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Author Topic:   LORAN-C system - R.I.P.
GreatBayNH posted 01-17-2010 07:08 PM ET (US)   Profile for GreatBayNH   Send Email to GreatBayNH  
By Associated Press
January 17, 2010 11:36 AM

PORTLAND, Maine - The plug is being pulled on a radio navigational system that for decades was the preferred choice of mariners in waters off the U.S.

As low-cost GPS has emerged in recent years, the Department of Homeland Security says the LORAN-C system has become obsolete and is no longer needed for navigation or safety.

Over the protests of some U.S. senators and others who say the LORAN network should be maintained as a GPS backup, most of the nation's LORAN transmission towers will be turned off Feb. 8, with the remainder being shut down by Oct. 1.

For decades, LORAN was the standard navigation system on many commercial fishing boats, recreational craft and other vessels, as well as a supplemental navigation aid on many small aircraft.

GreatBayNH posted 01-17-2010 07:12 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
Sorry, forgot to paste in the title of the AP article as found in our local paper.

Plug being pulled on decades-old navigation system

By Associated Press
January 17, 2010 11:36 AM
PORTLAND, Maine - The plug is being pulled on a radio navigational system that for decades was the preferred choice of mariners in waters off the U.S.

As low-cost GPS has emerged in recent years, the Department of Homeland Security says the LORAN-C system has become obsolete and is no longer needed for navigation or safety.

Over the protests of some U.S. senators and others who say the LORAN network should be maintained as a GPS backup, most of the nation's LORAN transmission towers will be turned off Feb. 8, with the remainder being shut down by Oct. 1.

For decades, LORAN was the standard navigation system on many commercial fishing boats, recreational craft and other vessels, as well as a supplemental navigation aid on many small aircraft.

dfmcintyre posted 01-18-2010 07:18 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Ah, LORAN.... brings back some interesting memories. Up in our neck of the woods, the Great Lakes charts all had the LORAN lines printed on them. LOP'S?, cannot remember.

Anyways, I remember talking to a guy who was prepping his boat to head across Lake Huron. Had a LORAN, but could not get the concept of Lat/Lon (I think it may have been a SiTex unit, which suffice it to say had a rather arcane user menu. I think it may have been used by other companies as an example of how NOT to make a user interface).

The way he navigated, was to head up the lake until his LORAN hit the proper LOP, then turned and held that indication until reaching the other side.

What could be easier?

Don

where2 posted 01-18-2010 10:58 PM ET (US)     Profile for where2  Send Email to where2     
Having worked at a marine retailer as a summer job in the early 90's, I had the pleasure of seeing a few of those SiTex units. The user interface was quite unintuitive. I was amazed at how archaic the LORAN navigation methodology was once I began my studies of Surveying/Mapping and understood how GPS worked a few short years later. I make my livelyhood with GPS, I cannot imagine working without it.

While in Maine shortly before Christmas, I read a newspaper story about the Maine maritime community's concerns about turning LORAN off, and the expense of upgrading to GPS. I was amazed to learn that anyone was still using LORAN, considering I'm on my third GPS receiver, and have even acquired a Garmin GPSMap 162 unit for free when someone I knew was upgrading.

jimh posted 01-18-2010 11:32 PM ET (US)     Profile for jimh  Send Email to jimh     
LORAN and GPS use the same method of radio location to determine position. The differences are found more in:

--terrestrial stations v. orbiting stations

--very high power v. very low power

--very low frequency v. very high frequency

--very high immunity to jamming v. very easily jammed

--excellent coverage and signal penetration into buldings v. reception need clear view of open sky

--covers primarily U.S. territory v. covers entire globe
(thus providing free service to all countries at our expense)

The use of charts printed with lines of position representing differential signal delays among stations is more a manifestation of the lack of computer processing power in the LORAN receiver than in a fundamental difference in the radio location technique. A modern LORAN system could be just about as accurate as the current GPS system at a fraction of the cost.

Each GPS satellite costs a billion dollars to build, launch, and maintain in orbit. We are junking LORAN with an operational cost of about $15-million per year. I think we could operate LORAN for about a century for the cost of one GPS satellite. The GPS constellation needs 24 satellites in orbit for full coverage, with usually six operational spares. That's 30 satellites in orbit. In other words, we could operate LORAN for the next 3,000 years at just the cost of the one set of GPS satellites. The lifespan of a GPS satellite is probably about ten years.

