Dear Capt. Paul:

Can you recommend a conversion program to get from W-X-Y to Lat Long (NAD 83). 

Thank you in advance, 

— S. Trout

Capt. Paul’s response:

I have some interesting information on the LORAN-C Navigation System which should assist you in making the conversion you need. 

But first here is a general insight on the now defunct LORAN system. The U.S. Coast Guard indicates that that the Loran system radio broadcast signals was shut down as of February 8, 2010. That means that charts, GPS units and other information converting software about the Loran system may not be available in the future. I strongly suggest that you make your conversions as soon as possible. Remember the U.S. Coast Guard says that any Loran position determined by a Loran receiver may be off as much as 1500 feet. Most standard GPS units can now display a position with an accuracy within seven (7) feet.

The U.S. Coast Guard Navigation Center has a site on the web that will allow you to convert Loran Time Differences (TD’s) to a latitude longitude format. This program uses the new DATUM Standard of NAD83 ~ WGS 84 in making the conversions.

It is a very efficient site that should suit your needs. This site can be found at

Once on the web site you will access a screen named CALCULATE POSITIONAL DATA. It as shown in the chart attached.

It is a very handy and accurate program for doing the conversions. I suggest that you place an icon on your desktop for easy access. The program will then require you to record the information as they are displayed. 

There is also another program for smart phone applications. It can be found at the Coordinates Converter Free By MASAKA Inc. web site. It can be found on their website at 

A second way for users of SOME more modern GPS models is to simply change the “Position Format” or as called by some units the “Location” configuration to LORAN TDs, and enter your Loran values, then switch back to your normal Lat-long settings and the GPS unit will automatically do the conversion for you. If your unit has the ability to show positions in the Loran TD format, it is an easy task for you to do the conversion using the above procedure. 

Or, the quickest way would be to use your manufacturer’s data transfer and by changing the Position Format Grid system in the program to LORAN TD and simply enter the TD’s into that format.

Then by simply changing the position format back to your latitude-longitude all of the data will be converted by the unit. In addition, by using the data transfer procedure on the program, you can download all of the new data into your GPS unit via the established protocol. The big advantage is that you will be logging in the positions by using your computer key board instead of manually entering them one at a time in the GPS unit.

Most if not all of these data transfer programs are available from the manufacture of your GPS. Be sure to get the one that is compatible with your GPS unit. Many are provided as a free download from their website.

Of course, you can plot the LORAN TD position on a chart that has Loran lines then replot these positions using the Latitude~Longitude markings on the chart. I have covered this “How To” in one of my other articles earlier this year. 

If the chart or your present LORAN positions has three sets of Loran overlays it means that you would or could receive TD signals form three different Loran transmitter towers. Most likely the chain number will be 7980 for the upper Gulf Coast.

On the chart each set of near parallel lines are displayed in a different color. If you are viewing three sets of such lines you have “W”, “X” and “Y” signals. Three such indicators is more accurate than only two. Locate one of the lines of your position and follow it to a point where you will see a LORAN overlay value number. That is the TD number for that line. Now search the other lines that are on the same angle. Every fifth line will have the “chain” listed and the “W”, ”X”, or “Y” designation. Note the letter designation for those sets of lines. Now locate one of the other sets of near parallel lines. Follow it until you find the Loran TD number value for that line. That is the TD for that line. Now as with the other sets of lines, every fifth set of lines will have the chain, the W, X, or Y designation and a numerical value. If the first set of lines were W, then these would have to be either the “X” or “Y” TD value.

The exact same situation would apply for the third set of near parallel lines. This set would be whatever was the other value left of the W, X, Y possible combination. 

Every fifth overlay line in all sets would list the chain the W, X, Y value and a numerical value for that line. 

In deciding which sets of lines to use, I have found that the smallest numerical number between lines offers the greatest accuracy in interpolating the actual TD figure if it is anywhere between the overlays. 

— Capt. Paul