Chapter    17

Where Are You?

If you think the accelerometer, gyroscope, and magnetometer are cool, you’re going to love this chapter. In addition to those instruments, many iOS devices contain radio receivers allowing them to triangulate their position by timing radio signals they receive from a network of satellites—either the Global Positioning System or the Russian Global Navigation Satellite System. This technology is generically referred to as GPS.

What does that mean to you? As a user, it means your iOS device knows where it is on the planet. As a developer, it means your app can get information about the device’s location and use that to show your user where they are, what’s around them, where they’ve come from, or how to get to where ...

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