12 ms·

Official U.S. government information about the Global Positioning System (GPS)

118 points by waterheater 3y ago

Thoreandan 3y ago
Relevant occurrence in GPS history: https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007 https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007
Isamu 3y ago
This is interesting >The 2024 GPS Testing for Critical Infrastructure (GET-CI) event is set for the fall of 2024. >This event provides an opportunity for CI O&O and manufacturers of commercial GPS receivers used in critical infrastructure to perform equipment evaluations in a rarely available live-sky spoofing and jamming environment. For the 2024 GET-CI event, S&T will create a live-sky GPS environment primarily for fixed infrastructure applications but will also support some ground-based mobile applications.
- WarOnPrivacy 3y ago
  > perform equipment evaluations in a rarely available live-sky spoofing and jamming environment I'm guessing there are aspects of this prepared interference that are unique. We've had a number of planned & unexplained outages/jammings in the US. I recall a planned one shaped like an inverted cone, with the impact broader area at higher altitudes. I was able to math the cone-point, somewhere out west and at a low alt. Diff sites track them. ref: https://gpsjam.org/ https://gpsjam.org/ ref: https://www.navcen.uscg.gov/gps-problem-report-status https://www.navcen.uscg.gov/gps-problem-report-status
- Lammy 3y ago
  I remember something like this from 2011: https://web.archive.org/web/20111015232120/http://navcen.uscg.gov/pdf/lnms/lnm07032011.pdf#page=4 https://web.archive.org/web/20111015232120/http://navcen.usc... “SOUTHEAST ATLANTIC COAST: GPS Testing Information THE GPS NAVIGATION SIGNALS MAY BE UNRELIABLE FROM 20 JAN 2011 - 22 FEB 2011 FROM 0000Z - 0245Z DUE TO TESTING ON GPS FREQUENCIES USED IN SHIPBOARD NAVIGATION AND HANDHELD SYSTEMS. GPS SYSTEMS THAT RELY ON GPS, SUCH AS E-911, AIS AND DSC, MAY BE AFFECTED WITHIN A 150 NM RADIUS OF POSITION 30 49.09N 80 28.18W. DURING THIS PERIOD GPS USERS ARE ENCOURAGED TO REPORT ANY GPS SERVICE OUTAGES THAT THEY MAY EXPERIENCE DURING THIS TESTING VIA THE NAVIGATION INFORMATION SERVICE (NIS) BY CALLING (703) 313-5900 OR BY USING THE NAVCEN WEB SITE'S GPS REPORT A PROBLEM WORKSHEET AT WWW.NAVCEN.USCG.GOV.” I specifically remember it because I was trying to navigate my roommate and I to the Atlanta IKEA but my phone showed me as being, like, south of Macon. ~100mi of error.
throw0101c 3y ago
See also "Phasing Out GPS Reliance in U.S. Military Operations: An Imperative in the Face of Emerging Threats": > Global Navigation Satellite Systems (GNSS), such as the American GPS, Europe's GALILEO, China's BEIDOU, and Russia's GLONASS, play an essential role in modern warfare. Despite their different technical specifications—like frequencies and orbits—these systems are designed to be compatible, allowing for greater positional accuracy. However, their signals are susceptible to various forms of interference, such as jamming and spoofing. While there are security measures like anti-spoofing in place, these are not foolproof. * https://www.realcleardefense.com/articles/2023/09/26/phasing_out_gps_reliance_in_us_military_operations_an_imperative_in_the_face_of_emerging_threats_981890.html https://www.realcleardefense.com/articles/2023/09/26/phasing...
- londons_explore 3y ago
  There are plenty of techniques the military could use to make jamming or spoofing almost impossible. For example, use a signal encrypted with a key not known to the enemy. That prevents spoofing. Jamming can be pretty much eliminated by using phased array antennas. They can reject signals coming from the wrong direction. To fully block a military unit receiving GPS, the enemy would need to have ~30 planes in the sky over the unit, between the unit and each GPS satellite, broadcasting the jamming signal. Pretty infeasible for them. There are other ways to make jamming far far harder. For example, if you are happy for your GPS receiver to be always on and have an atomic clock, you can make a new signal that replaces the 1024 bit PRN codes with multi-gigabyte codes which are secret. That effectively means rather than the enemy needing to overpower the real signal, the enemy needs to be billions of times stronger than the real signal to prevent you decoding it.
  - hiatus 3y ago
    > To fully block a military unit receiving GPS, the enemy would need to have ~30 planes in the sky over the unit, between the unit and each GPS satellite, broadcasting the jamming signal. Pretty infeasible for them. How did you arrive at this number?
    - 3y ago
abeppu 3y ago
Relevant this week: - GPS costs around $2B/yr to continue operating - Most of this comes from the defense budget - This year, because of shenanigans, the NDAA has _not_ yet been passed b/c there are significant and controversial amendments in the House version - We're careening towards a government shutdown I'm not saying this _will_ happen, or _should_ happen ... but if GPS went off with the rest of the government, would Congress reach a resolution faster? https://www.gps.gov/policy/funding/ https://www.gps.gov/policy/funding/
