--- a/artifacts/src/main/java/org/dive4elements/river/exports/WaterlevelExporter.java	Mon Nov 25 17:40:47 2013 +0100
+++ b/artifacts/src/main/java/org/dive4elements/river/exports/WaterlevelExporter.java	Wed Nov 27 16:21:00 2013 +0100
@@ -25,6 +25,13 @@
 
 import au.com.bytecode.opencsv.CSVWriter;
 
+import gnu.trove.TDoubleArrayList;
+
+import org.apache.commons.math.FunctionEvaluationException;
+import org.apache.commons.math.analysis.UnivariateRealFunction;
+
+import org.apache.commons.math.analysis.interpolation.LinearInterpolator;
+
 import org.dive4elements.river.artifacts.model.ConstantWQKms;
 
 import net.sf.jasperreports.engine.JasperExportManager;
@@ -48,6 +55,7 @@
 import org.dive4elements.river.artifacts.model.Segment;
 import org.dive4elements.river.artifacts.model.WQCKms;
 import org.dive4elements.river.artifacts.model.WQKms;
+import org.dive4elements.river.artifacts.model.WstLine;
 import org.dive4elements.river.artifacts.model.WKmsJRDataSource;
 import org.dive4elements.river.artifacts.model.WQKmsResult;
 import org.dive4elements.river.artifacts.resources.Resources;
@@ -761,7 +769,7 @@
     {
         logger.info("WaterlevelExporter.generateWST");
 
-        int cols = data.get(0).length;
+        int cols = data.get(0).length + officalFixings.size();
         WstWriter writer = new WstWriter(cols);
 
         writeWSTData(writer);
@@ -801,6 +809,67 @@
                 }
             }
         }
+
+        // Append the official fixing interpolated to the calculation steps
+        //
+        // There was some confusion how to implement this. see flys/issue1620
+        // for details.
+        for (WQKms wqkms: officalFixings) {
+            // To add some spaces here or to add them in the writer,..
+            writer.addColumn("   " + getDesc(wqkms, true));
+
+            // Get all lines from the calculation
+            Map <Double, WstLine> calcLines = writer.getLines();
+
+            // All KM values where we have a point for
+            TDoubleArrayList officialKms = wqkms.allKms();
+
+            for (Map.Entry<Double, WstLine> entry : calcLines.entrySet()) {
+                // Bad for perfomance but the user can wait a bit for WST
+                // so lets not spend time optimizing too much,.. *hides*
+                double km = entry.getKey().doubleValue();
+                int idx = officialKms.indexOf(km);
+                if (idx != -1) {
+                    entry.getValue().add(wqkms.getW(idx), entry.getValue().getQ(0));
+                }
+            }
+
+            /* Variant: Interpolate the values
+            // Now get the lines for the of the calculation
+            Map <Double, WstLine> calcLines = writer.getLines();
+
+            // Create an interpolater for the official KM -> W relation
+            UnivariateRealFunction wFunc = new LinearInterpolator(
+                    ).interpolate(wqkms.allKms().toNativeArray(),
+                        wqkms.allWs().toNativeArray());
+
+            // Now for each calculated point add the interpolated official
+            for (Map.Entry<Double, WstLine> entry : calcLines.entrySet()) {
+                try {
+                    double wVal = wFunc.value(entry.getKey().doubleValue());
+                    // Matching Q's are guranteed otherwise we would
+                    // not have an official line
+                    entry.getValue().add(wVal, entry.getValue().getQ(0));
+                }
+                catch (FunctionEvaluationException aode) {
+                    // should not happen
+                    logger.error("spline interpolation failed", aode);
+                    // entry.getValue().add(Double.NaN, entry.getValue().getQ(0));
+                }
+            }*/
+
+             /* Variant: Add all official fixings
+                // Warning the WSTWriter does not handle this properly
+                // as it writes the points for which only a calculation
+                // exists in the first column
+                int size = wqkms.size();
+                result = new double[4];
+                for (int i = 0; i < size; i++) {
+                    result = wqkms.get(i, result);
+                    writer.add(result);
+                }
+            */
+        }
     }