8 ms·

Galileo's actual value has always been murky. It's use case has changed a lot over the years. Originally it was meant to be a navigation system free of GPS's Se

Galileo's actual value has always been murky. It's use case has changed a lot over the years. Originally it was meant to be a navigation system free of GPS's Selective Availability "feature" that diluted precision for civilian use. The Clinton administration effectively killed SA (http://www.gps.gov/systems/gps/modernization/sa/ http://www.gps.gov/systems/gps/modernization/sa/) in 2000. Galileo was sold as a higher precision civilian alternative that was going to be commercially viable and make money. A few years later the US made improvements to the GPS ephemerides and effectively increased precision of GPS, making the benefits less obvious. The new block of GPS satellites offers even better precision and a lot of the Galileo features (like multiple civilian frequencies). It's honestly quite hard to compete with a free alternative that the US government throws billions of dollars at. Still, GPS can't hit sub-meter accuracy any time soon, so there's a real potential use case emerging for autonomous cars and aircraft. If you're excited and interested in Galileo it's really worth reading up on how GPS works and was built. The first satellite was launched almost forty years ago and it was operational in the 1980s. It's truly one of the coolest and most amazing things made by humans.

CalChris 10y ago
> Still, GPS can't hit sub-meter accuracy any time soon GPS has had sub-millimeter survey grade accuracy for quite some time. However, these require post-processing which takes maybe a day, read that as not realtime. WAAS+GPS currently gives 2-3 meters.
- ComodoHacker 10y ago
  >sub-millimeter survey grade accuracy Could you provide some links to read? I just can't imagine how it's possible.
  - CalChris 10y ago
    http://www.gpstk.org/foswiki/pub/Documentation/GPSTkPublications/precision-gps-hhstt-ion-gnss-2006.pdf http://www.gpstk.org/foswiki/pub/Documentation/GPSTkPublicat... I think I overstated but still it is possible. Millimeter survey grade is commercial.
  - nullc 10y ago
    Sub-millimeter is a little tricky. Very high (few centimeter) resolution can be done in real-time, in fact, under some limitations. Keyword: real-time kinematic. One important component is using a reasonably short baseline: you have a receiver at a known location somewhat nearby (in many places there are networks of stations run by the relevant governments), and you compute difference between your solution and the station's solution. Most of the errors are common between the two and so they cancel. Another important component is carrier phase tracking: The receiver processes the signal to recover the carrier phase. This boosts the resolution from the code timing to a level determined by the carrier frequency (and signal bandpass). Unfortunately, it leaves an integer ambiguity-- you know you are 'something' + 0.233 cycles from the sat, you need to solve for the 'something'; you can do this by collecting enough data as the sats move around or by starting at a known position and moving while holding a lock. Another component is multiple frequency operation. There is a set of GPS signals on the L2 band some 350MHz lower in frequency. If you imagine the lattice of integer solutions in 3D space for two different frequencies you can observe the the integer solutions coincide very infrequently, leaving few options to choose between. Dual frequency operation also allows for correction of ionospheric effects. Another component is semi-codeless tracking: The L1 and L2 GPS signals have a military P-code signal which is encrypted. The P code signal runs at 10x the speed and has a much longer repeat interval, this increases the accuracy of code tracking and improves multipath resistance. The L2 signal has historically only had the P-code stream. The encryption would be a barrier except it's kind of broken: The codestream is 10MHz but the stream cipher runs at only 500KHz and the same signal is sent on L1 and L2. Because of the first property you can still range against the P-code and because of the second you can find the phase offset between L1 and L2 quite precisely. (Trade name for this kind of codeless tracking is "Z-tracking"). --- this is hopefully becoming less necessary now with new civilian (unencrypted) signals on L2 and L5. The new signals also have better anti-multipath properties. Any survey receiver worth the name implements these techniques and many more. For realtime (non-postprocessed) output using the above, accuracy is 2cm +/- 2ppm (of the distance to your reference station) or so. What postprocessing does is lets you use very accurate orbital and ionospheric data which is available for download some hours later, built based on observations by many known-position ground stations. (I believe the Galileo sats even have retro-reflectors for laser based ranging, though I don't know if they're used yet.) ... plus using many hours of observations as the sats move through the sky. So like any modern technology, the state of the art result isn't given by any one technique but by many combined.
