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I often travel internationally (with no data roaming) and I've noticed that the iPhone's A-GPS is incapable of determining my location when I arrive in a new p

I often travel internationally (with no data roaming) and I've noticed that the iPhone's A-GPS is incapable of determining my location when I arrive in a new place, even if I've pre-loaded my route/maps in the maps application prior to arrival. But once I've connected to the internet - even for a few seconds - my phone is permanently able to track itself in that city, even after I've left and returned months later. It's going to be unfortunate when I can't do this anymore because of people blowing this issue out of proportion. I hope Apple will at least provide the option of caching this data for longer than 7 days.

pilif 15y ago
Well. If you are near an access point apple knows about or just by geolocating your IP address, the iPhone can still download datapoints from that central database that allow it to quickly locate you. That file on the iphone is just a local copy of the relevant parts of the central database. Sure. It might be 10 seconds instead of one second now, but that's a reasonable tradeoff compared to the huge log it currently makes. IMHO.
- pieter 15y ago
  Point is that he's turning roaming off, and probably doesn't have access to WiFi in the foreign city. By having the database, you don't need a data connection at all, thus saving money.
  - seabee 15y ago
    He had to connect to the internet in the foreign city at least once before. The difference is now it must be every time.
    - wlesieutre 15y ago
      Right, but if you travel there semi-frequently, it would be nice to not pay for it each time. Cheap relative to the airfare, but every bit helps.
diminish 15y ago
your need is too exotic and mainstream concerns about location/timestamp tracking on iphone are real, valid concerns.
- sounddust 15y ago
  It's a common scenario in Europe. It's not "exotic" to take a €39 train ride from Paris to Brussels to visit for the weekend. I don't think it's a privacy concern to store such data locally on the phone. In any case, it should be resolved by letting the user decide how long to cache the data; that would make everyone happy.
  - stitchy 15y ago
    Even so, the data should not be stored in a plain text file. Doing so gives any iPhone application access to that location data. Apple claims that it manages location preferences by application, but that's not true as long as this file exists in a plain text format.
    - Xuzz 15y ago
      That is incorrect. The iPhone employs sandboxing, so most areas of the filesystem are not accessible to iOS applications, and this cache is in one of those restricted locations. An app on the phone cannot read this information. However, it is included in the iTunes backups. Those can be read -- but only on your computer, not on the iPhone itself. (An exception to the above would be a jailbroken phone: the packages installed via Cydia would not have the same restrictions, although the recent jailbreaks do not remove the restrictions on apps from the App Store.)
      - stitchy 15y ago
        I was unaware of that. Good to know. I still think it's an issue; although, one that Apple is apparently resolving in the next major release.
  - wlesieutre 15y ago
jrockway 15y ago
Do you need to use AGPS? It only takes 12 minutes to download the ephemeris and almanac via the GPS satellite itself. So even without Internet connectivity, you'll eventually know where you are.
- sounddust 15y ago
  As far as I can tell, the iPhone cannot determine one's location solely from the GPS antenna. If you travel to a place where you haven't been before, location services simply won't work until you obtain internet connectivity for a few seconds. I don't know if this is because the iPhone's GPS functionality is crippled, or if it's a software limitation. I'd imagine that if you wanted to overcome this limitation, you'd need to jailbreak your phone and use 3rd party mapping software at a minimum. *Note: once it has located you, it will generally track you correctly while you're moving, even if you leave the area where you had internet connectivity.
  - jrockway 15y ago
    Are you sure you've had 12 minutes with a clear view of the sky? Each GPS satellite carries the entire constellation's almanac. After downloading that (which is a 12.5 minute process), then you can download the ephemeris from each satellite, which takes 30 seconds. You need 4 satellites to get a location fix. The almanac is valid for 180 days, so you only need to wait 12 minutes once. From then on, you only need the ephemeris from 4 visible satellites, which takes less than a minute to download. It confuses me that the iPhone wouldn't be able to do this, because I can buy a $10 microchip that's the size of a dime that can do it. Give it electricity, wait 15 minutes, the location comes out the other side. I would be shocked if the iPhone were incapable of doing this.
    - morganw 15y ago
      > I can buy a $10 microchip that's the size of a dime that can do it. Give it electricity, wait 15 minutes, the location comes out the other side. How do you know when the 15 minutes starts, though? Dedicated GPSs tell you things like how many satellites they have in view and how accurate their fix is, but dumbed-down devices like to pretend location is magic. I'd hope they'd at least provide the gritty details through CoreLocation so a user can buy an app if she wants to know which bench outside the train station to sit at sipping coffee while the phone orients itself.

