Has anyone in our area successfully accurately converted old loran TD’s to GPS Lat/Lon? I tried it with my GPS, but the numbers are not accurate. I tried it with a friends GPS and got slightly different numbers - still not accurate. I also downloaded and tried the USCG POSAID2 software and converted the numbers - they were different than the other two numbers - by 250 feet - and still not accurate. Is this even doable accurately? For my purpose accurately means +/- 25 ft.
Loran C was never accurate to within what current technology GPS can do, and you could only get under 100ft accuracy if you were using the same box each time and the TD’s came from that exact box. 60ft is about the best you can get converting, and you may not know which direction that 60ft is and which numbers are in what direction if you don’t know how many boxes your numbers all came from. I have done 10,000+ conversions, and I fish such spots/areas each time I fish. I know many others who have done the same, but they will say very little about how to do this and/or why. Some guys still don’t know any lat or long numbers off our coast. They still think 100% in TD’s. It’s pretty cool learning to count numbers and use a compass rather than doing stuff like kids do on a video game or something.
Anyway…
To get them under 100ft in accuracy you have to have local knowledge of the lat/long for small and easily ID’ed spots (with sonar) cross referenced with TD’s you’ve got from the same Loran receiver. And these cross references will have to be in as many places as possible. Almost like zeroing in a rifle, but you don’t know what rifle you’re using each time until you shoot it enough at different ranges to finally hammer it out and KNOW where your bullet will go each time.
If you don’t like long posts on here, then you can stop reading now as I tell you that it’s really complicated and takes a good bit of experience/knowledge/effort to get “accurate” conversions.
If you have numbers jumbled together from your granddaddy, uncle, their buddies and your neighbor’s dad’s girlfriend’s cousin’s partner’s banker’s whoever, then you are not going to get better than 100ft. 100ft will do it unless you are looking for something tiny and isolated. When I fish a reef it is usually 30ft+ in size and I want to run over it several times to map out where the fish are at that particular time per the current and how I want to set up on them. So being within 100ft is going to do it for me.
Like I said tho