--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/flowdepthdev/FlowDepthDevelopmentCalculation.java	Wed Mar 28 17:04:20 2018 +0200
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/flowdepthdev/FlowDepthDevelopmentCalculation.java	Thu Mar 29 15:48:17 2018 +0200
@@ -11,6 +11,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.TreeSet;
 
 import org.apache.commons.lang.math.DoubleRange;
 import org.dive4elements.artifacts.CallContext;
@@ -79,11 +80,11 @@
             final WstSoundingIdPair histPair, final Calculation problems, final RiverInfoProvider infoProvider) {
 
         /* access real input data from database */
-        final WaterlevelData currentWaterlevel = loadWaterlevel(currentPair, problems);
+        final WaterlevelData currentWaterlevel = loadWaterlevel(currentPair, calcRange, problems);
         if (currentWaterlevel == null)
             return null;
 
-        final WaterlevelData historicalWaterlevel = loadWaterlevel(histPair, problems);
+        final WaterlevelData historicalWaterlevel = loadWaterlevel(histPair, calcRange, problems);
         if (historicalWaterlevel == null)
             return null;
 
@@ -112,9 +113,6 @@
         FlowDepthUtils.checkYearDifference("", currentWstYear, currentSoundingYear, problems);
         FlowDepthUtils.checkYearDifference("", historicalWstYear, historicalSoundingYear, problems);
 
-        // checkWaterlevelDiscretisation(wstKms, calcRange, problems);
-        // TODO: prüfen, ob sohlhöhen die calcRange abdecken/überschneiden
-
         /* re-determine the reference gauge, in the same way as the WaterlevelArtifact would do it */
         final RiverInfoProvider currentRiverInfoProvider = infoProvider.forWaterlevel(currentWaterlevel);
         final RiverInfoProvider histRiverInfoProvider = infoProvider.forWaterlevel(historicalWaterlevel);
@@ -123,35 +121,27 @@
         final WstInfo historicalWstInfo = new WstInfo(historicalWaterlevel.getName(), historicalWstYear, histRiverInfoProvider.getReferenceGauge());
 
         final WKms currentWkms = currentWaterlevel.getWkms();
-        final WaterlevelValuesFinder currentWstProvider = WaterlevelValuesFinder.fromKms(currentWkms);
-        // final DischargeValuesFinder currentDischargeProvider = DischargeValuesFinder.fromKms(currentWkms);
+        final WaterlevelValuesFinder currentWstProvider = WaterlevelValuesFinder.fromKms(problems, currentWkms);
 
         final WKms historicalWkms = historicalWaterlevel.getWkms();
-        final WaterlevelValuesFinder historicalWstProvider = WaterlevelValuesFinder.fromKms(historicalWkms);
-        // final DischargeValuesFinder historicalDischargeProvider = DischargeValuesFinder.fromKms(historicalWkms);
+        final WaterlevelValuesFinder historicalWstProvider = WaterlevelValuesFinder.fromKms(problems, historicalWkms);
 
         final int currentMeanYear = (currentWstYear + currentSoundingYear) / 2;
         final int historcialMeanYear = (historicalWstYear + historicalSoundingYear) / 2;
 
-        // final String waterlevelLabel = waterlevel.getName();
-        // final String soundingLabel = buildSoundingLabel(minBedHeight, maxBedHeight);
-
         final double diffYear = currentMeanYear - historcialMeanYear;
 
         /* real calculation loop */
         final Collection<SInfoResultRow> rows = new ArrayList<>();
 
-        // FIXME: determine what is the spatial discretisation that we will use...
-        final double[] allKms = currentWkms.allKms().toNativeArray();
-        for (final double station : allKms) {
+        final Collection<Double> stations = determineCalculationSteps(currentSounding, historicalSounding);
+        for (final double station : stations) {
             if (calcRange.containsDouble(station)) {
 
                 final double currentWst = currentWstProvider.getWaterlevel(station);
-                // final double currentDischarge = currentDischargeProvider.getDischarge(station);
                 final double currentBedHeight = currentSounding.getMeanBedHeight(station);
 
                 final double historicalWst = historicalWstProvider.getWaterlevel(station);
-                // final double historicalDischarge = historicalDischargeProvider.getDischarge(station);
                 final double historicalBedHeight = historicalSounding.getMeanBedHeight(station);
 
                 final double diffWst = (currentWst - historicalWst) * 100;
@@ -186,6 +176,19 @@
                 rows);
     }
 
+    /**
+     * Calculation steps are simply the union of all stations of all involved bed-height datasets
+     */
+    private Collection<Double> determineCalculationSteps(final BedHeightsFinder currentSounding, final BedHeightsFinder historicalSounding) {
+
+        final Collection<Double> allStations = new TreeSet<>();
+
+        allStations.addAll(currentSounding.getStations());
+        allStations.addAll(historicalSounding.getStations());
+
+        return allStations;
+    }
+
     private String buildLabel(final WaterlevelData currentWaterlevel, final BedHeightInfo currentSounding, final WaterlevelData historicalWaterlevel,
             final BedHeightInfo historicalSounding) {
 
@@ -201,9 +204,9 @@
     }
 
     /* REMARK: fetch ALL wst kms, because we need to determine the original reference gauge */
-    private WaterlevelData loadWaterlevel(final WstSoundingIdPair pair, final Calculation problems) {
+    private WaterlevelData loadWaterlevel(final WstSoundingIdPair pair, final DoubleRange calcRange, final Calculation problems) {
         final String wstId = pair.getWstId();
-        return new WaterlevelFetcher().findWaterlevel(this.context, wstId, Double.NaN, Double.NaN, problems);
+        return new WaterlevelFetcher().findWaterlevel(this.context, wstId, calcRange, problems);
     }
 
     private BedHeightsFinder loadBedHeight(final WstSoundingIdPair pair, final DoubleRange calcRange, final Calculation problems) {