  - mikeha 10y ago
    http://www.leica-geosystems.us/common/shared/downloads/inc/downloader.asp?id=23474 http://www.leica-geosystems.us/common/shared/downloads/inc/d... (full disclosure: I work for Leica Geosystems.) With real-time kinematic service, our GPS receivers give you 8mm horizontally and 15mm vertically. And you will get 3mm hz and 4mm vertical with post processing.
    - CalChris 10y ago
      Does Galileo change this at all? Or is it just more better GPS,GLONASS,...
  - _coldfire 10y ago
    It is achievable with static post-processing of GPS data, kinematica claims 8mm. For real time requirements, there's consumer level products that offer accuracy of a few centimeters. https://www.advancednavigation.com.au/product/kinematica https://www.advancednavigation.com.au/product/kinematica https://emlid.com/reach/ https://emlid.com/reach/
  - lh7 10y ago
    RTK or PPP, to mention two possible techniques. The first of which is differential (requires data from a receiver at a known location) and the second of which is post-processed (requires that data be collected over a relatively long period of time, although the receiver does not need to be static).
nradov 10y ago
Perhaps the Europeans are concerned that if the USA gets into a shooting war with China or Russia in a few decades, our GPS satellites will be the first casualties.
- deleted 10y ago
  [deleted]
- vegabook 10y ago
  and perhaps that is a legitimate concern for more than just Europeans, and that includes Americans, and perhaps it's not just about war, but about competition, trade, and fair global access to a technology not being beholden to a single administration (especially in the new age of "America first").
- chiph 10y ago
  There's no question that GPS satellites will be a high-value target in the next super-regional conflict. The system was a primary reason why Saddam was defeated (temporarily!) in Desert Storm. The Iraqis were used to getting lost in the trackless desert from their war with Iran, and assumed that the coalition forces would be just as lost. GPS allowed the famous "left hook" that cut the Republican Guard off. https://www.scientificamerican.com/article/gps-and-the-world-s-first-space-war/ https://www.scientificamerican.com/article/gps-and-the-world...
flyinglizard 10y ago
Having an alternative to GPS in mission critical systems is enough of a case to justify the existence of Galileo in the first place. Things like drones or self driving cars are not just about accuracy, but also reliability, and civilian GPS is not bulletproof (especially not in urban area). We're already seeing triple band GPS implementations with Galileo, GPS and GLONASS (the Russian alternative).
- UnoriginalGuy 10y ago
  While I agree with the principle in your point, does Galileo operate on a different enough set of frequencies to avoid interference that would knock out GPS?
  - avar 10y ago
    It does now, see https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)#Tension_with_the_United_States https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)...
    - jhayward 10y ago
      This is not correct. The primary civilian signal for both Galileo and GPS have the same frequency on L1, 1575.42 MHz. Their modulation schemes and encoding are coordinated to not interfere. [1] http://www.navipedia.net/index.php/GNSS_signal http://www.navipedia.net/index.php/GNSS_signal
- digi_owl 10y ago
  Depending on the device SoC, you may see 4 different constellations, as China has their own. https://en.wikipedia.org/wiki/BeiDou_Navigation_Satellite_System https://en.wikipedia.org/wiki/BeiDou_Navigation_Satellite_Sy...
  - Rebelgecko 10y ago
    Also QZSS, if you're in the right part of the world
avar 10y ago
Selective Availability was replaced by regional denial capabilities with the GPS III satellites, i.e. instead of fuzzing the signal the US can now turn off GPS for entire countries[1]. It's strategically foolish for the major economies like the EU, Russia & China to depend on the US's goodwill in maintaining a system that drives a huge part of their economy, GPS is used pervasively for everything, and that's only increasing. Trump wants NATO countries to pay their fair share, how long until he gets the idea that all countries around the world should pay a GPS licensing fee least GPS regional denial be turned on? Those are the sort of reasons for why it makes sense to develop a GPS alternative, even if you're only aiming for feature parity, or even less than that. 1. https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/faq/gps/#ad1 https://www.faa.gov/about/office_org/headquarters_offices/at...
