Capt. Mooron wrote:

Astute.... but COG has been deprived of SOG and my ETA is now as
dubious as my DR ... now I need a drink of Rhumb! :-)

I now realise that the whole journey is a red herring - he never said
anything about the final position being worked out as a DR. It could just as
easly be observed or GPS. He might as well have said...

You start at X, sail about for a bit, and finish at Y.
What's the vector from X to Y called?


--
Wally
www.artbywally.com
www.wally.myby.co.uk