BlueMax posted 01-19-2010 12:45 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
I think that jimh is leaving out some very crucial factors in his GPS vs. Loran equations such as:

1) If we wish to discuss US government placement and maintenance, we must keep in mind that the GPS satellites are primarily for military use and the very popular use of GPS for commercial and civilian use is a by-product of the fact that the systems are in orbit and in use anyway. The GPS sats are not sent up simply to provide guidance to Tom-Tom, Garmin and Navigon users and you can bet that if they are - the companies paying for them to be there are making a lot of money off it.

2) GPS systems are extremely small, user-friendly, inexpensive and serve a much broader user-base (land and sea) globally; I would like Jim to further his cost benefit analysis by factoring in the amount of users for each system.

quote:
Ah, LORAN.... brings back some interesting memories. Up in our neck of the woods, the Great Lakes charts all had the LORAN lines printed on them. LOP'S?, cannot remember.

That about sums up why they are discontinuing LORAN.

I do think that maybe a smaller sub-set can be maintained around the Great Lakes region for the purpose of redundancy and safety in inclement weather though.

my .02,
Max

dfmcintyre posted 01-19-2010 05:36 AM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Max -

I think right now, the system can cover almost all of the US, with some exceptions. And towards the end, no pre-printed LOP's were needed on the charts. The newer loran units worked just like GPS units of today; i.e. the user interface was improved to where a cave man could use it. Or at least a UofM grad....

jimh posted 01-19-2010 09:25 AM ET (US)     Profile for jimh  Send Email to jimh     
I am afraid my points of argument have been poorly presented and need my elaboration. If I may:

Precisely because it is a global navigation system, the NAVSTAR GPS provides an enormously valuable resource to the entire planet of users. In China we have a billion people using our GPS system, however they are not paying for it. They get a free ride. In Europe, we have the same situation. The enlightened people of Europe enjoy the tremendous benefit of the GPS at the expense of me and the rest of the taxpayers of the United States. In contrast, the LORAN system provides a benefit primarily to users in the United States.

The underlying technique of radio location is fundamentally the same in both LORAN and GPS. If improvements were made to the LORAN transmitters with regard to the precision of their signals, the accuracy of LORAN could be improved to approach the accuracy of GPS. The cost of updating the transmitters in LORAN would be minimal, and much less than the next GPS satellite will cost.

A fundamental advantage of a terrestrial based transmitter is much easier access for repairs compared to one in space. LORAN sites are quite easily accessed compared to orbiting satellites. A problem in a satellite usually means the end of its service. It is thrown away. So far, in the 60 years of LORAN, I do not believe any LORAN sites have been discarded or abandoned because effective repairs could not be made.

The degree of sophistication in the receivers which used the LORAN system has been improved in modern devices, and there is really no reason why a modern LORAN receiver would not operate as easily as a modern GPS receiver. If we make a comparison between a 2010 GPS receiver and a 1950 LORAN receiver, it is easy to tilt the advantage to GPS. If two modern receivers were compared, the differences would be less noticeable.

The current status of the NAVSTAR GPS satellite constellation is questionable. We have been fortunate that the useful service life of several satellites has been greater than expected, keeping them in service after the end of their anticipated service life. However, even with this good fortune the current system is worrisome.

This article carries the headline

GPS system 'close to breakdown'
http://www.guardian.co.uk/technology/2009/may/19/gps-close-to-breakdown

and explains that the newer replacement satellites are not performing well. The source of the information is the government's own GAO report. It probably cost as much to prepare this report as it would to run the LORAN system for another year.

PeteB88 posted 01-19-2010 10:50 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
Jim, thanks for the details and low down regarding LORAN. I always thought the system makes sense including the ground station advantage and redundancy possible for mariners with both systems operating. The problem is, according to your assessment, LORAN is too cheap. I suppose if LORAN cost 50 times or more than it does the lobbying dudes would be fully deployed and LORAN would remain "on".


Oh well.....

dfmcintyre posted 01-19-2010 01:15 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Jim -

I used to have both a LORAN unit and a GPS unit in the plane I usually fly. Northstar LORAN and Garmin GPS. Both readouts were within 2kt's and 2 degrees of heading most of the time.

There is/was some unavoidable errors with the LORAN signal. I remember a conversation with someone from the Coast Guard, who had been stationed at one of the chain transmitters. He explained that because it was ground based, they had to "dither" the signal to account for the difference (minimal as it might be) between seasons, when the trees were naked.

