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Converting loran to GPS

Old 02-21-2013, 07:55 PM
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Default Converting loran to GPS

Has there been any new ways to convert Loren TD to GPS lat Lon?
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Old 02-21-2013, 08:19 PM
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I would be interested in this as well. I have hundreds of great hard bottom spots in the gulf. Must be a conversion program available. I would guess that the conversion would only get you close, then you would need to spend some time to find the zero.
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Old 02-21-2013, 08:40 PM
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Originally Posted by gregdp2486 View Post
Has there been any new ways to convert Loren TD to GPS lat Lon?
I don't quite understand what a "GPS lat Lon" is supposed to be. Is the "GPS lat Lon" different from the actual latitude and longitude of a location?
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Old 02-21-2013, 08:58 PM
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GPS gives true Lat/Lon. Loran used time diferences broadcast from shore from different points.
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Old 02-21-2013, 09:45 PM
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Originally Posted by 76 Stamas View Post
GPS gives true Lat/Lon. Loran used time diferences broadcast from shore from different points.
Actually, LORAN and GPS work in similar ways in deducing position from time differences in the arrival of signals. The signals just come from different places and use different frequencies. The method of deducing position is really similar. The accuracy of GPS is better, but the basic methods are the same.

I just do not understand what possible difference there could be between a "GPS lat Lon" and the actual latitude and longitude of a location. It seems like the interest would be in converting LORAN time delay data into latitude and longitude, without regard to the Global Positioning System.

In that regard, I have noticed that some modern chart plotters now include a built-in LORAN simulator. For example, on the Lowrance HDS there is a special mode of operation in which the device will calculate LORAN time delays as the cursor is moved on a chart. See

http://continuouswave.com/whaler/ref...antomLoranMenu
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Old 02-21-2013, 10:05 PM
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GPS uses Multiple satilites to TD a position. Thats why it is more accurate.
Loran was using 2,3,or 4 stations in a given area (at best) to determine the locaton. On a good day back in the 70's or 80's Loran was pretty darn good at accuracy. However GPS is heads ands shoulder above it.
Glad the government took the military factor off GPS a few years back and gave the civilians a more accurate platform for positioning.
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Old 02-22-2013, 02:36 AM
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www.andren.com is one way to convert.
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Old 02-22-2013, 03:33 AM
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Originally Posted by steve a59 View Post
www.andren.com is one way to convert.
This is the best I've found.

I begin by converting a few known spots, like confirmed channel markers or wrecks. Then check those against your known GPS coordinates. You can then tell if they are close and if they are consistently off in a certain direction(which I prefer). Then you know which direction/quadrant to start your search in.

C
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Old 02-22-2013, 05:39 AM
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well guys im in the process of looking into this myself. what i have found so far is that Garmin and Lowrance can convert Loran numbers to GPS. Now with that said alot of the people who have done this said that lowrance is not very accurate. Lowrance will get you to within a couple hundred yards. As for Garmin, everything i have read about them is that the program they use will convert the numbers to within a couple hundred feet. either way i think your going to be spending some time looking for the exact numbers. another way someone sugested was to buy an older loran unit and enter the numbers into it and next time your out on the water makesure to have both units on the boat and then get over the loran numbers and enter the position for the GPS.

Now i presently use a garmin gps so i pulled up the garmin software and i can input loran numbers and then convert them to gps this is what i will be using. if you have a lowrance unit or simrad or whatever other type of unit maybe you can look into buying the garmin software since it is the most reliable and enter the loran numbers. Once you get thementered you can convert them into gps numbers then look into converting the file to one that will be compatible to your unit.
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Old 02-22-2013, 07:58 AM
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Well. after posted the question I did some looking.(on THT) and found basically everthing there is to do for do the convertions. Thanks guys!! Andren.com seems to be the man!!
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Old 02-22-2013, 02:47 PM
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Originally Posted by steve a59 View Post
www.andren.com is one way to convert.
Is the only way to go...
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Old 02-22-2013, 06:43 PM
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Originally Posted by striperjunkie View Post
....another way someone sugested was to buy an older loran unit and enter the numbers into it and next time your out on the water make sure to have both units on the boat and then get over the loran numbers and enter the position for the GPS.
Will you require a Loran signal for this method?

