I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi <am@yellowjersey.org> wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
If the land continues to move, the survey markers will eventually sail
off the edge of the world: <https://www.google.com/search?q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem. Surveyors reduce the effects of
land movement by surveying nearby monuments and benchmarks. If the
land moves, it's a fair assumption that the benchmarks will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?" <https://www.usgs.gov/faqs/how-can-i-find-survey-benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been compiled
from many different sources: therefore, the accuracy of the individual
map layers varies significantly and some layers do not align exactly
with others. In the urban areas the parcel maps are generally accurate
within five to ten feet of their true geographic coordinates, and in
the rural and CZU burn areas the maps may be accurate to only within
three hundred feet."
I've lived in the mountains for about 50 years. During this time, the
road in front of my house has move along with the survey markers.
Accurately determining the property lines is somewhat of a challenge
and usually requires a $2,000 survey by a licensed surveyor. As long
as everything moves in unison, it's not a major problem. The real
problem is that some property owners have the irritating habit of
moving the survey markers a few hours after the survey was completed.
Your GPS receiver (or smartphone software) has pages for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth is not a
perfect sphere. For general use in the USA, I recommend WGS84. For
added confusion, sidereal (astronomical), solar and UTC times are not identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time. This
comparison is from about 25 years ago: <https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected several times in
the past 25 years using leap seconds.
Looking at: <https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html> it seems that California is moving about 44.4 mm/year to the
north-west. In the 50 years I've lived here, my house has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where "parcel maps are generally accurate within five to ten feet of their true geographic coordinates".
Don't worry about tectonic movements affecting your time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
On 8/9/2026 12:34 PM, Jeff Liebermann wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi
<am@yellowjersey.org> wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-
tectonics/gps-data.html
If the land continues to move, the survey markers will
eventually sail
off the edge of the world:
<https://www.google.com/search?
q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem.-a Surveyors reduce the
effects of
land movement by surveying nearby monuments and
benchmarks.-a If the
land moves, it's a fair assumption that the benchmarks
will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?"
<https://www.usgs.gov/faqs/how-can-i-find-survey-
benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz
County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been
compiled
from many different sources: therefore, the accuracy of
the individual
map layers varies significantly and some layers do not
align exactly
with others. In the urban areas the parcel maps are
generally accurate
within five to ten feet of their true geographic
coordinates, and in
the rural and CZU burn areas the maps may be accurate to
only within
three hundred feet."
I've lived in the mountains for about 50 years.-a During
this time, the
road in front of my house has move along with the survey
markers.
Accurately determining the property lines is somewhat of a
challenge
and usually requires a $2,000 survey by a licensed
surveyor.-a As long
as everything moves in unison, it's not a major problem.
The real
problem is that some property owners have the irritating
habit of
moving the survey markers a few hours after the survey was
completed.
Your GPS receiver (or smartphone software) has pages for
setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth
is not a
perfect sphere.-a For general use in the USA, I recommend
WGS84.-a For
added confusion, sidereal (astronomical), solar and UTC
times are not
identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time.
This
comparison is from about 25 years ago:
<https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected
several times in
the past 25 years using leap seconds.
Looking at:
<https://spotlight.unavco.org/how-gps-works/gps-and-
tectonics/gps-data.html>
it seems that California is moving about 44.4 mm/year to the
north-west.-a In the 50 years I've lived here, my house has
moved:
-a-a 50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where
"parcel maps are
generally accurate within five to ten feet of their true
geographic
coordinates".
Don't worry about tectonic movements affecting your time
or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
I wouldn't worry about it. Between the end of unix time and
GPS week rollover we're all going to die in 2038 anyway.
On 8/10/2026 6:31 AM, zen cycle wrote:
On 8/9/2026 12:34 PM, Jeff Liebermann wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi
<am@yellowjersey.org> wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-
tectonics/gps-data.html
If the land continues to move, the survey markers will
eventually sail off the edge of the world...
I wouldn't worry about it. Between the end of unix time and
GPS week rollover we're all going to die in 2038 anyway.
In the immortal words of Sen Ted Kennedy, "We'll cross that
bridge when we come to it."
