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Old 26-11-2009, 09:32   #1
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LORAN: Still Worth the Trouble?

I recently removed a Sitex 767c from my small sailing boat with the intention of putting it into long-term storage. I typically run one of 3 GPS units which have met my needs in varied situations. They all feed a laptop, send 0183 data to the radar display, the autopilot, etc., via various switching methods. They all run on the ship's mains, and 2 of the 3 run on batteries also. My cruising area has at various times covered the area from the Maritimes to the northern Caribbean and that's likely to remain the case. I have read that the US is considering eliminating funding for LORAN despite the recent buzz about eLORAN and other innovations and this factored into my removal decision.

I am currently investigating a potential cruise along the southern coast of Newfoundland and it has been pointed out to me by experienced visitors there that the charts in many cases do not correspond to the coordinates supplied by GPS (independent of datum and the fact that I have the latest charts corrected to the most recent Canadian Notices). In some cases the charts differ from GPS readings by a mile or so according to some reports. For a person like me who really enjoys the convenience of GPS-supplied piloting information, this adds an additional but certainly not insurmountable complication. It just means something more to think about and attend to.

While I was thinking about this I was recalling the old tricks we used to use in the Bahamas prior to GPS and some of the very good privately published charts such as the Explorer series and Steve Pavlidis' material. We would simply use the offset feature of the LORAN to get a relatively good position, and we would update the corrections as often as possible while in harbor to give the best rendering of LORAN data on the chart. None of my GPS units has a provision for entering an offset or correction. In fact I am not certain this feature is available in any GPS unit, although it may be.

However this feature is certainly still available with my trusty Sitex 767c, and from what I have read the LORAN chains available on the south coast of Newfoundland are reasonably good. So here I sit wondering if I should bother re-fitting the Sitex (which really only means plugging in a few cables and the antenna into the existing coupler). I would then have the option of using the corrected LORAN when the GPS gives unsatisfactory information.

Has anyone tried this in a similar situation (i.e., specifically where the GPS does not correspond to the latest charts)? Is this a good idea in the first place?
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Old 26-11-2009, 09:57   #2
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Why would you think that the GPS position is wrong and that an old chart and loran would be be correct? Recent notices do not represent a recent survey with modern technology. If there are modern charts of Nefoundland I could not find them to purchase in Nova Scotia. The one I found was clearly pre-GPS.

If in doubt use your 'Mark I Eyeballs'
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Old 26-11-2009, 10:12   #3
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I have a loran of some type I was prepared to donate to the Smithsonian for future generations to see the way it usta be. You are welcome to it for shipping only when I remove it. I guess they will display it, assuming you do not want it, right next to their sextant.

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Old 26-11-2009, 11:39   #4
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Why would you think that the GPS position is wrong and that an old chart and loran would be be correct?
Why would you think I think that? I never suggested the GPS position is "wrong." I specifically stated it does not match the chart when displayed by a plotter or computer.
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Recent notices do not represent a recent survey with modern technology. If there are modern charts of Nefoundland I could not find them to purchase in Nova Scotia. The one I found was clearly pre-GPS ...
I am aware of what Notices represent. My point, should it require reiteration, is that with the latest charts corrected to the latest Notices, there is a significant difference between the GPS position of the yacht, assumed to be "correct," and the position of the yacht when displayed on a chartplotter or computer. The difference is also apparent when the GPS data are plotted "by hand" on the latest corrected chart from the Hydrographic Office. I am suggesting that there may be a method using an old LORAN box to apply a useful compensation, something not usually available when employing a GPS.

Sorry if my phrasing suggested otherwise.
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Old 26-11-2009, 12:11   #5
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Well. It is not the GPS that is wrong but rather the chart. So, get a WGS (72 or 84) chart of that area first.

For any chart that is used with the correct geo grid from GPS the error will be much less than from Loran (my assumption, not a fact). Otherwise we would still be using Loran, not GPS.

Offshore, 1 Nm should be of little concern. Inshore you will be probably piloting rather than GPSing, unless it is foggy but then you will have radar to support you.

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Old 26-11-2009, 12:36   #6
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Sorry if my phrasing suggested otherwise.
I don't understand the confusion. I thought your first post was clear.

I like to use all the tools I have. If my loran hadn't died, I'd still have it on board. Why not?

Since your loran provides an offset function that you see a way to put to practical use, I say take it.

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Old 26-11-2009, 12:49   #7
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I don't understand the confusion. I thought your first post was clear.

I like to use all the tools I have. If my loran hadn't died, I'd still have it on board. Why not?

Since your loran provides an offset function that you see a way to put to practical use, I say take it.

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Old 26-11-2009, 16:45   #8
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Wonder when the eLoran will become available to recreational sailors. There had been much chatter on it but now it seems they got stuck or something. Also, where is the European GPS ??? It was supposed to be here errrr... two years ago?

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Old 26-11-2009, 18:29   #9
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FWIW, just unscrewed the Interphase Loran I had on the boat.

Worked just fine, as far as I could tell, but I never used it and it was in the way. The Admiral said get rid of it.

So I did.

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Old 26-11-2009, 20:51   #10
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KD, I would think that first it would be most worthwhile to contact the Canadian authorities and find out what the real facts are. I suspect that they will respond in the same way that US authorities do: With a precise knowledge of what is and is not current, an explanation of what the real differences and problems are known to be, and, quite often, if it is news to them they will have someone in the area do a little field conformation to see what really is going on.

