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BS

Bob Stewart

Sat, May 16, 2015 4:41 AM

I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy?

Bob - AE6RV

I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy? Bob - AE6RV

BC

Bob Camp

Sat, May 16, 2015 1:17 PM

Hi

Tides are complicated once you get on land. They aren’t as simple as you might think when you are on the sea. There are people out there
who are “Tide Nuts” and every bit as obsessive as Time Nuts.

Most of the time and most of the places, you get roughly a third of a meter change in altitude due to on tides on solid land. If you look at the speed
of light as 3 ns / meter - you get about 1 ns from tides.

Bob

On May 16, 2015, at 12:41 AM, Bob Stewart bob@evoria.net wrote:

I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy?

Bob - AE6RV

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.

Hi Tides are complicated once you get on land. They aren’t as simple as you might think when you are on the sea. There are people out there who are “Tide Nuts” and every bit as obsessive as Time Nuts. Most of the time and most of the places, you get roughly a third of a meter change in altitude due to on tides on solid land. If you look at the speed of light as 3 ns / meter - you get about 1 ns from tides. Bob > On May 16, 2015, at 12:41 AM, Bob Stewart <bob@evoria.net> wrote: > > I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy? > > Bob - AE6RV > > _______________________________________________ > 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.

LO

Lamar Owen

Sat, May 16, 2015 2:13 PM

On 05/16/2015 12:41 AM, Bob Stewart wrote:

I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy?

If you're interested in finding out more about this sinkage and plate
movement, we are affiliated with the EarthScope system and have one of
their instruments here onsite. The system map is at
http://www.earthscope.org/science/maps/current-status-map/ and details
about the plate boundary observatory component are at
http://pbo.unavco.org/ with the instrument at our site at
http://pbo.unavco.org/station/overview/P779

Positional changes of 2 inches per year should create sub-nanosecond
differences in signal arrival times. The survey receivers used by the
PBO utilitize several techniques for measuring these very small changes
in position; however, as you can see by looking at the position data
(such as http://pboshared.unavco.org/timeseries/P779_timeseries.png ),
it's a long-term averaging that is optimized for position, not timing,
data, and the precision in the z axis is not as good as that in the x
and y axes by a factor of four or more. For any given GPS frame, the
uncertainty of arrival time is more determined by ionospheric effects
than by absolute position. Meteor scatter and multipath also play a role.

Now I am by no means a GPS expert, but I would think a receiver
optimized for timing would need different techniques than a receiver
optimized for survey, but I reserve the right to be wrong.

On 05/16/2015 12:41 AM, Bob Stewart wrote: > I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy? > If you're interested in finding out more about this sinkage and plate movement, we are affiliated with the EarthScope system and have one of their instruments here onsite. The system map is at http://www.earthscope.org/science/maps/current-status-map/ and details about the plate boundary observatory component are at http://pbo.unavco.org/ with the instrument at our site at http://pbo.unavco.org/station/overview/P779 Positional changes of 2 inches per year should create sub-nanosecond differences in signal arrival times. The survey receivers used by the PBO utilitize several techniques for measuring these very small changes in position; however, as you can see by looking at the position data (such as http://pboshared.unavco.org/timeseries/P779_timeseries.png ), it's a long-term averaging that is optimized for position, not timing, data, and the precision in the z axis is not as good as that in the x and y axes by a factor of four or more. For any given GPS frame, the uncertainty of arrival time is more determined by ionospheric effects than by absolute position. Meteor scatter and multipath also play a role. Now I am by no means a GPS expert, but I would think a receiver optimized for timing would need different techniques than a receiver optimized for survey, but I reserve the right to be wrong.

BC

Brooke Clarke

Sun, May 17, 2015 10:04 PM

Hi Bob:

There may be two factors here.
One is the "sinking" that here in California is do to pumping out ground water. It's measured by the GRACE satellite
system.
https://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment
PS It's beginning to look like water is similar to oil, once you pump it out it can take a very long time until you can
pump more.

The other relates to "Love Numbers".
https://en.wikipedia.org/wiki/Love_number
PS not related to dating.

The APPOLO lunar ranging observatory uses a gravity meter to measure how much their bed rock mountain top moves due to
Earth Tides.
http://www.prc68.com/I/UkiahObs.shtml#Lunar_Ranging

Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Bob Stewart wrote:

I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy?

