iOS GPS
测试代码如下：
// LocationViewCtrl.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface LocationViewCtrl : UIViewController <CLLocationManagerDelegate>{
CLLocationManager *man;
}
@property(nonatomic, retain) CLLocationManager *man;
@end
LocationViewCtrl.m
#import "LocationViewCtrl.h"
#import <CoreLocation/CoreLocation.h>
@implementation LocationViewCtrl
@synthesize man;
- (void)viewDidLoad {
[super viewDidLoad];
man = [[CLLocationManager alloc] init];
// 如果可以利用本地服务时
if([man locationServicesEnabled]){
// 接收事件的实例
man.delegate = self;
// 发生事件的的最小距离间隔（缺省是不指定）
man.distanceFilter = kCLDistanceFilterNone;
// 精度 (缺省是Best)
man.desiredAccuracy = kCLLocationAccuracyBest;
// 开始测量
[man startUpdatingLocation];
}
}
// 如果GPS测量成果以下的函数被调用
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation{
// 取得经纬度
CLLocationCoordinate2D coordinate = newLocation.coordinate;
CLLocationDegrees latitude = coordinate.latitude;
CLLocationDegrees longitude = coordinate.longitude;
// 取得精度
CLLocationAccuracy horizontal = newLocation.horizontalAccuracy;
CLLocationAccuracy vertical = newLocation.verticalAccuracy;
// 取得高度
CLLocationDistance altitude = newLocation.altitude;
// 取得时刻
NSDate *timestamp = [newLocation timestamp];
// 以下面的格式输出 format: <latitude>, <longitude>> +/- <accuracy>m @ <date-time>
NSLog([newLocation description]);
// 与上次测量地点的间隔距离
if(oldLocation != nil){
CLLocationDistance d = [newLocation getDistanceFrom:oldLocation];
NSLog([NSString stringWithFormat:@"%f", d]);
}
}
// 如果GPS测量失败了，下面的函数被调用
- (void)locationManager:(CLLocationManager *)manager
didFailWithError:(NSError *)error{
NSLog([error localizedDescription]);
}
...
测量精度有以下几类，精度越高越消耗电力。
| kCLLocationAccuracyNearestTenMeters | 10m |
| kCLLocationAccuracyHundredMeters | 100m |
| kCLLocationAccuracyKilometer | 1km |
| kCLLocationAccuracyThreeKilometers | 3km |
因为在模拟器上不能设置经纬度，所以只能在实际设备中测试你的GPS程序
Core Location主要应用了GPS, 蜂窝基站三角网以及Wi_Fi(WPS)三种技术。
- 使用GPS定位系统，可以精确地定位你当前所在的地理位置，但由于GPS接收机需要对准天空才能工作，因此在室内环境基本无用。
- 另一个找到自己所在位置的有效方法是使用手机基站，手机开机时，它会与周围的基站保持联系，如果你知道这些基站的身份，就可以使用各种数据库(包含基站的身份和它们的确切地理位置)计算出手机的物理位置。基站不需要卫星，和GPS不同，它对室内环境一样管用。但它没有GPS那样精确，它的精度取决于基站的密度，它在基站密集型区域的准确度最高。
- 第三种方法是依赖Wi-Fi，使用这种方法时，设备连接到Wi-Fi网络，通过检查服务提供商的数据确定位置，它既不依赖卫星，也不依赖基站，因此这个方法对于可以连接到Wi-Fi网络的区域有效，但它的精确度也是这三个方法中最差的。
想得到定点的信息，需要涉及到几个类，CLLocationManager, CLLocation, CLLocationManagerdelegate协议，CLLocationCoodinate2D, CLLocationDegrees。
<一>先实例化一个CLLocationManager,同时设置委托及精确度等。
CCLocationManager *manager = [[CLLocationManager alloc] init];//初始化定位器 [manager setDelegate: self];//设置代理 [manager setDesiredAccuracy: kCLLocationAccuracyBest];//设置精确度
其中desiredAccuracy属性表示精确度，有5种选择如下:
| desiredAccuracy属性 |
描述 |
| kCLLocationAccuracyBest |
精确度最佳 |
| kCLLocationAccuracynearestTenMeters |
精确度10m以内 |
| kCLLocationAccuracyHundredMeters |
精确度100m以内 |
| kCLLocationAccuracyKilometer |
精确度1000m以内 |
| kCLLocationAccuracyThreeKilometers |
精确度3000m以内 |
NOTE:精确度越高，用点越多，就要根据实际情况而定。
manager.distanceFilter = 250;//这个表示在地图上每隔250m才更新一次定位信息。
[manager startUpdateLocation]; 启动定位器，如果不用的时候就必须调用stopUpdateLocation以关闭定位功能。
<二>CCLocation对像中包含着定点的相关信息数据。其属性主要包括coordinate, altitude,horizontalAccuracy,verticalAccuracy, timestamp等，分别如下：
coordinate 用来存储地理位置的latitude和longitude,分别表示纬度和经度，都是float类型.如可这样： float latitude = location.coordinat.latitude; location是CCLocation的实例。这里也把上面提到的CLLocationDegrees，它其实是一个double类型，在core Location框架中是用来储存CLLocationCoordinate2D实例coordinate的latitude 和longitude，
typedef double CLLocationDegrees;
typedef struct
{CLLocationDegrees latitude;
CLLocationDegrees longitude} CLLocationCoordinate2D;
altitude 表示位置的海拔高度，这个值是极不准确的。