- 1-6 3y ago
  [flagged]
  - abeppu 3y ago
    No, by shenanigans, I mean the NDAA amendments that put in stuff about abortion and transgender policies in an effort to make even basic continued national security part of the culture wars. https://www.politico.com/news/2023/07/14/house-passes-defense-bill-despite-controversial-abortion-transgender-policies-00106373 https://www.politico.com/news/2023/07/14/house-passes-defens...
    - salad-tycoon 3y ago
      In case anyone wonders what 1-6’s comment is reflecting I believe it’s the idea that convenient big news items come about whenever something unflattering comes out about Biden or fam or some other “protected” government Or corporate figure. Maybe or maybe not but at least all this alien nonsense has died down.
- orangepurple 3y ago
  EU Galileo, RU GLONASS, and CN BeiDou constellations all continue to operate but GPS receivers are not allowed to receive their broadcasts within the United States for political reasons only.
  - khuey 3y ago
hunglee2 3y ago
GPS spoofing will be an excellent technique for false flag operations
- moate 3y ago
  Building giant space lasers will be an excellent technique for holding the world ransom for ONE BILLION DOLLARS. (This is where we pitch one sentence villainous plots right?)
  - hunglee2 3y ago
    I make no recommendations! It is only observation of an imbalance of power that could be exploited by the dominant owners of satellite technology
    - moate 3y ago
      Water is wet. This statement is as useful as "The GPS's continued existence benefits systems built on the GPS" but with more fear implied. It doesn't really feel like a novel thought, more like one of the first 5 things you might throw up in the "cons" column when discussing it vs alternatives. Don't get me wrong, I have plenty of qualms with the US government, but walking into a discussion on say, foreign aid spending programs and saying "The Government will spend this money almost entirely in ways that advances its global agenda" is just sort of a Duh moment. I'm sorry, this is a very long way of saying "so what, who cares, what are you proposing?"
    - KaiserPro 3y ago
      I mean, that was the entire point of GPS in the first place. Allow the US to navigate quicker, more accurately so that they could get stuff where they needed to be quicker and more efficiently.
  - throw0101c 3y ago
    GPS spoofing, not jamming, is causing issues around Iran-Iraq such that the FAA put out a notice: * https://www.ainonline.com/aviation-news/air-transport/2023-09-28/increasing-fake-gps-signals-near-iran-prompt-faa-alert https://www.ainonline.com/aviation-news/air-transport/2023-0... There was/is speculation that spoofing may have been used in the capture of a US drone: * https://en.wikipedia.org/wiki/Iran–U.S._RQ-170_incident https://en.wikipedia.org/wiki/Iran–U.S._RQ-170_incident
throw0101c 3y ago
A bit of development history at "GPS Almost Ended Before it Began": > The death struggle: NRL wanted a two-dimensional system, and Parkinson and the Air Force wanted three dimensions plus time. The NRL patent called for atomic clocks in the user equipment, which would have made them prohibitively expensive. Parkinson and the Air Force wanted atomic clocks on the satellites instead, which would greatly simplify the GPS user receiver if atomic clocks could be modified to fly in the high-radiation environment of space. It wasn’t going to be easy to do, but space-qualifying atomic clocks turned out to be possible. NRL had tried to orbit a laboratory atomic clock, but it had quickly failed under the intensity of space radiation. > With these modified concepts all defined, Parkinson spent the next three months trying to, at least, convince the key players in DoD not to say no. In December 1973, the Defense System Acquisition Review Council reconvened and voted yes. It was not that everyone in the military liked what they saw. Many navigation officials in the services liked the systems they had such as TACAN, VOR, DME, LORAN, etc. The Air Force was particularly opposed to GPS and no doubt preferred more airplanes. * Embedded PDF: http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20 http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20 * https://en.wikipedia.org/wiki/Bradford_Parkinson https://en.wikipedia.org/wiki/Bradford_Parkinson
- nradov 3y ago
  It makes you wonder what other proposals actually were killed at an early stage that would have succeeded brilliantly had they been funded.
  - syncsynchalt 3y ago