Bob - AE6RV

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.

Hi Bob: There may be two factors here. One is the "sinking" that here in California is do to pumping out ground water. It's measured by the GRACE satellite system. https://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment PS It's beginning to look like water is similar to oil, once you pump it out it can take a very long time until you can pump more. The other relates to "Love Numbers". https://en.wikipedia.org/wiki/Love_number PS not related to dating. The APPOLO lunar ranging observatory uses a gravity meter to measure how much their bed rock mountain top moves due to Earth Tides. http://www.prc68.com/I/UkiahObs.shtml#Lunar_Ranging Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Stewart wrote: > I did some idle searching trying to see if there was a relationship between terrestrial tides and timing receivers. I couldn't find anything useful, but I did discover that the Jersey Village area, about 2 miles northeast of me, is sinking about 2 inches a year. So, my question is what effect do either of these, terrestrial tides or this local sinkage, have on timing accuracy? > > Bob - AE6RV > > _______________________________________________ > 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. >

AK

Attila Kinali

Sun, May 24, 2015 12:02 PM

On Sat, 16 May 2015 04:41:15 +0000 (UTC)
Bob Stewart bob@evoria.net wrote:

I did some idle searching trying to see if there was a relationship between
terrestrial tides and timing receivers. I couldn't find anything useful, but
I did discover that the Jersey Village area, about 2 miles northeast of me,
is sinking about 2 inches a year. So, my question is what effect do either
of these, terrestrial tides or this local sinkage, have on timing accuracy?

I guess you are looking for the relationship between earth movement
and GPS/GNSS time transfer? If so, solid earth tides (as they are
commonly called in the timing community) do not become an issue until
a lot of other factors are removed first. First you need a system
that reduces multipath to a minimum, then one that can measure the delay
induced by the ionosphere directly (ie an dual/tripple frequency GNSS
receiver). I am not sure whether tropospheric delay or solid earth tides
come next, my guess would be that both are in the same order of magnitude.

The size of solid earth tides can be up to 30cm (i think i read somewhere
that someone measured 50cm, but not sure), mostly in vertical direction
(horizontal to vertical has about a factor 10 difference in amplitude),
where GNSS precision is quite low (compared to horizontal precision).
It has to be corrected in precise GNSS augmentation systems like IGS
(see [1, page 12]).

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

		Attila Kinali

[1] "A guide to using international GNSS service (IGS) products",
by Jan Kouba, Version 2.1, 2009
https://igscb.jpl.nasa.gov/igscb/resource/pubs/UsingIGSProductsVer21.pdf

--
< av500> phd is easy
< av500> getting dsl is hard

On Sat, 16 May 2015 04:41:15 +0000 (UTC) Bob Stewart <bob@evoria.net> wrote: > I did some idle searching trying to see if there was a relationship between > terrestrial tides and timing receivers. I couldn't find anything useful, but > I did discover that the Jersey Village area, about 2 miles northeast of me, > is sinking about 2 inches a year. So, my question is what effect do either > of these, terrestrial tides or this local sinkage, have on timing accuracy? I guess you are looking for the relationship between earth movement and GPS/GNSS time transfer? If so, solid earth tides (as they are commonly called in the timing community) do not become an issue until a lot of other factors are removed first. First you need a system that reduces multipath to a minimum, then one that can measure the delay induced by the ionosphere directly (ie an dual/tripple frequency GNSS receiver). I am not sure whether tropospheric delay or solid earth tides come next, my guess would be that both are in the same order of magnitude. The size of solid earth tides can be up to 30cm (i think i read somewhere that someone measured 50cm, but not sure), mostly in vertical direction (horizontal to vertical has about a factor 10 difference in amplitude), where GNSS precision is quite low (compared to horizontal precision). It has to be corrected in precise GNSS augmentation systems like IGS (see [1, page 12]). I am not sure whether anyone accounts for continental drift in timing applications. I would guess that at least people in VLBI have to. Given that most GNSS high precision time transfer is used rather locally (a couple of 100km) and that few people are running it for more than a couple of months without recalibrating the system, i'd say that the drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) do not induce much error/jitter. Attila Kinali [1] "A guide to using international GNSS service (IGS) products", by Jan Kouba, Version 2.1, 2009 https://igscb.jpl.nasa.gov/igscb/resource/pubs/UsingIGSProductsVer21.pdf -- < _av500_> phd is easy < _av500_> getting dsl is hard

BC

Bob Camp

Sun, May 24, 2015 8:46 PM

Hi

If you believe the 3 ns / M applies in this case, tides will give you about
1 ns or so. If the geometry of the motion (vertical) and the orientation
of the sat’s is not same / same, the impact will be a bit less.

