Location
Core Location provides facilities for the device to determine and report its location (location services). It takes advantage of three sensors:
- Wi-Fi
- The device (if Wi-Fi is turned on) may scan for nearby Wi-Fi devices and compare these against an online database.
- Cell
- The device (if it has cell capabilities) may compare nearby telephone cell towers against an online database.
- GPS
- The device’s GPS (if it has one) may be able to obtain a position fix from GPS satellites.
Core Location will automatically use whatever facilities the device does have; all you have to do is ask for the device’s location. Core Location allows you to specify how accurate a position fix you want; more accurate fixes may require more time.
The notion of a location is encapsulated by the CLLocation class and its properties, which include:
-
coordinate - A CLLocationCoordinate2D; see Chapter 34.
-
altitude - A CLLocationDistance, which is a double representing a number of meters.
-
speed - A CLLocationSpeed, which is a double representing meters per second.
-
heading - A CLLocationDirection, which is a double representing degrees (not radians!) clockwise from north.
-
horizontalAccuracy - A CLLocationAccuracy, which is a double representing meters.
In addition to the sensor-related considerations I mentioned a moment ago, use of Core Location poses the following challenges:
- Accuracy of a reported location may vary depending on a number of factors. The GPS is the most accurate location sensor, but it takes ...
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