public static Double parseDoubleOrNull(String tag) {
    try {
      return tag == null ? null : Double.parseDouble(tag);
    } catch (NumberFormatException e) {
      return retryParseNumber(tag, Number::doubleValue, null);
    }
  }
Returns {@code tag} as a double or null if invalid.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/Parse.java