On an L1 system without some sort of ionosphere “help” and working just
off of broadcast data, you can / will / may see > 10 ns per day. Troposphere
is the same sort of thing only a bit less per day.

There are a whole raft of interesting relativity issues that get into GPS. Again
the L1 stuff does not do much beyond the in-system corrections.

The biggie is ionosphere ….

Bob

On May 24, 2015, at 8:02 AM, Attila Kinali attila@kinali.ch wrote:

On Sat, 16 May 2015 04:41:15 +0000 (UTC)
Bob Stewart bob@evoria.net wrote:

I did some idle searching trying to see if there was a relationship between
terrestrial tides and timing receivers. I couldn't find anything useful, but
I did discover that the Jersey Village area, about 2 miles northeast of me,
is sinking about 2 inches a year. So, my question is what effect do either
of these, terrestrial tides or this local sinkage, have on timing accuracy?

I guess you are looking for the relationship between earth movement
and GPS/GNSS time transfer? If so, solid earth tides (as they are
commonly called in the timing community) do not become an issue until
a lot of other factors are removed first. First you need a system
that reduces multipath to a minimum, then one that can measure the delay
induced by the ionosphere directly (ie an dual/tripple frequency GNSS
receiver). I am not sure whether tropospheric delay or solid earth tides
come next, my guess would be that both are in the same order of magnitude.

The size of solid earth tides can be up to 30cm (i think i read somewhere
that someone measured 50cm, but not sure), mostly in vertical direction
(horizontal to vertical has about a factor 10 difference in amplitude),
where GNSS precision is quite low (compared to horizontal precision).
It has to be corrected in precise GNSS augmentation systems like IGS
(see [1, page 12]).

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

		Attila Kinali

[1] "A guide to using international GNSS service (IGS) products",
by Jan Kouba, Version 2.1, 2009
https://igscb.jpl.nasa.gov/igscb/resource/pubs/UsingIGSProductsVer21.pdf

--
< av500> phd is easy
< av500> getting dsl is hard

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.

Hi If you believe the 3 ns / M applies in this case, tides will give you about 1 ns or so. If the geometry of the motion (vertical) and the orientation of the sat’s is not same / same, the impact will be a bit less. On an L1 system without some sort of ionosphere “help” and working just off of broadcast data, you can / will / may see > 10 ns per day. Troposphere is the same sort of thing only a bit less per day. There are a whole raft of interesting relativity issues that get into GPS. Again the L1 stuff does not do much beyond the in-system corrections. The biggie is ionosphere …. Bob > On May 24, 2015, at 8:02 AM, Attila Kinali <attila@kinali.ch> wrote: > > On Sat, 16 May 2015 04:41:15 +0000 (UTC) > Bob Stewart <bob@evoria.net> wrote: > >> I did some idle searching trying to see if there was a relationship between >> terrestrial tides and timing receivers. I couldn't find anything useful, but >> I did discover that the Jersey Village area, about 2 miles northeast of me, >> is sinking about 2 inches a year. So, my question is what effect do either >> of these, terrestrial tides or this local sinkage, have on timing accuracy? > > I guess you are looking for the relationship between earth movement > and GPS/GNSS time transfer? If so, solid earth tides (as they are > commonly called in the timing community) do not become an issue until > a lot of other factors are removed first. First you need a system > that reduces multipath to a minimum, then one that can measure the delay > induced by the ionosphere directly (ie an dual/tripple frequency GNSS > receiver). I am not sure whether tropospheric delay or solid earth tides > come next, my guess would be that both are in the same order of magnitude. > > The size of solid earth tides can be up to 30cm (i think i read somewhere > that someone measured 50cm, but not sure), mostly in vertical direction > (horizontal to vertical has about a factor 10 difference in amplitude), > where GNSS precision is quite low (compared to horizontal precision). > It has to be corrected in precise GNSS augmentation systems like IGS > (see [1, page 12]). > > I am not sure whether anyone accounts for continental drift in timing > applications. I would guess that at least people in VLBI have to. > Given that most GNSS high precision time transfer is used rather locally > (a couple of 100km) and that few people are running it for more than > a couple of months without recalibrating the system, i'd say that the > drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) > do not induce much error/jitter. > > Attila Kinali > > > [1] "A guide to using international GNSS service (IGS) products", > by Jan Kouba, Version 2.1, 2009 > https://igscb.jpl.nasa.gov/igscb/resource/pubs/UsingIGSProductsVer21.pdf > > -- > < _av500_> phd is easy > < _av500_> getting dsl is hard > _______________________________________________ > 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.