    I firmly believe that the GPS we got is the best option we could have picked. I've read a lot of the design papers from the 60s and 70s that formed GPS. The initial design was a 3-satellite constellation that would only cover Viet Nam. Options considered [1] included a receiver broadcasting to the satellite (wouldn't scale infinitely) or having an atomic clock in each receiver (high cost and weight). The expectation would be that there were about 100 GPS receivers worldwide: those installed in USAF and USN planes, and possibly some in USN ships or US Army tanks. One constraint they eventually settled on was that a receiver should be portable (less than 50kg) and inexpensive (less than $500k adjusted)[2]. It just goes to show how far we've come from what was at the time considered ambitious in its size and cost goals. [1] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 57 [2] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 73
ksherlock 3y ago
My second favorite part about GPS is that it's a general relativity experiment, for anybody still on the fence. GPS satellites run 38 microseconds faster/day (from our perspective) due to the difference in gravity which works out to being off by ~6 miles/day.
- 64operator 3y ago
  [dead]
OldGuyInTheClub 3y ago
The article on Consumer grade GPS receivers and their associated maps not being good enough for truckers was a surprise. That's something I had never thought about.
- supertrope 3y ago
  Low bridges are a hazard for inexperienced truck drivers. https://www.youtube.com/@11foot8plus8 https://www.youtube.com/@11foot8plus8
  - OldGuyInTheClub 3y ago
    This SoftStop barrier looks promising. https://www.laservision.com.au/portfolio/softstop/ https://www.laservision.com.au/portfolio/softstop/
burkaman 3y ago
Linked from this page: https://www.navcen.uscg.gov/gps-problem-report-status https://www.navcen.uscg.gov/gps-problem-report-status About 500 reports from people saying "GPS on my phone isn't working" and the US Coast Guard and Department of Homeland Security replying that "perhaps your phone is broken".
y04nn 3y ago
> Is military GPS more accurate than civilian GPS? > The user range error (URE) of the GPS signals in space is actually the same for the civilian and military GPS services. However, most of today's civilian devices use only one GPS frequency, while military receivers use two. > Using two GPS frequencies improves accuracy by correcting signal distortions caused by Earth's atmosphere. Dual-frequency GPS equipment is commercially available for civilian use, but its cost and size has limited it to professional applications. > With augmentation systems, civilian users can actually receive better GPS accuracy than the military. Is it fully true ? So the only advantages of the military GPS is that the codes are unknown and that it is more jamming proof ?
- smachiz 3y ago
  they also have the ability to fuzz civilian GPS while not doing so for the military... so probably, until they don't want it to be true.
  - y04nn 3y ago
    They only need to change the CDMA codes of the civilian GPS to render it unusable. Also at the beginning of GPS they purposely added inaccuracies into the timing to make it less precise for civilian use, but because of the FAA and other needs (and methods that have been developed to counter the injected inaccuracies) they finally removed it in 2000. To respond to my question. With long term measurements and the help of the L5 band it is possible to obtain sub-millimeter accuracy [1]! [1]: https://en.wikipedia.org/wiki/Global_Positioning_System https://en.wikipedia.org/wiki/Global_Positioning_System
- KaiserPro 3y ago
  Civilian GPS signal can be selectively diluted in certain areas, which is useful for stopping most non-military and a large number of military navigation kit.
ck2 3y ago
Fun fact: You know the "Hidden Figures" women who did the intense calculation for the military and space programs in the USA before computers were powerful enough? GPS was one of those systems needing intensely calculated orbits, Dr. Gladys West was responsible https://www.afspc.af.mil/News/Article-Display/Article/1707464/mathematician-inducted-into-space-and-missiles-pioneers-hall-of-fame/ https://www.afspc.af.mil/News/Article-Display/Article/170746...
franky47 3y ago
For a video form of this topic, Scott Manley did a review of how GPS actually performed better than initially designed: https://www.youtube.com/watch?v=qJ7ZAUjsycY https://www.youtube.com/watch?v=qJ7ZAUjsycY
sheepybloke 3y ago
Fun fact I learned recently: The GPS reference epoch was moved from 2000 to 2001 due to an Alaskan earthquake in 2002. It's crazy how an event like that can change something like GPS! https://en.wikipedia.org/wiki/International_Terrestrial_Reference_System_and_Frame https://en.wikipedia.org/wiki/International_Terrestrial_Refe...
siraben 3y ago
I didn’t know that they used to degrade GPS signals in something called Selective Availability.[0] [0] https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/
- globular-toast 3y ago
  This is why GPS only seemed to appear in the 00s despite having been around since the late 70s.

