Hi Tom:
I'm not worried about a single second, but rather an accumulation of them over many years leading to making sundials
obsolete.
The map is centered on China (PS the Chinese symbol for china is a circle with a vertical line i.e. China is the center
of the world) and all of China is on the same time, they don't use time zones. Northern California looks pretty good.
Where I live there's a lot of solar panels because we get a lot of sun.
Almost all the corrections you mention are built into heliochronometers. I made a Noon mark by driving a brass tack
into a hardwood floor at exactly noon. After a few years you could see a group of three close together tacks for each
day because of the effect of leap years.
http://www.prc68.com/I/Sundial.shtml#Indoor_analemma
Yes, you need to know where on Earth you are in order to tell what time it is
when using the sun.
I spent some time (TM: intended pun) looking into a way to use optical means to measure the Earth's period and the limit
is optical "seeing" which can amount to a few arc seconds of angle.
http://www.prc68.com/I/StellarTime.shtml
But I'm not convinced that a single optical observation defines the limit of precision. For example a fixed telescope
could time stamp each star meridian crossing and that data could be correlated with the known star positions to come up
with an averaged meridian crossing time. That would improve the accuracy by SQRT(# stars). So you might improve the
single shot observation error of 66 ms to maybe a hand full of ms. More than one fixed telescope could be used, &Etc.
I asked a scientist who works with the satellites that measure sea level how they can get the stated accuracy and the
answer was what I'd call massive averaging N=(tens of thousands).
I have a number of aircraft navigation instruments (Navigation, surveying & time are all areas I'm interested in) and
the MD1 Astro Compass may be able to track a star when mounted on a B-52 to better than 1 arc minute of angle. I
suspect better if mounted on a concrete pier on the ground. I've been told when mounted that way for testing it could
detect the deformation of the earth caused by a truck a mile away.
http://www.prc68.com/I/MD1.shtml
It's a marvel of mechanical and optical engineering. The sad thing is that the Air Force seems to burn all the manuals
for obsolete equipment. So far I have not been able to determine the electrical connections for the MD1.
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.
-------- Original Message --------
Hi Brooke,
About sundials, timezones and "precise" timekeeping ...
There's a wonderful map by Stefano Maggiolo that everyone should look at:
http://blog.poormansmath.net/images/SolarTimeVsStandardTime.png
"How much is time wrong around the world?"
http://blog.poormansmath.net/how-much-is-time-wrong-around-the-world/
Someone mentioned the effect of leap seconds on true solar time. Based on the
map, it's pretty common for civil noon (based on UTC) to be as much as an hour
or more different from solar noon. Part of that is timezones. Part of that is
DST. Part of that is seasonal, as in the equation of time (EoT). Given that, a
+/-1 second offset due to a leap second is lost in the noise. In fact according
to my EoT calculator the offset for today is 300 s and tomorrow its 309 s. So
even one day's worth of EoT is ten times more than a leap second.
I would be interested in Sun dials too, maybe even a solar disciplined oscillator (SoDO), except most weeks it would be in holdover mode up here in the Northwest. ;-) The PID code would be quite interesting, since you can forward predict EoT. I think this is something Mike Cook would want to build, yes?
One other calculation for you: Earth circumference is 40,000 km. At 45 degrees
latitude it's cos(45) = 0.707 as much. So an hour error from noon is 700 miles;
a minute is 12 miles; a second is 1000 feet; and 1 ms is 1 foot; just like the
speed of sound. That means a leap second is equivalent to walking 1000 feet,
while DST is being forced marched 700 miles.
/tvb
----- Original Message -----
From: "Brooke Clarke" <bro...@pacific.net>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Friday, July 22, 2016 12:16 PM
Subject: Re: [time-nuts] LSEM (Leap Second Every Month)
Hi Tom:
One of my interests is in Sun dials, so I like the idea of civil time
corresponding as close as possible to the Sun's
position. Heliochronometers can be accurate to some seconds.
