地图经纬度坐标系

在开发过程中用到地图服务，一般集成百度、高德、腾讯等，若仅仅是显示功能，使用ios自带MKMapView为首选（中国区为高德数据），但往往出现经纬度偏移等问题，原因莫过于各地图间使用的坐标系不同。

• WGS-84：是国际标准，GPS坐标（Google Earth使用、或者GPS模块）
• GCJ-02：中国坐标偏移标准，Google地图、高德、腾讯使用
• BD-09 ：百度坐标偏移标准，Baidu地图使用

转换工具类:

WJLocationTransform.h

#import <Foundation/Foundation.h>
#import <CoreLocation/CLLocation.h>

@interface WJLocationTransform : NSObject

/*
 坐标系：
 WGS-84：是国际标准，GPS坐标（Google Earth使用、或者GPS模块）
 GCJ-02：中国坐标偏移标准，Google Map、高德、腾讯使用
 BD-09 ：百度坐标偏移标准，Baidu Map使用
 */

#pragma mark - 中国坐标 转到 百度坐标
+ (CLLocationCoordinate2D)transformFromGCJToBaidu:(CLLocationCoordinate2D)p;

#pragma mark - 百度坐标 转到 中国坐标
+ (CLLocationCoordinate2D)transformFromBaiduToGCJ:(CLLocationCoordinate2D)p;

#pragma mark - GPS坐标 转到 中国坐标
+ (CLLocationCoordinate2D)transformFromWGSToGCJ:(CLLocationCoordinate2D)wgsLoc;

#pragma mark - 中国坐标 转到 GPS坐标
+ (CLLocationCoordinate2D)transformFromGCJToWGS:(CLLocationCoordinate2D)p;

@end

WJLocationTransform.m

#import "WJLocationTransform.h"

static const double a = 6378245.0;
static const double ee = 0.00669342162296594323;
static const double pi = M_PI;
static const double xPi = M_PI  * 3000.0 / 180.0;

@implementation WJLocationTransform

#pragma mark - 中国坐标 转到 百度坐标
+ (CLLocationCoordinate2D)transformFromGCJToBaidu:(CLLocationCoordinate2D)p {
    long double z = sqrt(p.longitude * p.longitude + p.latitude * p.latitude) + 0.00002 * sqrt(p.latitude * pi);
    long double theta = atan2(p.latitude, p.longitude) + 0.000003 * cos(p.longitude * pi);
    CLLocationCoordinate2D geoPoint;
    geoPoint.latitude  = (z * sin(theta) + 0.006);
    geoPoint.longitude = (z * cos(theta) + 0.0065);
    return geoPoint;
}

#pragma mark - 百度坐标 转到 中国坐标
+ (CLLocationCoordinate2D)transformFromBaiduToGCJ:(CLLocationCoordinate2D)p {
    double x = p.longitude - 0.0065, y = p.latitude - 0.006;
    double z = sqrt(x * x + y * y) - 0.00002 * sin(y * xPi);
    double theta = atan2(y, x) - 0.000003 * cos(x * xPi);
    CLLocationCoordinate2D geoPoint;
    geoPoint.latitude  = z * sin(theta);
    geoPoint.longitude = z * cos(theta);
    return geoPoint;
}

#pragma mark - GPS坐标 转到 中国坐标
+ (CLLocationCoordinate2D)transformFromWGSToGCJ:(CLLocationCoordinate2D)wgsLoc {
    CLLocationCoordinate2D adjustLoc;
    if([self isLocationOutOfChina:wgsLoc]) {
        adjustLoc = wgsLoc;
    }
    else {
        double adjustLat = [self transformLatWithX:wgsLoc.longitude - 105.0 withY:wgsLoc.latitude - 35.0];
        double adjustLon = [self transformLonWithX:wgsLoc.longitude - 105.0 withY:wgsLoc.latitude - 35.0];
        long double radLat = wgsLoc.latitude / 180.0 * pi;
        long double magic = sin(radLat);
        magic = 1 - ee * magic * magic;
        long double sqrtMagic = sqrt(magic);
        adjustLat = (adjustLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
        adjustLon = (adjustLon * 180.0) / (a / sqrtMagic * cos(radLat) * pi);
        adjustLoc.latitude = wgsLoc.latitude + adjustLat;
        adjustLoc.longitude = wgsLoc.longitude + adjustLon;
    }
    return adjustLoc;
}

