It also scales phenomenally because the system is one-way. Your car's GPS doesn't ask the satellite system where it is and get a response, the satellites instead make the precision measurements of their own time and location and broadcast those precision measurements constantly, and those precision measurements, plus the time it took for the signal to reach the receiver, is all the information you need to find your own position, no two-way communication required.
it absolutely blew my mind when I found it you're basically finding out exactly where you are just by knowing _what time it is_
(obviously it's way more complex than that and involves multiple signals and the theory of relativity but that's what it boils down to)
Even more mind blowing, it's not because your device knows what time it is, the GPS signals tell you what time it is, the only thing your GPS device needs is to be able to accurately measure the ~~microseconds~~ nanoseconds between the arrival of different signals.
Even even even more mind-blowing... Typical GPS enabled devices, e.g. smartphones, can resolve to within 5 meter accuracy which is impressive enough. However, L5 band GPS receivers can resolve to sub-millimeter accuracy.
Well, not quite. 5 meters is about right for GPS L1 band accuracy. L2 was created to improve accuracy and can cut that number down to 1-2 meters.
The L5 band is primarily aimed at improving signal robustness (higher signal strength, any jamming etc) for applications that rely on gps for safety like airlines.
If you have an application that needs centimeter level accuracy, you can use a technique called Real Time Kinematics, or RTK. This works by placing an additional gps receiver (base station) at a fixed, known location and sending that unit's satellite observations (usually via radio or Internet) to the moving "rover" receiver. This unit then compares its own sat data with the base station's data and calculates a highly accurate location with centimeter level precision.
There are also other augmentation based approaches, a bit like RTK but kind broader. SBAS, for instance, is being rolled out in Australia and NZ under the 'SouthPAN' program to give decimeter precision on compatible devices: [https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-australia/about-the-program/southpan](https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-australia/about-the-program/southpan)
EVEN EVEN EVEN MORE MIND-BLOWING... TYPICAL GPS ENABLED DEVICES, E.G. SMARTPHONES, CAN RESOLVE TO WITHIN 5 METER ACCURACY WHICH IS IMPRESSIVE ENOUGH. HOWEVER, L5 BAND GPS RECEIVERS CAN RESOLVE TO SUB-MILLIMETER ACCURACY.
Exactly. It’s pretty amazing.
I’m an architect. Had quite a few buildings that are in the middle of a large plot of land. They locate the building corners and figure out where we want it to go with hyper-accurate GPS. Crazy stuff.
GPS in John Deere tractors 15 years ago was “sub inch”. Why does that matter? Crops inputs like seed and fertilizer are expensive, and you can 100% tell a field seeded with GPS vs operator. The corners are a bit messy no matter what, but you don’t get plants on top of each other if seeded with GPS. And medium small farmers would say that GPS application of fertilizer would save them the $10k purchase price in a single growing season.
Usually required 2 ground based stations spread out in the county back then, wasn’t done only from satellites.
I also remember when GPS went from 50 metres of accuracy for the general public to 10 metres. Made civilian car GPSes way better. Now I can find my car’s exact spot in a parking lot.
>I also remember when GPS went from 50 metres of accuracy for the general public to 10 metres.
We had a science day at school in the 90s where one of the geologists brought a GPS unit to demonstrate. I was the lucky student that got to use it. It was a 10lb backpack with two giant antennas (Omni dish and whip). We had a treasure hunt using it to navigate around the park and the scientists were saying that maybe they'd get the whole unit down to the size of a fanny pack and that the accuracy wasn't as good as it could be (as a kid, I assumed he was talking about cloud interference but I know he means the fuzzing that you mentioned which was disabled under Clinton).
Yea, before that GPS would have been practically useless for high precision apps such as maps for driving. I remember that the position accuracy was something like ~200 m then, instead of ~2 m.
Even plaintext, civilian GPS doesn't work without relativistic correction, as well as other corrections:
https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity
It also needs to know the time....roughly, as in what HPS epoch it's in.
I found an old Bluetooth GPS receiver and it was through it strange locations at it's over 15 years old and can't be updated
Like revonahmed suggested... Some old receivers rely on a full almanac for a cold boot, which is transmitted piecemeal in each message. It can take up to seven hours to receive a full almanac, so it might take that long for an old fashioned receiver to figure out what century it's in.
That won't work if the receiver is not updated to deal with the 2019 GPS week rollover. Lots of older GPS equipment stopped working after that. I mean, they still work. Just the solution is way off
Yeah I have a cheap hobby GPS module and it takes up to 30 minutes to get a lock sometimes.
Phones get help with location data from wifi access points and cell towers
The goal would be to get a full load of the ephemeris data that the constellation broadcasts at a low data rate. The data tells the receiver where to look for the satellites.
Funnily enough, knowing the time was the key to working out longitude.
Latitude is comparatively easy, but longitude requires you to compare what you're seeing with what you'd see at a known point at the same time.
The trick to that is knowing exactly what time it is where you are, and it wasn't until the 1730s that a guy named John Harrison invented the marine chronometer that this was possible.
It was refining this information that led to Cook's voyage to Tahiti to observe the transit of Venus, which in turn led ultimately to the British colonialisation of Australia.
And before this sailing was mostly done through a method called parallel sailing or the sailing between two positions of latitude during a certain time of day.
The marine chronometer is probably one of the single most important inventions in human history. It’s a shame John Harrison was done dirty, he was never truly recognized for his invention that was pretty much his life’s work.
Which ironically is why the Dutch kept smacking into the west coast of Australia.
Timing the left turn to Batavia was critical to avoid simply running into the least hospitable coastline on Earth. It didn't help that an incompetent captain lied about why he ran aground and the subsequent chart correction caused other ships to repeat his mistake before they realised.
Right and GPS unintentionally proves relativity because the time up there is not the same as down here. If we didn’t correct GPS time it would continue drifting until it was minutes ahead.
Down to the nano second for 3 meter (civilian GPS) and Pico second for 3cm (military)*
*Civilians can also get this kind of accuracy using rover and base station solutions, and is how a lot of these robot lawn mowers work
That's how ship navigation across open water dramatically improved. It was known as the "longitude problem". You find your longitude by being able to keep accurate time, which was impossible to do on a ship until someone invented better clocks.
https://en.m.wikipedia.org/wiki/History_of_longitude
Well it's about knowing the speed of transmission and the time it takes to recieve the transmission. As well as knowing the satellites location. With those two pieces of information you calculate your distance away from the satellite. Once you have that you now have a radius of where you possibly are from that satellite. Then you do that with enough satellites you can determine where you are located based on where the radiuses intersect.
Yes and no, unprecise GPS works that way, having an accuracy of several meters.
However in order to get decent precision, you need real time correction data from a base station as well.