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Old 02-22-2013, 07:07 PM
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Lots of software programs to convert TDs to Lat-Long, and many GPS units allow you to input TDs and convert to Lat-Long.

But a few important points to consider:
1. The 'repeatable" accuracy of LORAN was excellent. It would do a very good job of getting back to the same TD position on different occasions.
2. The "absolute" accuracy of LORAN was never very good. The radio signals travel at 300 million meters per second, or 300 meters in one microsecond. Most LORAN units measured in tenths of microseconds, so that was 30 meters and the best accuracy you could expect, even as repeatable accuracy.
3. The conversion of TDs to Lat-Long, whether on a chart or using a software program or using a GPS, is all based on the theoretical speed of propagation of radio waves over the ocean. Some of the transmitter stations were far from the shore so the radio waves travelled over land, introducing a calculation error. Additionally, the theoretical speed is based on specific atmospheric conditions and additional errors are introduced when the temperature is different or the atmospheric pressure varies. In total, these are known as Additional Secondary Factors and there were published tables of these to use in various geographical areas, at various times of the year, and based on which TD station pairs you were using. These ASF corrections are NOT incorporated in the software programs, or in the GPS units that we use, so you can expect significant errors between the actual TD position and the derived Lat-Long.

The only good way to get Lat-Longs from those TD lists is to take a LORAN unit onboard, go to the TD position, then create a GPS waypoint. This was noted by at least one poster above.

More info: http://msi.nga.mil/MSISiteContent/St...N/Chapt-12.pdf

Brian
Commander, U.S. Navy (Ret)
Master, Oceans, Steam, Motor and Sail, 1600-Tons
Chief Mate, Oceans, Unlimited
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Old 02-22-2013, 07:13 PM
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Loran is no longer functioning, so using the old Loran unit is out.

Plugging into a GPS unit isn't very reliable.

Get the Andren program, trust me.

C
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Old 02-22-2013, 07:32 PM
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I have a small book of Loran numbers that I had previously converted on a Lowrance LMS 520....

It was a near bottom of the line chartplotter and I would find it hard to believe that most anything else out there couldn't do the same....

Plus, it was accurate. We would get within yards of the mark...
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Old 02-22-2013, 08:07 PM
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a lot of the accuracy of the conversion depends on the angle of the td's as they intersect in the area you are trying to convert in. if you are in an area that they meet @ 90*, pretty close. in a fringe area where they meet at less angle, not so good.
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Old 02-22-2013, 10:17 PM
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Originally Posted by 76 Stamas View Post
GPS uses Multiple satilites to TD a position. That[']s why it is more accurate.
The best simple explanation is that the LORAN system cost about $25-million and GPS has cost about $50-billion. One GPS satellite costs more than LORAN's entire project cost for 50-years.

It is unfortunate that LORAN was shut down when it was almost converted to eLORAN. I have read that it has actually cost more to dismantle the USA LORAN installations than it would have cost to finish the upgrade to eLORAN. It would have only taken maybe $20-million to upgrade.

eLORAN is now being used in the English Channel, one of the busiest shipping areas in the world. See

http://elorantechnologies.com/follow...la-initiative/

And, yes, without LORAN on the air, it is going to be rather difficult to use an old LORAN receiver to locate old TD coordinates.

