Considering how integral it is to our modern way of life, you could be excused for thinking that the Global Positioning System (GPS) is a product of the smartphone era. But the first satellites actually came online back in 1978, although the system didn’t reach full operational status until April of 1995. While none of the active GPS satellites currently in orbit are quite that old, several of them were launched in the early 2000s — and despite a few tweaks and upgrades, their core technology isn’t far removed from their 1990s era predecessors.
But in the coming years, that’s finally going to change. Just last week, the tenth GPS III satellite was placed in orbit by a SpaceX Falcon 9 rocket. Once it’s properly configured and operational, it will join its peers to form the first complete “block” of third-generation GPS satellites. Over the next decade, as many as 22 revised GPS III satellites are slated to take their position over the Earth, eventually replacing all of the aging satellites that billions of people currently rely on.
So what new capabilities do these third-generation GPS satellites offer, and why has it taken so long to implement needed upgrades in such a critical system?
GPS Is Good, But Could Be Better
To understand the future of GPS, it’s helpful to look at its past. Developed by the United States military during the Cold War, what we now call GPS was originally known as Navigation System with Timing and Ranging (NAVSTAR). While the intent was always to allow civilian use of NAVSTAR, the equipment necessary to receive the signal and get a position was cumbersome and expensive.
There was little public interest in the system until Korean Air Lines Flight 007 was shot down in 1983 after mistakenly entering the Soviet Union’s airspace. With the lifesaving potential of NAVSTAR clearly evident, pressure started building on the industry to develop smaller and more affordable receivers — GPS as we know it was born.
That the development of such devices was possible in the first place was thanks to the design of NAVSTAR. Each satellite in the constellation broadcasts a timed radio signal which receivers on the ground use to compute their distance from the source. By comparing the signals from multiple satellites, a receiver can plot its position without the need for any local infrastructure. Since the process is entirely one-way, it could be freely used by any device that can receive and decode the signal.
But while this operational simplicity was key to the proliferation of cheap ubiquitous GPS receivers, there’s certainly room for improvement given more modern technology. When NAVSTAR was designed knowing where a receiver was located within a radius of a few meters was more than sufficient, but today there’s a demand for greater accuracy by both civilian and military users. Given the essentially incalculable value of GPS to the global economy, improving reliability is also paramount. Not only has GPS jamming and spoofing become trivial, but even without the involvement of bad actors, legacy GPS struggles in urban environments.
Plans to deliver improved performance in these areas have been in the works for decades, with the United States Congress first authorizing the work on what would become GPS III all the way back in 2000. But when working on a system so critical that even a few minutes of downtime could put the entire planet into turmoil, such changes don’t come easy.
Can You Hear Me Now?
While modern GPS receivers are more sensitive than those in the past, there’s simply no getting over the fact that signals coming from a satellite more than 20,000 kilometers away will be by their very nature weak. So not only is it relatively easy for adverse environmental conditions to block or hinder the signal, but it doesn’t take much to override the signal with a local transmitter if somebody is looking to cause trouble.
As such, one of the key goals of the GPS III program was to deliver higher transmission power. This will lead to better reception for all GPS users across the board, but the new satellites also offer some special modes that offer even greater performance.
In addition to the backwards compatible signals transmitted by GPS III satellites, there’s also a new “Safety of Life” signal. This signal is transmitted at a different frequency, 1176 MHz, and at a higher power, so compatible receivers should hear it come in at approximately 3 dB above the “classic” signal. It’s intended primarily for high-performance applications such as aviation, but as compatible receivers get cheaper, it will start to show up in more devices.
These improvements should be enough for civilian use, but the military has higher expectations and operates under more challenging conditions. In such cases, future GPS III satellites will come equipped with a high-gain directional antenna that can project a “spot beam” signal anywhere on Earth. For receivers located within the beam, which is estimated to be a few hundred kilometers in diameter, the received signal from the satellite will be boosted by up to 20 dB. In contested environments, this should make it far more resistant to jamming and spoofing.
