GPS on 3GS works without cell coverage

[Galarina]

Actually aGPS doesn't even function without cell coverage. I find that it only takes about 30 seconds for GPS to work. If not less when I don't have cell coverage.

Acquiring a non-assisted GPS lock can take quite a while. I've measured times up to 20 minutes (!) but most of the time it's between 30 seconds and a couple of minutes.

Did anyone notice that on cloudy days (sky completely covered with huge clouds) the GPS will not lock/work at all?

 

[vwDavid]

So if GPS won't work in airplane mode, then you have to leave the cell-radio on to get GPS and if you are out in the boonies on a hike that will drain you batter more quickly.

it'd be nice to be able to turn the big battery drainers off but still use GPS

 

[redman042]

An attempt to clear things up here:

There's a regular GPS chip in the iPhone that determines position directly from the satellites without any cell coverage, just like a Garmin.

The iPhone also has an aGPS function that uses cell towers to assist the GPS chip and get the lock faster and more accurately. Without cell coverage, this enhancement won't work, but you can still get a position.

Airplane mode turns off all GPS functionality and there doesn't appear to be any way to just turn GPS back on. Would be nice for saving battery in no-coverage areas, and also for getting position on an airplane (even though this is technically against FAA regulations I believe). Oddly, you CAN turn Wifi back on in Airplane mode by turning the Wifi switch back on in settings, but this doesn't seem to work in location settings. Opportunity for a special jailbreak app here?

If you anticipate losing cell coverage somewhere and want maps, just preload them by opening maps while you still have coverage, zooming in to the level of detail you want, then scroll around until everything loads. You can also use 3rd party apps like MotionX-GPS, which allow you to set the cache size and type of map to load.

 

[Jimmy James]

So if GPS won't work in airplane mode, then you have to leave the cell-radio on to get GPS and if you are out in the boonies on a hike that will drain you batter more quickly.

If you're out in the boonies on a hike there is a reasonably good chance that you will be out of tower range.

An attempt to clear things up here:

There's a regular GPS chip in the iPhone that determines position directly from the satellites without any cell coverage, just like a Garmin.

Airplane mode turns off all GPS functionality and there doesn't appear to be any way to just turn GPS back on.

It's become evident that the GPS reception of the iPhone is severely sub-par as compared to a standalone unit.

Effectively, this makes the GPS of little value to someone who doesn't subscribe to a data plan - even if you've purchased maps from a vendor like TomTom.

 

[Richdmoore]

Does going into airplane mode, then turning on the wifi allow the GPS antenna to work? (I can't really tell myself, but I'm testing it now.)

 

[trainguy77]

If you're out in the boonies on a hike there is a reasonably good chance that you will be out of tower range.



It's become evident that the GPS reception of the iPhone is severely sub-par as compared to a standalone unit.

Effectively, this makes the GPS of little value to someone who doesn't subscribe to a data plan - even if you've purchased maps from a vendor like TomTom.

I would argue that. The GPS reception is not sub par. I find its very fast actually. Also using navigon it works great with no data connection.

And no turning wifi back on does not seem to re-enable GPS.