118 points by waterheater 3y ago

Relevant occurrence in GPS history: https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007 https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007

Isamu 3y ago

This is interesting >The 2024 GPS Testing for Critical Infrastructure (GET-CI) event is set for the fall of 2024. >This event provides an opportunity for CI O&O and manufacturers of commercial GPS receivers used in critical infrastructure to perform equipment evaluations in a rarely available live-sky spoofing and jamming environment. For the 2024 GET-CI event, S&T will create a live-sky GPS environment primarily for fixed infrastructure applications but will also support some ground-based mobile applications.

WarOnPrivacy 3y ago
> perform equipment evaluations in a rarely available live-sky spoofing and jamming environment I'm guessing there are aspects of this prepared interference that are unique. We've had a number of planned & unexplained outages/jammings in the US. I recall a planned one shaped like an inverted cone, with the impact broader area at higher altitudes. I was able to math the cone-point, somewhere out west and at a low alt. Diff sites track them. ref: https://gpsjam.org/ https://gpsjam.org/ ref: https://www.navcen.uscg.gov/gps-problem-report-status https://www.navcen.uscg.gov/gps-problem-report-status
Lammy 3y ago
I remember something like this from 2011: https://web.archive.org/web/20111015232120/http://navcen.uscg.gov/pdf/lnms/lnm07032011.pdf#page=4 https://web.archive.org/web/20111015232120/http://navcen.usc... “SOUTHEAST ATLANTIC COAST: GPS Testing Information THE GPS NAVIGATION SIGNALS MAY BE UNRELIABLE FROM 20 JAN 2011 - 22 FEB 2011 FROM 0000Z - 0245Z DUE TO TESTING ON GPS FREQUENCIES USED IN SHIPBOARD NAVIGATION AND HANDHELD SYSTEMS. GPS SYSTEMS THAT RELY ON GPS, SUCH AS E-911, AIS AND DSC, MAY BE AFFECTED WITHIN A 150 NM RADIUS OF POSITION 30 49.09N 80 28.18W. DURING THIS PERIOD GPS USERS ARE ENCOURAGED TO REPORT ANY GPS SERVICE OUTAGES THAT THEY MAY EXPERIENCE DURING THIS TESTING VIA THE NAVIGATION INFORMATION SERVICE (NIS) BY CALLING (703) 313-5900 OR BY USING THE NAVCEN WEB SITE'S GPS REPORT A PROBLEM WORKSHEET AT WWW.NAVCEN.USCG.GOV.” I specifically remember it because I was trying to navigate my roommate and I to the Atlanta IKEA but my phone showed me as being, like, south of Macon. ~100mi of error.