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi <am@yellowjersey.org> wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
If the land continues to move, the survey markers will eventually sail
off the edge of the world: <https://www.google.com/search?q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem. Surveyors reduce the effects of
land movement by surveying nearby monuments and benchmarks. If the
land moves, it's a fair assumption that the benchmarks will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?" <https://www.usgs.gov/faqs/how-can-i-find-survey-benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been compiled
from many different sources: therefore, the accuracy of the individual
map layers varies significantly and some layers do not align exactly
with others. In the urban areas the parcel maps are generally accurate
within five to ten feet of their true geographic coordinates, and in
the rural and CZU burn areas the maps may be accurate to only within
three hundred feet."
I've lived in the mountains for about 50 years. During this time, the
road in front of my house has move along with the survey markers.
Accurately determining the property lines is somewhat of a challenge
and usually requires a $2,000 survey by a licensed surveyor. As long
as everything moves in unison, it's not a major problem. The real
problem is that some property owners have the irritating habit of
moving the survey markers a few hours after the survey was completed.
Your GPS receiver (or smartphone software) has pages for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth is not a
perfect sphere. For general use in the USA, I recommend WGS84. For
added confusion, sidereal (astronomical), solar and UTC times are not identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time. This
comparison is from about 25 years ago: <https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected several times in
the past 25 years using leap seconds.
Looking at: <https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html> it seems that California is moving about 44.4 mm/year to the
north-west. In the 50 years I've lived here, my house has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where "parcel maps are generally accurate within five to ten feet of their true geographic coordinates".
Don't worry about tectonic movements affecting your time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi <am@yellowjersey.org> wrote:YourCOre rather closer to a fault line and tectonics in general than I am!
I had never thought of this but the world GPS (and similarIf the land continues to move, the survey markers will eventually sail
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html >>
off the edge of the world:
<https://www.google.com/search?q=sail%20off%20edge%20of%20the%20world&udm=2> >>
This is not a new or simple problem. Surveyors reduce the effects of
land movement by surveying nearby monuments and benchmarks. If the
land moves, it's a fair assumption that the benchmarks will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?"
<https://www.usgs.gov/faqs/how-can-i-find-survey-benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been compiled
from many different sources: therefore, the accuracy of the individual
map layers varies significantly and some layers do not align exactly
with others. In the urban areas the parcel maps are generally accurate
within five to ten feet of their true geographic coordinates, and in
the rural and CZU burn areas the maps may be accurate to only within
three hundred feet."
I've lived in the mountains for about 50 years. During this time, the
road in front of my house has move along with the survey markers.
Accurately determining the property lines is somewhat of a challenge
and usually requires a $2,000 survey by a licensed surveyor. As long
as everything moves in unison, it's not a major problem. The real
problem is that some property owners have the irritating habit of
moving the survey markers a few hours after the survey was completed.
Your GPS receiver (or smartphone software) has pages for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth is not a
perfect sphere. For general use in the USA, I recommend WGS84. For
added confusion, sidereal (astronomical), solar and UTC times are not
identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time. This
comparison is from about 25 years ago:
<https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected several times in
the past 25 years using leap seconds.
Looking at:
<https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html> >> it seems that California is moving about 44.4 mm/year to the
north-west. In the 50 years I've lived here, my house has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where "parcel maps are
generally accurate within five to ten feet of their true geographic
coordinates".
Don't worry about tectonic movements affecting your time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
The Blorange above Abergavenny has number of abandoned villages and
numerous forges with numerous rail roads ie predecessor to railways and
tram roads, and inclines, numerous tunnels and one old radio station from
the real rCLDads ArmyrCY.
so lots of stuff that is settling overtime! So the road which the roadies call the Tumble which is wrong as thatrCOs a particular part of the Blorange, as it passes near Keepers pond, which is a filler pond almost certainly was
a pond there before but has been enhanced, used during the industrial era,
ie the road cracking and moving is very unlikely to be tectonic in nature
but lord knows what buried under there settling, close by a old mine shaft opened up few years back taking away one footpath!
Ie seen the comments under the local newspaper reports on the road being investigated and do kind despair with folks lack of knowledge of the
history of the area or just you know look at it, and all of its lumps and bumps!
Is a fun death slide down the Tumble proper which gets the disks sizzling
or rather the water off the vegetation as you drop down! Definitely MTB not road or even Gravel bike!
Roger Merriman
I wouldn't worry about it. Between the end of unix time and GPS week >rollover we're all going to die in 2038 anyway.