TV

Tom Van Baak

Mon, May 25, 2015 5:29 PM

Attila,

Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about.

The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18.

Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally).

There's a nice (1 inch) 25 mm per year interactive drift map here:
http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html

The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car.

/tvb

----- Original Message -----
From: "Attila Kinali" attila@kinali.ch

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

Attila Kinali

Attila, Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about. The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18. Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally). There's a nice (1 inch) 25 mm per year interactive drift map here: http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car. /tvb See also: http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/14/1.GPS_Background.pdf http://www.unavco.org/education/resources/educational-resources/tutorial/how-quickly-are-we-moving-gps-tutorial.pdf ----- Original Message ----- From: "Attila Kinali" <attila@kinali.ch> I am not sure whether anyone accounts for continental drift in timing applications. I would guess that at least people in VLBI have to. Given that most GNSS high precision time transfer is used rather locally (a couple of 100km) and that few people are running it for more than a couple of months without recalibrating the system, i'd say that the drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) do not induce much error/jitter. Attila Kinali

BS

Bob Stewart

Mon, May 25, 2015 6:09 PM

Tom said: "The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house."
I don't get that. What's the purpose of doing a survey when you move your antenna if this the case?
Bob

 From: Tom Van Baak <tvb@LeapSecond.com>

To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Monday, May 25, 2015 12:29 PM
Subject: Re: [time-nuts] Terrestrial Tides and Land Movement

Attila,

Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about.

The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18.

Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally).

There's a nice (1 inch) 25 mm per year interactive drift map here:
http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html

The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car.

/tvb

----- Original Message -----
From: "Attila Kinali" attila@kinali.ch

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

Attila Kinali

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.

Tom said: "The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house." I don't get that. What's the purpose of doing a survey when you move your antenna if this the case? Bob From: Tom Van Baak <tvb@LeapSecond.com> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Sent: Monday, May 25, 2015 12:29 PM Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Attila, Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about. The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18. Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally). There's a nice (1 inch) 25 mm per year interactive drift map here: http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car. /tvb See also: http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/14/1.GPS_Background.pdf http://www.unavco.org/education/resources/educational-resources/tutorial/how-quickly-are-we-moving-gps-tutorial.pdf ----- Original Message ----- From: "Attila Kinali" <attila@kinali.ch> I am not sure whether anyone accounts for continental drift in timing applications. I would guess that at least people in VLBI have to. Given that most GNSS high precision time transfer is used rather locally (a couple of 100km) and that few people are running it for more than a couple of months without recalibrating the system, i'd say that the drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) do not induce much error/jitter. Attila Kinali _______________________________________________ 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.

BC

Bob Camp

Mon, May 25, 2015 6:46 PM

Hi

Add to that the fact that not everybody is moving at an inch per year. Around here the magic number
is in the 1.5 to 2 mm per year range. It’s enough to be worth correcting survey results vs benchmarks
every few years. It’s not enough to get into an L1 timing system any time soon ….

Bob

On May 25, 2015, at 1:29 PM, Tom Van Baak tvb@LeapSecond.com wrote:

Attila,

Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about.

The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18.

Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally).

There's a nice (1 inch) 25 mm per year interactive drift map here:
http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html

The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car.