throw0101c 3y ago

See also "Phasing Out GPS Reliance in U.S. Military Operations: An Imperative in the Face of Emerging Threats": > Global Navigation Satellite Systems (GNSS), such as the American GPS, Europe's GALILEO, China's BEIDOU, and Russia's GLONASS, play an essential role in modern warfare. Despite their different technical specifications—like frequencies and orbits—these systems are designed to be compatible, allowing for greater positional accuracy. However, their signals are susceptible to various forms of interference, such as jamming and spoofing. While there are security measures like anti-spoofing in place, these are not foolproof. * https://www.realcleardefense.com/articles/2023/09/26/phasing_out_gps_reliance_in_us_military_operations_an_imperative_in_the_face_of_emerging_threats_981890.html https://www.realcleardefense.com/articles/2023/09/26/phasing...

londons_explore 3y ago
There are plenty of techniques the military could use to make jamming or spoofing almost impossible. For example, use a signal encrypted with a key not known to the enemy. That prevents spoofing. Jamming can be pretty much eliminated by using phased array antennas. They can reject signals coming from the wrong direction. To fully block a military unit receiving GPS, the enemy would need to have ~30 planes in the sky over the unit, between the unit and each GPS satellite, broadcasting the jamming signal. Pretty infeasible for them. There are other ways to make jamming far far harder. For example, if you are happy for your GPS receiver to be always on and have an atomic clock, you can make a new signal that replaces the 1024 bit PRN codes with multi-gigabyte codes which are secret. That effectively means rather than the enemy needing to overpower the real signal, the enemy needs to be billions of times stronger than the real signal to prevent you decoding it.
- hiatus 3y ago
  > To fully block a military unit receiving GPS, the enemy would need to have ~30 planes in the sky over the unit, between the unit and each GPS satellite, broadcasting the jamming signal. Pretty infeasible for them. How did you arrive at this number?
  - 3y ago

abeppu 3y ago

Relevant this week: - GPS costs around $2B/yr to continue operating - Most of this comes from the defense budget - This year, because of shenanigans, the NDAA has _not_ yet been passed b/c there are significant and controversial amendments in the House version - We're careening towards a government shutdown I'm not saying this _will_ happen, or _should_ happen ... but if GPS went off with the rest of the government, would Congress reach a resolution faster? https://www.gps.gov/policy/funding/ https://www.gps.gov/policy/funding/

1-6 3y ago
[flagged]
- abeppu 3y ago
  No, by shenanigans, I mean the NDAA amendments that put in stuff about abortion and transgender policies in an effort to make even basic continued national security part of the culture wars. https://www.politico.com/news/2023/07/14/house-passes-defense-bill-despite-controversial-abortion-transgender-policies-00106373 https://www.politico.com/news/2023/07/14/house-passes-defens...
  - salad-tycoon 3y ago
    In case anyone wonders what 1-6’s comment is reflecting I believe it’s the idea that convenient big news items come about whenever something unflattering comes out about Biden or fam or some other “protected” government Or corporate figure. Maybe or maybe not but at least all this alien nonsense has died down.
orangepurple 3y ago
EU Galileo, RU GLONASS, and CN BeiDou constellations all continue to operate but GPS receivers are not allowed to receive their broadcasts within the United States for political reasons only.
- khuey 3y ago