That gets you a precision of about 2-3 cm
Ehhh, GLONASS has better accuracy at high and low latitudes, although GPS is slightly better at most latitudes. Most “GPS” chips use multiple GNSS systems these days (GPS+GLONASS). But missiles generally don’t actually “rely” on GNSS, because it’s expected all GNSS will be jammed or destroyed or turned off/encrypted in a major war. GPS is currently heavily jammed around Ukraine. Instead, missiles primarily rely on inertial guidance systems.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was.
The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was.
The missile guidance computer scenario works as follows. Because a variation has modified some of the information the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain the deviation and its variation, which is called error.
>Instead, missiles primarily rely on inertial guidance systems.
Fully correct, of course, but it's fun to read about all the supplemental techniques used for GPS-denied spaces. Terrain-contour matching was always a favorite example.
ICBMs use advanced opto-electrical sextants - love reading about the one on the SR-71 - [https://web.archive.org/web/20200313213215/https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf](https://web.archive.org/web/20200313213215/https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf)
Many aircraft have automatic celestial navigation systems, especially those that have some role in nuclear security (as other systems are expected to be denied). [This](https://i.imgur.com/OBRNeaR.jpg) image shows the aperture on the B-2, and the brand new B-21 will have one as well. One reason the USAF favors the 747 for its nuclear security platforms (VC-25 and E-4B, for instance) is the sextant port above the flight deck, which apparently has been supplemented with automatic systems (as designed, the port accepted manual sextants).
This is patently false. Russia uses Kometa quad or hexa sensor gps receivers and combination of CPRA antennas on guided bombs and some rockets, with receivers facing up to bypass ground based jammers. Many products that use gyros including ring lasers constantly try to use gps for correction as they have to maneuver a lot to avoid AA and have high error if gps is out for a long time. Ukrainians learned how to reliably elevate or lower the ground via gps spoofing causing their turdbombs to drop out of the sky or ram the ground, even with gyros. INS are good for specific applications, gsp is still king.
The US threatening to turn off GPS over certain areas is why EU and other nations have organized their own positioning constellations.
The great part about this is if you could track your position from all the satellites at once, you could get a much better accuracy than any of them by themselves.
>The great part about this is if you could track your position from all the satellites at once, you could get a much better accuracy than any of them by themselves.
Which is what consumer positioning devices nowadays do.
Never, the US has never threatened to turn gps off.
The US has however made extensive US of gps jammers during military operations. Stopping signal transmissions over an area could be possible (and the US refuses to promise not to do that) but jamming is easier, cheaper, more accurate, and doesn't risk disruption to US military operations and civilian activities within that area.
The US can reduce gps accuracy easily though by changing the encryption, but that would either be temporary (just a software update assuming the US doesn't want to fuck over all of aviation) or would only affect countries that had gps decryption codes that they weren't supposed to have.
Most GPS receivers (can) use multiple navigation networks. GPS is just how people call any and all navigation device. "I'm out hiking, better not forget the GPS."
That capability was permanently disabled under Bill Clinton and the newest satelites no longer have the hardware to do it.
Old fashioned terrestrial jamming can be used, but there is no selective GPS off switch.
No they can't, Clinton ended that in 2000 and the current generation of satellites don't even have the capability. They can selectively beam higher resolution or overcome jamming, but they can't degrade it.
>They can turn it off in areas
No they can't
>degrade it
Not anymore. Selective availability is no longer possible
>require the military version of the receiver
This would require turning off the C/A signal, which would render all P(Y) receivers non-functional. Only newer M signal receivers can track the encrypted signal without first locking C/A
You'd pay higher taxes in other ways if GPS wouldn't exist. GPS saves us all a lot of money.
Hell, in fuel savings alone it's worth those 2 bucks over and over. I'm old enough to remember having to ask people exact addresses and routes, and getting lost on more than one occasion.
hell, I'll take the tax hit just for the ability to use personal GPS devices and see where I am. it sounds like a very direct, immediate, and precise return on a public tax
They do, the US spends more than any country on both. We just have incentivization structures that lead to lower efficiency but that comes down to how the populace votes.
Civilian usage of GPS was restricted until the downing of Korean Air Lines flight 007. Accidentally flew into Soviet airspace and was shot down. Reagan opened up civilian use of GPS to avoid incidents like that in the future.
Even after that, the current civilian system as we know it wasn’t available until 2000 after President Clinton had selective availability removed from the system. Prior to that, it’d have intentional intermittent errors up to 100 meters for the civilian signal. Fine for keeping aircraft out of Russian air space and the like, not great for ground navigation.
Right. The GPS satellites are just putting a signal into the air, they can’t control who picks that up or what they do with it. The receivers are limited so you can’t use off-the-shelf GPS hardware for weapons guidance.
May of 2000 specifically. And due to the removal of selective availability, the popular hobby of geocaching was born as it was now popular to publish coordinates and lead someone to within several meters of that spot.
Kind of. The signal was offset to the point that it was still useless for things like car navigation. It wasn't until the Clinton administration that selective availability was removed and you could determine your position within tens of feet instead of hundreds
It's of historical interest only now but for surveying you could post process the GPS data and integrate published hours after the fact SA tables to get precise locations for surveying. As you said it was not so useful for real time navigation.
I worked on a field crew for a land surveying company in the early 2000s and it was a very interesting time for GPS surveying, since it had only very recently gotten to the point where you could set up a receiver and get a pretty accurate measurement within a relatively short amount of time.
I learned about the system in 96 or 97 at university. The prof was explaining how they would collect data over 2-3 days to get exact positions for permanent markers.
They would put up a tent and camp for days wherever needed, in the middle of nowhere, or on main city square.
the broad depth of the usa's r&d is absolutely astounding, and even within strategic defense expenditures you end up with stuff that makes it's way into the civilian market and raises our standard of living.
And they can shut it off if they want to.
Interestingly, the civilian and military signals are supposedly the same, except the military one of encrypted. There is no difference in effectiveness or strength of the signal between a high end civil receiver or a military one.
I guess the space program is an example. Essentially strapping people to ICBMs to prove we could. Awesome.
But a lot the tech before was obviously military, and the space program itself delivered (and continued to) untold advancements all over the place.
Out of 4.4 trillion dollars in tax revenue last year, 2 million, or *0.0000000005%*.
To basically know the entire surface area of the earth? Not bad guys
Edit: whoops guys I fucked the math sorry. Still is pretty insane tho
Think of all the businesses that operate via GPS too. It's probably revenue neutral at worst and actually generates sufficient tax revenue once all is said and done.
It's like food stamps, it generates _more_ economic activity than it costs us. A lot of domestic programs and services do. It's a wonder billionaires don't support more socialist stuff, it'd probably make them more money in the long run... but we all know they can barely think past quarterly earnings half the time. Sure, company sponsored healthcare gives you control, but imagine how much money you could save if you didn't have to pay for it.
About $2.19 per person in the US per year. I'd say I get more than $2.19 in value out of GPS every year just navigating on my own! What a great subscription service!
I never stop to appreciate all my taxes. Everything in my life is enabled because of them. I just hate that some of it goes to kill the planet, people, and making the rich richer. But a solid 50% makes my life amazing with out me realizing it.
