If a large part of the population was killed, but the infrastructure was basically unharmed (I know it take people to keep things going, but I guess that is part of the question), how long would I still be able to use my GPS? How long would communication satellites still send and receive data? What other satellites would be useful to a world where the technology is not destroyed, just declining? How long would such technology work? If I have solar power and can run my laptop and phone, how long until the supporting technologies collapses? Hours, Days, Weeks, months... Thanks - LWR
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 socket instead, in which case they should continue to work until the inverter breaks down (10-15 years) although the amount generated depends on the light. If a spare inverter can be found (or if someone knows how to repair the inverter) then the next limit will be the panels themselves: after 30 years they will be producing noticeably less power. The gadgets that you run with this power (light bulbs, heaters etc) will also need maintenance and/or replacement during this time.
The UK and USA landline phone systems are supposed to have enough battery backup to last 1 week without the power grid (although I don't think this has had a large-scale test). Only traditional wired phones will benefit, not cordless phones, and only voice calls will benefit, not broadband. If you pick up the phone and hear nothing, you should check for a circuit (blow in the microphone and see if it amplifies) and if so then wait a while because you may be in a queue to get a dial tone.
US cellphone towers have been known to cut out just hours after grid loss in a severe storm. UK mobile base-stations are not required to have backup power at all, but the UK government does recommend 1 hour of backup power in a base station and backup generators in switching centres, especially after the Tetra project to let emergency services use the same masts on a different frequency.
Data centres protected by UPS units can last anything from 5 minutes to 2 days without power, depending on how good a UPS system they've installed. Diesel standby generators come with 24, 48 or 72-hour fuel tanks. (They can last longer if someone is still around to refuel it and fuel is available, but faults are possible.) Thus an abandoned data centre would last anything from 5 minutes to 6 days without power, depending on how good it is.
For "the Internet" to work, you'll need the server you're trying to contact to be up and a route of still-working switches etc to get you there. Probably the first one to fail will be your local one (within hours of grid failure at best, possibly minutes or nothing), but if you can somehow get to a working data centre with good backup power then you might be able to use "the Internet" for anything up to 6 days although during that time you will see sites going down one by one (mostly on the first day) and speeds slowing to a crawl as the remaining routers are forced to map out strange ways of getting your packets to their destination.
GPS and similar systems may last many years, but without ground support they are likely to lose accuracy after 6 months (this can be corrected for if you're skilled) and after a few years it will become harder to get a GPS fix as the satellites break down one by one. Once the Internet is down, systems that use Assisted GPS (aGPS) will no longer be able to download their ephemeris data and will therefore start taking much longer to get a GPS fix than you might previously have been used to.
Vehicles are not likely to last more than a few years without maintenance, and in any event require fuel, which you will have to obtain without the use of electric pumps.
Amateur radio should work indefinitely if the equipment can be powered and maintained.
Municipal water services are not likely to be able to keep up water pressure in supply pipes for more than a few days at best. After that there will be no running water from mains taps. Old houses with header-tanks will still be able to use their header tanks, typically 40 gallons or so although it's not the nicest water. After that you will either have to collect rainwater, find a well, or (most likely) use supplies of bottled water from shops and warehouses. Toilets can be flushed once per toilet and after that you can fill them with rainwater etc, but a rather unpleasant thought is what happens to the sewage systems when the pumps stop working: depending on how the town/city is plumbed, sewage might start to back up into ground-floor toilets and/or manhole covers. But this is likely to affect only the places with the lowest altitude in town, and anyway it will not happen for some time if the amount of sewage is reduced due to fewer people being alive to generate it. Nevertheless if I knew a sewer is not maintained I would seek places to bury waste instead.
Natural gas usually needs to be pumped, and is usually pumped by electricity. If the pumps stop, there should still be some pressure already in the gas line, which can normally last a few days and probably much longer if very few people are around to use it. Most gas boilers and central heating systems (called "furnaces" in the USA) also need electricity and will shut down without it, but small self-contained gas heaters and cookers can continue to work as long as there is pressure in the pipe (and there will be pressure in the pipe for longer if all the larger heating systems cut off). Additionally, there are a few gas pumping stations that are powered by burning the gas itself, plus there just might be a few places that are close enough to the gas wellhead to still get some pressure from the natural wellhead, and in these exceptional places it is possible that gas could last for a few more months, but eventually the wellhead will stop working due to cold weather or something if nobody is there to adjust things.
Once survivors have organised themselves into a big enough society, they might wish to try and bring the power grid back online, which should be possible via black-start procedures but it will require knowledge and some of the equipment will require maintenance. On the other hand they might decide not to bother and just run their own micro-generation, or do something else entirely.
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.
So, in the near future we've got at least 5 backup satellites (but probably need a ground control station to turn them on), and a bunch in orbit - which will probably last a good decade or three.
You might be able to hack your GPS so that you can fix the inaccuracies that you're being fed by the satellites. You'd probably need to get a GPS location for a landmark, then see how much it varies from what the satellites are telling you now.
Cellphones will go down as soon as the cell towers run out of backup fuel (after the electrical grid goes down), if not sooner (network switching death). Of course most people will have run down their cellphones, searching for bars, by that time. If you've got spare power to charge your cellphone, why don't you adopt a tower? ;)
I'm also surprised that the US isn't charging the rest of the world to use our GPS system.
Russia has GLONASS (in orbit), China has Beidou/Compass (in orbit, covers China now - global by 2017/2020) and the EU has GALILEO (in orbit) each at varying stages of development or testing.
Differential GPS (DGPS) can obtain a much higher accuracy. DGPS requires an additional receiver fixed at a known location nearby. Observations made by the stationary receiver are used to correct positions recorded by the roving units, producing an accuracy greater than 1 meter.
Almanac data is one of three types of data that GPS satellites broadcast, it describes the orbital courses of the satellites. Every satellite broadcasts almanac data for EVERY satellite. A GPS receiver uses this data to determine which satellites it expects to see. A unit determines which satellites it should track from those that should be available. With Almanac data the receiver can concentrate on those satellites it should be able to see and forget about those that would be over the horizon and out of view. Almanac data is not precise and can be valid for many months.
The design life and mean-mission duration goals of the Block IIA, IIR, and IIF satellites are 7.5 and 6 years, 10 and 7.5 years, and 12 and 9.9 years, respectively.
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 average then they would have about 3.5 years left and as more and more die, the GPS would be more and more difficult to get a fix.
Cell phones on the other hand depend first and foremost on the power grid, and if that ain't working they ain't working. Satellite phones will do better, but since I don't think they directly connect peer to peer, they might not last much longer than cell phones. Walkie-talkies and shortwave are going to be the modes of communication without infrastructure. Some cities with enough people might be able to keep somethings going but it will be spotty at best between cites.
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 generated by power plants and those need to be actively restocked and maintained to stay operational. The networks themselves need to be managed too. All that is a lot of chances to fail somewhere, taking your phone call with it. I would give it a day or two before you can't make your calls anymore. If you plan on ending civilization i'd opt for the good old long wave radio for a means of communication.
GSM is a broadcast only system where all your GSM device needs to do is receive the signals and triangulate your position, so that suggest it will work as long as the satellites do. However that's not true. Due to various reasons satellites drift (gravitational waves by celestial objects for instance) a bit and that drift has to be actively compensated continuously, as it's done by the US military. If that stops then GPS will become imprecise very fast to the point it's unusable.
Comm satellites themselves will work for a long while but unless you also got the access technology up and running that won't do much good, unless, maybe you use a satellite phone to call another satellite phone (though I'm not sure that won't still go through a ground station).