical systems. We do plan on keeping at least a minimal GPS system on board too, but I like the knowledge that when we do get out on a long trip, if the electronics take a dive for whatever reason, we will still be able to make landfall where we want to.

Of course, I could blow up the electronics AND drop the sextant over the side. Then I guess we will be back to the REALLY old style of navigation, head west or east and figure we'll hit land eventually
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Quote:
Originally Posted by Flybyknight View Post
Wayne,
Am usually between 1/4 and 1/2 mile when my little deep full keeled sloop isn't being tossed about.
No gps aboard.
Dick
By the by, how do you know how accurate you are?
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