public static double getWorldX(double longitude) {
    return (longitude + 180) / 360;
  }
Returns the web mercator X coordinate for {@code longitude} where 0 is the international date line on the west
side, 1 is the international date line on the east side, and 0.5 is the prime meridian.
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/GeoUtils.java