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Loran to gps

Is it possible to convert loran numbers to gps. This is the way my numbers look 28 54.610 not sure what datum it is. My grand pa has a lot of loran numbers that's whynim asking. And is there a map of ubstructions and hang ups that the shrimpers use in the gulf. So we can possibly fish them
~ Captain Paul's response to: ~ No Mo Money ~

There are several commercial programs that can convert Loran A TDís to a Latitude Longitude format, but the U.S. Coast Guard Research and Development Center had a program they call Position Aid. It is no longer available, but a US government, public domain program is available from the International Loran Association home page at Go there to download

It appears to be the old USCG Position Aid program. You can download the program and keep is in your computer as a fail safe conversion program.
You may find others by searching the internet for such a conversion program.

But the easiest way is to let your GPS do the conversion for you.

Almost all modern GPS units have a Grid Format called Loran TD or maybe just TDís. First turn on your GPS and go to the main menu.
Go to the Configuration or GPS setup menu or what ever your unitís manufacture calls the configuration setup for the GPS unit.
Find the POSITION FORMAT or in some cases it is called LOCATION.

In the Position Format box, Select the 'TD' mode, Then enter the Loran coordinates you want to convert to lat-lon one at a time. Once you have entered the points, go back to the Configuration menu, choose 'Position Format' again and change the format back to your normal 'Latitude-Longitude' setting. All of your waypoints you entered as TDs will now be in the lat-long format.

The Position you stated is in H,DDD,MM.mmm, ie. Hemisphere, Degrees, Minutes and Thousandths of minutes, It is the most common used in GPS units for both land and on the water. A one digit change in the last position of the decimal minutes (.00X) equals about a change of 6.2 feet, which is way below the accuracy of a standard consumer GPS unit.

Captain Paul
zip file
Capt. Paul I went to the website but cannot find the zip file for converting. Am I looking on the wrong page? Thanks for any help.
Try the second web site
The first web site was the home page of the organization.

Try the second web site, which is a direct link to the zip file.

Captain Paul
Re: Loran to gps
When Loran first came out, the output was in a pairs of TD numbers 'time Distance or time delay'. These numbers were derived by using a combination of one Master Station and any 2 of 4 possible slave stations. The first two numbers of the 4 slave stations in my area began with 11, 24, 48 and 64. Several factors were used for the the best pair but generally those with a strong signal and crossed closest to 90 degrees to each other were used.

In the early 1980's, Loran units could convert the TD numbers to a Lat. Long. number and would look like today's GPS numbers in DMS or DM.M. The problem is if you were on anchor and switched to different TD's slave combinations, the Lat. Long numbers could change by as much as 1/4 mile. Loran TD numbers had a great repeatably, usually within 25' or so, but the Lat. Long. numbers could be more than the 1/4 mile off from the actual real world lat. long. numbers. Generally those who fished underwater structure used only TD numbers and those who fished rigs used Lat./Long. numbers.

The bottom line is if you have Loran TD numbers you can convert to GPS Lat./Long. and get close but if you have Loran lat./long numbers there is no conversion to GPS lat./long numbers. They are both on the same system' DMS or DM.M but realize they could easily be more than a 1/4 mile difference between the two.

It appears you have Loran Lat./Long. numbers and the hang books, if I remember right, are in TD's. If you are looking for a reef or other underwater structure while not impossible, it's like looking for a needle in a third of a haystack.

I spent 30 years looking for stuff in the gulf based on the hang books and would average finding 2-5 good spots per year using my Loran, including several ships sunk in WWII by U boats. Keep in mind many of the supposed hangs could be just mud balls. The best potential spots are those with 3 or more hangs in almost the exact same spot.