Maybe this is a Canadian ploy to keep us damn Yanks from invading Newfoundland...but I'd suspect they have accurate charts and the crux of the matter comes from folks using outdated ones, or something equally simple.

But ask them directly, see what the official response is.
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Old 27-11-2009, 11:32   #11
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The biggest source of error between charts and electronic navigation systems is in the DATUM, a much misunderstood concept. The earth isn't round, its a little egg- shaped, and the variations in datums reflect just how eggy the world was thought to be at the time they were used, give or take a bit of government/institutional inertia and a touch of trans-national intransigence. Nova Scotia is one of those parts of the world where eggy-ness matters more.

Back in the bad old days, charts were copied from older charts, and surveys were made by old salts with chronometers, lead lines, compasses, telescopes, sextants, hangovers, yellow fever, and severe colds. The compasses were affected by local variations in magnetic variation, how much the boat rocked, who was supposed to be rowing, and how cold everybody was.

Today, we have a better approximation of where the earth is out of shape, more agreement about how to measure it, and satellite photos accurate to within inches about where that rock is. You would think we could just adjust the old charts to fit the satellite pictures, and everybody would be happy, right? Obviously not.

Not even the United States can afford to update all its charts. I suppose that all the charts covering major maritime routes are getting top priority, but the backwaters may never be fixed.

GPS is accurate. It is repeatable, meaning you can mark a waypoint anywhere in the world, and come back to it years later. But the charts loaded into the chart plotter are the same as those used for all these years, and in many places the just don't match up to reality. So the GPS knows exactly where it is, but the chart its showing you is wrong. I've read its rarely more than 700 meters off.

The problem was exactly the same in the days of Loran. For exactly the same reasons. The Problem with Loran was that is was not uniformly inaccurate. It was real good in some places, and real bad in other places. But that doesn't matter. Loran is not long for this world. And eLoran is not a high priority for the penney-pinchers.

What makes it worse, the errors in charts are neither linear nor consistent. That chart may need to be moved 600 feet to the North east in one corner, 500 feet to the southeast in another corner, and completely ignored in the middle because the original surveyor in 1826 was being shot at by irate locals wearing war paint. You are better off looking at Google Earth. And NO, that's not a solution either.

In truth, in some corners of the world a prudent mariner makes informed decisions by looking at his chart datum, his radar, his depth sounder, and perhaps a radio direction finder before deciding to heave to and wait for sunlight.
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Old 30-11-2009, 06:26   #12
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Additional information is needed: specifically, why did you choose to remove the loran in the first place?

If the only reason was that you haven't used it in a while, then I agree with Dan: you might as well re-install it.

On the other hand, if there were issues of space or weight, then those issues probably remain worthy of consideration. There is only so much room in a small boat, and while redundancy is usually a good idea, not at any price.

BTW, Newfoundland is a wonderful place to visit: lovely scenery and very friendly people. The fjords on the west coast are especially beautiful, if you can make it up that way.

P.S. If you haven't yet read Farley Mowat's The Boat Who Wouldn't Float, you might want to check it out.
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Old 30-11-2009, 08:41   #13
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Given that LORAN chains are still functional, LORAN has the advantage of being more robust than GPS; and, that the 787C was a particulary good unit, and easily correctable to actual positions, I'd keep it. We still have our LORAN and find that with corrections applied, it's positional data is within 20 yards of indicated GPS Positions 99% of the time. Moreover, during a recent trip to Key West, GPS signals were unavailable (to any of our GPS devices) for several hours in the middle of the night while our LORAN continued to function without interruption.

Although we have the same waypoints recorded on our LORAN as we have on our GPS's, I typically plug in a convenient position on our chart, such as the intersection of whole degree Lat/Lon lines as a waypoint afterwhich the LORAN gives us range and beaing data to that position. In locations where charts and reported GPS coordinates are clearly at odds, one can locate ones position on a chart quite accurately with cross bearings and quickly apply corrections to the LORAN that allow one's reported position to agree with the coordinates appearing on the particular chart one is using which cannot be done with most GPS units.

FWIW...

s/v HyLyte

PS: If you choose to discard your 787c I know at least one fellow that will buy it.
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Old 01-12-2009, 10:04   #14
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... why did you choose to remove the loran in the first place?
Nothing mysterious here. Since about 1993 the only time I turned the unit on was out of curiosity. I'd compare the LORAN coordinates with those from one of the GPS units to get an idea of how well or how poorly they agreed.
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... if there were issues of space or weight, then those issues probably remain worthy of consideration. There is only so much room in a small boat, and while redundancy is usually a good idea, not at any price.
Space is ALWAYS a consideration, but does not in this instance have much significance. The Sitex in only about 6 x 10 inches on its face.
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BTW, Newfoundland is a wonderful place to visit: lovely scenery and very friendly people. The fjords on the west coast are especially beautiful, if you can make it up that way.
I am looking closely at the south and southwest coast. One bite at a time.
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Old 01-12-2009, 10:09   #15
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Given that LORAN chains are still functional ... and, that the 787C was a particulary good unit, and easily correctable ... I'd keep it. We ... find that with corrections applied, it's positional data is within 20 yards of indicated GPS Positions 99% of the time ... ... where charts and reported GPS coordinates are clearly at odds ... corrections to the LORAN ... allow one's reported position to agree with the ... chart ... which cannot be done with most GPS units ...
I would say you have summarized my position quite well.
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