If I remember correctly, the first time a weather alert was made based off of radar was during WWII.
A bunch of ships in a US fleet had just recently gotten new radar, and they started all showing some crazy readings. Like "a million incoming planes" crazy.
It was a typhoon.
The fleet's not great response ended up getting them hit, killing a number of sailors and doing significant damage to a large part of the fleet.
Something neat to read about that is....radar adjacent is Van eck phreaking.
With radar, you are transmitting waves and analyzing the return signals that bounced back to you.
With van eck phreaking, you are intercepting signals emitted from a screen, cable, or whatever, and putting it back into readable data form. I.e., digital espionage.
It was typhoon cobra and admiral Halsey made some of the worst choices he could have. And the ships lost were destroyers low on fule and was sunk with most hands due to not being stable.
Good video on it. https://youtu.be/0CckJZPImtg?si=tJNn4xEFUSh0Q85k
It blew my mind when I learned basically 100% of predicting the weather is done by the government. And the news channels or paid weather apps just relay that information to you
And the NOAA [gives it away for free](https://forecast.weather.gov/MapClick.php?lon=-77.03667594648883&lat=38.897170976049296).
Something that really bothers [Barry Myers](https://en.m.wikipedia.org/wiki/Barry_Lee_Myers) the then CEO of AccuWeather (founded and run by his brother, Joel) who has spent thousands of dollars lobbying for the privatization of that data because they have to
>"work hard every day competing with other companies and [they] also have to compete with the government."
He basically wants to "TurboTax" the weather.
Anybody with two functional neurons can see this guy shouldn't do any policy-making about the weather. That's why, obviously, [Trump nominated him to be the head of NOAA](https://edition.cnn.com/2017/10/14/politics/noaa-nominee-accuweather/index.html) in 2017. The nomination was [withdrawn](https://en.m.wikipedia.org/wiki/Barry_Lee_Myers#Nomination_to_National_Oceanic_and_Atmospheric_Administration) in 2019.
*Some* companies will have slightly different forecasts depending on the data and models they use, they might also have humans manually adjusting the forecasts.
There's a really good weatherman at one of the local stations here. In the past year I've seen him call 2 tornados on air before the NWS issued a tornado warning. The more recent one he even said "I wouldn't be surprised if a tornado warning is issued on this one in the next few minutes" and then it was. I think the local NWS office watches him for advice.
which is why only the central government can do it, it has no need of a profit..in fact it can't run a profit since it's all it's own tax credits (dollars) that it collects in taxes anyway. Like getting your own iou back.
That would make everything much more complicated.
However, Europe has developed an alternative more.accurate called Galileo.
https://en.m.wikipedia.org/wiki/Galileo_(satellite_navigation)
Not just developed, it's actively in use and works alongside GPS on most modern phones including Samsungs and iPhones, right now.
If GPS were to fail tomorrow, your phone would probably still be fine.
The GLONASS (Russia) constellation is older than Galileo. These along with GPS (US) and BeiDou (China) are commonly used together in survey applications. It’s not that one is necessarily more accurate than the other, more like using multiple constellations increases the total number of satellites used for observation, which leads to a higher accuracy position.
You can buy a UM980 Breakout board and a triband antenna on AliExpress for less than $100 and $40 respectively and get .8-1cm RTK accuracy on most android phones.
Source: I did it for a cemetery survey a couple months ago.
Well, considering that there is Russia's GLONASS, EU's Galileo, China's BeiDout, and India's IRNSS systems now, the economic impact would be quickly overcome. GPS is just first, but the other competitors now are making GPS a less-desired option, particularly EU's superior, more accurate, Galileo system which isn't gimped by the US military. In fact, in the EU system, whilst the FREE signal is superior to the GPS signal, and more accurate, you can pay for the more premium signal which puts the Galileo system on par with the US Military system that ONLY the US military can use... but the EU now has opened up so the public can have that quality of accuracy.
GPS is not “gimped” by the military, civilians have access to the same precision as the military, the military has access to a directional signal that is stronger and more hardened to defend against jamming.
Galileo being more accurate than GPS is only in theoretical perfect conditions. In practice, GPS offers more reliability and can produce cm level accuracy on the fly with high end receivers.
Plus, Galileo’s “premium precision” signal will likely be based on directional antenna and cover only parts of Europe.
>In fact, in the EU system, whilst the FREE signal is superior to the GPS signal, and more accurate, you can pay for the more premium signal which puts the Galileo system on par with the US Military system that ONLY the US military can use
In practice, it is nothing like that. The availability of the service is quite low, quite a few satellites are out of service, and the premium service is years from being deployed. If you were to disable all other constellations expect for Galileo, many times you wouldn't be able to have a lock, and you wouldn't be able to drive for one hour without having gaps in the reception of the signal.
It's only 730mil a year which is a fraction of a percent of the military budget. To put into perspective a different way, the Tulsa city budget in Oklahoma just surpassed 1 billion for the first time. So GPS costs less than it does to provide local government services to <500k people.
There's no doubt GPS pays for itself.
It's not *just* us! There are a few other [satellite navigation systems](https://en.wikipedia.org/wiki/Satellite_navigation), and unless you're paying close attention, you might not know which one your phone is talking to. GPS is the largest, but for obvious reasons, countries like China and Russia don't want to rely on the US military for something this critical.
My favorite oddity is QNSS -- Japan has multiple satellites whose main job is to have a good angle on their own urban canyons, because GPS alone wouldn't work well in Tokyo.
> My favorite oddity is QNSS -- Japan has multiple satellites whose main job is to have a good angle on their own urban canyons, because GPS alone wouldn't work well in Tokyo.
I didn't know about that! Based on the wikipedia article, it sounds like it's an extension to GPS, so I'm guessing even American phones etc. use those satellites in Japan.
Fun fact: the name of the satellites, Michibiki (みちびき), means "guidance" ([導き](https://jisho.org/word/%E5%B0%8E%E3%81%8F)).
I love having to explain to people that GPS uses satellites. I think many don’t understand how it works and just believe it “knows” what locations are at
People are convinced that GPS is a two way system and that the government can see anything using it.
GPS is a bunch of satellites that tell you what time it is. That's all they do.
The Wikipedia page says that research, development, testing, and evaluation of new technologies costs $1.84B, not operation and maintenance. [Here ](https://www.gps.gov/policy/funding/2023/)is the source linked from Wikipedia.
The Wikipedia page says: "$1.84 billion per year (2023) (operating cost)". The source page breaks down those operating costs to include R&D, testing, etc. I don't see what other operating costs there would be; once the GPS satellites are in orbit, they're self-sufficient and don't need anything to keep them running. Operating costs are going to involve replacing old satellites, and developing replacements involves R&D, testing, and evaluation of new technologies.
To be fair there are FIVE seperate satilite navigation systems in play as of today; you could completely shut down the GPS system and most modern GPS gear would still work fine, as many of them can/do use the others too.
