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Re: Historical charts and mapping
From: Don Seltzer
Date: 2016 Aug 17, 16:22 -0400
From: Don Seltzer
Date: 2016 Aug 17, 16:22 -0400
On Wed, Aug 17, 2016 at 3:03 PM, Frank Reed <NoReply_FrankReed@fer3.com> wrote:
Mark Coady, you wrote (in the GPS jamming discussion):
...While it's certainly possible that an astronomical determination of position was made right there in Stonington, it's also possible that a large area triangulation effectively transfered an astronomically-determined position from New York or Boston perhaps. The astronomical position is the end of the chain; the links in the chain to local features are made by ground survey triangulation. Incidentally, the deflection of the vertical is close to zero in this area so you don't need to consider that difference between astronomical latitude and longitude and geodetic.
"Your chart explanation brought me back to another question I was pondering and saving. I attached a jpg of an 1847 chart of fisher's island...it set me to thinking... considering this has been my home port stomping ground, off and on...since I was a child....I looked at this and was stunned to see how well defined it seemed to be...and presumably similarly accurate? I hope to print it on tracing paper and overlay it on a similarly scaled modern chart at some point. I should be able to fudge scales using the legend."
But which reference meridian would have been in use in 1847? Would surveys be referenced to the Washington meridian of that time, providing a different offset to WGS84 coordinates?
Don Seltzer
