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38

GPS satellites - almost all satellites, really - need to have the capacity to be remotely "disabled" as part of their end-of-life protocol. Satellites degrade over time like all things do (especially things exposed to the orbital environment) and they're also steadily rendered obsolete. To avoid old satellites cluttering up the most useful orbits and ...


17

This is from the Wikipedia entry for GPS, regarding its control segment: The flight paths of the satellites are tracked by dedicated U.S. Air Force monitoring stations in Hawaii, Kwajalein Atoll, Ascension Island, Diego Garcia, Colorado Springs, Colorado and Cape Canaveral, along with shared NGA monitor stations operated in England, Argentina, Ecuador, ...


16

Global positioning is not dependent on geosynchronous orbit - as covered in the wikipedia article: Orbiting at an altitude of approximately 20,200 km (12,600 mi); orbital radius of approximately 26,600 km (16,500 mi), each SV makes two complete orbits each sidereal day, repeating the same ground track each day. As illustrated in the excellent animation ...


10

Realistically, they'd use multiple factors. Deriving location from multiple independent sources is always better than any single solution however neat. Some suggestions: GPS Practically free, so there is absolutely no reason to use it. Celltowers and Wifi Gives independent verification that the phone is in the area reported by the GPS. Mesh networking ...


9

Our GPS system isn't based on geosynchronous orbit, only on knowing the orbits of the satellites with a high level of precision. Consider this illustration, which demonstrates multiple different orbits on different planes (none equatorial, it would seem); geosynchronous orbit is only possible on the equatorial plane. (Edit: As pointed out in the comments, ...


7

GPS transmissions come to Earth very attenuated, and hence are very sensitive to jamming (radio blabbering) and spoofing (fake messages impersonating sattelites). A radio station switched to the appropriate frequency would deny a large area. The catch is that it automatically broadcasts the jamming source location. A missile could literally lock on to the ...


7

National power grids are likely to go down within hours if their monitoring stations are abandoned; the exact number of hours will vary from country to country. Rooftop solar panels that are connected to the grid will automatically cut off if the grid goes (as a safeguard for people working on the line), but some systems can be switched to power an off-grid ...


6

Also in addition to the aforementioned DoD stations, we were past the expected lifetime of our GPS satellites. But, in 2014 we put some more back in space. At some point those satellites will come down. One of those has lasted like 23 years, which is a bit past it's 7.5 year design lifespan. http://www.space.com/24767-gps-satellite-launch-success-delta4-...


6

'GPS' in the form of radio beacons was available long before satellite GPS. Even if you cleared the orbits, if someone really wanted an area to be navigable with GPS they'd just need to set up radio beacons at high points around the perimeter. An area could not yet be covered by such beacons but it wouldn't prevent someone setting them up if needed. The ...


6

Communications and GPS must either both or neither be present First off, you imply that you want communication satellites to be possible, but not GPS satellites. This is simply impossible. Communications satellites and their ground stations depend on GPS in order to operate. A ground station must know its exact GPS coordinates in order to meet its timing ...


5

"Maybe": GPS, and the other services, satellites contain communications and state control interfaces because they are designed to be able to be controlled from ground stations. One of the key functionalities of those state controls are what level of encryption is used to broadcast their signals - the US's GPS is first and foremost a military service, that ...


5

Certainly -- if you're the United States Government. They temporarily turned off the "dithering" of the system at various times (including during the first Gulf War, due to shortage of mil-spec GPS devices) and did so permanently in the late 1990s (I don't recall the exact year, and it doesn't really matter here). They could, in theory, turn it back on at ...


5

If the Kessler Effect were to happen tomorrow, we could easily replace the GPS satellites by the mobile phone towers. GPS systems already uses the higher degree of accuracy of phone towers to pinpoint precise location in a city. Of course, that would work only wherever there is such a tower, thus the scientists doing field research and tagging animals in ...


4

Have a look at aviation beacons from the pre-GPS era. Look at NDB's and VOR's. There was even older technology, Omega, (https://en.wikipedia.org/wiki/Omega_%28navigation_system%29). Have few of these land-based systems, and then triangulate their signals to obtain your position.


3

All GPS satellites have two-way ground communications, they need semi-continuous (the longest maximum no check-in time is measured in months) ground telemetry updates. You wouldn't need to hack the satellites, individually or collectively, you'd just need to corrupt that data and crash everything. By which I mean literally crash it, hot metal falling from ...