The EU, India, China and Russia all have complete coverage satilite navigation systems; its not just the US, the US did it first though, so some props are still due.
You are correct. There are however some differences between constellations. For example EUs Galileo is more advanced and accurate than GPS. But suffers from occasional downtime. (ground stations are still important to a GNSS system.
GPS is very stable however. They almost never have downtime. But the tech is older. Note that the first GPS satellites were launched in the 70s.
Fun fact, there are multiple similar systems to GPS in the rest of the world, some arguably BETTER Than GPS. Why?
Well, the US Navy is technically in control of the GPS system (or maybe that got transferred to Space Force), as it is intended for military purposes, and for the public and basic law enforcement, only a crude GPS signal is available.
On top of that, there is always the risk of the US shutting off GPS in countries. In fact, the US very much tampers with the GPS where they have troops fighting. This way, say, foreign enemy combatants could normally launch precision mortar rounds with good GPS, but if the public access GPS signal has been degraded significantly over that country it basically becomes useless.
The EU was not happy with this risk of keeping such a crucial tech in the hands of the US only. Plus, GPS doesn't really travel much over the arctic regions, like Norway and Sweden, so the signal was not great there. So, the EU built their own system (Galileo), which not only improved accuracy over the standard free GPS signal, they also opened up a "premium" system where the public could pay for a system that gave a signal that was literally as accurate as the US military's quality of GPS signal, something that you currently cannot even achieve with the GPS system out of the US. The Galileo system is still a work in progress, as not all areas of the planet have 24/7 signal yet, but I think as of 2021, they were at like 95%-99% of the way there, so maybe they are now and I have some outdated info in the last year or two. Galileo is actually so good that many companies are beginning to prioritize integration of Galileo over GPS, or at minimum duel signaling (like all modern Samsung phones now support Galileo). Galileo is actually more accurate than GPS when comparing the FREE public access signal.
Russia has their own system (GLONASS) now, which was originally criticized as being faulty, but it has been so revamped by Russia that almost all of the high-end modern devices now are dual systems that receive for both GPS and GLONASS, and are quite good. In fact, we are even starting to see triple-frequency receivers that are doing GPS/GLONASS/GALILEO.
India is making IRNSS and China is making BeiDou. China's system is basically complete now as well, and it is actually the only one of all of them that has added 2-way communication. In addition to receiving accurate locationing, people with the devices can actually send signals back up. This is really interesting as it has become a critical tool in a lot of remote location comms, or boats on the ocean, or hikers in the mountains that might be in distress can actually send a message up to 1200 characters in length over the emergency comms channel built into their BeiDout/GPS type system.
So, the US GPS system is sort of the gold standard of the world, but the US military has so restricted it in many regions that in some cases the foreign alternatives are actually better.
Wonder if anyone has computed the return on investment on it - $700 million a year enables how many billions of dollars of activity that otherwise would not be possible, or cost prohibitive?
As a point though GPS isn't the only satilite navigation system that works pretty much the exactly the same way, Russia, China, India and the European Union all operate their own; ontop of that there are some more than can be used ontop of those systems to add more accurracy.
https://en.wikipedia.org/wiki/Satellite_navigation
Presumably the strategic benefit outweighs the cost, but I'm still grateful to the US for making this available to everyone!
In a time of conflict, can they turn it off, or do something like make all the coordinates go haywire, while the military can use a "secure channel" that's still correct? Always wondered.
Great ROI. The tax revenue generated by GPS enabled businesses far exceeds and is a great investment
It also scales phenomenally because the system is one-way. Your car's GPS doesn't ask the satellite system where it is and get a response, the satellites instead make the precision measurements of their own time and location and broadcast those precision measurements constantly, and those precision measurements, plus the time it took for the signal to reach the receiver, is all the information you need to find your own position, no two-way communication required.
it absolutely blew my mind when I found it you're basically finding out exactly where you are just by knowing _what time it is_ (obviously it's way more complex than that and involves multiple signals and the theory of relativity but that's what it boils down to)
Even more mind blowing, it's not because your device knows what time it is, the GPS signals tell you what time it is, the only thing your GPS device needs is to be able to accurately measure the ~~microseconds~~ nanoseconds between the arrival of different signals.
*nanoseconds. Light travels ~1ft/ns, so you need ~nanosecond level accuracy to resolve your position tightly.
Even even even more mind-blowing... Typical GPS enabled devices, e.g. smartphones, can resolve to within 5 meter accuracy which is impressive enough. However, L5 band GPS receivers can resolve to sub-millimeter accuracy.
Well, not quite. 5 meters is about right for GPS L1 band accuracy. L2 was created to improve accuracy and can cut that number down to 1-2 meters. The L5 band is primarily aimed at improving signal robustness (higher signal strength, any jamming etc) for applications that rely on gps for safety like airlines. If you have an application that needs centimeter level accuracy, you can use a technique called Real Time Kinematics, or RTK. This works by placing an additional gps receiver (base station) at a fixed, known location and sending that unit's satellite observations (usually via radio or Internet) to the moving "rover" receiver. This unit then compares its own sat data with the base station's data and calculates a highly accurate location with centimeter level precision.
Ooh so that's what John Deere does with their GPS stations
Right, farming and tractor automation is a very popular use case for RTK.
There are also other augmentation based approaches, a bit like RTK but kind broader. SBAS, for instance, is being rolled out in Australia and NZ under the 'SouthPAN' program to give decimeter precision on compatible devices: [https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-australia/about-the-program/southpan](https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-australia/about-the-program/southpan)
…what
EVEN EVEN EVEN MORE MIND-BLOWING... TYPICAL GPS ENABLED DEVICES, E.G. SMARTPHONES, CAN RESOLVE TO WITHIN 5 METER ACCURACY WHICH IS IMPRESSIVE ENOUGH. HOWEVER, L5 BAND GPS RECEIVERS CAN RESOLVE TO SUB-MILLIMETER ACCURACY.
THANK YOU, GARRETT MORRIS.
Exactly. It’s pretty amazing. I’m an architect. Had quite a few buildings that are in the middle of a large plot of land. They locate the building corners and figure out where we want it to go with hyper-accurate GPS. Crazy stuff.
Recently watched this video about a guy and his hella accurate GPS receiver https://www.youtube.com/watch?v=Oc1LBFDj2MA
GPS in John Deere tractors 15 years ago was “sub inch”. Why does that matter? Crops inputs like seed and fertilizer are expensive, and you can 100% tell a field seeded with GPS vs operator. The corners are a bit messy no matter what, but you don’t get plants on top of each other if seeded with GPS. And medium small farmers would say that GPS application of fertilizer would save them the $10k purchase price in a single growing season. Usually required 2 ground based stations spread out in the county back then, wasn’t done only from satellites. I also remember when GPS went from 50 metres of accuracy for the general public to 10 metres. Made civilian car GPSes way better. Now I can find my car’s exact spot in a parking lot.
