GPS and data roaming

Although the iPhone uses A-GPS or assisted GPS, the iPhone includes a dedicated GPS receiver and the same for the iPad. The assisted part helps to speed up the initial GPS acquisition from a cold start only - it is not required to maintain GPS reception or used with GPS reception unless you are using an app that doesn't store map data locally on the device such as the included Maps app.

If you had data roaming off, it should not have mattered regardless. That should prevent data access when roaming internationally. If you turn wi-fi access off, you can't connect to an available wi-fi network and have internet access via an available wi-fi network. The same should apply for data access via the cellular network when roaming internationally when data roaming is off, which is off by default.

You're welcome.

If you had Data Roamimg off which is off by default, you should not have been able to download/upload any data when connected to a cellular network while you were roaming internationally. The data wasn't downloaded with the GPS navigation app regardless.

Wi-Fi access will not result in extra fees from AT&T. Data accessed via an available wi-fi network is done via the wi-fi network your iPhone is connected with, which is completely separate from AT&T or the cellular network you were also connected with at the time. With Data Roamimg off, you should not be able to access any data via a cellular network when roaming internationally which doesn't apply any way when your iPhone is connected to an available wi-fi network. A no longer activated iPhone can have wi-fi access. You can remove the SIM card from an activated iPhone and have wi-fi access, and you can do the same with an activated iPhone by enabling Airplane mode followed by turning on wi-fi.

Hi Allan, I´m sorry but I just don´t get it. I went to Europe as well and turned the iphone 4 to airplane mode, turned data roaming off, cellular data off, and used the phone with free Wi-fi only where available. Now I come back and have the over a 1000 US bill for GPRS navegation in international roaming...what is the problem and thanks for your help.

If you had Airplane mode enabled the entire time with wi-fi turned on only while Airplane mode was enabled, it is impossible for any data access via the cellular network.

If you turned Airplane mode off at any time and had Cellular Data off when doing so, you could place and receive calls and the same for SMS/MMS when you were roaming internationally, but having Cellular Data off prevents internet access via the cellular network.

Did you have Airplane mode enabled with wi-fi turned on only the ENTIRE time while you were roaming internationally?

Hey, Allan. I'm getting ready to travel overseas myself and want to avoid these same issues. Outside of a WiFi connection, all I'm interested in doing is geotagging photos and using a GPS map. If I pull the SIM card, could I do all that without incurring any roaming costs?

Hi.

Copied from my first post in this thread.

Although the iPhone uses A-GPS or assisted GPS, the iPhone includes a dedicated GPS receiver and the same for the iPad. The assisted part helps to speed up the initial GPS acquisition from a cold start only - it is not required to maintain GPS reception or used with GPS reception unless you are using an app that doesn't store map data locally on the device such as the included Maps app.

So you don't need cellular access for a GPS fix but an initial/new GPS fix will take longer. This may not provide for a very accurate location fix when capturing photos unless you have already made an initial/new GPS fix with a new location before capturing any photos at a new location.

iOS4 includes a Cellular Data on/off selection. Make sure Cellular Data is off when Airplane Mode is not enabled for a GPS fix if you don't remove the SIM card when doing so.

Hello Allan,

I have some similar questions and would like to confirm some previous answers that were posted on this thread. I am travelling to Mexico next week and would like to use the GPS on my iPhone in conjunction with the app PlaceTagger, and I would not like to incur any cellular data or roaming charges on my cell phone account.

Question #1: Are the settings in General settings on the iPhone the "Master" settings for the phone or can an app override these settings? PlaceTagger does not store its maps locally whereas it uses the internet to provide them. Will using the app override the "Master" settings in General settings to get its infomation?

Question #2: To confirm, if I turn off 3G, Cellular Data and Data Roaming in General settings, the iPhone will only use the dedicated GPS to acquire its location?

Question #3: How does putting the iPhone in Airplane mode affect any of the above? Will the Airplane mode be a back up if those features were turned off?

Question #4: Will placing an unactivated Sim card in the device essentially take the cell phone company out of the equation for data and roaming charges, and allow the dedicated GPS to only function?

Any info would be great, Thank you for your time.

Alvin

Hello.

Question #1: Are the settings in General settings on the iPhone the "Master" settings for the phone or can an app override these settings? PlaceTagger does not store its maps locally whereas it uses the internet to provide them. Will using the app override the "Master" settings in General settings to get its infomation?

An app cannot override your settings. With wi-fi access off or when not connected to an available wi-fi network, and with Cellular Data turned off on the iPhone, if you select an app that requires internet access, you will be provided a warning or error message that internet access is required with the app and is not enabled. An app won't arbitrarily turn on Cellular Data without your knowledge or consent and approval.

Question #2: To confirm, if I turn off 3G, Cellular Data and Data Roaming in General settings, the iPhone will only use the dedicated GPS to acquire its location?

Turning Cellular Data off prevents cellular data or internet access via the cellular network entirely with the iPhone via 3G, EDGE, or GPRS - whichever is available at the time. Turning 3G network access off only turns 3G network access off only. Doing this only does not prevent data or internet access via the cellular network via EDGE or GPRS unless you have Data Roaming off (which is off by default) when roaming internationally. To ensure there is no data or internet access via the cellular network when roaming internationally, turn Cellular Data off. If you turn Cellular Data on and Data Roaming is off, you shouldn't be able to access the internet via the cellular network either when roaming internationally, but having Cellular Data turned off ensures this.

When Cellular Data turned off, the iPhone will not be able to make use of A-GPS or assisted GPS unless you have wi-fi access enabled and are connected to an available wi-fi network. Without A-GPS, the initial GPS acquisition with a new location will take much longer, but GPS access alone without A-GPS via the cellular network or an available wi-fi network does not use any data, which isn't possible anyway when Cellular Data is off.

Question #3: How does putting the iPhone in Airplane mode affect any of the above? Will the Airplane mode be a back up if those features were turned off?

Airplane mode turns off all iPhone radios - cellular for calls and SMS/MMS, cellular for internet access via the cellular network, wi-fi access, bluetooth, and GPS. With the iPhone, you can turn on wi-fi access and bluetooth only after enabling Airplane mode. With Airplane mode enabled, GPS reception and acquisition is not possible.

Question #4: Will placing an unactivated Sim card in the device essentially take the cell phone company out of the equation for data and roaming charges, and allow the dedicated GPS to only function?

No need to insert an unactivated SIM card in the device. Just remove the activated SIM card from the device which takes all cellular functions out of the equation. Doing so does not prevent wi-fi access or GPS reception. With Cellular Data turned off, this does not prevent you from placing or receiving any calls and the same for SMS/MMS. Cellular Data turned off prevents internet access via the cellular network.

Excellent, thanks for the info.