@Override
    protected StationHelper createStationHelper() throws IOException {
      StationHelper stationHelper = new StationHelper();

      for (StationFeature stationFeat : this.stationFeats) {
        stationHelper.addStation(
            new CompositeStationFeature(
                stationFeat,
                timeUnit,
                altUnits,
                stationFeat.getFeatureData(),
                from.dataCollection));
      }

      return stationHelper;
    }
 @Override
 public StationTimeSeriesFeature getStationFeature(Station s) throws IOException {
   StationFeature stnFeature = getStationHelper().getStationFeature(s);
   return new CompositeStationFeature(
       stnFeature, timeUnit, altUnits, stnFeature.getFeatureData(), dataCollection);
 }