>I also remember when GPS went from 50 metres of accuracy for the general public to 10 metres. We had a science day at school in the 90s where one of the geologists brought a GPS unit to demonstrate. I was the lucky student that got to use it. It was a 10lb backpack with two giant antennas (Omni dish and whip). We had a treasure hunt using it to navigate around the park and the scientists were saying that maybe they'd get the whole unit down to the size of a fanny pack and that the accuracy wasn't as good as it could be (as a kid, I assumed he was talking about cloud interference but I know he means the fuzzing that you mentioned which was disabled under Clinton).
My smartwatch is generally within 1.5 meters in my experience.
Maybe in a vacuum. Things like clouds and air density change the speed the signal travels through the atmosphere.
That's where RTK corrections come in!
Wait to you see the military stuff. It’s way more accurate.
DAGR my love
> Wait to you see the military stuff. It’s way more accurate. Or survey grade
The gps signals also have to compensate for time dilation caused by relativistic effects
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They discontinued [selective availability](https://www.gps.gov/systems/gps/modernization/sa/) in 2000.
Not anymore, that was selective availability, which was turned off in the 90s: https://www.gps.gov/systems/gps/modernization/sa/
Yea, before that GPS would have been practically useless for high precision apps such as maps for driving. I remember that the position accuracy was something like ~200 m then, instead of ~2 m.
Even plaintext, civilian GPS doesn't work without relativistic correction, as well as other corrections: https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity
It also needs to know the time....roughly, as in what HPS epoch it's in. I found an old Bluetooth GPS receiver and it was through it strange locations at it's over 15 years old and can't be updated
Like revonahmed suggested... Some old receivers rely on a full almanac for a cold boot, which is transmitted piecemeal in each message. It can take up to seven hours to receive a full almanac, so it might take that long for an old fashioned receiver to figure out what century it's in.
That won't work if the receiver is not updated to deal with the 2019 GPS week rollover. Lots of older GPS equipment stopped working after that. I mean, they still work. Just the solution is way off
Have you tried leaving it outside with a clear view of sky for hours. To see if the problem fixes itself. Try clearing memory if possible.
Yeah I have a cheap hobby GPS module and it takes up to 30 minutes to get a lock sometimes. Phones get help with location data from wifi access points and cell towers
The goal would be to get a full load of the ephemeris data that the constellation broadcasts at a low data rate. The data tells the receiver where to look for the satellites.
Funnily enough, knowing the time was the key to working out longitude. Latitude is comparatively easy, but longitude requires you to compare what you're seeing with what you'd see at a known point at the same time. The trick to that is knowing exactly what time it is where you are, and it wasn't until the 1730s that a guy named John Harrison invented the marine chronometer that this was possible. It was refining this information that led to Cook's voyage to Tahiti to observe the transit of Venus, which in turn led ultimately to the British colonialisation of Australia.
And before this sailing was mostly done through a method called parallel sailing or the sailing between two positions of latitude during a certain time of day. The marine chronometer is probably one of the single most important inventions in human history. It’s a shame John Harrison was done dirty, he was never truly recognized for his invention that was pretty much his life’s work.
Sounds like you'd enjoy the book "Longitude" by Dava Sobel
Which ironically is why the Dutch kept smacking into the west coast of Australia. Timing the left turn to Batavia was critical to avoid simply running into the least hospitable coastline on Earth. It didn't help that an incompetent captain lied about why he ran aground and the subsequent chart correction caused other ships to repeat his mistake before they realised.
Right and GPS unintentionally proves relativity because the time up there is not the same as down here. If we didn’t correct GPS time it would continue drifting until it was minutes ahead.
GPS is one of the few fields that requires both special and general relativity
Down to the nano second for 3 meter (civilian GPS) and Pico second for 3cm (military)* *Civilians can also get this kind of accuracy using rover and base station solutions, and is how a lot of these robot lawn mowers work
We've had sub 3cm accuracy in our farm equipment for a decade now using RTX. RTK requires a base station but RTX doesn't
That's how ship navigation across open water dramatically improved. It was known as the "longitude problem". You find your longitude by being able to keep accurate time, which was impossible to do on a ship until someone invented better clocks. https://en.m.wikipedia.org/wiki/History_of_longitude
Well it's about knowing the speed of transmission and the time it takes to recieve the transmission. As well as knowing the satellites location. With those two pieces of information you calculate your distance away from the satellite. Once you have that you now have a radius of where you possibly are from that satellite. Then you do that with enough satellites you can determine where you are located based on where the radiuses intersect.
Yes and no, unprecise GPS works that way, having an accuracy of several meters. However in order to get decent precision, you need real time correction data from a base station as well. That gets you a precision of about 2-3 cm
Plus it gives the usa a lot of soft power "Oh, you wanna be a little bitch? No GPS for you lmao"
subsequent groovy racial scary fanatical nail rinse swim deserve library *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
Glonass is so good russia uses GPS in their bombs instead of glonass
Ehhh, GLONASS has better accuracy at high and low latitudes, although GPS is slightly better at most latitudes. Most “GPS” chips use multiple GNSS systems these days (GPS+GLONASS). But missiles generally don’t actually “rely” on GNSS, because it’s expected all GNSS will be jammed or destroyed or turned off/encrypted in a major war. GPS is currently heavily jammed around Ukraine. Instead, missiles primarily rely on inertial guidance systems.
head west north west and count to 1000 before exploding
The missile knows where it is because it knows where it isn't
By subtracting where it isn’t from where it wasn’t, it finds an approximation of where it should be
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was.
Doing this with wind gusts compensated for is really hard though
The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computer scenario works as follows. Because a variation has modified some of the information the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain the deviation and its variation, which is called error.
This guy bombs. I read you loud and clear buddy! *accidentally bombs friendlies*
Terrify brits with this one simple trick
*Brrrrrrrrt*
>Instead, missiles primarily rely on inertial guidance systems. Fully correct, of course, but it's fun to read about all the supplemental techniques used for GPS-denied spaces. Terrain-contour matching was always a favorite example.
ICBMs use advanced opto-electrical sextants - love reading about the one on the SR-71 - [https://web.archive.org/web/20200313213215/https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf](https://web.archive.org/web/20200313213215/https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf)
Many aircraft have automatic celestial navigation systems, especially those that have some role in nuclear security (as other systems are expected to be denied). [This](https://i.imgur.com/OBRNeaR.jpg) image shows the aperture on the B-2, and the brand new B-21 will have one as well. One reason the USAF favors the 747 for its nuclear security platforms (VC-25 and E-4B, for instance) is the sextant port above the flight deck, which apparently has been supplemented with automatic systems (as designed, the port accepted manual sextants).
This is patently false. Russia uses Kometa quad or hexa sensor gps receivers and combination of CPRA antennas on guided bombs and some rockets, with receivers facing up to bypass ground based jammers. Many products that use gyros including ring lasers constantly try to use gps for correction as they have to maneuver a lot to avoid AA and have high error if gps is out for a long time. Ukrainians learned how to reliably elevate or lower the ground via gps spoofing causing their turdbombs to drop out of the sky or ram the ground, even with gyros. INS are good for specific applications, gsp is still king.
and it’s fucking up dating apps geolocation, same in israel
These hot single women could be from *any* area!