#pragma mark - 中国坐标 转到 GPS坐标
+ (CLLocationCoordinate2D)transformFromGCJToWGS:(CLLocationCoordinate2D)p {
    double threshold = 0.00001;
    
    // The boundary
    double minLat = p.latitude - 0.5;
    double maxLat = p.latitude + 0.5;
    double minLng = p.longitude - 0.5;
    double maxLng = p.longitude + 0.5;
    
    double delta = 1;
    int maxIteration = 30;
    // Binary search
    while(true) {
        CLLocationCoordinate2D leftBottom  = [[self class] transformFromWGSToGCJ:(CLLocationCoordinate2D){.latitude = minLat,.longitude = minLng}];
        CLLocationCoordinate2D rightBottom = [[self class] transformFromWGSToGCJ:(CLLocationCoordinate2D){.latitude = minLat,.longitude = maxLng}];
        CLLocationCoordinate2D leftUp      = [[self class] transformFromWGSToGCJ:(CLLocationCoordinate2D){.latitude = maxLat,.longitude = minLng}];
        CLLocationCoordinate2D midPoint    = [[self class] transformFromWGSToGCJ:(CLLocationCoordinate2D){.latitude = ((minLat + maxLat) / 2),.longitude = ((minLng + maxLng) / 2)}];
        delta = fabs(midPoint.latitude - p.latitude) + fabs(midPoint.longitude - p.longitude);
        
        if(maxIteration-- <= 0 || delta <= threshold) {
            return (CLLocationCoordinate2D){.latitude = ((minLat + maxLat) / 2),.longitude = ((minLng + maxLng) / 2)};
        }
        
        if(isContains(p, leftBottom, midPoint)) {
            maxLat = (minLat + maxLat) / 2;
            maxLng = (minLng + maxLng) / 2;
        } else if(isContains(p, rightBottom, midPoint)) {
            maxLat = (minLat + maxLat) / 2;
            minLng = (minLng + maxLng) / 2;
        } else if(isContains(p, leftUp, midPoint)) {
            minLat = (minLat + maxLat) / 2;
            maxLng = (minLng + maxLng) / 2;
        } else {
            minLat = (minLat + maxLat) / 2;
            minLng = (minLng + maxLng) / 2;
        }
    }
    
}

+ (double)transformLatWithX:(double)x withY:(double)y {
    double lat = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * sqrt(fabs(x));
    
    lat += (20.0 * sin(6.0 * x * pi) + 20.0 *sin(2.0 * x * pi)) * 2.0 / 3.0;
    lat += (20.0 * sin(y * pi) + 40.0 * sin(y / 3.0 * pi)) * 2.0 / 3.0;
    lat += (160.0 * sin(y / 12.0 * pi) + 320 * sin(y * pi / 30.0)) * 2.0 / 3.0;
    return lat;
}

+ (double)transformLonWithX:(double)x withY:(double)y {
    double lon = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * sqrt(fabs(x));
    lon += (20.0 * sin(6.0 * x * pi) + 20.0 * sin(2.0 * x * pi)) * 2.0 / 3.0;
    lon += (20.0 * sin(x * pi) + 40.0 * sin(x / 3.0 * pi)) * 2.0 / 3.0;
    lon += (150.0 * sin(x / 12.0 * pi) + 300.0 * sin(x / 30.0 * pi)) * 2.0 / 3.0;
    return lon;
}

#pragma mark - 判断某个点point是否在p1和p2之间
static bool isContains(CLLocationCoordinate2D point, CLLocationCoordinate2D p1, CLLocationCoordinate2D p2) {
    return (point.latitude >= MIN(p1.latitude, p2.latitude) && point.latitude <= MAX(p1.latitude, p2.latitude)) && (point.longitude >= MIN(p1.longitude,p2.longitude) && point.longitude <= MAX(p1.longitude, p2.longitude));
}

#pragma mark - 判断是不是在中国
+ (BOOL)isLocationOutOfChina:(CLLocationCoordinate2D)location {
    if (location.longitude < 72.004 || location.longitude > 137.8347 || location.latitude < 0.8293 || location.latitude > 55.8271)
        return YES;
    return NO;
}

@end

附:

百度地图转换为自家经纬度坐标:
http://lbsyun.baidu.com/index.php?title=webapi/guide/changeposition

高德地图转换为自家经纬度坐标:
http://lbs.amap.com/api/webservice/guide/api/convert