IPHONE实景导航开发总结（二）
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9.使用GPS设定其精度并，取得方位（经度，纬度），方向的数据
使用CLLocationManager来取得当前的GPS经度，纬度，方位的数据，首先初始化CLLocationManager，设定其精度，更新回调，更新的距离筛选，通过方法startUpdatingHeading来开启方向的更新，通过方法startUpdatingLocation来开启方位的更新。
//初始化方位类self.localManager = [[CLLocationManager alloc] init];localManager.delegate = self;//开启电子罗盘if (localManager.headingAvailable) [localManager startUpdatingHeading];//启动//开启GPSif(localManager.locationServicesEnabled) {localManager.desiredAccuracy = kCLLocationAccuracyBest;//设定为最佳精度localManager.distanceFilter = 5.0f;//响应位置变化的最小距离(m)[localManager startUpdatingLocation];}//方位变化的回调函数- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {//初始化方位if ([fileLoader isKindOfClass:[TestLoader class]]) {if (localDir == 0) {baseDir = newHeading.magneticHeading;localDir = newHeading.magneticHeading;}}float newlocalDir = newHeading.magneticHeading;//当变化超过一定范围，刷新标志显示if (abs(newlocalDir - localDir) > FLASH_DEGREE) {localDir = newlocalDir;[self computer];}//更新指南针方向[overlayView updateHeading:newHeading];}//方位变化的回调函数- (BOOL)locationManagerShouldDisplayHeadingCalibration:(CLLocationManager *)manager {return YES;}//GPS位置变化的回调- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {self.local = newLocation;//更新经纬度表示值[overlayView updateLocation:self.local];if ([fileLoader isKindOfClass:[GPSLoader class]]) {[fileLoader computerDis:allTags andLocal:local];//重新计算当前标志点的位置[self computer];}//关闭定位//[localManager stopUpdatingLocation];}//GPS初始化失败- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {NSLog(@"Location manager error: %@", [error description]);}CLLocation* location1 = [[CLLocation alloc] initWithLatitude:latin1 longitude:lonin1];CLLocation* location2 = [[CLLocation alloc] initWithLatitude:latin2 longitude:lonin2];return [location1 getDistanceFrom:location2];
//计算GPS两点间的经度距离+ (CGFloat) calcuLoninM:(CGFloat) latin1 withLonin:(CGFloat) lonin1 withDisLatin:(CGFloat) latin2 withDisLonin:(CGFloat) lonin2 {CGFloat retval = 0.0;CGFloat latin = latin1;CGFloat latinStep = (latin1 - latin2) / MAX_LENGTH;CGFloat loninStep = (lonin1 - lonin2) / MAX_LENGTH;if (loninStep < 0) {loninStep = -1.0 * loninStep;}for (int i = 0 ; i < MAX_LENGTH; i++) {retval += EARTH_RADIUS * [GPSHelp toRadians:loninStep] * cos([GPSHelp toRadians:latin]);latin += latinStep;}return retval;}//计算GPS两点间的纬度距离+ (CGFloat) calcuLatinM:(CGFloat) latin1 withLonin:(CGFloat) lonin1 withDisLatin:(CGFloat) latin2 withDisLonin:(CGFloat) lonin2 {CGFloat angle = latin1 - latin2;if (angle < 0) {angle = -1.0 * angle;}return [GPSHelp toRadians:angle] * EARTH_RADIUS;}//角度转弧度+ (CGFloat)toRadians:(CGFloat)degree {return degree / 180.0 * M_PI;}//弧度转角度+ (CGFloat)toDegrees:(CGFloat)radian {return radian / M_PI * 180.0;}@end @implementation GPSHelp//计算GPS两点间的角度（正北方向为0度）+ (CGFloat) calcuAngle:(CGFloat) latin1 withLonin:(CGFloat) lonin1 withDisLatin:(CGFloat) latin2 withDisLonin:(CGFloat) lonin2 {CGFloat loninM = [GPSHelp calcuLoninM:latin1 withLonin:lonin1 withDisLatin:latin2 withDisLonin:lonin2];CGFloat latinM = [GPSHelp calcuLatinM:latin1 withLonin:lonin1 withDisLatin:latin2 withDisLonin:lonin2];CGFloat radian = atan2f(loninM, latinM);if (lonin2 >= lonin1) {if (latin2 >= latin1) {;} else {radian = M_PI - radian;}} else {if (latin2 >= latin1) {radian = 2.0 * M_PI - radian;;} else {radian = M_PI + radian;}}return [GPSHelp toDegrees:radian];}