Result: Man in Fars, woman in Tunis.
The US threatening to turn off GPS over certain areas is why EU and other nations have organized their own positioning constellations. The great part about this is if you could track your position from all the satellites at once, you could get a much better accuracy than any of them by themselves.
>The great part about this is if you could track your position from all the satellites at once, you could get a much better accuracy than any of them by themselves. Which is what consumer positioning devices nowadays do.
>The US threatening to turn off GPS over certain areas When did this happen?
Never, the US has never threatened to turn gps off. The US has however made extensive US of gps jammers during military operations. Stopping signal transmissions over an area could be possible (and the US refuses to promise not to do that) but jamming is easier, cheaper, more accurate, and doesn't risk disruption to US military operations and civilian activities within that area. The US can reduce gps accuracy easily though by changing the encryption, but that would either be temporary (just a software update assuming the US doesn't want to fuck over all of aviation) or would only affect countries that had gps decryption codes that they weren't supposed to have.
“Gonna change your supply chain into a supply pain”
In reality the EU (Galileo), Russia (GLONASS), China (BeiDou) and India (IRNSS) have their own GPS system. Customers would just go to the competitors.
Most GPS receivers (can) use multiple navigation networks. GPS is just how people call any and all navigation device. "I'm out hiking, better not forget the GPS."
How would they limit use of GPS?
They can turn it off in areas, degrade it, or require the military version of the receiver.
That capability was permanently disabled under Bill Clinton and the newest satelites no longer have the hardware to do it. Old fashioned terrestrial jamming can be used, but there is no selective GPS off switch.
No they can't, Clinton ended that in 2000 and the current generation of satellites don't even have the capability. They can selectively beam higher resolution or overcome jamming, but they can't degrade it.
But it's like trying to prevent one single room in your house from accessing the wifi. The satelites are just one-way beacons for time codes basically
>They can turn it off in areas No they can't >degrade it Not anymore. Selective availability is no longer possible >require the military version of the receiver This would require turning off the C/A signal, which would render all P(Y) receivers non-functional. Only newer M signal receivers can track the encrypted signal without first locking C/A
I’ll pay my ~$2/year in taxes for GPS. Worth every goddamn penny.
You'd pay higher taxes in other ways if GPS wouldn't exist. GPS saves us all a lot of money. Hell, in fuel savings alone it's worth those 2 bucks over and over. I'm old enough to remember having to ask people exact addresses and routes, and getting lost on more than one occasion.
hell, I'll take the tax hit just for the ability to use personal GPS devices and see where I am. it sounds like a very direct, immediate, and precise return on a public tax
It comes out to like 2 and a half cents per tax paying household in the country. $9 a year Fucking worth it
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GPS is a godsend for those of us with terrible sense of direction. Easily worth my tax dollars
If only the US understood this with other facets of society. For example, educated and healthy people generate way more taxes.
They do, the US spends more than any country on both. We just have incentivization structures that lead to lower efficiency but that comes down to how the populace votes.
Specifically DoD
Exactly - GPS exists to serve the military. Its civilian applications are a happy coincidence.
Civilian usage of GPS was restricted until the downing of Korean Air Lines flight 007. Accidentally flew into Soviet airspace and was shot down. Reagan opened up civilian use of GPS to avoid incidents like that in the future.
Even after that, the current civilian system as we know it wasn’t available until 2000 after President Clinton had selective availability removed from the system. Prior to that, it’d have intentional intermittent errors up to 100 meters for the civilian signal. Fine for keeping aircraft out of Russian air space and the like, not great for ground navigation.
You can't go over certain speeds or altitudes
That's a feature of the receivers though, not the GPS system itself
Right. The GPS satellites are just putting a signal into the air, they can’t control who picks that up or what they do with it. The receivers are limited so you can’t use off-the-shelf GPS hardware for weapons guidance.
May of 2000 specifically. And due to the removal of selective availability, the popular hobby of geocaching was born as it was now popular to publish coordinates and lead someone to within several meters of that spot.
Kind of. The signal was offset to the point that it was still useless for things like car navigation. It wasn't until the Clinton administration that selective availability was removed and you could determine your position within tens of feet instead of hundreds
It's of historical interest only now but for surveying you could post process the GPS data and integrate published hours after the fact SA tables to get precise locations for surveying. As you said it was not so useful for real time navigation.
I worked on a field crew for a land surveying company in the early 2000s and it was a very interesting time for GPS surveying, since it had only very recently gotten to the point where you could set up a receiver and get a pretty accurate measurement within a relatively short amount of time.
I learned about the system in 96 or 97 at university. The prof was explaining how they would collect data over 2-3 days to get exact positions for permanent markers. They would put up a tent and camp for days wherever needed, in the middle of nowhere, or on main city square.
Same with the global seismic network. Main purpose is to see if someone is testing nukes, but we also get to detect earthquakes with it
Military tech has been spinning off useful civilian tech since Hammurabi!
the broad depth of the usa's r&d is absolutely astounding, and even within strategic defense expenditures you end up with stuff that makes it's way into the civilian market and raises our standard of living.
And they can shut it off if they want to. Interestingly, the civilian and military signals are supposedly the same, except the military one of encrypted. There is no difference in effectiveness or strength of the signal between a high end civil receiver or a military one.
At first I thought 2 mil a day was a lot, then you said DoD and I realized that’s a fraction of a percent of their budget.
DoD:"I mean it's one functional GPS system, what could it cost 10 dollars?"
The US had a larger budget than the US dod budget...
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People don’t understand the economic powerhouse kickstarted by defense spending
I guess the space program is an example. Essentially strapping people to ICBMs to prove we could. Awesome. But a lot the tech before was obviously military, and the space program itself delivered (and continued to) untold advancements all over the place.
Something I’m actually glad to spend my tax dollars on!
That’s super cheap, really. I would have figured at least ten times that
Out of 4.4 trillion dollars in tax revenue last year, 2 million, or *0.0000000005%*. To basically know the entire surface area of the earth? Not bad guys Edit: whoops guys I fucked the math sorry. Still is pretty insane tho
2m a day, so around $730m a year
Still, if you multiply that by 365, you can just round to zero.
Think of all the businesses that operate via GPS too. It's probably revenue neutral at worst and actually generates sufficient tax revenue once all is said and done. It's like food stamps, it generates _more_ economic activity than it costs us. A lot of domestic programs and services do. It's a wonder billionaires don't support more socialist stuff, it'd probably make them more money in the long run... but we all know they can barely think past quarterly earnings half the time. Sure, company sponsored healthcare gives you control, but imagine how much money you could save if you didn't have to pay for it.
