The best conversion I know of is using a Furuno GP-32 or GP-35. Enter the loran number in, change the Furuno to GPS, they are spot on. (slow process) Andren will give a fairly good conversion, it will get you in the ball park. I'd still use the Furuno to get pinpoint accuracy with the TD's. I keep one on my boat with the display in TD's for use when I'm looking for an old reading.