Here is my experience with the Lowrance Phantom LORAN function:

Looking over NOAA Chart 14830 (Lake Erie) I noticed that three lines of position from LORAN time delays cross nicely at the flashing red on the Southwest tip of South Bass Island. I compared the charted values of LORAN time delays with the computed values of LORAN time delays made by the HDS. The results are very good:

Flashing Red at SW end of South Bass Island
LORAN TIME DELAY COMPARISON

Charted values----HDS vales
9960-Y = 43670 v. 43670.59
9960-W = 16501 v. 16500.5
9960-Z = 56920 v. 56920.04

The X and Z values are almost exactly the same. The W value is off just one microsecond, a nominal error. This comparison shows the HDS computed time delays to be closely correlated with the NOAA chart overlays.

For more on Lowrance Phantom LORAN see

http://continuouswave.com/ubb/Forum6/HTML/003142.html

http://continuouswave.com/whaler/ref...antomLoranMenu

http://continuouswave.com/whaler/ref...ansettingsMenu
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Old 02-23-2013, 01:45 AM
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I have had the worst of luck using a ghost loran trying to get on old TD's. I was using both a furuno or garmin GPS. After reading what some of the above posters are saying it seems that Lowrance may have a better unit for conversion? I've had a lot of my old numbers converted by andren and all is well. I could have saved myself a lot of trouble by doing this before the gov.took out Loran c.
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Old 02-23-2013, 10:30 AM
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The Lowrance Phantom LORAN calculations showed reasonably good agreement with the LORAN lines over-printed on a NOAA chart. Of course, the LORAN lines on a NOAA chart are not necessarily highly correlated with some Time Delay numbers that someone's individual LORAN receiver obtained at some random location 20-years ago on a certain rainy day in the summer at 5 a.m. in the morning.

One of the problems in LORAN accuracy was predicting the propagation speed of the signal over varying terrain. Variations in signal propagation with terrain paths caused LORAN to lose accuracy. The GPS system has this same problem; propagation through the ionosphere varies. The purpose of augmentation systems like WAAS is to provide near real-time data to correct for those variations. LORAN accuracy could have been and would have been improved if a similar augmentation system was employed. A correction signal, like the one sent by WAAS, would have improved LORAN.

In my opinion, LORAN is too often dismissed as being inaccurate compared to GPS, but on a fundamental level they are similar and have similar problems. GPS employs enormously more complex technology and mathematics than old-fashioned LORAN did. If some of that technology had been applied to LORAN, it would have been a comparable system for position finding.

It is great that the USA spend a trillion on a global system so now a cab driver in Mumbai can find his location on a $50 GPS receiver on this dashboard. The irony of LORAN was its coverage was just in the USA, so the beneficiaries were primarily residents of the USA. The real deal killer was there was no military application for LORAN for global war fighting. Good-bye LORAN.
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Old 06-25-2018, 09:59 AM
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Default Chains need changing with LORAN. Got a plane shot down too

The antiquated TD (LORAN) long Range RADIO navigation system had to have the area # set to match.


Worse yet LORANs were NOT EVEN repeatable between manufacturers. You'd see a change using a Micrologic and the number would be the same on a Raytheon or Apelco. The charts would print which LORAN unit was used in the chart.


LORAN is coastal. And are simply radio signals. Not differential signals from up to 12 different satellites.


The LORAN chain changes where you are on earth. Not updating the TD Chain # got KAL flight 007 shot down by the Russians over Kamchatka USSR killing everyone on board. Because of KAL 007 Reagan let the civilians use the GPS system already created AND IN USE for the military.


LORAN was not all that accurate and varied between manufacturers. 100 yard differences. Find a wreck in that LORAN search.


Capt. Frank D.
NJBoatingCollege.com




Originally Posted by 76 Stamas View Post
GPS uses Multiple satilites to TD a position. Thats why it is more accurate.
Loran was using 2,3,or 4 stations in a given area (at best) to determine the locaton. On a good day back in the 70's or 80's Loran was pretty darn good at accuracy. However GPS is heads ands shoulder above it.
Glad the government took the military factor off GPS a few years back and gave the civilians a more accurate platform for positioning.

Last edited by NJBoatingCollege; 06-25-2018 at 10:02 AM. Reason: tyypos
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