CYLocationManager use CoreLocation Framework to track user travel distance.

• iOS 5.0 or later
• support ARC

Simply add CYLocationManager.h and CYLocationManager.m to your project, and import "CYLocationManager.h".

typedef enum {
    CYGPSSignalStrengthInvalid = 0,
    CYGPSSignalStrengthWeak,
    CYGPSSignalStrengthStrong
} CYGPSSignalStrength;

• GPS signal strength depend on the horizontalAccuracy of updated location. (see CLLocation.horizontalAccuracy).
• you can change the parameters kRequiredHorizontalAccuracy and kMaxAcceptableHorizontalAccuracy in CYLocationManager.m to make the program determine the signal strength in a different way.
• If the horizontalAccuracy of latest updated location is less then kRequiredHorizontalAccuracy, the GPS signal strength suppose to be strong, else it will be weak.

@interface CYLocationManager : NSObject

@property (nonatomic, weak) id<CYLocationManagerDelegate> delegate;
@property (nonatomic, readonly) CYGPSSignalStrength signalStrength;
@property (nonatomic, readonly) CLLocationDistance distance;

+ (CYLocationManager *)shareManager;

- (BOOL)prepareLocationUpdates;
- (BOOL)startLocationUpdates;
- (void)stopLocationUpdates;
- (void)resetLocationUpdates;

@end

• You should use the shareManager method to access the manager. However you also can alloc and init a new instance by yourself.
• I recommend you set the delegate first before any operation, in order to get the callback when something you cared changed. However, you are not asked to do that, it's optional.
• You should always prepareLocationUpdates first before you startLocationUpdates.
• When you stopLocationUpdates, you could use startLocationUpdates to restart it, it won't reset the current calculation unless you use the resetLocationUpdates.
• prepareLocationUpdates and startLocationUpdates will return a boolean value to determine whether it can do that. (Something like, GPS is not available and device can not connect the internet, or user reject your app to get his/her location)

@protocol CYLocationManagerDelegate <NSObject>

@optional
- (void)locationManager:(CYLocationManager *)locationManager didUpdateSignalStrength:(CYGPSSignalStrength)signalStrength;
- (void)locationManagerSignalConsistentlyWeak:(CYLocationManager *)locationManager;
- (void)locationManager:(CYLocationManager *)locationManager didUpdateDistance:(CLLocationDistance)distance;
- (void)locationManager:(CYLocationManager *)locationManager didFailWithError:(NSError *)error;

@end

• Pretty straight forward, I'm sure your will know how to use them.
• didFailWithError return the same error from CLLocationManager.

static const NSUInteger kDistanceFilter = 10;
static const NSUInteger kHeadingFilter = 30;
static const NSUInteger kNumberOfLocationsToKeep = 5;
static const NSUInteger kMinNumberOfLocationsRequiredToCalculate = 3;
static const NSUInteger kGPSSignalRecheckInterval = 15;
static const CGFloat kRequiredHorizontalAccuracy = 20.0;
static const CGFloat kRequiredHorizontalAccuracy = 70.0;
static const NSTimeInterval kCalculationInterval = 3;
static const NSTimeInterval kValidIntervalWithKeptLocation = 3;
static const NSUInteger kUpdateLocationMaxInterval = 10;

• kDistanceFilter see CLLocationManager.distanceFilter
• kHeadingFilter see CLLocationManager.headingFilter
• kNumberOfLocationsToKeep, kMinNumberOfLocationsRequiredToCalculate: We keep multi location in order to pick up the datas which have the best accuracy to calculate the distance.
• kGPSSignalRecheckInterval, interval of rechecking GPS Signal.
• kRequiredHorizontalAccuracy, kRequiredHorizontalAccuracy: discussed in GPS signal strength.
• kCalculationInterval: We calculate the distance kCalculationInterval seconds once.
• kValidIntervalWithKeptLocation: The valid interval between current location and kept locations.
• kUpdateLocationMaxInterval: if user stop walking or running, CoreLocation won't update the location, we need to force it to request a new location. It's mean we alway get a new location during kUpdateLocationMaxInterval seconds.

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