- user837387 10y ago
  >>Trump wants NATO countries to pay their fair share, how long until he gets the idea that all countries around the world should pay a GPS licensing fee least GPS regional denial be turned on?<< Now now, do not insert political commentary into this discussions. I got yelled at for doing that. [1] [1]https://news.ycombinator.com/item?id=13197536 https://news.ycombinator.com/item?id=13197536
  - mattnewton 10y ago
    I don't think this is unwarranted political comentary, the reasons to build the alternative to gps are largely political according to GP
    - Normal_gaussian 10y ago
      I am largely with you, however the direct Trump referencing is unwarranted - it is the institution he will represent, not the man, which is involved in this political battleground. EDIT: to wit, the institution is the most powerful military force, active across the globe https://en.wikipedia.org/wiki/List_of_wars_involving_the_United_States https://en.wikipedia.org/wiki/List_of_wars_involving_the_Uni...
CamperBob2 10y ago
Galileo's actual value has always been murky. Not even remotely. GNSS is far too important to be left up to one or two militaristic providers whose interests (to put it mildly) may not always coincide with your own. If anything we need more systems up there.
- int_19h 10y ago
  And more satellites are good for everyone, at least so long as all these systems remain open for use. It means more accuracy, and some redundancy never hurts, either.
PunchTornado 10y ago
The benefits of Galileo are very clear for me as an EU taxpayer. Don't rely on GPS because it is controlled by a single country and that country can shut it down whenever it likes. No country is your friend forever, you only have to look at the Trump administration. It takes 1 election and everything can swing in the wrong direction.
- pg_is_a_butt 10y ago
  but in your example, the election swung in the RIGHT direction
- 6t6t6t6 10y ago
  Completely agree. GPS is so essential, that is becoming more and more a "single point of failure" for our civilization. Without having any data, I have the intuition that the cost of deploying our own GPS system may be worth just as an "insurance".
  - MBCook 10y ago
    I wonder if we've gotten to the point were attempting to turn it off would harm us (United States) directly as much as anyone else, even if we only do it in certain sections of the world.
    - gizmo686 10y ago
      Turing off GPS would not have to be binary. There is a seperate, encrypted, GPS frequency that the US government can continue using even in places that they shut down GPS for everyone else. Additionally, they can degrade the accuracy of civilian GPS (also in a targeted area if they wanted).
      - dsl 10y ago
        During the Iraq war everyone kept trying to find these magic encrypted GPS devices that used military only frequencies. I never saw one, or heard of anyone using one. Even SEALs are issued the same Garmin Foretrex 401 you can get at Best Buy.
vegabook 10y ago
what is murky about 10x more precision?? Sounds like sour grapes. Sure GPS is amazing. Now there's something better. Just because it isn't American doesn't mean its value is questionable. Nothing is being taken away here. Choice is being added.
matthewmcg 10y ago
Is there a good, wide-ranging treatment of the history of GPS? Something like Rhodes' Making of the Atomic Bomb but for electronic navigation?
lh7 10y ago
> Galileo's actual value has always been murky. Not to me, as a professional user. Presumably not to the policy-makers either who, having recognised the strategic value of satellite-based navigation, would be negligent not to minimise their reliance on foreign powers. > It's honestly quite hard to compete with a free alternative The licensing models of NAVSTAR and Galileo-based solutions are closely comparable from a user point of view. Both are free at a certain service level, beyond that, both require, in the general case, payment of a licence or other form of disbursement in order to access a higher service level (e.g., real-time differential corrections). Galileo, being a latter solution, simply offers a more integrated solution (not depending on Inmarsat or other providers) based on the experience acquired from NAVSTAR. The rest of your commentary is a bit of a non-sequitur, I'm afraid.
ajross 10y ago
> It's honestly quite hard to compete with a free alternative that the US government throws billions of dollars at. Yes, but it's not a commercial venture. Surely there is equivalent value in having a satellite system that European governments throw billions of euros at, no?

