Location Services allows applications such as Maps Camera, and Compass to gather and use data indicating your location. Location Services doesn’t correlate the data it collects with your personally identifiable information. Your approximate location is determined using available information from cellular network data, local Wi-Fi networks (if you have Wi-Fi turned on), and GPS (iPhone 3G or later; GPS may not be available in all locations).
You can turn Location Services off if you don’t want to use this feature. If you turn Location Services off, you’ll be prompted to turn it on again the next time an application tries to use this feature.
Choose General > Location Services and turn location services on or off.
To conserve battery life, turn Location Services off when you’re not using it.