The end users of the LORAN chain got the signal for free.
If we blanketed the globe with an acceptable LORAN signal, the end users would still receive the signal for free, just like they do now, with GPS.

Don

Buckda posted 01-19-2010 03:12 PM ET (US)     Profile for Buckda  Send Email to Buckda     
I agree with Don - and logistically (if not implementally) GPS is easier to deploy worldwide than LORAN. GPS is, after all, a military expenditure meant to help our troops identify where they are, where the enemy is, and how best to achieve mission objectives and get home quickly and safely.

For that, I'm willing to pay some tax dollars.

gss036 posted 01-19-2010 05:10 PM ET (US)     Profile for gss036  Send Email to gss036     
Actually, I still use my Loran.I have one MAP and chart plotter GPS. I very seldom use the GPS plotter, but it is there if needed, purchased the unit for the depth finder w/o know it was also GPS capable. Having said all that, I think the Loran is more accurate to find a pentacle for bottom fishing that GPS. The Loran seems to put you spot on and you are close with GPS and have to do some looking to find the top of the pentacle. I will surly miss not having it when it goes away. Our bottom fishing is really lousy now and only allowed 1 fish anyway. ;-)
K Albus posted 01-19-2010 05:30 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Witch kind of fish do you catch near an underwater pentacle? Surely not angelfish?
RLSmith posted 01-19-2010 08:44 PM ET (US)     Profile for RLSmith  Send Email to RLSmith     
An important difference between Loran and GPS that probably doesn't matter to mariners: Loran fixes 2D position, GPS fixes 3D position.
BlueMax posted 01-19-2010 09:48 PM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Given the fact that GPS being readily available is dependant on military needs for the application or restriction of resources, and therefore a prime target for our very capable adversaries, I would hope that the US military if not Civil government would be a little more forward thinking by keeping the redundancy of Loran in place for continued mariner, OTR and air traffic uses and safety should the military application of GPS require or succumb to commercial denial.

Keeping it in use would allow people to keep using and improving it, and would thus maintain the knowledge base should we once again need to rely solely upon it.

Just my thoughts...

jimh posted 01-20-2010 01:09 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding the problems of LORAN signals being affected by propagation factors--the GPS signals have this same problem, too.

With LORAN it was well known that there were influences on the propagation of the signal which affected the accuracy of the system. Don mentions seasonal influences as from foliage on trees. GPS is not immune to this type of variation. The signal from a satellite passes through at least 25,000 miles of atmosphere. The thickness of the ionosphere influences the signal. Variations in thickness of the ionosphere result in variations in the signal. These variations produce errors in the system accuracy. One of the [principal] functions of the WAAS precision enhancement system is to measure these variations and publish a real-time correction factor. In a similar manner, a real-time correction factor could be applied to a LORAN radio location system.

My guess is that the ultimate decision on LORAN came down to the cost-benefit ratio. Although GPS is very expensive, there are millions of users. Even with LORAN substantially less expensive, there were probably only 1/10,000th as many users. The result was the cost per user for LORAN was probably ten-thousand times more expensive than GPS

David Pendleton posted 01-20-2010 02:23 AM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
All this esoteric information about LORAN is wonderful.

Actually it's just that--esoterica.

I can honestly say I don't know of one single person who will be adversely affected by the discontinuation of LORAN broadcasts.

I doubt you can either.

I know pilots, both commercial and military; Great Lakes commercial mariners, Mississippi River commercial mariners and recreational boaters. No one cares. None of them use LORAN.

Why is this considered such a travesty?


dfmcintyre posted 01-20-2010 05:46 AM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Jim -

I'm wondering if the timeline in advances in electronics during the, oh, mid-80's may have had a more major impact with this LORAN / GPS issue?

Your much more in tune with electronics. Could a low frequency receiver, be currently built that would have the portability of the current GPS receivers? Or due to inherent LF requirements would the receiver be too large to be truly portable?

number9 posted 01-20-2010 06:56 AM ET (US)     Profile for number9  Send Email to number9     
Are there any plans for Loran's frequencies to be used?

One benefit to doing away with the system is the elimination of the tall towers/antennas required.