CalChris 10y ago

> Still, GPS can't hit sub-meter accuracy any time soon GPS has had sub-millimeter survey grade accuracy for quite some time. However, these require post-processing which takes maybe a day, read that as not realtime. WAAS+GPS currently gives 2-3 meters.

ComodoHacker 10y ago
>sub-millimeter survey grade accuracy Could you provide some links to read? I just can't imagine how it's possible.
- CalChris 10y ago
  http://www.gpstk.org/foswiki/pub/Documentation/GPSTkPublications/precision-gps-hhstt-ion-gnss-2006.pdf http://www.gpstk.org/foswiki/pub/Documentation/GPSTkPublicat... I think I overstated but still it is possible. Millimeter survey grade is commercial.
- nullc 10y ago
  Sub-millimeter is a little tricky. Very high (few centimeter) resolution can be done in real-time, in fact, under some limitations. Keyword: real-time kinematic. One important component is using a reasonably short baseline: you have a receiver at a known location somewhat nearby (in many places there are networks of stations run by the relevant governments), and you compute difference between your solution and the station's solution. Most of the errors are common between the two and so they cancel. Another important component is carrier phase tracking: The receiver processes the signal to recover the carrier phase. This boosts the resolution from the code timing to a level determined by the carrier frequency (and signal bandpass). Unfortunately, it leaves an integer ambiguity-- you know you are 'something' + 0.233 cycles from the sat, you need to solve for the 'something'; you can do this by collecting enough data as the sats move around or by starting at a known position and moving while holding a lock. Another component is multiple frequency operation. There is a set of GPS signals on the L2 band some 350MHz lower in frequency. If you imagine the lattice of integer solutions in 3D space for two different frequencies you can observe the the integer solutions coincide very infrequently, leaving few options to choose between. Dual frequency operation also allows for correction of ionospheric effects. Another component is semi-codeless tracking: The L1 and L2 GPS signals have a military P-code signal which is encrypted. The P code signal runs at 10x the speed and has a much longer repeat interval, this increases the accuracy of code tracking and improves multipath resistance. The L2 signal has historically only had the P-code stream. The encryption would be a barrier except it's kind of broken: The codestream is 10MHz but the stream cipher runs at only 500KHz and the same signal is sent on L1 and L2. Because of the first property you can still range against the P-code and because of the second you can find the phase offset between L1 and L2 quite precisely. (Trade name for this kind of codeless tracking is "Z-tracking"). --- this is hopefully becoming less necessary now with new civilian (unencrypted) signals on L2 and L5. The new signals also have better anti-multipath properties. Any survey receiver worth the name implements these techniques and many more. For realtime (non-postprocessed) output using the above, accuracy is 2cm +/- 2ppm (of the distance to your reference station) or so. What postprocessing does is lets you use very accurate orbital and ionospheric data which is available for download some hours later, built based on observations by many known-position ground stations. (I believe the Galileo sats even have retro-reflectors for laser based ranging, though I don't know if they're used yet.) ... plus using many hours of observations as the sats move through the sky. So like any modern technology, the state of the art result isn't given by any one technique but by many combined.
- mikeha 10y ago
  http://www.leica-geosystems.us/common/shared/downloads/inc/downloader.asp?id=23474 http://www.leica-geosystems.us/common/shared/downloads/inc/d... (full disclosure: I work for Leica Geosystems.) With real-time kinematic service, our GPS receivers give you 8mm horizontally and 15mm vertically. And you will get 3mm hz and 4mm vertical with post processing.
  - CalChris 10y ago
    Does Galileo change this at all? Or is it just more better GPS,GLONASS,...
- _coldfire 10y ago
  It is achievable with static post-processing of GPS data, kinematica claims 8mm. For real time requirements, there's consumer level products that offer accuracy of a few centimeters. https://www.advancednavigation.com.au/product/kinematica https://www.advancednavigation.com.au/product/kinematica https://emlid.com/reach/ https://emlid.com/reach/
- lh7 10y ago
  RTK or PPP, to mention two possible techniques. The first of which is differential (requires data from a receiver at a known location) and the second of which is post-processed (requires that data be collected over a relatively long period of time, although the receiver does not need to be static).

