On Mon, Nov 13, 2017 at 12:32 PM, Gregory Beat <w...@icloud.com> wrote:
> As a second’s error in time will be about a nautical mile in US > latitudes, I wonder if anyone has measured with GPS, how good the original > surveys were? > > Sent from iPad Air > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > I think one nautical mile per second is a bit off: 86,400 sec/day Earth's circumference at lat. 41 is about 16,200 nautical miles, so it's about 16200/86400 or 0.187 mi/sec There is an interesting book "Longitude by Wire" by Richard Stachurski that describes efforts in the mid 19th century to improve the accuracy of surveys and determine the precise position of North America relative to Europe. This culminated in the use of pulses on telegraph lines to transfer observatory time to remote stations. With this technique, very careful measurements, and mathematical advances they were able reduce the longitude uncertainty to less than 10 feet. -- --Jim Harman _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
