[Galaxy S II Q&A, Help & Troubleshooting] Joao Clemente:
Initial GPS Lock possible with no data? (abroad, flight mode, no wifi)

Hi all,

Maybe this belongs on this thread or in a separate one as it is specific to the initial lock...

I just wanted to share this (strange) experience I had with my Samsung Galaxy S2.

I bought my SGS II in Germany and every time I tried my GPS it worked fine, locking my position in a couple of seconds. By the way, I use only "Use GPS satellites" and no "Use wireless networks" and also no "Use sensor aiding" so I assume the SGS II is able to act as a "pure GPS" (in opposition to A-GSP).

Note I'm not talking about any particular application here, simply the GPS lock/triangulation.

It happens I flown to USA and before departing I set my phone with no WiFi, Flight mode ( so my phone would also not try to connect to any mobile operator 2G/3G network ) and "Data network mode deactivated". I had a second phone to do calls/txt so I thought about using my SGS II just for browsing or Skyp'ing via WiFi while in the USA... and for GPS in case of emergency.

Anyway, I got to the USA (west shore) and rented a car. Only for curiosity I decided to turn on the GPS. As I had no data connection I was aware the google maps would not load maps.... however my expectation is that the phone would lock a location via GPS (the GSP symbol would stop blinking and lock).

The outcome? In roughly

one hour

driving along the highway with the phone located in dashboard the GPS never locked. I even rebooted the phone, "just in case".

I thought "funny... the GSP only works in Europe?!?"

Moving on, I got to my destination where there was WiFi and turned the WiFi on for some browsing. If I remember correctly I kept the flight mode on (although I am not 100% sure of this, I may have set it off to let the phone get the correct date/time from the mobile network and then set the flight mode back on).

I decided to try the GPS again, just for fun, and by then it locked in a couple of seconds?!? After that every time I tried it worked fine.

So I had two theories to explain this, all based to the fact that I was on the other side of the world:

( I was on the USA west shore = 9 hours Time zone difference = roughly the other side of the world :p )

a) The GPS HW tries to lock to only a small set of the possible satellites, depending on a roughly estimated position ( maybe by detecting the country-code from the mobile operator , or by the time-zone ... ) and even not locking to these it will not try other set of satellites.

b) There are so many possible satellites to triangulate with (?!? can this be ?!?) that the GPS HW only keeps a subset of them and needs a data connection to fetch info about more sets of satellites, based on some criteria I cannot think of as this is not my area of expertise.

I decided to record my experience here more for curiosity than a request for help.

Just in case someone happens to think "this is obvious" please let me (us) know why as until now the searches I've done both in the forum and outside did not came with an obvious reason: I was expecting the phone to take some time to lock the GPS location with but as I mentioned, after one hour I still had no lock and decided to gave up.

Oh, same thing was happening to a Nokia (N7?N8?) that also had roaming data and wifi disabled.

Thanks

Joao Clemente