horizontalAccuracy 表示水平准确度，这么理解，它是以coordinate为圆心的半径，返回的值越小，证明准确度越好，如果是负数，则表示core location定位失败。
verticalAccuracy表示垂直准确度，它的返回值与altitude相关，所以不准确。
Timestamp 返回的是定位时的时间，是NSDate类型。
<三>CLLocationMangerDelegate协议
我们只需实现两个方法就可以了，如下:
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation ;
- (void)locationManager:(CLLocationManager *)manager
didFailWithError:(NSError *)error;
上面第一个是定位时候回访调，后者定位出错时被调。
<四>现在可以去实现定位了：
新建一个view-based application模板的工程，假设项目名称为coreLocation.我们在contronller的头文件和源文件中的代码大概有如下：
.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface CoreLocationViewController : UIViewController
<CLLocationManagerDelegate>{
CLLocationManager *locManager;
}
@property (nonatomic, retain) CLLocationManager *locManager;
@end
.m
#import "CoreLocationViewController.h"
@implementation CoreLocationViewController
@synthesize locManager;
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
locManager = [[CLLocationManager alloc] init];
locManager.delegate = self;
locManager.desiredAccuracy = kCLLocationAccuracyBest;
[locManager startUpdatingLocation];
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)dealloc {
[locManager stopUpdatingLocation];
[locManager release];
[textView release];
[super dealloc];
}
#pragma mark -
#pragma mark CoreLocation Delegate Methods
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation {
CLLocationCoordinate2D locat = [newLocation coordinate];
float lattitude = locat.latitude;
float longitude = locat.longitude;
float horizon = newLocation.horizontalAccuracy;
float vertical = newLocation.verticalAccuracy;
NSString *strShow = [[NSString alloc] initWithFormat:
@"currentpos: 经度＝%f 维度＝%f 水平准确读＝%f 垂直准确度＝%f ",
lattitude, longitude, horizon, vertical];
UIAlertView *show = [[UIAlertView alloc] initWithTitle:@"coreLoacation"
message:strShow delegate:nil cancelButtonTitle:@"i got it"
otherButtonTitles:nil];
[show show];
[show release];
}
- (void)locationManager:(CLLocationManager *)manager
didFailWithError:(NSError *)error{
NSString *errorMessage;
if ([error code] == kCLErrorDenied){
errorMessage = @"你的访问被拒绝";}
if ([error code] == kCLErrorLocationUnknown) {
errorMessage = @"无法定位到你的位置!";}
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle:nil message:errorMessage
delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
[alert show];
[alert release];
}
@end
//根据经纬度计算两点的距离
#define PI 3.1415926
double LantitudeLongitudeDist(double lon1,double lat1,
double lon2,double lat2)
{
double er = 6378137; // 6378700.0f;
//ave. radius = 6371.315 (someone said more accurate is 6366.707)
//equatorial radius = 6378.388
//nautical mile = 1.15078
double radlat1 = PI*lat1/180.0f;
double radlat2 = PI*lat2/180.0f;
//now long.
double radlong1 = PI*lon1/180.0f;
double radlong2 = PI*lon2/180.0f;
if( radlat1 < 0 ) radlat1 = PI/2 + fabs(radlat1);// south
if( radlat1 > 0 ) radlat1 = PI/2 - fabs(radlat1);// north
if( radlong1 < 0 ) radlong1 = PI*2 - fabs(radlong1);//west
if( radlat2 < 0 ) radlat2 = PI/2 + fabs(radlat2);// south
if( radlat2 > 0 ) radlat2 = PI/2 - fabs(radlat2);// north
if( radlong2 < 0 ) radlong2 = PI*2 - fabs(radlong2);// west
//spherical coordinates x=r*cos(ag)sin(at), y=r*sin(ag)*sin(at), z=r*cos(at)
//zero ag is up so reverse lat
double x1 = er * cos(radlong1) * sin(radlat1);
double y1 = er * sin(radlong1) * sin(radlat1);
double z1 = er * cos(radlat1);
double x2 = er * cos(radlong2) * sin(radlat2);
double y2 = er * sin(radlong2) * sin(radlat2);
double z2 = er * cos(radlat2);
double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));
//side, side, side, law of cosines and arccos
double theta = acos((er*er+er*er-d*d)/(2*er*er));
double dist = theta*er;
return dist;
}