/tvb

----- Original Message -----
From: "Attila Kinali" attila@kinali.ch

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

Attila Kinali

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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Hi Add to that the fact that not everybody is moving at an inch per year. Around here the magic number is in the 1.5 to 2 mm per year range. It’s enough to be worth correcting survey results vs benchmarks every few years. It’s not enough to get into an L1 timing system any time soon …. Bob > On May 25, 2015, at 1:29 PM, Tom Van Baak <tvb@LeapSecond.com> wrote: > > Attila, > > Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about. > > The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18. > > Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally). > > There's a nice (1 inch) 25 mm per year interactive drift map here: > http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html > > The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car. > > /tvb > > See also: > http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/14/1.GPS_Background.pdf > http://www.unavco.org/education/resources/educational-resources/tutorial/how-quickly-are-we-moving-gps-tutorial.pdf > > > ----- Original Message ----- > From: "Attila Kinali" <attila@kinali.ch> > > I am not sure whether anyone accounts for continental drift in timing > applications. I would guess that at least people in VLBI have to. > Given that most GNSS high precision time transfer is used rather locally > (a couple of 100km) and that few people are running it for more than > a couple of months without recalibrating the system, i'd say that the > drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) > do not induce much error/jitter. > > Attila Kinali > > _______________________________________________ > 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.

BC

Bob Camp

Mon, May 25, 2015 6:53 PM

Hi

If you happen to need precise time on a moving platform, then GPS can
do that as well. There are a number of military systems that have this need.
There are also some things like mobile direction finding by TDOA that have
multiple use cases.

Bob

On May 25, 2015, at 2:09 PM, Bob Stewart bob@evoria.net wrote:

Tom said: "The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house."
I don't get that. What's the purpose of doing a survey when you move your antenna if this the case?
Bob

 From: Tom Van Baak <tvb@LeapSecond.com>

To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Monday, May 25, 2015 12:29 PM
Subject: Re: [time-nuts] Terrestrial Tides and Land Movement

Attila,

Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about.

The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18.

Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally).

There's a nice (1 inch) 25 mm per year interactive drift map here:
http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html

The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car.

/tvb

----- Original Message -----
From: "Attila Kinali" attila@kinali.ch

I am not sure whether anyone accounts for continental drift in timing
applications. I would guess that at least people in VLBI have to.
Given that most GNSS high precision time transfer is used rather locally
(a couple of 100km) and that few people are running it for more than
a couple of months without recalibrating the system, i'd say that the
drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year)
do not induce much error/jitter.

Attila Kinali

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.

Hi If you happen to *need* precise time on a moving platform, then GPS can do that as well. There are a number of military systems that have this need. There are also some things like mobile direction finding by TDOA that have multiple use cases. Bob > On May 25, 2015, at 2:09 PM, Bob Stewart <bob@evoria.net> wrote: > > Tom said: "The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house." > I don't get that. What's the purpose of doing a survey when you move your antenna if this the case? > Bob > > > From: Tom Van Baak <tvb@LeapSecond.com> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Monday, May 25, 2015 12:29 PM > Subject: Re: [time-nuts] Terrestrial Tides and Land Movement > > Attila, > > Timing people account for everything that's important. A continental drift of an inch per year acts like a slow phase change over time, which by definition, is a frequency offset. So an inch per year is at most 1/12 * 1e-9 / (365*86400) or 3e-18. For the current precision with which UTC/TAI is calculated this is too small to worry about. > > The other way to think of the frequency offset is simply the ratio of speed-of-continent vs. speed-of-light. A continent is slow, about 1e-9 m/s and light is fast, 3e8 m/s. This ratio is about 3e-18. > > Note that an inch-per-year is about a nanometer-per-second. I'm also told fingernails grow about an inch a year. How's that for a rule of thumb (literally). > > There's a nice (1 inch) 25 mm per year interactive drift map here: > http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html > > The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. Just think of continental drift as a slow moving car. > > /tvb > > See also: > http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/14/1.GPS_Background.pdf > http://www.unavco.org/education/resources/educational-resources/tutorial/how-quickly-are-we-moving-gps-tutorial.pdf > > > ----- Original Message ----- > From: "Attila Kinali" <attila@kinali.ch> > > I am not sure whether anyone accounts for continental drift in timing > applications. I would guess that at least people in VLBI have to. > Given that most GNSS high precision time transfer is used rather locally > (a couple of 100km) and that few people are running it for more than > a couple of months without recalibrating the system, i'd say that the > drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) > do not induce much error/jitter. > > Attila Kinali > > _______________________________________________ > 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.

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Terrestrial Tides and Land Movement