On 8/10/2026 11:20 AM, Roger Merriman wrote:
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi <am@yellowjersey.org> wrote:YourCOre rather closer to a fault line and tectonics in general than I am! >>
I had never thought of this but the world GPS (and similarIf the land continues to move, the survey markers will eventually sail
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html >>>
off the edge of the world:
<https://www.google.com/search?q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem. Surveyors reduce the effects of
land movement by surveying nearby monuments and benchmarks. If the
land moves, it's a fair assumption that the benchmarks will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?"
<https://www.usgs.gov/faqs/how-can-i-find-survey-benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been compiled
from many different sources: therefore, the accuracy of the individual
map layers varies significantly and some layers do not align exactly
with others. In the urban areas the parcel maps are generally accurate
within five to ten feet of their true geographic coordinates, and in
the rural and CZU burn areas the maps may be accurate to only within
three hundred feet."
I've lived in the mountains for about 50 years. During this time, the
road in front of my house has move along with the survey markers.
Accurately determining the property lines is somewhat of a challenge
and usually requires a $2,000 survey by a licensed surveyor. As long
as everything moves in unison, it's not a major problem. The real
problem is that some property owners have the irritating habit of
moving the survey markers a few hours after the survey was completed.
Your GPS receiver (or smartphone software) has pages for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth is not a
perfect sphere. For general use in the USA, I recommend WGS84. For
added confusion, sidereal (astronomical), solar and UTC times are not
identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time. This
comparison is from about 25 years ago:
<https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected several times in
the past 25 years using leap seconds.
Looking at:
<https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html>
it seems that California is moving about 44.4 mm/year to the
north-west. In the 50 years I've lived here, my house has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where "parcel maps are
generally accurate within five to ten feet of their true geographic
coordinates".
Don't worry about tectonic movements affecting your time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
The Blorange above Abergavenny has number of abandoned villages and
numerous forges with numerous rail roads ie predecessor to railways and
tram roads, and inclines, numerous tunnels and one old radio station from
the real rCLDads ArmyrCY.
so lots of stuff that is settling overtime! So the road which the roadies
call the Tumble which is wrong as thatrCOs a particular part of the Blorange,
as it passes near Keepers pond, which is a filler pond almost certainly was >> a pond there before but has been enhanced, used during the industrial era, >> ie the road cracking and moving is very unlikely to be tectonic in nature
but lord knows what buried under there settling, close by a old mine shaft >> opened up few years back taking away one footpath!
Ie seen the comments under the local newspaper reports on the road being
investigated and do kind despair with folks lack of knowledge of the
history of the area or just you know look at it, and all of its lumps and
bumps!
Is a fun death slide down the Tumble proper which gets the disks sizzling
or rather the water off the vegetation as you drop down! Definitely MTB not >> road or even Gravel bike!
Roger Merriman
See map B here:
https://www.researchgate.net/figure/a-A-plate-tectonic-setting-map-for-the-North-Patagonian-Andes-and-the-North-Patagonian_fig11_344813909
You're moving north, just not quickly.
I had never thought of this but the world GPS (and similarIn most of the world, there is almost no movement. It is the Pacific Coast where GPS has motions of an inch per year or so. So I wouldn't worry about it.
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
On Sun Aug 9 08:59:07 2026 AMuzi wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
In most of the world, there is almost no movement. It is the Pacific
Coast where GPS has motions of an inch per year or so. So I wouldn't worry about it.
And GPS gives positiob in latitude and longitude not map coordinates.
cyclintom <cyclintom@yahoo.com> wrote:
On Sun Aug 9 08:59:07 2026 AMuzi wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html >>
In most of the world, there is almost no movement. It is the Pacific
Coast where GPS has motions of an inch per year or so. So I wouldn't worry about it.
And GPS gives positiob in latitude and longitude not map coordinates.
AMuzi <am@yellowjersey.org> wrote:
On 8/10/2026 11:20 AM, Roger Merriman wrote:I believe that the land is in some places still rebounding after the ice
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuzi <am@yellowjersey.org> wrote:YourCOre rather closer to a fault line and tectonics in general than I am! >>>
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
If the land continues to move, the survey markers will eventually sail >>>> off the edge of the world:
<https://www.google.com/search?q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem. Surveyors reduce the effects of
land movement by surveying nearby monuments and benchmarks. If the
land moves, it's a fair assumption that the benchmarks will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?"
