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How to Change TD to Latitude & Longitude

After years of steep decline in use in favor of GPS, in February 2010, the Loran (long range navigation) system went off-air in the U.S. and Canada, rendering Loran systems non-functional and their saved time distances (TD) obsolete. Thankfully for Loran enthusiasts, TD can be easily recovered. Most Loran-C devices have TD-to-latitude-and-longitude conversion programs built in. While the example used here is specific to Raymarine Multifunction Display products, other models convert in a similar way.

Instructions

On Devise
- 1
  Press "Menu" on the face of the Loran-C devise.
- 2
  Select "System Set-Up" then "Position Mode."
- 3
  Choose "Lat/Lon" from the menu. Waypoints entered in TD will now display in latitude and longitude. You can switch back to TDs at any time by repeating the process and selecting "TDs."
Free Software
- 4
  Go to www.loran.org and click "Library" third from the right on the top of the page.
- 5
  Click the link "Researching the ILA Archives," then scroll down to "Other Loran Publications of Interest" under the fourth heading down, "Index to other Loran publications."
- 6
  Click "2000-Receiver Coordinate Computation Information," the last link in the left column. Click the first link on the page, "Fixed! Link to Loran-C Coordinate Conversion Software from Dr. Paul Williams, Univ. Wales," and download the software.
- 7
  Unzip the downloaded folder and open "TD2LL.exe."
- 8
  Enter your TDs into the text boxes in the top left and click the "LL" button toward the bottom of the window. The conversions will appear.

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