private int lowerIndex(double length) {
    int idx = Arrays.binarySearch(nodeLocations, length);
    return idx < 0 ? (-idx - 2) : idx - 1;
  }
Returns a partial segment of this line from {@code start} to {@code end} where 0 is the beginning of the line and 1
is the end.
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/LineSplitter.java