Location-services

Location services are a set of different methods to determine the current location of a devices (and its user). This location data might be stored in pictures taken or used for navigation. The available methods vary on device type.

WLAN

Signatures (SSIDs) of WLANs in the current location are polled and sent to a database which has also the location information of all known WLANs. Such database services are provided by Google and skyhookwireless. Apple claims that they are not using these services since iOS 3.2 - and provide a similar service themselves. An active Internet connection is required to send signatures to the database and get location coordinates in return. This is the only method used for iPod touch devices.

A-GPS (Assisted GPS)

This method uses GSM/UTMS protocols to quickly identify the approximate current location. The GSM/UMTS network is organized in cells and from currently subscribed cell ID it is possible to get a first guestimate on the current location. If neighbourhood cells can be taken into account as well a more precise location estimation might be possible. In addition these direct location information network operators may also provide so-called almanach data for faster satellite GPS synchronisation. Read more details here: Assisted GPS.

However, none of these services are mandatory standards. If provided, network operators usually charge for these services and this is one of the reasons why costs are generated even without initiated phone calls. Another disadvantage is that reponse is rather inaccurate, at least insufficient for navigation purposes. Avantages are fast response and coverage in buildings.

GPS (satellite)

Satellite GPS is the most accurate method and hence suitable for even navigation purposes. On the other hand it may take up to 10minutes to "fix" and will most likely work only outdoors. In idevices various (different) chipsets are used for GPS but they have all in common that these are controlled by the baseband firmware. So idevices without bandbase don't have GPS, too.

ipadBB 6.15.00 losing GPS function

If an iPad baseband 6.15.00 is installed on iPhone 3G or 3GS it is resulting in loss of (satellite) GPS functionality. Reason is that for GSM/UMTS radio function ipad1 and iphone 3G or 3GS using the same GSM/UTMS chipset X-Gold 608 but different GPS chips: BCM4750 in iPad 1 while Infineon PMB2525 in iphone 3G and 3GS. So the ipad baseband is (assumingly) not containing a device driver for the Infineon PMB2525 and hence this CPS chip cannot be used. As baseband is totally separated from rest of the iPhone logic - only communicating over a serial link - there is no alternative way to address the unused GPS chip. Meanwhile all hopes have been burried of a downgrade option for iPad baseband. So if for unlocking a vulnerable baseband firmware is needed always check if an older version of iOS is installed or can be restored (if SHSH blobs are available) and then using sn0wbreeze for iOS upgrade without baseband upgrade. Only if this is no option consider installing iPad baseband.