[time-nuts] Discussion of precise time and frequency measurement
apolloeme at gmail.com
Mon Nov 13 16:51:36 EST 2017
Longitude by Wire by Richard Stachurski :
from Professional Surveyor Magazine, November 2003.
Best, 73, Pat Barthelow AA6EG
apol <apolloeme at gmail.com>loeme at gmail.com
*"The most exciting phrase to hear in Science, the one that heraldsnew
discoveries, is not "Eureka, I have found it!" but:*
"That's funny..." ----Isaac Asimov
On Mon, Nov 13, 2017 at 11:39 AM, Jim Harman <j99harman at gmail.com> wrote:
> On Mon, Nov 13, 2017 at 12:32 PM, Gregory Beat <w9gb at 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
> > surveys were?
> > Sent from iPad Air
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> 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
> 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
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