hunglee2 3y ago

GPS spoofing will be an excellent technique for false flag operations

moate 3y ago
Building giant space lasers will be an excellent technique for holding the world ransom for ONE BILLION DOLLARS. (This is where we pitch one sentence villainous plots right?)
- hunglee2 3y ago
  I make no recommendations! It is only observation of an imbalance of power that could be exploited by the dominant owners of satellite technology
  - moate 3y ago
    Water is wet. This statement is as useful as "The GPS's continued existence benefits systems built on the GPS" but with more fear implied. It doesn't really feel like a novel thought, more like one of the first 5 things you might throw up in the "cons" column when discussing it vs alternatives. Don't get me wrong, I have plenty of qualms with the US government, but walking into a discussion on say, foreign aid spending programs and saying "The Government will spend this money almost entirely in ways that advances its global agenda" is just sort of a Duh moment. I'm sorry, this is a very long way of saying "so what, who cares, what are you proposing?"
  - KaiserPro 3y ago
    I mean, that was the entire point of GPS in the first place. Allow the US to navigate quicker, more accurately so that they could get stuff where they needed to be quicker and more efficiently.
- throw0101c 3y ago
  GPS spoofing, not jamming, is causing issues around Iran-Iraq such that the FAA put out a notice: * https://www.ainonline.com/aviation-news/air-transport/2023-09-28/increasing-fake-gps-signals-near-iran-prompt-faa-alert https://www.ainonline.com/aviation-news/air-transport/2023-0... There was/is speculation that spoofing may have been used in the capture of a US drone: * https://en.wikipedia.org/wiki/Iran–U.S._RQ-170_incident https://en.wikipedia.org/wiki/Iran–U.S._RQ-170_incident

throw0101c 3y ago

A bit of development history at "GPS Almost Ended Before it Began": > The death struggle: NRL wanted a two-dimensional system, and Parkinson and the Air Force wanted three dimensions plus time. The NRL patent called for atomic clocks in the user equipment, which would have made them prohibitively expensive. Parkinson and the Air Force wanted atomic clocks on the satellites instead, which would greatly simplify the GPS user receiver if atomic clocks could be modified to fly in the high-radiation environment of space. It wasn’t going to be easy to do, but space-qualifying atomic clocks turned out to be possible. NRL had tried to orbit a laboratory atomic clock, but it had quickly failed under the intensity of space radiation. > With these modified concepts all defined, Parkinson spent the next three months trying to, at least, convince the key players in DoD not to say no. In December 1973, the Defense System Acquisition Review Council reconvened and voted yes. It was not that everyone in the military liked what they saw. Many navigation officials in the services liked the systems they had such as TACAN, VOR, DME, LORAN, etc. The Air Force was particularly opposed to GPS and no doubt preferred more airplanes. * Embedded PDF: http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20 http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20 * https://en.wikipedia.org/wiki/Bradford_Parkinson https://en.wikipedia.org/wiki/Bradford_Parkinson

nradov 3y ago
It makes you wonder what other proposals actually were killed at an early stage that would have succeeded brilliantly had they been funded.
- syncsynchalt 3y ago
  I firmly believe that the GPS we got is the best option we could have picked. I've read a lot of the design papers from the 60s and 70s that formed GPS. The initial design was a 3-satellite constellation that would only cover Viet Nam. Options considered [1] included a receiver broadcasting to the satellite (wouldn't scale infinitely) or having an atomic clock in each receiver (high cost and weight). The expectation would be that there were about 100 GPS receivers worldwide: those installed in USAF and USN planes, and possibly some in USN ships or US Army tanks. One constraint they eventually settled on was that a receiver should be portable (less than 50kg) and inexpensive (less than $500k adjusted)[2]. It just goes to show how far we've come from what was at the time considered ambitious in its size and cost goals. [1] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 57 [2] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 73

ksherlock 3y ago

My second favorite part about GPS is that it's a general relativity experiment, for anybody still on the fence. GPS satellites run 38 microseconds faster/day (from our perspective) due to the difference in gravity which works out to being off by ~6 miles/day.

