gistfile1.m

const double a  = 6378245.0;
const double ee = 0.00669342162296594323;

static BOOL outOfChina(double lat, double lon){
    if(lon < 72.004 || lon > 137.8347){
        return true;
    }
    
    if(lat < 0.8293 || lat > 55.8271){
        return true;
    }
    
    return false;
}

static double transformLat(double x, double y)
{
    double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * sqrt(abs(x));
    ret += (20.0 * sin(6.0 * x * M_PI) + 20.0 * sin(2.0 * x * M_PI)) * 2.0 / 3.0;
    ret += (20.0 * sin(y * M_PI) + 40.0 * sin(y / 3.0 * M_PI)) * 2.0 / 3.0;
    ret += (160.0 * sin(y / 12.0 * M_PI) + 320 * sin(y * M_PI / 30.0)) * 2.0 / 3.0;
    return ret;
}

static double transformLon(double x, double y)
{
    double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * sqrt(abs(x));
    ret += (20.0 * sin(6.0 * x * M_PI) + 20.0 * sin(2.0 * x * M_PI)) * 2.0 / 3.0;
    ret += (20.0 * sin(x * M_PI) + 40.0 * sin(x / 3.0 * M_PI)) * 2.0 / 3.0;
    ret += (150.0 * sin(x / 12.0 * M_PI) + 300.0 * sin(x / 30.0 * M_PI)) * 2.0 / 3.0;
    return ret;
}

// World Geodetic System ==> Mars Geodetic System
static CLLocationCoordinate2D transform(double wgLat, double wgLon){
    if (outOfChina(wgLat, wgLon)){
        return CLLocationCoordinate2DMake(wgLat, wgLon);
    }
    
    double dLat = transformLat(wgLon - 105.0, wgLat - 35.0);
    double dLon = transformLon(wgLon - 105.0, wgLat - 35.0);
    double radLat = wgLat / 180.0 * M_PI;
    double magic = sin(radLat);
    magic = 1 - ee * magic * magic;
    double sqrtMagic = sqrt(magic);
    dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * M_PI);
    dLon = (dLon * 180.0) / (a / sqrtMagic *cos(radLat) * M_PI);
    
    return CLLocationCoordinate2DMake(wgLat + dLat, wgLon + dLon);
}