Speaking New Languages
The new signals being transmitted by GPS III satellites won’t just be louder than their predecessors, they’ll gain some new features as well.
For one thing, GPS III satellites will transmit a standardized signal known as L1C which offers interoperability with other global navigation systems such as Europe’s Galileo, China’s BeiDou, the Indian Regional Navigation Satellite System (IRNSS), and Japan’s Quasi-Zenith Satellite System. In theory a compatible receiver will be able to process signals from any combination of these systems simultaneously, improving overall performance.
The new satellites will also support the L2C signal. While this signal was technically available on earlier generation satellites, it’s still not considered fully operational and its adoption is expected to accelerate as more GPS III satellites come online. Compared with the legacy GPS protocol, L2C offers improved faster acquisition of signal, better error correction, and a more capable packet format.
To make GPS III transmissions even more secure, the military is also getting their own signal known as M-code. As you might expect, little is publicly known about M-code currently, but it’s a safe bet that it utilizes encryption and other features to make it more difficult for adversaries to create spoofed transmissions. For what it’s worth, a recent press release from the US Space Force claims that the use of M-code makes the next-generation GPS satellites “three-times more accurate and eight times more resistant to jamming than the previous constellation.”
Testing Out New Toys
Although all ten GPS III satellites are now in orbit, that doesn’t mean the constellation is complete. Starting in 2027, a new fleet of revised satellites known as GPS IIIF will start launching. They will take the lessons learned from the initial GPS III deployment to create a smaller, lighter, and more efficient platform that should have a service life of at least 15 years.
They’ll also include new in-development equipment that wasn’t quite ready for deployment when the current GPS III satellites were being assembled. This includes optical reflectors that will allow ground stations to more accurately track the position of each satellite, laser data links that provide high-speed communication between satellites, and an improved atomic clock known as the Digital Rubidium Atomic Frequency Standard (DRAFS).
Of course, the vast majority of the people who use GPS every day will never be aware of all the changes and improvements happening behind the scenes. When they get a new phone with a GPS III-compatible receiver, they may notice that their navigation app locks on a bit faster or that the position shown on the screen is a little closer to where they are actually standing, but only if they are particularly attentive. But that’s entirely by design — the most important aspect of implementing GPS III is making the whole process as invisible as possible.
“can could” to signal could and “can can” to that can.
I still suspect some sort of steganography.
We doin’ the Can Can in this one.
The fix is in the can!
More power and it can send signals compatible with other GNSS systems systems. I got it: Signal spoofing on steroids in those hotspots.
Does it really matter. As we learned during the Shuttle Columbia accident, commercially available GPS units are dumbed down, less accurate. They only wanted the government GPS units to map the locations of debris.
Could it be possible for a country to build a local gps based on 3 geostationary satellites?
Yarr matey. LORAN might be what you be looking for. Satelites might be something only big rich countries can do, and have done, where LORAN you just need some radio towers. Might even be amateur level with deuce tech. Couple hundred feet accuracy is good enough to keep you off the rocks, need closer, and use your eyes. Look into what got Amelia Airheart lost, she be using ships broadcasting along her path to find her way. Or go old school, and use what the universe gave us, and a sextant. A smell phone could be used as a sextant recognizing the stars, it’s angles and whatnot, and doing the computation, but, might as well just use the gypsy. Those fake stars are everywhere. yarr.
You can also do the triangulation based on cell towers and wifi acess points, that’s what location services on smartphones do to speed up the GPS lock, and on computers without such a signal.
Big LORAN-C fan
Akshualy, there’s that project and the space for a human could also fit a 2. stage/launcher, to put a vew cubesats in 200 km, no? If not, maybe next iteration.
edit: But yeah, then also a atomic clock, or some other hack, to keep it sufficiently exact. So maybe no hobbyist GPS for a while.
Rubidium time bases do pop up from time to time on ebay. Getting them in a satellite might be a challenge though.