nradov 10y ago

Perhaps the Europeans are concerned that if the USA gets into a shooting war with China or Russia in a few decades, our GPS satellites will be the first casualties.

deleted 10y ago
[deleted]
vegabook 10y ago
and perhaps that is a legitimate concern for more than just Europeans, and that includes Americans, and perhaps it's not just about war, but about competition, trade, and fair global access to a technology not being beholden to a single administration (especially in the new age of "America first").
chiph 10y ago
There's no question that GPS satellites will be a high-value target in the next super-regional conflict. The system was a primary reason why Saddam was defeated (temporarily!) in Desert Storm. The Iraqis were used to getting lost in the trackless desert from their war with Iran, and assumed that the coalition forces would be just as lost. GPS allowed the famous "left hook" that cut the Republican Guard off. https://www.scientificamerican.com/article/gps-and-the-world-s-first-space-war/ https://www.scientificamerican.com/article/gps-and-the-world...

flyinglizard 10y ago

Having an alternative to GPS in mission critical systems is enough of a case to justify the existence of Galileo in the first place. Things like drones or self driving cars are not just about accuracy, but also reliability, and civilian GPS is not bulletproof (especially not in urban area). We're already seeing triple band GPS implementations with Galileo, GPS and GLONASS (the Russian alternative).

UnoriginalGuy 10y ago
While I agree with the principle in your point, does Galileo operate on a different enough set of frequencies to avoid interference that would knock out GPS?
- avar 10y ago
  It does now, see https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)#Tension_with_the_United_States https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)...
  - jhayward 10y ago
    This is not correct. The primary civilian signal for both Galileo and GPS have the same frequency on L1, 1575.42 MHz. Their modulation schemes and encoding are coordinated to not interfere. [1] http://www.navipedia.net/index.php/GNSS_signal http://www.navipedia.net/index.php/GNSS_signal
digi_owl 10y ago
Depending on the device SoC, you may see 4 different constellations, as China has their own. https://en.wikipedia.org/wiki/BeiDou_Navigation_Satellite_System https://en.wikipedia.org/wiki/BeiDou_Navigation_Satellite_Sy...
- Rebelgecko 10y ago
  Also QZSS, if you're in the right part of the world

avar 10y ago

Selective Availability was replaced by regional denial capabilities with the GPS III satellites, i.e. instead of fuzzing the signal the US can now turn off GPS for entire countries[1]. It's strategically foolish for the major economies like the EU, Russia & China to depend on the US's goodwill in maintaining a system that drives a huge part of their economy, GPS is used pervasively for everything, and that's only increasing. Trump wants NATO countries to pay their fair share, how long until he gets the idea that all countries around the world should pay a GPS licensing fee least GPS regional denial be turned on? Those are the sort of reasons for why it makes sense to develop a GPS alternative, even if you're only aiming for feature parity, or even less than that. 1. https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/faq/gps/#ad1 https://www.faa.gov/about/office_org/headquarters_offices/at...