BlueMax posted 01-20-2010 07:48 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Number9 - good point raised about the consumption of frequencies. Pure speculation on my part but I am sure that the DHS and local/National WAN/MAN needs may have also played a part in targeting these "lesser used" freq's for propagation of wider area coverage (not for purpose of attaching to, but for purpose of extending network).

jimh posted 01-20-2010 09:04 AM ET (US)     Profile for jimh  Send Email to jimh     
LORAN-C is a global system of stations. Other nations are continuing to use the LORAN system. The spectrum used for LORAN cannot be reassigned to other services in the United States without coordination of international frequency assignment commissions. All LORAN-C stations in the U.S. were on the same carrier frequency, 0.1-MHz.

In the 1950's antennas for LORAN-C receivers were typically large whip antennas, but modern designs used voltage probe (E-plane) or magnetic probe (H-plane) techniques which reduced the antenna size. A modern LORAN-C antenna is not any larger than a GPS hockey puck type antenna.

I wouldn't characterize the very fundamental information about LORAN that has been presented as esoterica. For esoterica, see the Wikipedia article:

http://en.wikipedia.org/wiki/LORAN

I don't see a particularly large benefit in removal of a few 900-foot towers. In fact, it has been estimated that the cost of decommissioning the LORAN system will be equal to the cost of upgrading it and maintaining it in use. This is not because it will cost a fortune to decommission it, but because it would have cost so little to maintain and upgrade it.

jimh posted 01-20-2010 09:11 AM ET (US)     Profile for jimh  Send Email to jimh     
"Why is [the shut down of LORAN-C] considered such a travesty?"

The Wikipedia article (link above) gives good background on the politics involved. Until the election of the current administration, the government was supportive of LORAN modernization. With the change in administration, the government has made a 180-degree reversal in course. With many new policy makers in place, the government adopted an entirely new policy.

BlueMax posted 01-20-2010 12:24 PM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Change we can all believe in - Maybe not change we can live with or actually believe is happening, but change we can all believe has happened and change is all we will be left with.....

My new Motto? "Change Happens" [it is so much less vulgar]

I do like the change that has happened in Massachusetts though.

[okay Tony, air it out and let's hear it before we both get canc'd. ha]

Mambo Minnow posted 01-20-2010 12:26 PM ET (US)     Profile for Mambo Minnow  Send Email to Mambo Minnow     
When an intelligent adversary takes out our GPS constellation either through cyber or space attack, we will regret not keeping LORAN-C as a back up system.

Time to dust off my dead reckoning skills and pull the sextant out of the box :)

GreatBayNH posted 01-20-2010 12:49 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
quote:
Until the election of the current administration, the government was supportive of LORAN modernization. With the change in administration, the government has made a 180-degree reversal in course. With many new policy makers in place, the government adopted an entirely new policy.

The last administration as supportive of A LOT of things that cost us dearly. Maybe the state of the Union the new administration was handed required cuts to be made where cuts could be made. Just a thought.

BlueMax posted 01-20-2010 02:26 PM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Then explain all the extensive political largess and over-expanded Gov't spending in areas where it was not needed (or helpful) at a time when cuts needed to be made......just a rationalthought. ^@^
GreatBayNH posted 01-20-2010 03:36 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
Name one.
jimh posted 01-20-2010 10:15 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't want to get into politics. Let's stick to the technical.

There is no doubt that Dave's observation is correct: I can't think of anyone I know that uses LORAN at the moment, either.

However, I also want to say that LORAN was still a useful system, and could have relatively easily been updated to improve its accuracy as a radio location system as well as a time base standard system. Just because a system or a technology has been around for a while does not mean it must be useless or out of date.

I recall many years ago reading an article in which the idea was put forth that if transistors had been developed before vacuum tubes, the later invention of the vacuum tube would still have been a significant development, and the use of vacuum tubes in certain applications would have been a break through in technology.

A2J15Sport posted 01-20-2010 10:44 PM ET (US)     Profile for A2J15Sport  Send Email to A2J15Sport     
From what I have read, our GPS system is aging fast and nobody in government seems to be concerned about it.

Satellites do have a finite life. My understanding is that we (USA) are not replacing them. Maybe some other country is. I don't like that. They can shut them off.

BlueMax posted 01-21-2010 12:01 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Seth - You're kidding, right? Salt Marsh Harvest Mouse - $30 Million

-0r how bout...
Mary Landrieu - $300 Million.

