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I understand Chuck Taylor's logic supporting Bowditch's strictly-limited
definition of the DR plot. But there have to be practical limits. Chuck wrote:

> 5. Navigate in such a manner that both my DR and my intended track stay out of
> harm's way, allowing plenty of margin for error.

If I was navigating my way towards Avonmouth, at the head of the Bristol
Channel (and so to the commercial and yacht harbour of Bristol's City
Docks), in order to follow a safe track, my DR plot would necessarily
cross a number of dangerous sand banks and would likely end up far
inland -- unless I constantly re-started it from frequent fixes. Much
the same would be true if I attempted a less probable (but not
impossible) cruise through the Minas Basin at the head of the Bay of
Fundy and indeed anywhere else where strong tidal streams are combined
with a curved coastline.

What practical use does the DR plot have in such a situation?


Trevor Kenchington


--
Trevor J. Kenchington PhD                         Gadus@iStar.ca
Gadus Associates,                                 Office(902) 889-9250
R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555

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