[time-nuts] Discussion of precise time and frequency measurement

[Magnus Danielson]

Hi,

On 11/13/2017 06:32 PM, Gregory Beat wrote:
> I grew up east of the Iowa/Missouri border, so this boundary dispute was well-known ... and occurred at same time Joseph Smith (Mormons) was at Nauvoo, IL (1839-1844).
> In 2006, the Iowa-Missouri border was investigated with GPS, as much an archeology project as locating the historic Sullivan & Brown survey markers.
> http://www.theamericansurveyor.com/PDF/TheAmericanSurveyor_MO-IABoundaryLineInvestigation_Mar-Apr2006.pdf
> Iowa-Missouri Border War (1826-1849)
> http://iagenweb.org/history/soi/soi32.htm
> 
> NOAA’s : National Geodetic Survey (NGS) made news in 2009 when media reported that the Four Corners monument was in wrong place (by 2.5 miles).
> Deseret News
> https://www.deseretnews.com/article/705299160/Four-Corners-Monument-is-indeed-off-mark.html
> NOAA statement and clarification
> https://www.ngs.noaa.gov/INFO/fourcorners.shtml
> ==
> I’m in France and I don’t think that any borders in Europe were defined by astronomical observation, but in the US I believe that at least some of the state borders were thus fixed. 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?

There is a lovely article about the Dixon-Mason line and how they now 
used GPS to measure it accurately. Turns out that Dixon-Mason measured 
wrong, but not because they where hacks, they did it very accuratly with 
the tools they had, but the mercury of their star-scope was not 
completely flat due to gravitational pull from mountains, so when 
correcting for that with now known data, they are very accurate with 
what they had.

I think there was a thread about it some time back, but you should be 
able to find it knowing what o search for.

I learned about what the whole issue was about from start.

Cheers,
Magnus