public static SortKey orderByDouble(double value, double start, double end, int levels) {
    return new SortKey().thenByDouble(value, start, end, levels);
  }
Returns a new sort key where elements with {@code value == start} appear before elements with {@code value == end}
and the entire range is compressed into {@code levels} distinct levels for comparison.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/SortKey.java