NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: on finding Pitcairn Island
From: Robert Gainer
Date: 2004 Sep 21, 18:43 +0000
From: Robert Gainer
Date: 2004 Sep 21, 18:43 +0000
Trevor, I think that for the most part a wave will not feel the bottom until the depth of water is less then � of the wavelength. At that point you will begin to see some difference in the wave pattern. All the best, Robert Gainer >From: "Trevor J. Kenchington">Reply-To: Navigation Mailing List >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM >Subject: Re: on finding Pitcairn Island >Date: Tue, 21 Sep 2004 11:45:56 +0000 > >Peter Fogg wrote: > >>What is found between New Zealand and Australia are a number of underwater >>sea mounts, mountains >>that rise from the sea floor about 4000 metres below to within a >>comparitively short distance, some of >>them, from the surface. When the sea is agitated the area above the mounts >>has a different characterisitic >>compared to the open ocean, and could lead to speculation; such as land >>being near. > > >Could Peter elaborate on his sources for the contention that the sea >surface gets a detectably different "characteristic" above a seamount? > >I have a very little experience fishing over seamounts in the general >area in question, though rather further south (around 49 degrees >latitude). We certainly had times down there when the sea was agitated, >as would be expected, but nothing that suggested to me that land was >anywhere near. [In my case, the summits of the seamounts were around 700 >metres depth. They stand on the South Tasman Rise at around 1400, while >the surrounding area is 4000 metres or so in depth. Clearly, a seamount >which comes very much closer to the surface would be more likely to have >effects visible to a surface observer.] > >Of course, we had SatNav and charts to tell us that land wasn't close, >plus a powerful sounder to tell us just how deep the water was, and thus >were not looking for subtle signs. Add in an enclosed wheelhouse and >work to do that kept me from watching the sea all day long: Maybe there >were features in the wave patterns that a sailing-ship master, running >his easting down across the same area, would have observed. > > >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 > > Science Serving the Fisheries > http://home.istar.ca/~gadus _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/