-Or-
TARP1 & 2 - Untold BILLIONS

In fact, given that it would be the US gov't involved, I bet discontinuing LORAN (and likely dismantling the stations for the environment's sake) will cost us more than it would to keep them operating.

^@^

BlueMax posted 01-21-2010 12:04 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Seth - You're kidding, right? Salt Marsh Harvest Mouse - $30 Million

-0r how bout...
Mary Landrieu - $300 Million.

In fact, given that it would be the US gov't involved, I bet discontinuing LORAN (and likely dismantling the stations for the environment's sake) will cost us more than it would to keep them operating. ^@^

I still think we should maintain it for safety net redundancy and National Security.

BlueMax posted 01-21-2010 12:12 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
Dagnabit! First one was a little too much but didn't go out so I thought I could clean it up - then they both posted when I submitted the second time. Jim (and Seth), my apologies, can you please clean this up - hank You.

But you have to admit, naming wasteful spending is way too easy when talking US government (or any body politic that has authority to spend other peoples money at will).

Do they intend to dismantle it entirely, or simply mothball the system? I wonder how quickly it could be reactivated should the need arise?

jimh posted 01-21-2010 12:31 AM ET (US)     Profile for jimh  Send Email to jimh     
To clarify something I mentioned above, when the current administration orders the end of LORAN, the carrier frequencies of the LORAN stations in the U.S. will go silent, and these frequencies will effectively be abandoned. I doubt they can be re-used because other countries are using them for their LORAN stations. There are international treaties regarding frequency allocation which apply to use of the spectrum, so by shutting off LORAN we just lose this spectrum for any other purpose in the U.S.
towboater posted 01-21-2010 03:57 AM ET (US)     Profile for towboater  Send Email to towboater     
Thanks for the post GBH.

Mark this date.
2010, end of Loran.
Good riddance.

One day someone will calculate the per ca-pita rate of Loran era vrs GPS era Maritime Incidents.

Im betting GPS era has 40% fewer incidents.
The cost of the entire GPS system (incl the necessary Military factor and consumer benifits mentioned earlier) is quite a savings overall.

DHS has somebody on the ball.

mk

towboater posted 01-21-2010 03:59 AM ET (US)     Profile for towboater  Send Email to towboater     
[Mentioned a well known marine casualty and said it] qualifies for a Loran era incident.
jimh posted 01-21-2010 09:48 AM ET (US)     Profile for jimh  Send Email to jimh     
I have read quite a bit on that marine casualty, but I have never heard any mention of the role that the LORAN system played in causing the grounding, which is what I believe is being implied by that statement. I encourage the author of that statement to fully explain how LORAN was responsible. But please do it in another thread.
jimp posted 01-21-2010 11:06 AM ET (US)     Profile for jimp  Send Email to jimp     
Well, in Southeast Alaska I always used my LORAN C last summer, right next to my GPS, and they pretty much agreed with each other to 1/10th knot of speed and a few degrees on the compass heading. But, after 19 years the NorthStar LORAN was starting to experience a few "difficulties" at speed (losing tracking).

As for the [marine casualty], [the ship owner and the captain] can make all their excuses and others can provide excuse for them about electronics, the Coast Guard, etc, but it was just EXTREMELY poor seamanship on [the captain's] part. The Master of the ship was responsibile. I've sailed [that same region] many times and there are no excuses.

As for LORAN in Alaska, Attu (at the far end of the Aleutians) and Shoal Cove (in Southeast near Ketchikan) will stay operational as they are part of the Russian-American Chain (Attu) and Shoal Cove works with the Canadians.

JimP

Kevin Cook posted 01-21-2010 11:32 AM ET (US)     Profile for Kevin Cook  Send Email to Kevin Cook     
When was the last time you could actually buy a new LORAN receiver in the US?

Kevin

BlueMax posted 01-21-2010 11:59 AM ET (US)     Profile for BlueMax  Send Email to BlueMax     
I got one with my Sony BetaMax player. It came with a cassette tape on how to use it. ^@^
Tohsgib posted 01-21-2010 12:02 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
I bought one in 1994 for I think $199 plus the ant. Back then it was better than GPS. It came with a VHS instruction tape...cool!
contender posted 01-21-2010 02:42 PM ET (US)     Profile for contender  Send Email to contender     
At least I still have my sextant and compass.
David Pendleton posted 01-21-2010 04:43 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
quote:
When was the last time you could actually buy a new LORAN receiver in the US?