3

Cheap and compact handheld GPS receivers depend on the reception of signals. As Separatrix pointed out, there have been ground transmitters for similar systems. Interfere with radio reception in general. That would also limit smartphones. A lifeform with natural radio transmitters and receivers? Or simply "electric eels" producing static? The moon suffered ...


1

Okay, so they can in theory be hacked. That's already been explored enough there is no need to delve any deeper, but they are one of the world's most secure networks because they are intrinsically so simple. They only need to accept a few commands such that securing all of your vectors of attack is much easier than most systems you'll otherwise encounter. ...


1

Watch them. https://www.pinterest.co.uk/pin/313563192797507356/ A time tested way to keep track of another person: have someone watch that person. A watcher who is good at seeing and not being seen. If this is for a fiction, it would be a great way to inject the story with a contrasting human energy that has deep roots in pretech thrillers.


1

You need multiple systems. Firstly, for location spoofing, you could use a combination of the GPS and radio location systems already discussed. If they disagree, they go with whatever's considered more accurate for that specific case. It's a lot harder to spoof two systems than one. You could roll this into other methods - occasional NFC/RFID tags to be ...


1

I left a comment to another answer but then it was starting to turn into an answer. So I'm copying it here and continuing the thread: Using only the phone, you won't be able to tell whether it is a real person holding the phone or it is fastened to a drone that moves around in the city and the player is sitting home and operating their phone remotely. Maybe ...


1

Radio direction finding from cell towers. That's how the police could triangulate on phones before GPS became ubiquitous. Two not-big-deal issues: The cell phone companies would need to be involved. Real-line RDF isn't as near as accurate as GPS. Many towers and technobabble would make it very accurate. https://en.wikipedia.org/wiki/...


1

Realistically, any civilization capable of colonizing another planet will blanket its orbits with satellites first. Satellite imaging and communication will simply be too important for maintaining a developing colony, especially if contact with the home world is valued. GPS would absolutely be one of the vital services provided by the satellite arrays any ...


1

GPS satellites need to have their known positions and clocks calibrated from time to time, otherwise these could drift. Once a satellite has a wrong reading, it will disrupt all readings that involve its usage. On real Earth, this calibration is done by the 2nd Space Operation Squadron. In your world, central command may have lost access to the satellites, ...


1

This is not a physical explanation not to have GPS but how about an economical? The company who won the tender for setting up the satellites went bankrupt and the contract is tied up in lengthy legal battles surrounding the bankruptcy and until they are done, no one else can just go and establish a system for legal reasons.


1

hmm, why does it need to be impossible/unfeasible? So you want a planet without GPS but with maps? Possible solutions: There is GPS but it is military use only. (Because some countries fight at the moment or have a cold war) GPS is too expansive too install when they just make some photos from orbit and have a program make a map. GPS on that world can ...


1

It is hard to find stable orbits around our own moon. Low altitude orbits are unstable due to uneven distribution of mass within the moon ("lunar mascons"). High altitude orbits are unstable due to interference of earth's gravity. It is possible to find stable orbits, but I'm not sure if it would be possible to create a constellation of satellites such as ...


1

All thought not GPS until the Mid 2010s the US maintained Loran-C. I have used it on a couple of boats back in the late 1980s before we had access to GPS. It was not as accurate as GPS but it used huge ground based antennas and allowed you to use a FANCY box to find your current lat long and then plot the course you wanted. I remember a US Coast Guard ...


1

There is nothing stopping satellites from giving your GPS coordinates even if they aren't Geostationary, the only problem is that satellites that aren't geosynchronous will move away from you and be unable to communicate to you when they rotate away from above your location. The solution is a network of satellites that cover the whole planet and all share ...


1

As mentioned, cell phones towers work from the power grid and to be able to call someone it takes two working towers (assuming there is some range between the phones) and an infrastructure (network) in between, all requiring power. That infrastructure might be on different power networks and if one fails you can't connect. Power (Electricity) itself is ...


1

To the best of my knowledge, GPS would work for a while as long as what devastated society didn't break them, (such as a massive solar flare). Assuming they were working then they should continue to work for the rest of their lifespan, it appears their life expectancy is about 7.5 years. So it would continue to work for several years without much help. On ...


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