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From: Trevor J. Kenchington (no email)
Date: Sun Nov 02 2003 - 23:00:27 EST
Rodney Myrvaagnes wrote:
> No doubt the Admiralty charts in the Channel and surrounds have been
> refined to a fare-thee-well over the centuries, but I can find survey
> errors in modern charts of the Maine coast, based on Admiralty surveys
> in the 17th and 18th centuries.
> [snip]
> Sorry for wandering, but this is important for anyone using a really
> tight navigation system like GPS.
I could not agree more, though I'd extend the caution even further:
On the Nova Scotian coast, not 20 miles from Halifax Harbour, there is a
charted island (shown as dry at high water) which is really a shoal that
is covered even at the lowest tides. Fortunately, it is so far out of
the way that not even the kyakers or windsurfers ever encounter it
(though a couple of us hauled SCUBA gear down to the adjacent beach and
took a closer look).
A bit further on, there is a well-known error where the charts show the
channel up Petpeswick Inlet passing west of one particular island,
whereas yachts bound up to the club at the head of the Inlet really have
to make a sharp dog-leg to the east.
I could continue -- and without citing any cases where the last survey
predates 1850.
Moral: You don't need to be using GPS to treat charts with a healthy
dose of scepticism, particularly if you are operating a small boat in
places where neither warships nor freighters ever go.
Trevor Kenchington
--
Trevor J. Kenchington PhD
Gadus Associates, Office(902) 889-9250
R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251
Nova Scotia B0J 2L0, CANADA Home (902) 889-3555
Science Serving the Fisheries
http://home.istar.ca/~gadus
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