You need satellites at different inclinations to get North/South position. I suppose you could have inclined geostationary orbits, there would be accuracy issues, especially when two are at the same latitude.
Also, you would need at least four to use a time based method like GPS does. (you are solving equations for values that represent latitude, longitude, altitude, and time.
“I suppose you could have inclined geostationary orbits”
By definition, you cannot have inclined geostationary orbits. You can have inclined geosynchronous orbits, but geostationary orbits are defined as geosynchronous with an inclination of zero.
GPS relies of Doppler Effect and precise timing for geolocation. Therefore a satellite needs to have apparent movement (and be pretty low besides)
Wouldn’t that be called LPS?
“Could it be possible for a country to build a local gps based on 3 geostationary satellites?”
As others mentioned you can’t do it with geostationary satellites since they’re (by definition) coplanar. There are regional positioning satellites, though: Japan has the QZSS system, which is a 5-satellite system with 2 geostationary and 3 sharing a Tundra orbit. So yes, countries obviously can build local positioning systems.
Cruise missile tech is likely what helped give us smartphones. GPS was for guidance ordnance.
https://www.gpsworld.com/from-we-dont-need-it-to-we-cant-live-without-it/
Space advocates were mistreated by the defense community:
https://www.thespacereview.com/article/2966/1
Don’t let anyone tell you we don’t need Space Force.
It is the USAF that needs to die:
https://www.amazon.com/Grounded-Abolishing-Studies-Conflict-Diplomacy/dp/0813165571
USN also needs a haircut
https://www.usni.org/magazines/proceedings/2011/may/twilight-uperfluous-carrier
Ironically, submariners kept the peace by not firing.
Fighter Jocks get most of the defense budget….and destabilize things:
https://phys.org/news/2026-04-conventional-weapons-mass-violence.html
And Hormuz shows they aren’t worth their pay.
https://www.reddit.com/r/aviation/comments/1elmwv3/why_did_the_us_perform_so_poorly_in_vietnam/
GREAT stuff, Jeff!
Of course optimum solutions too often conflict with MONEY and powerful, ingrained power structures, so don’t count on any of that happening.
If your GPS signal suddenly jumps up by 20db, run away…
Different frequencies for citizen science.
My nephew is a surveyor, and he has a $40,000 GPS receiver. It receives the US GPS, Russian Glonass, Chinese Beidu, and Europe’s Galileo. It also picks up on TV and FM radio towers (and cell towers, but for whatever reason the TV and FM is better). It’s accurate to under a centimeter in longitude, latitude, and altitude. And he can place 2 additional transmitters on known survey markers and it becomes accurate to under a millimeter. It’s on the top of a tall staff, with a button on the bottom. He just walks around tapping it on the ground and it records the coordinates. Doesn’t even have to hold it straight up, it compensates for the angle. Even works in water up to the depth of the height of the staff (as long as the head remains above the surface).
On some of the construction sites the bulldozers are equipped with a similar system that precisely sets the position of the blade as the driver simply goes back and forth.
Friggin’ amazing!
You can also get nearly that same precision for far less than $40,000. The Sparkfun kit is rated down to 18mm for only $600. That’s also about the same accuracy as my robotic lawnmower
https://www.sparkfun.com/sparkfun-rtk-surveying-kit.html
Oh yes, the ZED-F9P from u-blox!
Welcome to RTK positioning and machine control.
Agriculture and construction including crop dusting, dirt work and site layout.
mm accuracy when you can get a good base station setup or work in a lps total station.
Btw, you can now pay for service to a fixed base station for position corrections and do all the work you described but with only a SIM card with internet access. Saves the frustration of someone stealing the base station when you walk away from it to survey.
“Service might not be available in your area. Contact us to get a quote for our position correction subscription service. This aint a socialist country”
Let’ not forget that GPS allows access to highly accurate clock signals, and there’s a number of such modules on the surplus market that are easy to interface.