I had a Raytheon NAV398 in my boat in 1999. It was a combination GPS/LORAN, but you needed two antennas.

I used mine for GPS. They went out of production sometime in the mid-nineties, I believe.

elaelap posted 01-21-2010 05:09 PM ET (US)     Profile for elaelap  Send Email to elaelap     
I had to learn LORAN basics, including figuring out the confusing (for me) chart lines three years ago to pass my Masters license exam. Luckily one of the skippers I've apprenticed with still had LORAN on board, and taught me something about it way back when. GPS is much simpler for slow-witted guys like me. It's sorta like when I got into computing via a user-friendly Mac Plus, and, thank goodness, didn't have to learn all that DOSS stuff, or whatever it was called.

As for other nations supposedly using "our" GPS system for free...who the hell cares? Doesn't cost us any more, so why not?

Only thing that bothers me about GPS is the same free-floating anxiety I sometimes feel regarding our totally computerized society: what if a big solar flare or some other unforeseen cosmic event shuts the whole thing down for a while? End of the world as we know it, I guess...and maybe that wouldn't be altogether the worst thing that could happen.

Tony

A2J15Sport posted 01-21-2010 06:16 PM ET (US)     Profile for A2J15Sport  Send Email to A2J15Sport     
"As for other nations supposedly using "our" GPS system for free...who the hell cares? Doesn't cost us any more, so why not?"

If you haven't noticed, the rest of the world hates us and wants us eliminated. GPS was a trump card we have now lost. So goes LORAN too.

elaelap posted 01-21-2010 06:37 PM ET (US)     Profile for elaelap  Send Email to elaelap     
Huh?
GreatBayNH posted 01-21-2010 06:52 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
When big oil bought up all the clean, green, electric trolley's thoughout the U.S., in the beginning of the 20th century, no one was crying then about how we needed a backup transportation system in case all the oil dried up or if our oil supply fell into the hands of our enemies. Or did they? Discuss.
A2J15Sport posted 01-21-2010 07:28 PM ET (US)     Profile for A2J15Sport  Send Email to A2J15Sport     
elaelap,

"Huh"

You said it, I just quoted you and pointed out other issues. Where the "huh" comes from is entirely yours.

However, I mistakenly forgot about your superior intelligence, compared to the rest of us commoners.

jimh posted 01-21-2010 08:10 PM ET (US)     Profile for jimh  Send Email to jimh     
I am sure by now everyone in Europe and elsewhere considers it their birthright to be able to use the United States NAVSTAR GPS system. If we undertook some change to prevent it from being used it would just add to the general animosity toward us.

In any case, the current administration just gave away more money to Haiti than would be needed to run LORAN for a couple of decades. I guess the budget was not as tight as they made out when they said they had to shut down LORAN to save money.

elaelap posted 01-21-2010 08:21 PM ET (US)     Profile for elaelap  Send Email to elaelap     
"[T]he rest of the world hates us and wants us eliminated..."

I understand that great strides have been made in the psychopharmaceutical treatment of paranoia, pal. Check with your mental health care provider, if they have such a thing in Gilbert, Arizona. Man oh man...

Tony

A2J15Sport posted 01-21-2010 08:32 PM ET (US)     Profile for A2J15Sport  Send Email to A2J15Sport     
Phoenix (Gilbert) isn't Frisco but we do have the Mayo.

I'm fine, just a realist.

jimh posted 01-21-2010 08:36 PM ET (US)     Profile for jimh  Send Email to jimh     
There are LORAN receivers available for sale now. The volume of production never reached the huge scale of GPS receivers, which have become a commodity item and sell for about $20 nowawdays, so the price is not as attractive as a GPS receiver.
GreatBayNH posted 01-21-2010 09:03 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
GPS timeline snipett as found on Wikipedia:

"In 1996, recognizing the importance of GPS to civilian users as well as military users, U.S. President Bill Clinton issued a policy directive declaring GPS to be a dual-use system and establishing an Interagency GPS Executive Board to manage it as a national asset."

So, for all you people out there right of center; you can think of and thank Bill Clinton every time you navigate your Boston Whaler with an electronic GPS navigation device.

-Seth

David Pendleton posted 01-21-2010 11:32 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Seth, I think what you're referring to is Clinton's decision to turn off Selective Availability. The GPS constellation predates Clinton by a number of years.
jimh posted 01-22-2010 09:10 AM ET (US)     Profile for jimh  Send Email to jimh     
Selective Availability (SA) was an option in GPS. It reduced the precision of the fix for non-military users. The NAVSTAR GPS was still quite useful even when SA was in use.

