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Most phones use Assisted GPS. It's a combination of cell tower triangulation and GPS. You'll get a potentially inaccurate "GPS" location based on the cell tower
by kiallmacinnes 7y ago
Most phones use Assisted GPS. It's a combination of cell tower triangulation and GPS. You'll get a potentially inaccurate "GPS" location based on the cell towers and signals you can see, and this will eventually turn into a real GPS lock.
As I understand it, this cell tower location actually helps achieve a real GPS location faster that would be normal - but I'm unsure how that would work .. I'd be guessing at best ;)
- int_19h 7y agoAs I understand it, roughly knowing your position lets it get a lock on enough satellites faster, because, given position and time, it knows where they're supposed to be. http://gpsinformation.net/main/gpslock.htm http://gpsinformation.net/main/gpslock.htm Also, I believe that part of the reason why Google wants that SSID info is because they can later use it for location purposes as well, making that initial position determination more accurate than with just the cell towers alone. In general, the more environmental data they can correlate with accurate GPS coordinates, the better they can predict location when GPS is unavailable.
- drivebycomment 7y agoFor non-assisted GPS, the GPS device needs to download orbital information from the satellite directly when first powered on - with only ~50 bits/s of bandwidth, it can take a while - minutes to tens of minutes. With Assisted GPS, the GPS device can download the satellite orbital information and almanac directly from AGPS server (e.g. cell phone tower), usually at much higher bandwidth - as those local, always-running servers can constantly download and cache all satellite information.
- lucb1e 7y agoThe sats don't change orbit every few hours though, also without AGPS you usually can use the ephemerides from last time you used it. This is fun to observe when you buy a new phone and don't connect network yet, it takes a good while to find any satellites and finally find a fix. Then after cycling GPS, it finds it almost instantly.
- j1elo 7y agoThen how do the classic driving GPS devices work? I'm thinking here good old TomTom models, mine must have like what, 10 years? It typically claimed (not using it much lately) to have GPS reception after maybe 20 or 30 seconds since power up. I believe it cached the position of the GPS satellites, or something similar... could that be it?
- lucb1e 7y agoNo, that involve sending data to Google (one of the reasons I mentioned turning all that crap off), or a relatively complex config to swap out the location provider for Mozilla's which I haven't done yet on this phone.