As an example, search for “Trimble GPS Receiver 46240-25” on eBay. Standard serial port interface, with a 1 Hz clock accurate to about 50 nS. (You will need a powered antenna, also available for thin money.) Paired with a free running clock/counter register on a micro, this allows a hacker to make very accurate timestamps of events.
Much of the inaccuracy of GPS is due to differences in the speed of light in the atmosphere due to varying moisture content. The more signals you receive, the better accuracy you can get. Also, the longer you receive the signals, the better accuracy. Older survey equipment would take several minutes to get that accuracy, but today it’s much quicker.
And as mentioned, to combat the inaccuracies you can take into account cell tower and wifi measurements.
(I was once hired to drive around every road in Boston with a bespoke receiver for exactly that reason. Go down at night with a map and cross off all the streets one-by-one.)
So yeah – using a GPS receiver in your project is totally doable.
“Paired with a free running clock/counter register on a micro, this allows a hacker to make very accurate timestamps of events.”
Plenty of GPS units have a time marking input (sometimes called a photoshutter interface, since the idea was precision tagging of a camera’s shutter) so you don’t really need anything. From what I’ve seen they’re more like 100 ns-ish, though. GPS timing can be weird, though so it’s worth studying each one you get. Older ones especially ended up with device-specific static phase offsets which translated into fixed receiver-to-receiver time offsets of around +/-50 ns.
And if you’re really looking for accuracy at that level, you either want one with time-RAIM capability or the ability to postprocess and filter the timing yourself (and a good local clock). Satellite time solutions can jump a lot in poor viewing conditions.
As I remember it, GPS was originally designed to mask the exact positioning unless you had the military’s key to decrypt the low bits, for fear of it being used as a precision guidance system. Then the military had sudden need of a large number of GPS receivers, and solved their problem by buying commercial units and turning that mask off… and the improved precision proved commercially valuable enough that they have left it that way. The fact that, even with the masking, one additional ground transmitter at a known location permitted surprisingly precise location determination even with the injected error may have been part of that decision.
So the sudden improvement in commercial GPS accuracy wasn’t less a matter of new technology as a simple decision.
(My favorite experience with an early automotive GPS was trying to use it in the concrete canyons of NYC, with multipath signal reflection causing it to believe we were driving in the river. I also remember the backpack rig Bob (“Ribo”) Flaven created with a GPS receiver hooked to a portable computer to precisely survey hiking trails; I wouldn’t be surprised if he was the first to do so.)
Mostly. There were other ways to get around selective availability (SA), and by 2000 (when it was turned off), it was essentially pointless. It wasn’t exactly a precision guidance system worry – it was just a “we don’t want it to work as well for our enemies” thing (hence the name – the system was available for those the military selected). And because another military had ways to get around SA, all it was doing was limiting civil/commercial benefits anyway. As a note GPS III satellites don’t even have the capability for SA, so it’s now permanently gone.
But SA was gone back in 2000, and GPS still wasn’t nearly as good as it is now, so that wasn’t the whole story. The biggest improvement is just in processing capability (both signal and post) and in the signals that the satellites transmit. Receivers back in 2000 were usually 8-channel receivers, running at like, 10-25 MHz, and utilizing only the L1 C/A codes.
The article mentioned the L2C and L5 (here they call it ‘Safety of Life’ or whatever – it’s just L5 in like, every manual and datasheet I’ve ever read) – even though as the GPS III satellites come online, those signals will move to ‘healthy’, GPSes have been decoding and using those signals for years anyway.
I have an old Garmin GPSMap 76CS. Garmin doesn’t support it anymore.
They want to sell you a new unit. I also have a Garmin Nuvi that’s several years old.
It’s kind of sad that Garmin won’t support the old 76CS anymore, but I don’t know what
to replace it with. Anyone have any suggestions?
Get a model with LM in the model number. Those are the lifetime maps versions. They still work fine. Or just download new maps from open maps and copy to your device