NavList:

Hello Ed,

You said with respect to Traverse Boards (6 November) : My question was how did they use that information to determine their position from those eight board settings. Did they graphically do a kind of vector addition, were there tables that summarized? 

I see Norie’s 1839 book describes collation of hourly course and speed/distance data and methods for using that data in finding a DR position, including graphical vector additions, calculations, and use of tables. The book describes the hourly data as coming from a painted Log Board on which the data for 24 hours has been marked up, rather than mentioning the 4-hour Traverse Board.  Presumably the same processes for finding a DR position might have been used directly from the Traverse Board data after the four hours - but what I'm not sure about is whether the methods described by Norie were all available during the Traverse Boards era.

The link to the book is in the Resources section here (Bowditch and More).  Relevant sections seem to be :

• Traverse Sailing from page 73 onwards (including graphical vectors)
• Method of Keeping a Journal at Sea, at page 300 on
• Journal of a Voyage, page 311 onwards

I found all of it interesting.

Regards,

Adrian F