In the first Gulf War, I believe that SA was turned off. The military did not have enough receivers capable of obtaining an enhanced fix with SA turned on, and they ended up using a lot of civilian grade receivers in the field. So as it happened, SA was not particularly useful for the military. That is probably why it was eventually turned off on a permanent basis.

Salty Tricks posted 01-22-2010 12:27 PM ET (US)     Profile for Salty Tricks  Send Email to Salty Tricks     
"When was the last time you could actually buy a new LORAN receiver in the US?"
Kevin


I have a brandy new Si-Tex Colormax Wide Chart/Map/FF ( 2008)that also has the optional "E Loran", as they market it, whereas you can choose what you would like to use for navigation or integrate the two. I thought the "E" stood for enhanced although I am not certain what that meant. I still believe that repeatability with Loran beats out GPS. I have no science to back this up ...just my observation.

towboater posted 01-22-2010 01:57 PM ET (US)     Profile for towboater  Send Email to towboater     
Im not going to start another thread Jim.
If you want to delete it, be my guest.

The topic is confirmation Loran era has ended, hello GPS.

The subject turned to value, tax saving etc.
Based on over 35 years of Commercial experience with both Loran and GPS, I will wager against anyone, GPS era Maritime incidents will be proven to be far less than the Loran era...thus saving money.

[Continued to attempt to link LORAN with a marine casualty. Please note that this discussion is about the decision to terminate LORAN. If you wish to invent or revise history, please start your own separate thread to continue with your efforts in that regard. You were explicitly cautioned to not proceed on this line of discussion in this thread.--jimh]

dfmcintyre posted 01-22-2010 05:37 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Towboater -

I'm confused (ah, happens more often nowadays, I digress...) about the last post of yours regarding LORAN was essentially useless for dead reckoning. Why?

Regards - Don (confused mode on)

towboater posted 01-24-2010 02:13 AM ET (US)     Profile for towboater  Send Email to towboater     
I guess you can't say Loran is usless for dead reckoning. Hehe. You betcha. Sorry to confuse you Dan.

Compared to GPS, Loran is useless junk. [Changed the topic of discussion to the discussion itself. Please, we are not discussing this discussion. We are discussing the decision to shut off LORAN. If you would like to express you views to the moderator about how this discussion as been conducted, please send the moderator an email.--jimh]

jimh posted 01-24-2010 09:16 AM ET (US)     Profile for jimh  Send Email to jimh     
LORAN and GPS use the same radio location technique to determine position. LORAN has the advantage in that the location of the transmitters are fixed. LORAN stations do not move. In GPS the location of the transmitters are in earth orbit and are rapidly moving. In order to know the position of the transmitters, it is necessary to know their orbital mechanics and well as to know the precise time. None of this is necessary in LORAN. A LORAN receiver can deduce its position without knowing the time or date. A GPS receiver cannot deduce its position without knowing the date and the precise time. In addition, the time accuracy must be fantastically precise.
dfmcintyre posted 01-24-2010 11:18 AM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Jim -

As I posted earlier, when I flew a plane equipped with both a Northstar LORAN and a Garmin 195 GPS, both were almost always within 2 degrees and 2kts of each other. If we flew into a turn, the LORAN unit took a longer to stabilize on the current heading. I attribute that with the difference in processing power; the Northstar unit was (by then) ten years older then the Garmin.

In re-reading the some earlier posts, I think where Towboater and I diverse is that he may be referring to the lack of the modern day display screen interface that's become quite common in GPS units. Just about all of the LORAN units, of the time didn't have that interface, nor did the early portable GPS units. I've still got an early Magellan portable, in my attic that only gave out L/L, plus altitude that was the size of the large paperbacks.

I think that if GPS was not every created, we'd probably have a more robust LORAN chain system and with screens showing position with built in charts. With one possible problem:

The question I've got Jim (since your the electronics expert here), is as follows: due to the low frequency that the LORAN chain used, how small could a receiving antenna become? Isn't there a limit? If the designers couldn't develop an antenna small enough, that could be a deal breaker.

