Resolved Location services without using GPS?

[kdarling]

Tower triangulation has nothing to do with GPS or aGPS. Towers are only used by aGPS to obtain the ephemeris data. The ephemeris data reveals nothing about the receiver's location. It's used to locate the satellites. Non aGPS receivers have to download this information from the satellites and because of the bandwidth it takes a very long time. Interruptions can also increase the time to first fix as the download has to start over. aGPS cuts down on the time to first fix by using faster download methods.

This.

I would add that a device could also access the Assistance Server via WiFi if cell service wasn't available.

There are plenty of reputable resources you can read on the matter instead of relying on speculation and forum posts.

The problem is, there are a lot of websites who have repeated incorrect info.

Already stated that gps info does not come from the phone with a-gps. Yes the GPS info does come from somewhere...in the case of a-gps the internet delivers the appropriate gps info from back-end servers.

As takeshi74 noted above, in the case of A-GPS the internet delivers only the initial satellite status and orbit info. This is so the GPS chip can look for the correct satellites and know exactly where they are.

(GPS satellites orbit the earth twice a day, so they're constantly going in and out of sight. Also, orbital info is only good for about four hours because of solar winds, gravity anomalies, etc.)

After the initial startup info assistance, however, it's all up to the GPS chip. It is constantly receiving signals from GPS satellites, switching satellites, and downloading updated orbital information from the satellites themselves.

An iPod touch can use location services and it has no GPS. There are databases of wifi MAC addresses along with the location of the wifi router. I think this is some of the data that Google collects as they drive their streetview cars around. An iPod touch can often come up with a pretty close location just based on what wifi signals it "sees".

Correct, Google collects hotspot locations with their streetview cars.

Apple collects the same info from all the iPhones in use. When you make or end a call with diagnostics on, or drop a call, or an app requests your location, it collects hotspot info and transmits it back up to the Apple mothership.

The OP was questioning if his weather app is using GPS. I'm guessing yes.

Absolutely not. The whole point was that they said they were not using GPS, and as you just pointed out, GPS is not needed to get a location. A weather app especially only needs a general area, which is easily satisfied by cell id.

As mentioned wifi, LTE and GPS are all options for the phone to determine your location. I don't which one it relies mostly on though.

LTE is a comm protocol, not a locating method.

Which locating method it relies on is determined by the accuracy requested by the apps you use. A weather app only needs the rough cell coverage center. A store sales app might only need WiFi hotspot to know you're near the store. A driving app needs GPS for accuracy and independence from civilization.

 

[iolinux333]

Let me give this a shot (trying to give a simple explanation):


Plain GPS without assist: The radio starts to look for satellites. It finds one. I needs to find the rest which can take a long time. Part of the satellite transmission is a data stream containing the location of all the other satellites which move around all over the place and their orbits are too complicated to predict very far into the future. This info is saved as a file on your phone, then when the file is complete, the app can tell the GPS receiver in your phone where all the other satellites are so it can finally find them and lock on. The problem here is that the data is being transmitted VERY slowly, slower than an old dial up modem. The process can take ten minutes sometimes longer.

Assisted GPS: that file, the one containing the current whereabouts of the satellites, is smacked into your phone with high speed data connection in a few milliseconds. Now the GPS receiver instantly knows where to look for all the satellites and locks on within seconds. Assisted just means you get the file faster, that's all! It means nothing else.

 

[iMacBooked]

Yes, but as I said, I seriously doubt that the app is using any active locating. It's almost certainly using the passive check for a "significant change" (see below).

Note: there are multiple location symbols. A grey one simply means that LS has been used in the past day.


Probably because the app isn't doing the checking, the OS is. It's been asked to watch all the time, and wake up the app when a gross location change has occurred, which can be triggered by switching between cells.

For a weather app, that's all the accuracy that's needed. No need for GPS, or WiFi, or Bluetooth iBeacons.

The great thing about this method is how low power it is. The phone's baseband code is already constantly checking for towers, so there's almost no extra overhead until the app needs to be notified.

Thank you, this makes sense to me.
It's just the regular symbol, not grey.