user837387 10y ago
>>Trump wants NATO countries to pay their fair share, how long until he gets the idea that all countries around the world should pay a GPS licensing fee least GPS regional denial be turned on?<< Now now, do not insert political commentary into this discussions. I got yelled at for doing that. [1] [1]https://news.ycombinator.com/item?id=13197536 https://news.ycombinator.com/item?id=13197536
- mattnewton 10y ago
  I don't think this is unwarranted political comentary, the reasons to build the alternative to gps are largely political according to GP
  - Normal_gaussian 10y ago
    I am largely with you, however the direct Trump referencing is unwarranted - it is the institution he will represent, not the man, which is involved in this political battleground. EDIT: to wit, the institution is the most powerful military force, active across the globe https://en.wikipedia.org/wiki/List_of_wars_involving_the_United_States https://en.wikipedia.org/wiki/List_of_wars_involving_the_Uni...

CamperBob2 10y ago

Galileo's actual value has always been murky. Not even remotely. GNSS is far too important to be left up to one or two militaristic providers whose interests (to put it mildly) may not always coincide with your own. If anything we need more systems up there.

int_19h 10y ago
And more satellites are good for everyone, at least so long as all these systems remain open for use. It means more accuracy, and some redundancy never hurts, either.

PunchTornado 10y ago

The benefits of Galileo are very clear for me as an EU taxpayer. Don't rely on GPS because it is controlled by a single country and that country can shut it down whenever it likes. No country is your friend forever, you only have to look at the Trump administration. It takes 1 election and everything can swing in the wrong direction.

pg_is_a_butt 10y ago
but in your example, the election swung in the RIGHT direction
6t6t6t6 10y ago
Completely agree. GPS is so essential, that is becoming more and more a "single point of failure" for our civilization. Without having any data, I have the intuition that the cost of deploying our own GPS system may be worth just as an "insurance".
- MBCook 10y ago
  I wonder if we've gotten to the point were attempting to turn it off would harm us (United States) directly as much as anyone else, even if we only do it in certain sections of the world.
  - gizmo686 10y ago
    Turing off GPS would not have to be binary. There is a seperate, encrypted, GPS frequency that the US government can continue using even in places that they shut down GPS for everyone else. Additionally, they can degrade the accuracy of civilian GPS (also in a targeted area if they wanted).
    - dsl 10y ago
      During the Iraq war everyone kept trying to find these magic encrypted GPS devices that used military only frequencies. I never saw one, or heard of anyone using one. Even SEALs are issued the same Garmin Foretrex 401 you can get at Best Buy.

vegabook 10y ago

what is murky about 10x more precision?? Sounds like sour grapes. Sure GPS is amazing. Now there's something better. Just because it isn't American doesn't mean its value is questionable. Nothing is being taken away here. Choice is being added.

matthewmcg 10y ago

Is there a good, wide-ranging treatment of the history of GPS? Something like Rhodes' Making of the Atomic Bomb but for electronic navigation?

lh7 10y ago

> Galileo's actual value has always been murky. Not to me, as a professional user. Presumably not to the policy-makers either who, having recognised the strategic value of satellite-based navigation, would be negligent not to minimise their reliance on foreign powers. > It's honestly quite hard to compete with a free alternative The licensing models of NAVSTAR and Galileo-based solutions are closely comparable from a user point of view. Both are free at a certain service level, beyond that, both require, in the general case, payment of a licence or other form of disbursement in order to access a higher service level (e.g., real-time differential corrections). Galileo, being a latter solution, simply offers a more integrated solution (not depending on Inmarsat or other providers) based on the experience acquired from NAVSTAR. The rest of your commentary is a bit of a non-sequitur, I'm afraid.

ajross 10y ago

> It's honestly quite hard to compete with a free alternative that the US government throws billions of dollars at. Yes, but it's not a commercial venture. Surely there is equivalent value in having a satellite system that European governments throw billions of euros at, no?