pilif 15y ago

Well. If you are near an access point apple knows about or just by geolocating your IP address, the iPhone can still download datapoints from that central database that allow it to quickly locate you. That file on the iphone is just a local copy of the relevant parts of the central database. Sure. It might be 10 seconds instead of one second now, but that's a reasonable tradeoff compared to the huge log it currently makes. IMHO.

pieter 15y ago
Point is that he's turning roaming off, and probably doesn't have access to WiFi in the foreign city. By having the database, you don't need a data connection at all, thus saving money.
- seabee 15y ago
  He had to connect to the internet in the foreign city at least once before. The difference is now it must be every time.
  - wlesieutre 15y ago
    Right, but if you travel there semi-frequently, it would be nice to not pay for it each time. Cheap relative to the airfare, but every bit helps.

diminish 15y ago

your need is too exotic and mainstream concerns about location/timestamp tracking on iphone are real, valid concerns.

sounddust 15y ago
It's a common scenario in Europe. It's not "exotic" to take a €39 train ride from Paris to Brussels to visit for the weekend. I don't think it's a privacy concern to store such data locally on the phone. In any case, it should be resolved by letting the user decide how long to cache the data; that would make everyone happy.
- stitchy 15y ago
  Even so, the data should not be stored in a plain text file. Doing so gives any iPhone application access to that location data. Apple claims that it manages location preferences by application, but that's not true as long as this file exists in a plain text format.
  - Xuzz 15y ago
    That is incorrect. The iPhone employs sandboxing, so most areas of the filesystem are not accessible to iOS applications, and this cache is in one of those restricted locations. An app on the phone cannot read this information. However, it is included in the iTunes backups. Those can be read -- but only on your computer, not on the iPhone itself. (An exception to the above would be a jailbroken phone: the packages installed via Cydia would not have the same restrictions, although the recent jailbreaks do not remove the restrictions on apps from the App Store.)
    - stitchy 15y ago
      I was unaware of that. Good to know. I still think it's an issue; although, one that Apple is apparently resolving in the next major release.
- wlesieutre 15y ago

jrockway 15y ago

Do you need to use AGPS? It only takes 12 minutes to download the ephemeris and almanac via the GPS satellite itself. So even without Internet connectivity, you'll eventually know where you are.

sounddust 15y ago
As far as I can tell, the iPhone cannot determine one's location solely from the GPS antenna. If you travel to a place where you haven't been before, location services simply won't work until you obtain internet connectivity for a few seconds. I don't know if this is because the iPhone's GPS functionality is crippled, or if it's a software limitation. I'd imagine that if you wanted to overcome this limitation, you'd need to jailbreak your phone and use 3rd party mapping software at a minimum. *Note: once it has located you, it will generally track you correctly while you're moving, even if you leave the area where you had internet connectivity.
- jrockway 15y ago
  Are you sure you've had 12 minutes with a clear view of the sky? Each GPS satellite carries the entire constellation's almanac. After downloading that (which is a 12.5 minute process), then you can download the ephemeris from each satellite, which takes 30 seconds. You need 4 satellites to get a location fix. The almanac is valid for 180 days, so you only need to wait 12 minutes once. From then on, you only need the ephemeris from 4 visible satellites, which takes less than a minute to download. It confuses me that the iPhone wouldn't be able to do this, because I can buy a $10 microchip that's the size of a dime that can do it. Give it electricity, wait 15 minutes, the location comes out the other side. I would be shocked if the iPhone were incapable of doing this.
  - morganw 15y ago
    > I can buy a $10 microchip that's the size of a dime that can do it. Give it electricity, wait 15 minutes, the location comes out the other side. How do you know when the 15 minutes starts, though? Dedicated GPSs tell you things like how many satellites they have in view and how accurate their fix is, but dumbed-down devices like to pretend location is magic. I'd hope they'd at least provide the gritty details through CoreLocation so a user can buy an app if she wants to know which bench outside the train station to sit at sipping coffee while the phone orients itself.