<https://www.usgs.gov/faqs/how-can-i-find-survey-benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have been compiled
from many different sources: therefore, the accuracy of the individual >>>> map layers varies significantly and some layers do not align exactly
with others. In the urban areas the parcel maps are generally accurate >>>> within five to ten feet of their true geographic coordinates, and in
the rural and CZU burn areas the maps may be accurate to only within
three hundred feet."
I've lived in the mountains for about 50 years. During this time, the >>>> road in front of my house has move along with the survey markers.
Accurately determining the property lines is somewhat of a challenge
and usually requires a $2,000 survey by a licensed surveyor. As long
as everything moves in unison, it's not a major problem. The real
problem is that some property owners have the irritating habit of
moving the survey markers a few hours after the survey was completed.
Your GPS receiver (or smartphone software) has pages for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the earth is not a
perfect sphere. For general use in the USA, I recommend WGS84. For
added confusion, sidereal (astronomical), solar and UTC times are not
identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS time. This
comparison is from about 25 years ago:
<https://www.learnbydestroying.com/jeffl/crud/GPS-vs-UTC.jpg>
It would be much worse if UTC hadn't been corrected several times in
the past 25 years using leap seconds.
Looking at:
<https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html>
it seems that California is moving about 44.4 mm/year to the
north-west. In the 50 years I've lived here, my house has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where "parcel maps are
generally accurate within five to ten feet of their true geographic
coordinates".
Don't worry about tectonic movements affecting your time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
The Blorange above Abergavenny has number of abandoned villages and
numerous forges with numerous rail roads ie predecessor to railways and
tram roads, and inclines, numerous tunnels and one old radio station from >>> the real rCLDads ArmyrCY.
so lots of stuff that is settling overtime! So the road which the roadies >>> call the Tumble which is wrong as thatrCOs a particular part of the Blorange,
as it passes near Keepers pond, which is a filler pond almost certainly was >>> a pond there before but has been enhanced, used during the industrial era, >>> ie the road cracking and moving is very unlikely to be tectonic in nature >>> but lord knows what buried under there settling, close by a old mine shaft >>> opened up few years back taking away one footpath!
Ie seen the comments under the local newspaper reports on the road being >>> investigated and do kind despair with folks lack of knowledge of the
history of the area or just you know look at it, and all of its lumps and >>> bumps!
Is a fun death slide down the Tumble proper which gets the disks sizzling >>> or rather the water off the vegetation as you drop down! Definitely MTB not >>> road or even Gravel bike!
Roger Merriman
See map B here:
https://www.researchgate.net/figure/a-A-plate-tectonic-setting-map-for-the-North-Patagonian-Andes-and-the-North-Patagonian_fig11_344813909
You're moving north, just not quickly.
age ie decompressing, Scotland for example so the land is slightly rising
up, either way clearly GPS and indeed boundaryrCOs and mapping in general arenrCOt static. One of the rivers in wales has apparently changed its course somewhat ie making or will be in time an oxbow lake.
Some boundaries based on rivers donrCOt follow the exact course now, as the river has shifted but the boundaries havenrCOt!
Roger Merriman
On 8/10/2026 6:27 PM, Roger Merriman wrote:
AMuzi <am@yellowjersey.org> wrote:
On 8/10/2026 11:20 AM, Roger Merriman wrote:I believe that the land is in some places still rebounding
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 9 Aug 2026 08:59:07 -0500, AMuziYourCOre rather closer to a fault line and tectonics in
<am@yellowjersey.org> wrote:
I had never thought of this but the world GPS (and
similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything
from
property lines to military targeting, in some places
up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-
tectonics/gps-data.html
If the land continues to move, the survey markers will
eventually sail
off the edge of the world:
<https://www.google.com/search?
q=sail%20off%20edge%20of%20the%20world&udm=2>
This is not a new or simple problem.-a Surveyors reduce
the effects of
land movement by surveying nearby monuments and
benchmarks.-a If the
land moves, it's a fair assumption that the benchmarks
will move the
same amount and in the same direction.
"How can I find survey benchmark and triangulation station
information?"
<https://www.usgs.gov/faqs/how-can-i-find-survey-
benchmark-and-triangulation-station-information>
This warning is on the splash screen of the Santa Cruz
County (CALIF)
GIS data page:
<https://sccgis.santacruzcountyca.gov/gisweb/>
"The maps and tabular data used on this web site have
been compiled
from many different sources: therefore, the accuracy of
the individual
map layers varies significantly and some layers do not
align exactly
with others. In the urban areas the parcel maps are
generally accurate
within five to ten feet of their true geographic
coordinates, and in
the rural and CZU burn areas the maps may be accurate
to only within
three hundred feet."
