iOS地圖定位偏差問題解決（不同座標系轉化）
國際共識：WGS84的座標系統，以經緯度的形式來表示地球平面上的某一個位置；
中國：GCJ-02的座標系統。在我國，出於國家安全考慮，國內所有導航電子地圖必須使用國家測繪局制定的加密座標系統，即將一個真實的經緯度座標加密成一個不正確的經緯度座標，稱之為火星座標；
百度：BD-09的座標系統，百度座標是在國測局制定的GCJ-02,對地理位置進行首次加密的基礎上，進行了BD-09二次加密措施,更加保護了個人隱私。
下面直接上程式碼，直接建立一個座標轉化類，用的時候將定位到的CLLocationCoordinate2D，直接通過所定義的類轉化一下，再用的時候，地圖定位偏差較大的問題即可解決。
建立一個座標轉化類
.h檔案
#import《Foundation/Foundation.h》
#import《CoreLocation/CoreLocation.h》
@interface KNLocationConverter : NSObject
/**
* 判斷是否在中國
*/
+(BOOL)isLocationOutOfChina:(CLLocationCoordinate2D)location;
/**
* 將WGS-84轉為GCJ-02(火星座標):
*/
+(CLLocationCoordinate2D)transformFromWGSToGCJ:(CLLocationCoordinate2D)wgsLoc;
/**
* 將GCJ-02(火星座標)轉為百度座標:
*/
+(CLLocationCoordinate2D)transformFromGCJToBaidu:(CLLocationCoordinate2D)p;
/**
* 將百度座標轉為GCJ-02(火星座標):
*/
+(CLLocationCoordinate2D)transformFromBaiduToGCJ:(CLLocationCoordinate2D)p;
/**
* 將GCJ-02(火星座標)轉為WGS-84:
*/
+(CLLocationCoordinate2D)transformFromGCJToWGS:(CLLocationCoordinate2D)p;
@end
.m檔案
#import "TQLocationConverter.h"
#import《math.h》
static const double a = 6378245.0;
static const double ee = 0.00669342162296594323;
static const double pi = 3.14159265358979324;
static const double xPi = M_PI * 3000.0 / 180.0;
@implementation KNLocationConverter
+(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;
}
+ (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;
}
+(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;
}
+(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;
}
+(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;
}
}
}
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));
}
/**
* 判斷是不是在中國
*/
+(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
用的時候，直接把國際座標轉換成火星座標，就可以直接顯示定位資訊了