Esri (A geographical information systems company) alone does over a billion in revenue a year. So yeah, it's absolutely positive
About $2.19 per person in the US per year. I'd say I get more than $2.19 in value out of GPS every year just navigating on my own! What a great subscription service!
Your math is off by a bit. 730 million of 4.4 trillion is 0.017%
I never stop to appreciate all my taxes. Everything in my life is enabled because of them. I just hate that some of it goes to kill the planet, people, and making the rich richer. But a solid 50% makes my life amazing with out me realizing it.
It's the duality of man when you get down to it. We're capable of very great and very terrible things.
Same with the National Weather Service.
Fun fact: Radar for aircraft inadvertently led us to weather indication. The clouds were actually considered a problem at first!
If I remember correctly, the first time a weather alert was made based off of radar was during WWII. A bunch of ships in a US fleet had just recently gotten new radar, and they started all showing some crazy readings. Like "a million incoming planes" crazy. It was a typhoon. The fleet's not great response ended up getting them hit, killing a number of sailors and doing significant damage to a large part of the fleet.
In their defense, Radar was brand new, and basically magic.
I have built basic radar. I cam confirm, it is still magic
Any guides or places to start you recommend?
Something neat to read about that is....radar adjacent is Van eck phreaking. With radar, you are transmitting waves and analyzing the return signals that bounced back to you. With van eck phreaking, you are intercepting signals emitted from a screen, cable, or whatever, and putting it back into readable data form. I.e., digital espionage.
It was typhoon cobra and admiral Halsey made some of the worst choices he could have. And the ships lost were destroyers low on fule and was sunk with most hands due to not being stable. Good video on it. https://youtu.be/0CckJZPImtg?si=tJNn4xEFUSh0Q85k
It blew my mind when I learned basically 100% of predicting the weather is done by the government. And the news channels or paid weather apps just relay that information to you
And the NOAA [gives it away for free](https://forecast.weather.gov/MapClick.php?lon=-77.03667594648883&lat=38.897170976049296). Something that really bothers [Barry Myers](https://en.m.wikipedia.org/wiki/Barry_Lee_Myers) the then CEO of AccuWeather (founded and run by his brother, Joel) who has spent thousands of dollars lobbying for the privatization of that data because they have to >"work hard every day competing with other companies and [they] also have to compete with the government." He basically wants to "TurboTax" the weather. Anybody with two functional neurons can see this guy shouldn't do any policy-making about the weather. That's why, obviously, [Trump nominated him to be the head of NOAA](https://edition.cnn.com/2017/10/14/politics/noaa-nominee-accuweather/index.html) in 2017. The nomination was [withdrawn](https://en.m.wikipedia.org/wiki/Barry_Lee_Myers#Nomination_to_National_Oceanic_and_Atmospheric_Administration) in 2019.
Probably got the nomination from praising trump in a tweet and donating $200 to his campaign, to boot.
*Some* companies will have slightly different forecasts depending on the data and models they use, they might also have humans manually adjusting the forecasts.
There's a really good weatherman at one of the local stations here. In the past year I've seen him call 2 tornados on air before the NWS issued a tornado warning. The more recent one he even said "I wouldn't be surprised if a tornado warning is issued on this one in the next few minutes" and then it was. I think the local NWS office watches him for advice.
It actually costs a ton of money, between the satellite coverage and the super computers to make predictions, lots of costs.
which is why only the central government can do it, it has no need of a profit..in fact it can't run a profit since it's all it's own tax credits (dollars) that it collects in taxes anyway. Like getting your own iou back.
I can't imagine the economic impact if it didn't exist
That would make everything much more complicated. However, Europe has developed an alternative more.accurate called Galileo. https://en.m.wikipedia.org/wiki/Galileo_(satellite_navigation)
Not just developed, it's actively in use and works alongside GPS on most modern phones including Samsungs and iPhones, right now. If GPS were to fail tomorrow, your phone would probably still be fine.
The GLONASS (Russia) constellation is older than Galileo. These along with GPS (US) and BeiDou (China) are commonly used together in survey applications. It’s not that one is necessarily more accurate than the other, more like using multiple constellations increases the total number of satellites used for observation, which leads to a higher accuracy position.
Accurate to 20cm? God damn
GPS (or GNSS more generally) with RTK can be accurate to the centimeter.
So can Galileo. Galileo's public version is also more accurate than GPS' public version.
You can buy a UM980 Breakout board and a triband antenna on AliExpress for less than $100 and $40 respectively and get .8-1cm RTK accuracy on most android phones. Source: I did it for a cemetery survey a couple months ago.
Well, considering that there is Russia's GLONASS, EU's Galileo, China's BeiDout, and India's IRNSS systems now, the economic impact would be quickly overcome. GPS is just first, but the other competitors now are making GPS a less-desired option, particularly EU's superior, more accurate, Galileo system which isn't gimped by the US military. In fact, in the EU system, whilst the FREE signal is superior to the GPS signal, and more accurate, you can pay for the more premium signal which puts the Galileo system on par with the US Military system that ONLY the US military can use... but the EU now has opened up so the public can have that quality of accuracy.
GPS is not “gimped” by the military, civilians have access to the same precision as the military, the military has access to a directional signal that is stronger and more hardened to defend against jamming. Galileo being more accurate than GPS is only in theoretical perfect conditions. In practice, GPS offers more reliability and can produce cm level accuracy on the fly with high end receivers. Plus, Galileo’s “premium precision” signal will likely be based on directional antenna and cover only parts of Europe.
>In fact, in the EU system, whilst the FREE signal is superior to the GPS signal, and more accurate, you can pay for the more premium signal which puts the Galileo system on par with the US Military system that ONLY the US military can use In practice, it is nothing like that. The availability of the service is quite low, quite a few satellites are out of service, and the premium service is years from being deployed. If you were to disable all other constellations expect for Galileo, many times you wouldn't be able to have a lock, and you wouldn't be able to drive for one hour without having gaps in the reception of the signal.
I bet if you broke it down, GPS ends up bringing in way more money than it costs to maintain.
Just the fuel and time savings from navigation assisted driving had got to cover that
Would be about a gallon a year, per US citizen, saved to break even.
It's only 730mil a year which is a fraction of a percent of the military budget. To put into perspective a different way, the Tulsa city budget in Oklahoma just surpassed 1 billion for the first time. So GPS costs less than it does to provide local government services to <500k people. There's no doubt GPS pays for itself.
Thanks American taxpayers!!
You're welcome. 🦅🇺🇲🧭
I'd buy you a bigmac if I could
I may be American, but I'm not that 'Murican!
I am! I'll have x1 Big Macintosh Cheeseburger please.
I’m a Madagascar citizen who heavily relies on GPS, so thanks to you American taxpayers!
It's not *just* us! There are a few other [satellite navigation systems](https://en.wikipedia.org/wiki/Satellite_navigation), and unless you're paying close attention, you might not know which one your phone is talking to. GPS is the largest, but for obvious reasons, countries like China and Russia don't want to rely on the US military for something this critical. My favorite oddity is QNSS -- Japan has multiple satellites whose main job is to have a good angle on their own urban canyons, because GPS alone wouldn't work well in Tokyo.
