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On Sun, 2 Nov 2003 17:35:39 +0000, George Huxtable wrote:

>
>Rather to my surprise, even modern GPS and modern mapping resulted in
>problems, in that several features recorded by the early explorers had
>become corrupted, with their names for certain hills transferred in error
>to other hills. Perhaps one shouldn't expect perfect maps in such a
>seldom-visited land.
>
This shouldn't be such a big surprise. GPS receivers come with a
built-in chart datum list. Modern charts name the appropriate datum,
but Capt Cook neglected to do so.

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.

For a notorious modern survey error, for which Admiralty surveys bear
no blame, recall the expensive grounding of the QE II off Cuttyhunk
Island in Massachusetts a few years ago. The Coast Guard was in the
process of surveying the bottom in 1939, and had a grid of
rectangularly spaced soundings. WW2 interrupted, and charts used those
soundings, with nothing between them, even though there was clearly an
unlocated peak between some of them.

I have saved my pre-QE II chart for historical reference. It makes an
interesting comparison to the new one.

Sorry for wandering, but this is important for anyone using a really
tight navigation system like GPS.




Rodney Myrvaagnes                     J36 Gjo/a


"I met about a dozen people who voted for me, and generally I can't say I 
really agree with their reasoning."
Bernard Goetz, subway gunman

   

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