The Dent <http://www.prc68.com/I/Dent.shtml>Dipleidoscope
<http://www.prc68.com/I/Dent.shtml> was used to set railroad
clocks based on the Sun's position.
Another area of interest is astronomy where UTC1 adds a correction to a tenth
of a second to UTC that essentially
bridges the gap between the leap second corrections.
It would be interesting to learn how the Software Bisque Paramount telescope
mount handles time. It does not have any
provision for a time nuts oscillator/clock, but maybe should?
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.
-------- Original Message --------
If UTC time was adjusted every month would stick with one full second? Or
some smaller quantity?
Hi Scott,
The LSEM month suggestion retains the UTC policy of leaps being exactly +1 or
-1 second, never larger, never smaller.
There's a world of hurt if anyone even dreamed of shifting UTC by a fraction of
a second. In fact, one of the main reasons UTC was created in the 70's was to
put an end to the dreaded fractional jumps in atomic timekeeping during that
era. Fractional steps atomic frequency and fractional steps in atomic time were
both tried during 60's. For example:
http://www.leapsecond.com/history/wwvb1966.htm
Eliminating frequency jumps completely (by defining the UTC second to be
9,192,631,770 Hz cesium), and
changing any steps to be full +1 or -1 second integers (and not fractions) was
why UTC was created.
/tvb
----- Original Message -----
From: "Scott Stobbe" <scott.j.sto...@gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Thursday, July 21, 2016 3:06 PM
Subject: Re: [time-nuts] LSEM (Leap Second Every Month)
If UTC time was adjusted every month would stick with one full second? Or
some smaller quantity?
On Thursday, 21 July 2016, Brooke Clarke <bro...@pacific.net> wrote:
Hi Tom:
I like this idea. I addresses the lesson from Y2K that something done
often works much better than something done only occasionally.
That's way you see the firetruck at the local store, because it's used all
the time and so is more likely to work when needed.
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.
-------- Original Message --------
Hi Tom...
Does your proposal allow for a Zero leap second, or does it require
either plus or minus 1 to work? Seems like you could stay closer to the
true value if you also have a zero option. Might also cause less
consternation for some services, like the finance and scientific worlds,
that seem to have critical issues when an LS appears.
I like your point that by having it occur monthly it forces systems to
address issues promptly, and maybe that's the argument for the non-zero
option.
Tom Holmes, N8ZM
-----Original Message-----
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Thursday, July 21, 2016 1:28 PM
To: Discussion of precise time and frequency measurement <
time-nuts@febo.com>
Cc: Leap Second Discussion List <leaps...@leapsecond.com>
Subject: Re: [time-nuts] Leap second to be introduced at midnight UTC
December 31 this year
Time to mention this again...
If we adopted the LSEM (Leap Second Every Month) model then none of this
would be a problem. The idea is not to decide *if* there will be leap
second, but to force every month to have a leap second. The IERS decision
is then what the *sign* of the leap second should be this month.
Note this would keep |DUT1| < 1 s as now. UT1 would stay in sync with
UTC, not so much by rare steps but by dithering. There would be no change
to UTC or timing infrastructure because the definition of UTC already
allows for positive or negative leap seconds in any given month.
Every UTC-aware device would 1) know how to reliably insert or delete a
leap second, because bugs would be found by developers within a month or
two, not by end-users years or decades in the future, and 2) every
UTC-aware device would have an often tested direct or indirect path to IERS
to know what the sign of the leap second will be for the current month.
The leap second would then become a normal part of UTC, a regular monthly
event, instead of a rare, newsworthy exception. None of the weird bugs we
continue to see year after year in leap second handling by NTP and OS's and
GPS receiver firmware would occur.
Historical leap second tables would consist of little more than 12 bits
per year.
Moreover, in the next decade or two or three, if we slide into an era
where average earth rotation slows from 86400.1 to 86400.0 to 86399.9
seconds a day, there will be zero impact if LSEM is already in place.
/tvb
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
_______________________________________________
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.
