NavList:

I will begin by admitting that I have not attended any of Franks' courses so I do  not know what his "ABC" method is.  However I do have a suspicion that it involves the ABC tables which can be used to determine azimuth. I asked Mr AI about the "ABC method of navigation" and he told be that it was indeed the A+B=C method for azimuth.

I was interested  to note Frank using this method given that I thought that the ABC tables were from British rather than US tradition.  Out of interest I pulled my 1958  edition of Bowditch from the bookshelf. I could not find an ABC table. But on page 530 I found reference to  George Waller a USN navigation instructor. Apparantly in 1946 Waller devised an ABC method. Its publication was prevented by the untimely death of Watler.

The A & B tables date from the early 19th century. The C table was added  in the late 19th, early 20th century. Without  referring to other books ISTR that Lecky, Blackburne and  Cloudy Weather Johnson were involved. This was well before Waller.

While glancing through this thread I noted reference to "two points." Are you in fact describing the Sumner chord method? Are the LOPs Sumner lines?

I will add that in my opinion the ABC tables are the simplest navigation tables ever devised. Extract two three digit numbers, add/subtract then according to rules (the hardest bit) and then use the three digit answer to extract the azimuth from table C.

David C