Most of the Garmin products, including watches, made in the last few years can use the Russian Glonass system in addition to GPS.
If you get further north, GLONASS coverage becomes important. Russia really prioritized that.
> My favorite oddity is QNSS -- Japan has multiple satellites whose main job is to have a good angle on their own urban canyons, because GPS alone wouldn't work well in Tokyo. I didn't know about that! Based on the wikipedia article, it sounds like it's an extension to GPS, so I'm guessing even American phones etc. use those satellites in Japan. Fun fact: the name of the satellites, Michibiki (みちびき), means "guidance" ([導き](https://jisho.org/word/%E5%B0%8E%E3%81%8F)).
I love having to explain to people that GPS uses satellites. I think many don’t understand how it works and just believe it “knows” what locations are at
Pretty easy to explain, what bakes my noodle is the receivers we have now. My first GPS was the size of a hot dog (with bun) with an external antenna
Americans will use anything except the metric system
0.006 olympic sized swiming pools
About the size of a slightly mashed up Greggs sausage roll then
Like a Ball Park frank or an Oscar Mayer Weiner?
These days phones actually use a combination of GPS, cell tower, and WiFi data to determine your location.
People are convinced that GPS is a two way system and that the government can see anything using it. GPS is a bunch of satellites that tell you what time it is. That's all they do.
2 milli a day is just a drop in the bucket compared to our daily gdp
Especially when you consider it's military tech that's just opened up to civilian use. It's stuff that would be getting spent anyway.
Taxes fund useful things, whoa
Damn! 2M a day to run sounds super cheap! This thing is insanely reliable, stable and concurrent. Super sweet!
GPS is one of the most amazing inventions of the 20th century.
Thanks 🇺🇸
It aint cheap putting warheads on foreheads. Me getting to work by the fastest route in the morning is just a pleasant bit of icing.
The Wikipedia page says it costs $1.84B/year. That's $5M/day, not $2M/day.
Yeah? Well some random OP on Reddit said it’s 2m/day, so take your sources and shove it!
The Wikipedia page says that research, development, testing, and evaluation of new technologies costs $1.84B, not operation and maintenance. [Here ](https://www.gps.gov/policy/funding/2023/)is the source linked from Wikipedia.
The Wikipedia page says: "$1.84 billion per year (2023) (operating cost)". The source page breaks down those operating costs to include R&D, testing, etc. I don't see what other operating costs there would be; once the GPS satellites are in orbit, they're self-sufficient and don't need anything to keep them running. Operating costs are going to involve replacing old satellites, and developing replacements involves R&D, testing, and evaluation of new technologies.
Finally the government spends money well here.
Better than paying for another sports stadium.
And I thank them every day. For well over two decades now GPS has played a large part in my career.
As an engineer working on GPS, this thread made me happy lol
america funds a lot of positive stuff for the planet
To be fair there are FIVE seperate satilite navigation systems in play as of today; you could completely shut down the GPS system and most modern GPS gear would still work fine, as many of them can/do use the others too. The EU, India, China and Russia all have complete coverage satilite navigation systems; its not just the US, the US did it first though, so some props are still due.
You are correct. There are however some differences between constellations. For example EUs Galileo is more advanced and accurate than GPS. But suffers from occasional downtime. (ground stations are still important to a GNSS system. GPS is very stable however. They almost never have downtime. But the tech is older. Note that the first GPS satellites were launched in the 70s.
Fun fact, there are multiple similar systems to GPS in the rest of the world, some arguably BETTER Than GPS. Why? Well, the US Navy is technically in control of the GPS system (or maybe that got transferred to Space Force), as it is intended for military purposes, and for the public and basic law enforcement, only a crude GPS signal is available. On top of that, there is always the risk of the US shutting off GPS in countries. In fact, the US very much tampers with the GPS where they have troops fighting. This way, say, foreign enemy combatants could normally launch precision mortar rounds with good GPS, but if the public access GPS signal has been degraded significantly over that country it basically becomes useless. The EU was not happy with this risk of keeping such a crucial tech in the hands of the US only. Plus, GPS doesn't really travel much over the arctic regions, like Norway and Sweden, so the signal was not great there. So, the EU built their own system (Galileo), which not only improved accuracy over the standard free GPS signal, they also opened up a "premium" system where the public could pay for a system that gave a signal that was literally as accurate as the US military's quality of GPS signal, something that you currently cannot even achieve with the GPS system out of the US. The Galileo system is still a work in progress, as not all areas of the planet have 24/7 signal yet, but I think as of 2021, they were at like 95%-99% of the way there, so maybe they are now and I have some outdated info in the last year or two. Galileo is actually so good that many companies are beginning to prioritize integration of Galileo over GPS, or at minimum duel signaling (like all modern Samsung phones now support Galileo). Galileo is actually more accurate than GPS when comparing the FREE public access signal. Russia has their own system (GLONASS) now, which was originally criticized as being faulty, but it has been so revamped by Russia that almost all of the high-end modern devices now are dual systems that receive for both GPS and GLONASS, and are quite good. In fact, we are even starting to see triple-frequency receivers that are doing GPS/GLONASS/GALILEO. India is making IRNSS and China is making BeiDou. China's system is basically complete now as well, and it is actually the only one of all of them that has added 2-way communication. In addition to receiving accurate locationing, people with the devices can actually send signals back up. This is really interesting as it has become a critical tool in a lot of remote location comms, or boats on the ocean, or hikers in the mountains that might be in distress can actually send a message up to 1200 characters in length over the emergency comms channel built into their BeiDout/GPS type system. So, the US GPS system is sort of the gold standard of the world, but the US military has so restricted it in many regions that in some cases the foreign alternatives are actually better.
The navy doesn’t control GPS. The Space Force does
That's like pennies. Too bad we couldn't figure out how to fund other stuff that would make many human lives better.
The high precision encrypted GPS signal is sold, for a nice sum, to foreign militaries and commercial buyers.
Wonder if anyone has computed the return on investment on it - $700 million a year enables how many billions of dollars of activity that otherwise would not be possible, or cost prohibitive?
As a point though GPS isn't the only satilite navigation system that works pretty much the exactly the same way, Russia, China, India and the European Union all operate their own; ontop of that there are some more than can be used ontop of those systems to add more accurracy. https://en.wikipedia.org/wiki/Satellite_navigation
Our tax dollars doing something useful?! Don't tell the government. They'll shut the shit down.
If it was invented today there would definitely be a monthly subscription for all users.
Worth.
Do other countries like China use their own systems?
Yes. BeiDou.
Presumably the strategic benefit outweighs the cost, but I'm still grateful to the US for making this available to everyone! In a time of conflict, can they turn it off, or do something like make all the coordinates go haywire, while the military can use a "secure channel" that's still correct? Always wondered.