64operator 3y ago
[dead]

OldGuyInTheClub 3y ago

The article on Consumer grade GPS receivers and their associated maps not being good enough for truckers was a surprise. That's something I had never thought about.

supertrope 3y ago
Low bridges are a hazard for inexperienced truck drivers. https://www.youtube.com/@11foot8plus8 https://www.youtube.com/@11foot8plus8
- OldGuyInTheClub 3y ago
  This SoftStop barrier looks promising. https://www.laservision.com.au/portfolio/softstop/ https://www.laservision.com.au/portfolio/softstop/

burkaman 3y ago

Linked from this page: https://www.navcen.uscg.gov/gps-problem-report-status https://www.navcen.uscg.gov/gps-problem-report-status About 500 reports from people saying "GPS on my phone isn't working" and the US Coast Guard and Department of Homeland Security replying that "perhaps your phone is broken".

y04nn 3y ago

> Is military GPS more accurate than civilian GPS? > The user range error (URE) of the GPS signals in space is actually the same for the civilian and military GPS services. However, most of today's civilian devices use only one GPS frequency, while military receivers use two. > Using two GPS frequencies improves accuracy by correcting signal distortions caused by Earth's atmosphere. Dual-frequency GPS equipment is commercially available for civilian use, but its cost and size has limited it to professional applications. > With augmentation systems, civilian users can actually receive better GPS accuracy than the military. Is it fully true ? So the only advantages of the military GPS is that the codes are unknown and that it is more jamming proof ?

smachiz 3y ago
they also have the ability to fuzz civilian GPS while not doing so for the military... so probably, until they don't want it to be true.
- y04nn 3y ago
  They only need to change the CDMA codes of the civilian GPS to render it unusable. Also at the beginning of GPS they purposely added inaccuracies into the timing to make it less precise for civilian use, but because of the FAA and other needs (and methods that have been developed to counter the injected inaccuracies) they finally removed it in 2000. To respond to my question. With long term measurements and the help of the L5 band it is possible to obtain sub-millimeter accuracy [1]! [1]: https://en.wikipedia.org/wiki/Global_Positioning_System https://en.wikipedia.org/wiki/Global_Positioning_System
KaiserPro 3y ago
Civilian GPS signal can be selectively diluted in certain areas, which is useful for stopping most non-military and a large number of military navigation kit.

ck2 3y ago

Fun fact: You know the "Hidden Figures" women who did the intense calculation for the military and space programs in the USA before computers were powerful enough? GPS was one of those systems needing intensely calculated orbits, Dr. Gladys West was responsible https://www.afspc.af.mil/News/Article-Display/Article/1707464/mathematician-inducted-into-space-and-missiles-pioneers-hall-of-fame/ https://www.afspc.af.mil/News/Article-Display/Article/170746...

franky47 3y ago

For a video form of this topic, Scott Manley did a review of how GPS actually performed better than initially designed: https://www.youtube.com/watch?v=qJ7ZAUjsycY https://www.youtube.com/watch?v=qJ7ZAUjsycY

sheepybloke 3y ago

Fun fact I learned recently: The GPS reference epoch was moved from 2000 to 2001 due to an Alaskan earthquake in 2002. It's crazy how an event like that can change something like GPS! https://en.wikipedia.org/wiki/International_Terrestrial_Reference_System_and_Frame https://en.wikipedia.org/wiki/International_Terrestrial_Refe...

siraben 3y ago

I didn’t know that they used to degrade GPS signals in something called Selective Availability.[0] [0] https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/

globular-toast 3y ago
This is why GPS only seemed to appear in the 00s despite having been around since the late 70s.