toys/gps/docs/wgs84toWebm.cpp

//方法一
PointD latLng2WebMercator(double lng, double lat)
{
    auto earthRad = 6378137.0;
    auto x = lng * PI / 180 * earthRad;
    auto a = lat * PI / 180;
    auto y = earthRad / 2 * std::log((1.0 + std::sin(a)) / (1.0 - std::sin(a)));
    return PointD {x, y};
}

//方法二
PointD latLng2WebMercator2(double lng, double lat)
{
    auto x = lng *20037508.34/180;
    auto y = std::log(std::tan((90+lat)*PI/360))/(PI/180);
    y = y *20037508.34/180;
    return PointD {x, y};
}

PointD webMercator2LngLat(double x, double y)
{
    auto lng = x / 20037508.34 * 180;
    auto lat = y / 20037508.34 * 180;
    lat = 180 / PI * (2 * std::atan(std::exp(lat * PI / 180)) - PI / 2);
    return PointD {lng, lat};
}