Regards - Don

jimh posted 01-24-2010 01:21 PM ET (US)     Profile for jimh  Send Email to jimh     
The efficiency of an antenna is generally related to its size as compared to a wavelength of the radio frequency involved. LORAN uses a very low radio frequency, 0.1-MHz, and as a consequence the wavelength is very long. For example, the length of a half-wave antenna at 0.1-MHz would be 4,860-feet. Generally one finds that a half-wave antenna is the minimum antenna that would be satisfactory for general use. Smaller antennas will become less efficient.

For transmitting, the efficiency of an antenna is very important. If the radio frequency energy applied to an antenna from the transmitter is not efficiently converted into radio waves, the antenna will not work very well. Most of the energy will go into warming up the worms in the ground around the antenna. For receiving, however, efficiency is not as worrisome. When receiving it is possible to add additional gain to make up for any loss suffered in the antenna. Without getting too technical, as long as the amplifiers used in a receiver are well designed for low noise contribution, there is practically no limit to how much gain can be added. Therefore if a receiving antenna has losses compared to a full-size half-wave antenna, those losses can very easily be overcome with more gain in the receiver. If we use a receiving antenna that has substantial loss, say - -20dB compared to a full size antenna, this means 99-percent of the power received by the antenna is lost. However, if we use an antenna preamplifier with a gain of 20-dB, we can produce the same signal level from the antenna as we would get from a full-size antenna. This technique cannot be used on transmit because generally there is a limit on the transmitter power, either from license restrictions or from practical considerations.

In modern LORAN receivers the antenna can be reduced in size. The antenna technology is called a voltage probe active antenna. The antenna consists of a very sensitive and low-noise preamplifier which is coupled to a small input antenna. Advances in modern semiconductors have created the very high input impedance devices needed for these applications.

In addition to voltage-sensitive antennas, modern LORAN receivers can also use magnetically sensitive antennas. Recall that radio waves are a form of electro-magnetic radiation. Generally we use antennas that intercept the voltage wave variations in radio signals, but antennas can also be constructed to detect the magnetic wave variations. These are called H-plane antennas (H being the symbol for magnetic force). By using diversity antennas with both E-plane (voltage) and H-plane detectors, LORAN reception can be improved.

Don is absolutely correct when he observes that the method of display of position on a LORAN receiver as seen in the 1950's or the method of position plotting using lines of time delay intervals as seen on many older navigation charts are only manifestations of the limited electronic technology of that era. They have nothing to do with the fundament nature of LORAN, which--as I have already said a number of times--uses the same radio location technique as GPS. There is nothing about LORAN that precludes development of a chart plotter type display. Persons who make uninformed comments about LORAN as being limited to these antique display methods apparently do not understand the nature of the LORAN system and how similar to GPS it really is.

Salty Tricks posted 01-24-2010 08:09 PM ET (US)     Profile for Salty Tricks  Send Email to Salty Tricks     
Not to repeat myself here but I have a modern Map/Plot/Chart unit that can use LORAN TD,s to plot course and show location exactly as it does when I use the GPS processor. The antenna is a combined Loran/GPS unit that is a little larger than your typical GPS 3-5" dome. It requires no significant height installation. Check the Si-Tex site if you like. I believe several manufacturers were about to release Loran compatibility with their GPS units. Si-Tex gambled by releasing theirs thinking Loran was here to stay longer as per the previous administration....they gambled and lost.
jimh posted 01-25-2010 09:04 AM ET (US)     Profile for jimh  Send Email to jimh     
LORAN and GPS are also similar in that all transmitters operate on the same carrier frequency. In GPS a spread spectrum technique using pseudo-random noise modulation techniques (CDMA) prevents mutual interference, and all transmitters transmit continuously. In LORAN, the signals are interwoven using precise synchronization of when they transmit (TDMA), and transmitters take turns transmitting. Part of the enhancement of the accuracy of LORAN would be obtained by increasing the accuracy of the time base used to synchronize the system.

Regarding H-plane antennas, I recall that many years ago we needed to monitor a local broadcast station (760-kHz) which was designated as the primary station in the Emergency Broadcast System. This station, although very powerful (50,000-watts) and very local (only about 20-miles distant) was impossible to receive inside our building using an E-plane antenna due to the very good shielding and grounding in our plant. We installed a small H-plane antenna and found it provided an excellent and very stable signal.

jimh posted 02-06-2010 12:28 PM ET (US)     Profile for jimh  Send Email to jimh     
Only two days remain until the LORAN shut down on February 8, 2010.

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