Saturday, February 13, 2010

Convert those obsolete LORAN TD's into Lat/Longs sort of,,,

As you all know now, all of those top secret fishing spot LORAN numbers you have written down in your special dog eared book, and that are also in-bedded in your now non-functional LORAN reciever are worthless now if you don't convert them into Lat/Longs usable by the GPS you are now shopping for. There is good news, and bad news here. The TD's will convert, but in many, or most cases the conversion will not be perfect. Close, but again not perfect. The LORAN system was not very accurate, but very repeatable. By this I mean that if you went to the chart, and picked a location, and said "goto" this place, it would take you within .1NM to .25nm. If  you made a waypoint at your vessel with the LORAN, it would take you back there almost on the money, or at least within a few yards.

It is possible to convert those TD's, and many GPS units have the capability to input TD's, and convert then to Lat/Longs, to a point. The picture below is a screen shot of a Garmin 5208's TD page. You can see you can input the waypoints in TD's by inputing your Chain and selecting two secondary stations. then you can add the offsest from your conveniently at hand ASF tables (Additional Secondary Factors). Once you have done that, switch the units back to Lat/Longs, and you're done.

Piece of cake, if you can find the the right ASF tables, read them correctly, and understand what your doing. By the way, these ASF tables are not easy to locate, and there are variations in their accuracy. If you do not want to muck around with the ASF offsets, it will still do the conversion, and you will be in the the general neighborhood, but not likely on top of the tiny ledge you caught the big one at.

There is another way, and that is to to acquire software to solve this problem. The first is the cheap solution, and that is to use the the Department of Homeland Security's freebie software (We are from the gummit, and here to help). This can be downloaded from this link.

There are two other solutions that are reasonably priced that I think would work better for most boaters. Both of these packages have gotten good reviews, The first is from Andren software  ($85.00) and provides the conversions, and the ability to upload via your laptop, along with lots of other features. The link to Andren is -

The second option is from Offshore Hunter, and provides the conversions, along with many fishing, diving , and wreck sites, along with tide tables, and other toys, priced at $100.00. This is the link for them.

If your numbers are of value, the two programs above will do a pretty good job of converting them, and now go shopping for your new GPS!

Here is another piece I did about about Andren software.

"I told you I was sick", LORAN circa 2010