I've lived in the mountains for about 50 years.-a During
this time, the
road in front of my house has move along with the
survey markers.
Accurately determining the property lines is somewhat
of a challenge
and usually requires a $2,000 survey by a licensed
surveyor.-a As long
as everything moves in unison, it's not a major
problem.-a The real
problem is that some property owners have the
irritating habit of
moving the survey markers a few hours after the survey
was completed.
Your GPS receiver (or smartphone software) has pages
for setting the
datum.
<https://www.oc.nps.edu/oc2902w/coord/datums.pdf>
These compensate for the inconvenient fact that the
earth is not a
perfect sphere.-a For general use in the USA, I
recommend WGS84.-a For
added confusion, sidereal (astronomical), solar and UTC
times are not
identical and area diverging.
<http://leapsecond.com/java/gpsclock.htm>
Looks like 18 second difference between UTC and GPS
time.-a This
comparison is from about 25 years ago:
<https://www.learnbydestroying.com/jeffl/crud/GPS-vs-
UTC.jpg>
It would be much worse if UTC hadn't been corrected
several times in
the past 25 years using leap seconds.
Looking at:
<https://spotlight.unavco.org/how-gps-works/gps-and-
tectonics/gps-data.html>
it seems that California is moving about 44.4 mm/year
to the
north-west.-a In the 50 years I've lived here, my house
has moved:
50 yrs * 44.4mm/year = 2.2 meters or about 7.2 ft
I consider that a tolerable amount in a county where
"parcel maps are
generally accurate within five to ten feet of their
true geographic
coordinates".
Don't worry about tectonic movements affecting your
time or location.
Just remember to wind your GPS clock and you should be ok.
"The NTP Timescale and Leap Seconds"
<https://www.ntp.org/reflib/leap/>
general than I am!
The Blorange above Abergavenny has number of abandoned
villages and
numerous forges with numerous rail roads ie predecessor
to railways and
tram roads, and inclines, numerous tunnels and one old
radio station from
the real rCLDads ArmyrCY.
so lots of stuff that is settling overtime! So the road
which the roadies
call the Tumble which is wrong as thatrCOs a particular
part of the Blorange,
as it passes near Keepers pond, which is a filler pond
almost certainly was
a pond there before but has been enhanced, used during
the industrial era,
ie the road cracking and moving is very unlikely to be
tectonic in nature
but lord knows what buried under there settling, close
by a old mine shaft
opened up few years back taking away one footpath!
Ie seen the comments under the local newspaper reports
on the road being
investigated and do kind despair with folks lack of
knowledge of the
history of the area or just you know look at it, and all
of its lumps and
bumps!
Is a fun death slide down the Tumble proper which gets
the disks sizzling
or rather the water off the vegetation as you drop down!
Definitely MTB not
road or even Gravel bike!
Roger Merriman
See map B here:
https://www.researchgate.net/figure/a-A-plate-tectonic-
setting-map-for-the-North-Patagonian-Andes-and-the-North-
Patagonian_fig11_344813909
You're moving north, just not quickly.
after the ice
age ie decompressing, Scotland for example so the land is
slightly rising
up, either way clearly GPS and indeed boundaryrCOs and
mapping in general
arenrCOt static. One of the rivers in wales has apparently
changed its course
somewhat ie making or will be in time an oxbow lake.
Some boundaries based on rivers donrCOt follow the exact
course now, as the
river has shifted but the boundaries havenrCOt!
Roger Merriman
Classic image of a california citrus farm
https://www.reddit.com/r/interestingasfuck/comments/njy0eg/ decades_ago_these_trees_were_in_a_perfect/
On Sun Aug 9 08:59:07 2026 AMuzi wrote:
I had never thought of this but the world GPS (and similar
systems) network is degrading in precision due to normal
inexorable tectonic movements. This affects everything from
property lines to military targeting, in some places up to
2~3 meters.
https://spotlight.unavco.org/how-gps-works/gps-and-tectonics/gps-data.html
In most of the world, there is almost no movement.
It is the Pacific Coast where GPS has motions of an inch per year or so. So I wouldn't worry about it.
And GPS gives positiob in latitude and longitude not map coordinates.
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